124 results on '"Steven A. Johnson"'
Search Results
2. Native honeybees as flower visitors and pollinators in wild plant communities in a biodiversity hotspot
- Author
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Dara A. Stanley, Simangele M. Msweli, and Steven D. Johnson
- Subjects
Apis mellifera ,biodiversity hotspot ,honey bee ,pollination ,Ecology ,QH540-549.5 - Abstract
Abstract Western honeybees (Apis mellifera L.), native to Europe and Africa, have been transported worldwide and are now one of the most important global crop pollinator species. Although the relative contribution of honeybees to global crop pollination is increasingly recognized, relatively little is known about their importance as pollinators in wild plant communities. The only remaining wild and unmanaged western honeybee populations are in Africa. We investigated the importance of honeybees as pollinators of diverse wild plant communities in two protected areas within the Maputaland–Pondoland–Albany biodiversity hotspot in South Africa. Sites were far from any known areas of beekeeping, and so all honeybees were most likely from wild colonies. Honeybees visited a large proportion of flowering plant species within these two communities (40% and 35%) and also provided a substantial proportion of visits to the plants they visited (40% and 32%, respectively). However, when pollinator importance indices (based on abundance and the size and purity of pollen loads) were calculated for a small subset of plants, honeybees were only important pollinators of 29% of the plants they visited. Our data provide a first step in determining the importance of honeybees as flower visitors and pollinators in wild plant communities and the potential impacts of honeybee declines on these highly diverse grassland ecosystems. Our work suggests that many plants in the grassland systems studied are visited by non‐Apis flower visitors and therefore that conservation efforts should also focus on these pollinator groups.
- Published
- 2020
- Full Text
- View/download PDF
3. Long‐term camera trapping needed to identify sunbird species that pollinate the endangered South African orchid Satyrium rhodanthum
- Author
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Timotheüs van der Niet, Ruth J. Cozien, Miguel Castañeda‐Zárate, and Steven D. Johnson
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Ecology, Evolution, Behavior and Systematics - Published
- 2022
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4. Beyond P:O ratios: evolutionary consequences of pollinator dependence and pollination efficiency for pollen and ovule production in angiosperms
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Lawrence D. Harder and Steven D. Johnson
- Subjects
Genetics ,Plant Science ,Ecology, Evolution, Behavior and Systematics - Published
- 2023
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5. ‘Bleeding’ flowers of Ceropegia gerrardii (Apocynaceae‐Asclepiadoideae) mimic wounded insects to attract kleptoparasitic fly pollinators
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Annemarie Heiduk, Irina Brake, Adam Shuttleworth, and Steven D. Johnson
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Physiology ,Plant Science - Published
- 2023
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6. Development and application of quality measures of clinical pharmacist services provided in inpatient/acute care settings
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Craig J. Beavers, Christopher K. Finch, Sarah M. Hayes, Steven T. Johnson, Danielle B. Holdren, Sandra L. Kane-Gill, Nicole M. Acquisto, Ishaq Lat, Scott Bolesta, Kelsey F. Dobbins, and Mitchell S. Buckley
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medicine.medical_specialty ,business.industry ,media_common.quotation_subject ,Pharmaceutical Science ,Pharmacy ,medicine.disease ,Clinical pharmacy ,Acute care ,medicine ,Pharmacology (medical) ,Quality (business) ,Medical emergency ,business ,media_common - Published
- 2021
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7. Information Models Offer Value to Standardize Electronic Health Record Flowsheet Data: A Fall Prevention Exemplar
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Theresa Tess Settergren, Steven G. Johnson, Kay S Lytle, Bonnie L. Westra, Meg Furukawa, Mary L Hook, Stephanie Hartleben, Mischa Adams, Mariaelena Thibodeaux, Mari Akre, Luann Whittenburg, and Samira Ali
- Subjects
Knowledge management ,Standardization ,Nursing Records ,Computer science ,Health information technology ,Big data ,Documentation ,03 medical and health sciences ,0302 clinical medicine ,Electronic Health Records ,Humans ,030212 general & internal medicine ,book ,General Nursing ,Information exchange ,Retrospective Studies ,030504 nursing ,business.industry ,Models, Theoretical ,Reference Standards ,Nursing standard ,Metadata ,Data exchange ,ComputingMilieux_COMPUTERSANDSOCIETY ,book.journal ,Accidental Falls ,0305 other medical science ,business - Abstract
Purpose The rapid implementation of electronic health records (EHRs) resulted in a lack of data standardization and created considerable difficulty for secondary use of EHR documentation data within and between organizations. While EHRs contain documentation data (input), nurses and healthcare organizations rarely have useable documentation data (output). The purpose of this article is to describe a method of standardizing EHR flowsheet documentation data using information models (IMs) to support exchange, quality improvement, and big data research. As an exemplar, EHR flowsheet metadata (input) from multiple organizations was used to validate a fall prevention IM. Design A consensus-based, qualitative, descriptive approach was used to identify a minimum set of essential fall prevention data concepts documented by staff nurses in acute care. The goal was to increase generalizable and comparable nurse-sensitive data on the prevention of falls across organizations for big data research. Methods The research team conducted a retrospective, observational study using an iterative, consensus-based approach to map, analyze, and evaluate nursing flowsheet metadata contributed by eight health systems. The team used FloMap software to aggregate flowsheet data across organizations for mapping and comparison of data to a reference IM. The FloMap analysis was refined with input from staff nurse subject matter experts, review of published evidence, current documentation standards, Magnet Recognition nursing standards, and informal fall prevention nursing use cases. Findings Flowsheet metadata analyzed from the EHR systems represented 6.6 million patients, 27 million encounters, and 683 million observations. Compared to the original reference IM, five new IM classes were added, concepts were reduced by 14 (from 57 to 43), and 157 value set items were added. The final fall prevention IM incorporated 11 condition or age-specific fall risk screening tools and a fall event details class with 14 concepts. Conclusion The iterative, consensus-based refinement and validation of the fall prevention IM from actual EHR fall prevention flowsheet documentation contributes to the ability to semantically exchange and compare fall prevention data across multiple health systems and organizations. This method and approach provides a process for standardizing flowsheet data as coded data for information exchange and use in big data research. Clinical relevance Opportunities exist to work with EHR vendors and the Office of the National Coordinator for Health Information Technology to implement standardized IMs within EHRs to expand interoperability of nurse-sensitive data.
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- 2021
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8. The functional ecology of bat pollination in the African sausage tree Kigelia africana (Bignoniaceae)
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Keeveshnee Govender, Steven D. Johnson, Sandy E van Niekerk, and Ethan Newman
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Kigelia ,Epomophorus wahlbergi ,Functional ecology ,Tree (data structure) ,Pollination ,Botany ,Nectar ,Bignoniaceae ,Biology ,biology.organism_classification ,Ecology, Evolution, Behavior and Systematics - Published
- 2021
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9. How reliable are motion‐triggered camera traps for detecting small mammals and birds in ecological studies?
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Steven D. Johnson and C. R. Ortmann
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Ecology ,Animal Science and Zoology ,Biology ,Ecology, Evolution, Behavior and Systematics ,Motion (physics) - Published
- 2020
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10. Formulary management challenges and opportunities: 2020 and beyond ‐ an opinion paper of the drug information practice and research network of the American College of Clinical Pharmacy
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Rena Gosser, Janine S. Douglas, Gregory A. Heindel, Keri C. Anderson, Steven T. Johnson, Radha Manian, Karen L. Kier, Krisy-Ann Thornby, and Daniel Majerczyk
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Drug ,Medical education ,Cost–benefit analysis ,business.industry ,media_common.quotation_subject ,Pharmaceutical Science ,Pharmacy ,Evidence-based medicine ,Clinical pharmacy ,Pharmacology (medical) ,Business ,Formulary ,media_common - Published
- 2020
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11. Using two confluent capillary columns for improved gas chromatography‐electroantennographic detection (GC‐EAD)
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Steven D. Johnson and Adam Shuttleworth
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0106 biological sciences ,Chromatography ,Resolution (mass spectrometry) ,Capillary action ,Insect olfaction ,Biology ,010603 evolutionary biology ,01 natural sciences ,Volumetric flow rate ,010602 entomology ,Stationary phase ,Insect Science ,Gas chromatography ,Ecology, Evolution, Behavior and Systematics - Abstract
We discuss the modification of an old method of connecting two capillary columns in a confluent configuration which elegantly allows introduction of make‐up gas at a controlled flow rate when the effluent is split for electroantennographic detection experiments, and allows for easy switching of the stationary phase between successive GC runs. Being able to run samples on different phases is extremely beneficial, both for optimal resolution of active compounds and for compound identification. This method warrants greater consideration by GC‐EAD practitioners.
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- 2020
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12. Allosteric differences dictate GroEL complementation of E. coli
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Jared Sivinski, Duc Ngo, Christopher J. Zerio, Andrew J. Ambrose, Edmond R. Watson, Lynn K. Kaneko, Marius M. Kostelic, Mckayla Stevens, Anne‐Marie Ray, Yangshin Park, Chunxiang Wu, Michael T. Marty, Quyen Q. Hoang, Donna D. Zhang, Gabriel C. Lander, Steven M. Johnson, and Eli Chapman
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Escherichia coli Proteins ,Biochemistry ,Article ,Adenosine Diphosphate ,Protein Subunits ,Adenosine Triphosphate ,Allosteric Regulation ,Chaperonin 10 ,Escherichia coli ,Genetics ,Molecular Biology ,Allosteric Site ,Heat-Shock Proteins ,Biotechnology - Abstract
GroES/GroEL is the only bacterial chaperone essential under all conditions, making it a potential antibiotic target. Rationally targeting ESKAPE GroES/GroEL as an antibiotic strategy necessitates studying their structure and function. Herein, we outline the structural similarities between Escherichia coli and ESKAPE GroES/GroEL and identify significant differences in intra- and inter-ring cooperativity, required in the refolding cycle of client polypeptides. Previously, we observed that one-half of ESKAPE GroES/GroEL family members could not support cell viability when each was individually expressed in GroES/GroEL-deficient E. coli cells. Cell viability was found to be dependent on the allosteric compatibility between ESKAPE and E. coli subunits within mixed (E. coli and ESKAPE) tetradecameric GroEL complexes. Interestingly, differences in allostery did not necessarily result in differences in refolding rate for a given homotetradecameric chaperonin. Characterization of ESKAPE GroEL allostery, ATPase, and refolding rates in this study will serve to inform future studies focused on inhibitor design and mechanism of action studies.
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- 2022
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13. Does acoustic priming ‘sweeten the pot’ of floral nectar?
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Lawrence D. Harder, Steven D. Johnson, and Robert A. Raguso
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0106 biological sciences ,Additional concerns ,food.ingredient ,Plant Nectar ,Pollination ,Ecology ,010604 marine biology & hydrobiology ,Oenothera ,Acoustics ,Flowers ,Priming (agriculture) ,Bees ,Motor Activity ,Biology ,theater ,010603 evolutionary biology ,01 natural sciences ,Evening primrose ,food ,Botany ,Animals ,Nectar ,theater.play ,Ecology, Evolution, Behavior and Systematics - Abstract
A recent claim that evening primrose flowers adaptively secrete nectar in response to vibrations from hovering bees lacks supporting evidence. The authors fail to demonstrate that bees can access the concealed nectar and that their visits enhance plant fitness. Reanalysis of the authors' data raises additional concerns about their conclusions.
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- 2020
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14. From dusk till dawn: camera traps reveal the diel patterns of flower feeding by hawkmoths
- Author
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Alison Bijl, Ruth J. Cozien, Steven D. Johnson, Miguel Castañeda-Zárate, Marco G. Balducci, Carmen R. Ortmann, and Timotheüs van der Niet
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Ecology ,biology ,Pollination ,Insect Science ,Sphingidae ,Noctuidae ,Dusk ,biology.organism_classification ,Diel vertical migration - Published
- 2019
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15. The spider orchid trapped in its molecular web: Phylogeny and morphological evolution of the orchid genera Bartholina and Holothrix (Orchidaceae: Orchidoideae)
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Benny Bytebier, Timothée Le Péchon, and Steven D. Johnson
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Synapomorphy ,Orchidaceae ,Spider ,biology ,Phylogenetics ,Evolutionary biology ,Orchideae ,Taxonomy (biology) ,Plant Science ,Orchidoideae ,biology.organism_classification ,Ecology, Evolution, Behavior and Systematics ,Holothrix - Published
- 2019
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16. Spit it out: Monkeys disperse the unorthodox and toxic seeds ofClivia miniata(Amaryllidaceae)
- Author
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Ian Kiepiel and Steven D. Johnson
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0106 biological sciences ,010504 meteorology & atmospheric sciences ,biology ,Clivia miniata ,Seed dispersal ,food and beverages ,Amaryllidaceae ,Understory ,biology.organism_classification ,010603 evolutionary biology ,01 natural sciences ,Seedling ,Germination ,Clivia ,Botany ,Biological dispersal ,Ecology, Evolution, Behavior and Systematics ,0105 earth and related environmental sciences - Abstract
Seeds of many Amaryllidaceae are unorthodox (recalcitrant) and toxic, and cannot survive ingestion, yet are packaged in brightly colored fruits suggestive of zoochory. Seed dispersal and germination of the understory amaryllid, Clivia miniata, were investigated in KwaZulu‐Natal, South Africa. Motion‐activated cameras revealed that samango monkeys (Cercopithecus mitis labiatus) are the primary disperser of C. miniata seeds. They eat the mesocarp and, to a lesser extent, the exocarp, and spit the large (13 mm diameter) seeds whole and cleaned onto the forest floor. Most seeds were dispersed farther than 1 m from the parent. Experimental removal of the fruit pulp had a small positive effect on the rate of seed germination, but did not affect subsequent seedling growth rates. The main advantages of monkey dispersal of Clivia seeds appear to be short‐distance dispersal away from the dense foliage of clumped parent plants and occasional long‐distance dispersal through cheek‐pouching behavior.
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- 2019
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17. Scent chemistry is key in the evolutionary transition between insect and mammal pollination in African pineapple lilies
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Steven D. Johnson, Petra Wester, and Anton Pauw
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0106 biological sciences ,0301 basic medicine ,Insecta ,Plant Nectar ,Pollination ,Physiology ,media_common.quotation_subject ,Zoology ,Flowers ,Plant Science ,Insect ,Breeding ,medicine.disease_cause ,Choice Behavior ,01 natural sciences ,Eucomis ,Mice ,South Africa ,03 medical and health sciences ,Asparagaceae ,Pollen ,parasitic diseases ,medicine ,Animals ,Nectar ,reproductive and urinary physiology ,media_common ,Mammals ,Volatile Organic Compounds ,Geography ,biology ,Pigmentation ,Shrews ,fungi ,food and beverages ,biology.organism_classification ,Biological Evolution ,030104 developmental biology ,Odorants ,Seeds ,Key (lock) ,Mammal ,Lilium ,010606 plant biology & botany - Abstract
Volatile emissions may play a key role in structuring pollination systems of plants with morphologically unspecialised flowers. Here we test for pollination by small mammals in Eucomis regia and investigate whether its floral scent differs markedly from fly- and wasp-pollinated congeners and attracts mammals. We measured floral traits of E. regia and made comparisons with insect-pollinated congeners. We observed floral visitors and examined fur and faeces of live-trapped mammals for pollen. We determined the contributions of different floral visitors to seed set with selective exclusion and established the breeding system with controlled pollination experiments. Using bioassays, we examined whether mammals are attracted by the floral scent and are effective agents of pollen transfer. Eucomis regia differs from closely related insect-pollinated species mainly in floral scent, with morphology, colour and nectar properties being similar. We found that mice and elephant-shrews pollinate E. regia, which is self-incompatible and reliant on vertebrates for seed production. Mammals are strongly attracted to the overall floral scent, which contains unusual sulphur compounds, including methional (which imparts the distinctive potato-like scent and which was shown to be attractive to small mammals). The results highlight the important role of scent chemistry in shifts between insect and mammal pollination systems.
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- 2019
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18. Inverse‐Designed Meta‐Optics with Spectral‐Spatial Engineered Response to Mimic Color Perception
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Chris Munley, Wenchao Ma, Johannes E. Fröch, Quentin A. A. Tanguy, Elyas Bayati, Karl F. Böhringer, Zin Lin, Raphaël Pestourie, Steven G. Johnson, and Arka Majumdar
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Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials - Published
- 2022
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19. Author response for 'The role of plant‐pollinator interactions in structuring nectar microbial communities'
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Rafael G. Albaladejo, Steven D. Johnson, Carlos M. Herrera, Clara de Vega, Marc-André Lachance, Sandy‐Lynn Stennhuisen, and Sergio Álvarez-Pérez
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Ecology ,Pollinator ,Nectar ,Biology ,Structuring - Published
- 2021
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20. Native honeybees as flower visitors and pollinators in wild plant communities in a biodiversity hotspot
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Steven D. Johnson, Dara A. Stanley, and Simangele M. Msweli
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biodiversity hotspot ,pollination ,Ecology ,Pollination ,Plant community ,Honey bee ,Biology ,Biodiversity hotspot ,Pollinator ,lcsh:QH540-549.5 ,honey bee ,lcsh:Ecology ,Apis mellifera ,Ecology, Evolution, Behavior and Systematics - Abstract
Western honeybees (Apis mellifera L.), native to Europe and Africa, have been transported worldwide and are now one of the most important global crop pollinator species. Although the relative contribution of honeybees to global crop pollination is increasingly recognized, relatively little is known about their importance as pollinators in wild plant communities. The only remaining wild and unmanaged western honeybee populations are in Africa. We investigated the importance of honeybees as pollinators of diverse wild plant communities in two protected areas within the Maputaland–Pondoland–Albany biodiversity hotspot in South Africa. Sites were far from any known areas of beekeeping, and so all honeybees were most likely from wild colonies. Honeybees visited a large proportion of flowering plant species within these two communities (40% and 35%) and also provided a substantial proportion of visits to the plants they visited (40% and 32%, respectively). However, when pollinator importance indices (based on abundance and the size and purity of pollen loads) were calculated for a small subset of plants, honeybees were only important pollinators of 29% of the plants they visited. Our data provide a first step in determining the importance of honeybees as flower visitors and pollinators in wild plant communities and the potential impacts of honeybee declines on these highly diverse grassland ecosystems. Our work suggests that many plants in the grassland systems studied are visited by non‐Apis flower visitors and therefore that conservation efforts should also focus on these pollinator groups.
- Published
- 2020
21. Evaluation of intraductal delivery of poly(ethylene glycol)-doxorubicin conjugate nanocarriers for the treatment of ductal carcinoma in situ (DCIS)-like lesions in rats
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Jennifer Holloway, Dayuan Gao, Patrick J. Sinko, Derek Adler, Firas Al-Zubaydi, Zichao Gu, Susan Love, Shike Li, Steven R Johnson, Zoltan Szekely, and Puja Prasad
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0301 basic medicine ,Chemistry ,organic chemicals ,technology, industry, and agriculture ,macromolecular substances ,Ductal carcinoma ,medicine.disease ,3. Good health ,carbohydrates (lipids) ,03 medical and health sciences ,030104 developmental biology ,0302 clinical medicine ,In vivo ,030220 oncology & carcinogenesis ,Cancer cell ,Ductal carcinoma in situ (DCIS) ,PEG ratio ,polycyclic compounds ,medicine ,Cancer research ,MTT assay ,Doxorubicin ,Nanocarriers ,medicine.drug - Abstract
Ductal carcinoma in situ is the most commonly diagnosed early stage breast cancer. The efficacy of intraductally delivered poly(ethylene glycol)-doxorubicin (PEG-DOX) nanocarriers, composed of one or more DOX conjugated to various PEG polymers, was investigated in an orthotopic ductal carcinoma in situ-like rat model. In vitro cytotoxicity was evaluated against 13762 Mat B III cells using MTT assay. The orthotopic model was developed by inoculating cancer cells into mammary ducts of female Fischer 344 retired breeder rats. The ductal retention and in vivo antitumour efficacy of two of the six nanocarriers (5 kDa PEG-DOX and 40 kDa PEG-(DOX)4) were investigated based on in vitro results. Mammary retention of DOX and PEG-DOX nanocarriers was quantified using in vivo imaging. Histopathologic effects of DOX and PEG-DOX nanocarriers on mammary ductal structure were also investigated. Cytotoxicities of small linear PEG-DOX nanocarriers (5 and 10 kDa) were not different from DOX whereas larger PEG-DOX nanocarriers showed reduced potency. The order of mammary retention was 40 kDa PEG-(DOX)4 > 5 kDa PEG-DOX >> DOX, in normal and tumour-bearing rats. Intraductally administered PEG-DOX nanocarriers and DOX were effective in reducing tumour incidence and increasing survival rate, with no significant differences found among the three treatment groups. However, nanocarriers administered intravenously at the same doses were not effective, and intraductally administered free DOX caused severe local toxicity. Intraductal administration of PEG-DOX nanocarriers is effective and less toxic than that of free DOX, as well as IV DOX/PEG-DOX. Furthermore, PEG-DOX nanocarriers demonstrate the added benefit of prolonging DOX ductal retention, which would necessitate less frequent dosing.
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- 2018
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22. Differential actions of AMP kinase on ATP-sensitive K+currents in ventral tegmental area and substantia nigra zona compacta neurons
- Author
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Yan Na Wu, Steven W. Johnson, and Ke Zhong Shen
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0301 basic medicine ,ATP-sensitive potassium channel ,musculoskeletal, neural, and ocular physiology ,General Neuroscience ,AMPK ,Substantia nigra ,Biology ,Ventral tegmental area ,Midbrain ,03 medical and health sciences ,030104 developmental biology ,0302 clinical medicine ,medicine.anatomical_structure ,nervous system ,Dopamine ,mental disorders ,medicine ,Diazoxide ,Patch clamp ,Neuroscience ,psychological phenomena and processes ,030217 neurology & neurosurgery ,medicine.drug - Abstract
ATP-sensitive K+ (K-ATP) channels play significant roles in regulating the excitability of dopamine neurons in the substantia nigra zona compacta (SNC). We showed previously that K-ATP channel function is up-regulated by AMP-activated protein kinase (AMPK). This study extended these studies to the neurons adjacent to the SNC in the ventral tegmental area (VTA). Using patch pipettes to record whole-cell currents in slices of rat midbrain, we found that the AMPK activator A769662 increased the amplitude of currents evoked by the K-ATP channel opener diazoxide in presumed dopamine-containing VTA neurons. However, current evoked by diazoxide with A769662 was significantly smaller in VTA neurons compared to SNC neurons. Moreover, a significantly lower proportion of VTA neurons responded to diazoxide with outward current. However, A769662 was able to increase the incidence of diazoxide-responsive neurons in the VTA. In contrast, A769662 did not potentiate diazoxide-evoked currents in presumed non-dopamine VTA neurons. These results show that AMPK activation augments K-ATP currents in presumed dopamine neurons in the VTA and SNC, although diazoxide-evoked currents remain less robust in the VTA. We conclude that K-ATP channels may play important physiological roles in VTA and SNC dopamine neurons.
- Published
- 2017
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23. Pollination and breeding system of the enigmatic South African parasitic plantMystropetalon thomii(Mystropetalaceae): rodents welcome, but not needed
- Author
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Nina Hobbhahn, Toni Olsen, Jeremy J. Midgley, Sandy-Lynn Steenhuisen, and Steven D. Johnson
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0106 biological sciences ,Plant Nectar ,Pollination ,Rodentia ,Flowers ,Plant Science ,Breeding ,Biology ,medicine.disease_cause ,Pollination syndrome ,010603 evolutionary biology ,01 natural sciences ,Birds ,Pollinator ,Pollen ,Botany ,medicine ,Animals ,Nectar ,Plant reproductive morphology ,Zoophily ,Ecology, Evolution, Behavior and Systematics ,fungi ,food and beverages ,General Medicine ,Inflorescence ,010606 plant biology & botany - Abstract
Unrelated plants adapted to particular pollinator types tend to exhibit convergent evolution in floral traits. However, inferences about likely pollinators from “pollination syndromes” can be problematic due to trait overlap among some syndromes and unusual floral architecture in some lineages. An example is the rare South African parasitic plant Mystropetalon thomii (Mystropetalaceae), which has highly unusual brush-like inflorescences that exhibit features of both bird- and rodent-pollination syndromes. We used camera traps to record flower visitors, quantified floral spectral reflectance and nectar and scent production, experimentally determined self-compatibility and breeding system, and studied pollen dispersal using fluorescent dyes. The dark-red inflorescences are usually monoecious, with female flowers maturing before male flowers, but some inflorescences are purely female (gynoecious). Inflorescences were visited intensively by several rodent species that carried large pollen loads, while visits by birds were extremely rare. Rodents prefer male- over female-phase inflorescences, likely because of the male flowers’ higher nectar and scent production. The floral scent contains several compounds known to attract rodents. Despite the obvious pollen transfer by rodents, we found that flowers on both monoecious and gynoecious inflorescences readily set seed in the absence of rodents and even when all flower visitors are excluded. Our findings suggest that seed production occurs at least partially through apomixis and that M. thomii is not ecologically dependent on its rodent pollinators. Our study adds another species and family to the growing list of rodent-pollinated plants, thus contributing to our understanding of the floral traits associated with pollination by non-flying mammals. This article is protected by copyright. All rights reserved.
- Published
- 2017
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24. Time-Resolved X-Ray Powder Diffraction Study of Photoinduced Phase Transitions in Ti3 O5 Nanoparticles
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Paul Beaud, Vincent Esposito, Kelin R. Tasca, Gabriel Lantz, Steven L. Johnson, Matteo Savoini, Carlos Giles, and M. Kubli
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Phase transition ,Materials science ,Relaxation (NMR) ,Analytical chemistry ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Molecular physics ,Atomic and Molecular Physics, and Optics ,0104 chemical sciences ,Microsecond ,Lattice constant ,Phase (matter) ,Physical and Theoretical Chemistry ,Exponential decay ,0210 nano-technology ,Ground state ,Powder diffraction - Abstract
Nanoparticles of Ti3 O5 have been reported to show a permanent photoinduced phase transition at room temperature. This suggests that light-induced phase transformations of Ti3 O5 nanoparticles may be promising for technological applications. Here, we report a photoinduced semiconductor-to-metal phase transition from β-Ti3 O5 to λ-Ti3 O5 nanoparticles at room temperature observed directly by time-resolved X-ray powder diffraction in a pump-probe setup. The results show a partial structural change, limited by differences between pumped and probed volumes, which persists a few microseconds after excitation. The first step in the relaxation back to the ground state can be described by a single exponential decay with time constant within microsecond timescales. Analysis of the change in lattice constants enables us to estimate an average temperature increase across the phase transition, consistent with a thermally driven process.
- Published
- 2017
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25. Severe acute Q fever pneumonia complicated by presumed persistent localized Q fever endocarditis in a renal transplant recipient: A case report and review of the literature
- Author
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Maheen Z. Abidi, Matthew A Miller, Angela M. Budgin, Valida Bajrovic, and Steven C. Johnson
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medicine.medical_specialty ,Q fever pneumonia ,Q fever ,030230 surgery ,Kidney ,03 medical and health sciences ,0302 clinical medicine ,Internal medicine ,Pneumonia, Bacterial ,Humans ,Medicine ,Endocarditis ,Transplantation ,business.industry ,Endocarditis, Bacterial ,Middle Aged ,medicine.disease ,Kidney Transplantation ,Transplant Recipients ,Anti-Bacterial Agents ,Q fever endocarditis ,Infectious Diseases ,Renal transplant ,Female ,030211 gastroenterology & hepatology ,Q Fever ,Tomography, X-Ray Computed ,business ,Solid organ transplantation ,Medical literature - Abstract
Q fever in solid organ transplant (SOT) recipients is rarely described in the medical literature. We present a case of severe acute Q fever pneumonia that evolved into persistent localized Q fever endocarditis in a renal transplant recipient.
- Published
- 2019
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26. Incorporating Sex and Gender‐based Medical Education Into Residency Curricula
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Steven A. Johnson, Jeannette Wolfe, Ashley L. Deutsch, Alyson J. McGregor, Gillian A. Beauchamp Md, Marna Rayl Greenberg, Derek A. Robinett, Lauren A. Walter, and Rebecca Barron
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Medical education ,Debriefing ,education ,MEDLINE ,Emergency Nursing ,Education ,Clinical Practice ,Concept Papers ,Current practice ,Interest group ,Emergency Medicine ,Training program ,Psychology ,Curriculum ,Residency training - Abstract
Background Emergency medicine (EM) residents do not generally receive sex- and gender-specific education. There will be increasing attention to this gap as undergraduate medical education integrates it within their curriculum. Methodology Members of the Sex and Gender in Emergency Medicine (SGEM) Interest Group set out to develop a SGEM toolkit and pilot integrating developed components at multiple residency sites. The curriculum initiative involved a pre- and posttraining assessment that included basic demographics and queries regarding previous training in sex-/gender-based medicine (SGBM). It was administered to PGY-1 to -4 residents who participated in a 3-hour training session that included one small group case-based discussion, two oral board cases, and one simulation and group debriefing. Analysis Components of the developed toolkit (https://www.sexandgenderhealth.org) were implemented at four unique SGEM Interest Group member residency programs. Residents (n = 82/174, 47%) participated; 64% (n = 49) were male and 36% (n = 28) were female. Twenty-six percent (n = 21) of the residents reported that they had less than 1 hour of training in this domain during residency; 59% (n = 48) reported they had 1 to 6 hours and 16% (n = 13) reported they had >6 hours. The average preassessment score was 61% and postassessment was 88%. After training, 74% (n = 60) felt that their current practice would have benefited from further training in sex-/gender-based topics in medicine during medical school and 83% (n = 67) felt their clinical practice would have benefited from further training in this domain during residency. Implications The majority of EM residents who participated in this training program reported that they had limited instruction in this domain in medical school or residency. This initiative demonstrated a method that can be emulated for the incorporation of SGBM educational components into an EM residency training educational day. After training, the majority of residents who participated felt that their current practice would have benefited from further training in sex- and gender-based topics in residency.
- Published
- 2019
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27. The mating consequences of rewarding vs. deceptive pollination systems: Is there a quantity-quality trade-off?
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Lawrence D. Harder, Nina Hobbhahn, and Steven D. Johnson
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0106 biological sciences ,Pollination ,Ecology ,food and beverages ,Biology ,medicine.disease_cause ,010603 evolutionary biology ,01 natural sciences ,Geitonogamy ,Pollinator ,Pollen ,Botany ,medicine ,Biological dispersal ,Nectar ,Mating ,Zoophily ,Ecology, Evolution, Behavior and Systematics ,010606 plant biology & botany - Abstract
Plant mating commonly involves quality–quantity trade-offs. Such a trade-off features explicitly in the cross-promotion hypothesis for the evolution of pollination by deceit. According to this hypothesis, rewardlessness enhances mating quality by altering pollinator behavior in ways that reduce self-pollination and increase outcrossing, thus compensating for the reduced pollen dispersal and seed production resulting from lack of reinforcement of pollinator visitation behavior. The high prevalence of rewardlessness in orchids suggests that deceit pollination conveys benefits that outweigh the fecundity advantages of reward production. We test the cross-promotion hypothesis in Disa, an African orchid genus in which nectar rewards have evolved repeatedly from rewardless ancestors. To address this hypothesis directly, we quantified pollinator behavior and the associated dispersal of stained pollen for four nectar-producing (N+) and 10 nectarless (N−) species. We also assessed more extensive, if less direct, evidence from a survey of lifetime pollination outcomes for 15 N+ and 32 N− species. Pollinators visited N+ species more frequently and visited 1.5 times more flowers per inflorescence than in N− species. In contrast, pollinators skipped more conspecific plants between visits to donor and recipient plants when visiting N− species than when visiting N+ species. Over floral lifetimes, both N− and N+ species exhibited similar overall pollen-transfer efficiency (8.2%) and did not differ in the overall fractions of pollen involved in self-pollination (26% of all pollen deposited), geitonogamy (82% of all self-pollination), or export to other conspecific plants (74%). N+ species set more fruit per flower (68.8% vs. 48.8%), but equivalent fractions of ovules per fruit were fertilized and subsequently developed into seeds in N− and N+ species. These findings provide only limited evidence that deceit pollination enhances mating quality (nectar production causes more local mating in N+ species than in N− species). Contrary to the hypothesis, deceit does not generally affect pollinator-mediated self-pollination. The repeated evolution of nectar production from rewardless ancestors in Disa likely occurred under severe visit limitation, favoring nectar-producing mutants with higher reproductive output. Given that we did not find any mating quality advantage for rewardlessness in Disa, its persistence in some lineages remains an evolutionary enigma.
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- 2016
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28. Magnetic resonance imaging reveals the complementary effects of decongestant and Breathe Right Nasal Strips on internal nasal anatomy
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Steven M. Johnson, Matthew B. Wall, Courtney A. Bishop, Robert L. Janiczek, Richard G. Wise, Gilbert Shanga, Philip S. Murphy, and Rexford D. Newbould
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medicine.medical_specialty ,medicine.diagnostic_test ,business.industry ,medicine.drug_class ,Magnetic resonance imaging ,Nasal congestion ,Significant negative correlation ,Placebo ,Crossover study ,Surgery ,Decongestant ,03 medical and health sciences ,0302 clinical medicine ,medicine.anatomical_structure ,030228 respiratory system ,Otorhinolaryngology ,Anesthesia ,otorhinolaryngologic diseases ,medicine ,medicine.symptom ,030223 otorhinolaryngology ,business ,Nose ,Nasal passages - Abstract
Objectives/Hypothesis This magnetic resonance imaging (MRI) study of 26 subjects with nasal congestion was performed to assess in the complete nasal passage both the anatomical effect of the marketed Breathe Right Nasal Strip (BRNS) relative to placebo and the potential adjunctive effect of using a decongestant in combination with the BRNS. Study Design Randomized, crossover study. Methods The study consisted of two parts, the first involving application of either the BRNS or the placebo strip in a randomized, crossover design with evaluator blinding, and repeated MRI scanning; and the second a sequential process of decongestant administration, MRI scanning, application of the BRNS, and repeated MRI. The same anatomical MRI protocol was used throughout. Nasal patency was assessed in the whole nasal passage and eight subregions (by inferior–superior, anterior–posterior division). Numerical response scores representing subjective nasal congestion were also obtained. Results Results demonstrate significant anatomical enlargement with the BRNS relative to placebo (P < .001), as well as an additive effect of using a decongestant in combination with the BRNS; both supported by a strong and significant negative correlation with the subjective nasal response measures of nasal congestion (r = −0.98, P = .002). Furthermore, analysis of the nasal subregions indicates that this adjunctive effect arises from a partially localized action of the complementary products: the BRNS acting primarily anteriorly in the nose and the decongestant mainly posteriorly. Conclusions The BRNS alone significantly increases nasal patency and alleviates perceived nasal congestion, and additional relief of symptoms can be obtained with simultaneous use of a decongestant. Level of Evidence 1b. Laryngoscope, 2016
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- 2016
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29. Floral trait evolution associated with shifts between insect and wind pollination in the dioecious genusLeucadendron(Proteaceae)
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Jeremy J. Midgley, Nina Hobbhahn, Megan R. Welsford, and Steven D. Johnson
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0106 biological sciences ,Pollination ,Dioecy ,fungi ,food and beverages ,Biology ,medicine.disease_cause ,biology.organism_classification ,010603 evolutionary biology ,01 natural sciences ,Proteaceae ,Leucadendron ,Inflorescence ,Pollen ,Botany ,Anemophily ,Genetics ,medicine ,Zoophily ,General Agricultural and Biological Sciences ,Ecology, Evolution, Behavior and Systematics ,010606 plant biology & botany - Abstract
Transitions between animal and wind pollination have occurred in many lineages and have been linked to various floral modifications, but these have seldom been assessed in a phylogenetic framework. In the dioecious genus Leucadendron (Proteaceae), transitions from insect to wind pollination have occurred at least four times. Using analyses that controlled for relatedness among Leucadendron species, we investigated how these transitions shaped the evolution of floral structural and signaling traits, including the degree of sexual dimorphism in these traits. Pollen grains of wind-pollinated species were found to be smaller, more numerous, and dispersed more efficiently in wind than were those of insect-pollinated species. Wind-pollinated species also exhibited a reduction in spectral contrast between showy subtending leaves and background foliage, reduced volatile emissions, and a greater degree of sexual dimorphism in color and scent. Uniovulate flowers and inflorescence condensation are conserved ancestral features in Leucadendron and likely served as exaptations in shifts to wind pollination. These results offer insights into the key modifications of male and female floral traits involved in transitions between insect and wind pollination.
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- 2015
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30. Reproductive isolation betweenZaluzianskyaspecies: the influence of volatiles and flower orientation on hawkmoth foraging choices
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Andreas Jürgens, Diane R. Campbell, and Steven D. Johnson
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0106 biological sciences ,Reproductive Isolation ,Pollination ,Physiology ,Foraging ,Flowers ,Plant Science ,Moths ,Choice Behavior ,010603 evolutionary biology ,01 natural sciences ,chemistry.chemical_compound ,Quantitative Trait, Heritable ,Species Specificity ,Linalool ,Pollinator ,Botany ,Animals ,Herbivory ,Hybrid ,Principal Component Analysis ,Volatile Organic Compounds ,biology ,Pigmentation ,Reproductive isolation ,biology.organism_classification ,Attraction ,Zaluzianskya ,chemistry ,Seeds ,Hybridization, Genetic ,Scrophulariaceae ,010606 plant biology & botany - Abstract
Floral trait differences between related species may play a key role in reproductive isolation imposed by pollinators. Volatile emissions can influence pollinator choice, but how they act in combination with traits such as flower orientation is rarely studied. We compared flower-opening patterns, morphology, colour, orientation and volatile emissions for two closely related species of Zaluzianskya and their natural hybrids. Hawkmoth pollinators were tested for preference between flowers of the two species, and between flowers with manipulations of volatiles or orientation. Flowers of Z. natalensis and Z. microsiphon open at night and day, respectively, but they overlap during early evening, when hawkmoths showed a strong preference for Z. natalensis. The species have similar flower size and colour, but Z. natalensis emits more floral volatiles in the evening and presents flowers vertically face-up as opposed to horizontally in Z. microsiphon, whereas natural hybrids are intermediate. Adding methyl benzoate and linalool to flowers of Z. microsiphon did not increase hawkmoth attraction, but re-orientation of flowers to face vertically increased attraction when scent cues were present, whereas re-orientation of Z. natalensis flowers to face horizontally decreased attraction. This study highlights the importance of flower orientation in imposing reproductive isolation.
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- 2015
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31. The functional significance of complex floral colour pattern in a food‐deceptive orchid
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Zhong-Jian Liu, Xiaokai Ma, Yangna Sun, Yi-Bo Luo, Hans Bänziger, Steven D. Johnson, Jun Shi, and Yan-Yan Guo
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0106 biological sciences ,Paphiopedilum micranthum ,biology ,Pollination ,Ecology ,Foraging ,Zoology ,biology.organism_classification ,010603 evolutionary biology ,01 natural sciences ,Paphiopedilum ,Sympatric speciation ,Pollinator ,Mimicry ,Ecology, Evolution, Behavior and Systematics ,Bumblebee ,010606 plant biology & botany - Abstract
Summary Many non-rewarding orchid species mimic the signals of co-occurring food flowers and thereby attract food-seeking animal pollinators. These signals are often visually complex with a colour pattern that contrasts between outer and central parts. The significance of this colour complexity for the pollination success of flowers of deceptive orchids has scarcely been investigated. We tested the effects of the colour patterns of the food-deceptive orchid Paphiopedilum micranthum on bumblebee visitation choices and pollination success using behavioural experiments in a community context. Using comparative phylogenetic analysis and a bee vision model, we also compared the colour patterns of P. micranthum with those of its congeners and sympatric food flowers. The probability of both long-range approach and close-up choice by bumblebees to orchids was all enhanced in communities with food flowers similar in colour pattern to the orchid. Probability of long-range approach and close-up choice was negatively correlated with colour distance between orchid and food flowers in floral outer and centre, respectively. Flowers of P. micranthum that were manipulated to reduce visual complexity had reduced male and female pollination success. Phylogenetic analysis revealed that the outer floral colour of P. micranthum is apomorphic and thus likely represents an evolutionary innovation, whereas the central colour is plesiomorphic and thus likely to function in the bumblebee pollination system as an exaptation. The contrast between the inner and outer colours appears to exploit visual preferences of bumblebees acquired during foraging on local food plants with similar colour patterns. This study highlights the adaptive significance of colour patterns in successful food deception and the importance of complex signals in facilitating interspecific interactions.
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- 2015
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32. A One-Step Staining Probe for Phosphatidylethanolamine
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Ming Zhao, Songwang Hou, and Steven E. Johnson
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Phosphatidylethanolamine ,Chemistry ,Organic Chemistry ,Phospholipid ,Biological membrane ,Lantibiotics ,Biochemistry ,Green fluorescent protein ,chemistry.chemical_compound ,Membrane ,Molecular Medicine ,Molecular probe ,Molecular Biology ,Linker - Abstract
Phosphatidylethanolamine (PE) is an abundant phospholipid in cellular membranes, but relatively little is known about the kinetics of PE in biological membrane systems. Characterizing PE on a cellular level has been challenging owing to a lack of proper molecular tools. The lantibiotic duramycin and its structural analogue, cinnamycin, are currently the only known polypeptides that have an established stereospecific structure for binding membrane PE with high affinity and high specificity. These lantibiotics are recognized for their potential as molecular probes for studying PE kinetics in various membranes. However, owing to their antibiotic nature, duramycin and cinnamycin exhibit appreciable levels of cytotoxicity at low micromolar concentrations in cultured mammalian cells by inducing membrane distortion and possible PE redistribution. These issues can potentially complicate study design and data interpretation. Here, we report the construction of a molecular probe consisting of duramycin attached to the C terminus of green fluorescent protein (GFP) by a PEG linker at a stoichiometry of 1. The construct retained specific binding toward PE and essentially no cytotoxicity compared to native duramycin. The biological utilities of this probe were demonstrated in a number of cellular staining studies involving PE dynamics. The availability of a one-step, nontoxic molecular probe for PE will enable characterization of the biology of this important phospholipid.
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- 2015
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33. Carnivorous mammals feed on nectar ofProteaspecies (Proteaceae) in South Africa and likely contribute to their pollination
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Dennis M. Hansen, Jeremy J. Midgley, Sandy-Lynn Steenhuisen, Nicola Kühn, Alice Balmer, Steven D. Johnson, and Kim C. Zoeller
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Pollination ,biology ,Ecology ,Botany ,Nectar ,biology.organism_classification ,Protea ,Ecology, Evolution, Behavior and Systematics ,Proteaceae - Published
- 2015
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34. Classical and fluctuation-induced electromagnetic interactions in micron-scale systems: designer bonding, antibonding, and Casimir forces
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Steven G. Johnson, Pui-Chuen Hui, Alejandro W. Rodriguez, David P. Woolf, Marko Loncar, and Federico Capasso
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Casimir effect ,Momentum ,Physics ,Classical mechanics ,Stiction ,General Physics and Astronomy ,Virtual particle ,Thermal fluctuations ,Antibonding molecular orbital ,Quantum ,Optomechanics - Abstract
Whether intentionally introduced to exert control over particles and macroscopic objects, such as for trapping or cooling, or whether arising from the quantum and thermal fluctuations of charges in otherwise neutral bodies, leading to unwanted stiction between nearby mechanical parts, electromagnetic interactions play a fundamental role in many naturally occurring processes and technologies. In this review, we survey recent progress in the understanding and experimental observation of optomechanical and quantum-fluctuation forces. Although both of these effects arise from exchange of electromagnetic momentum, their dramatically different origins, involving either real or virtual photons, lead to different physical manifestations and design principles. Specifically, we describe recent predictions and measurements of attractive and repulsive optomechanical forces, based on the bonding and antibonding interactions of evanescent waves, as well as predictions of modified and even repulsive Casimir forces between nanostructured bodies. Finally, we discuss the potential impact and interplay of these forces in emerging experimental regimes of micromechanical devices.
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- 2014
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35. Social support, self-efficacy and motivation: a qualitative study of the journey through HEALD (Healthy Eating and Active Living for Diabetes)
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Ana B. Mladenovic, Lisa Wozniak, Steven T. Johnson, Jeffrey A. Johnson, and Ronald C. Plotnikoff
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Self-efficacy ,business.industry ,Endocrinology, Diabetes and Metabolism ,media_common.quotation_subject ,Peer support ,Social support ,Feeling ,Diabetes management ,Active living ,Internal Medicine ,Medicine ,business ,Social cognitive theory ,Clinical psychology ,media_common ,Qualitative research - Abstract
This study aimed to describe the influence of social support on participants’ self-efficacy and motivation to perform physical activity before, during and after the Healthy Eating and Active Living for Diabetes in primary care networks (HEALD) programme. HEALD was a controlled trial of a 24-week primary care-based walking programme for people with type 2 diabetes, proven effective in increasing physical activity. Data used in this qualitative sub-study were derived from semi-structured interviews with purposefully selected HEALD completers (n = 13) six months after the programme ended. Qualitative data were analysed using content analysis. Prior to HEALD, participants reported feeling a lack of social support for diabetes management and fear of diabetes consequences. During the programme, they reported feeling supported by exercise specialists and peers in general and specifically to do physical activity; they reported weakening social support after HEALD ended. Accordingly, participants reported having self-efficacy and motivation to increase their physical activity during HEALD, but these did not persist after HEALD ended; many relapsed into former behaviours. Participants recommended a longer programme, with more contacts. Our findings are congruent with Social Cognitive Theory. Participants’ reported self-efficacy and motivation to adopt physical activity during HEALD were tied to feeling supported by the exercise specialists who led the programme and peers participating in the programme. However, these perceived improvements were compromised when social support was no longer available through HEALD. Periodic contacts with a health care provider post-programme may promote maintenance of positive behaviour changes following diabetes self-management programmes. Furthermore, an optimal mode of peer support requires study. Copyright © 2014 John Wiley & Sons, Ltd.
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- 2014
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36. Prompted awareness and use of Eating Well with Canada's Food Guide : a population-based study
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L. Van der Meer, Steven T. Johnson, Nonsikelelo Mathe, Calypse B Agborsangaya, Kate E. Storey, Jeffrey A. Johnson, Terra C. Murray, and Christina C. Loitz
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Adult ,Male ,Health Knowledge, Attitudes, Practice ,Future studies ,Ethnic group ,Medicine (miscellaneous) ,Guidelines as Topic ,Motor Activity ,Logistic regression ,White People ,Alberta ,Eating ,Young Adult ,Sex Factors ,Surveys and Questionnaires ,Canada's Food Guide ,Vegetables ,Ethnicity ,Odds Ratio ,Humans ,Medicine ,Aged ,Family Characteristics ,Nutrition and Dietetics ,Consumer Health Information ,business.industry ,Body Weight ,Feeding Behavior ,Odds ratio ,Middle Aged ,Confidence interval ,Telephone ,Telephone survey ,Population based study ,Cross-Sectional Studies ,Logistic Models ,Food ,Fruit ,Income ,Female ,business ,Demography - Abstract
Background Little is known about the awareness of Canada's Food Guide (CFG). The present study aimed to report the general and specific awareness of CFG recommendations among adults in Alberta, Canada. Methods For this cross-sectional study, respondents (aged >18 years) from randomly selected households completed a telephone survey. Questions pertaining to CFG, physical activity, and vegetable and fruit consumption were included. Logistic regression determined associations between demographic characteristics and awareness of CFG. Results Thousand two hundred and ten Albertans (50% female, mean age 50.5 years) responded. Most [86.5%; 95% confidence interval (CI) = 84.6–88.4] indicated being generally aware of CFG when prompted and 82.5% were aware of specific CFG recommendations. There were no differences in age between those generally aware and unaware of CFG. Female sex [odds ratio (OR) = 3.6; 95%CI = 24–5.4], Caucasian ethnicity (OR = 3.7; 95% CI = 2.3–5.8), income ≥ Canadian $100 000 per annum (OR = 1.6; 95% CI = 1.1–2.3), reporting ≥5 vegetables and fruit per day (OR = 2.1; 95% CI = 1.4–3.2), exceeding recommended levels for physical activity (OR = 2.0; 95% CI = 1.3–2.9) and perception of current weight as healthy (OR = 1.8; 95% CI = 1.2–2.8) were associated with an awareness of CFG. Conclusions Sex, ethnicity and income were associated with general awareness of CFG. Future studies could explore the relationship between awareness and other health-related behaviours
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- 2014
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37. Shift from bird to butterfly pollination in Clivia (Amaryllidaceae)
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Steven D. Johnson and Ian Kiepiel
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Behavior, Animal ,biology ,Pollination ,Plant Science ,Amaryllidaceae ,biology.organism_classification ,medicine.disease_cause ,Pollination syndrome ,Birds ,Fertility ,Pollinator ,Clivia ,Pollen ,Africa ,Butterfly ,Botany ,Liliaceae ,Genetics ,medicine ,Animals ,Nectar ,Butterflies ,Ecology, Evolution, Behavior and Systematics - Abstract
Premise of the study: Pollinator shifts have been implicated as a driver of divergence in angiosperms. We tested the hypothesis that there was a transition from bird- to butterfl y pollination in the African genus Clivia (Amaryllidaceae) and investigated how fl oral traits may have been either modifi ed or retained during this transition. Methods: We identifi ed pollinators using fi eld observations, correlations between lepidopteran wing scales and pollen on stigmas, and single-visit and selective exclusion experiments. We also quantifi ed fl oral rewards and advertising traits. Key results: The upright trumpet-shaped fl owers of C. miniata were found to be pollinated effectively by swallowtail butterfl ies during both nectar-feeding and brush visits. These butterfl ies transfer pollen on their wings, as evidenced by positive correlations between wing scales and pollen loads on stigmas. All other Clivia species have narrow pendulous fl owers that are visited by sunbirds. Selective exclusion of birds and large butterfl ies from fl owers of two Clivia species resulted in a signifi cant decline in seed production. Conclusions: From the distribution of pollination systems on available phylogenies, it is apparent that a shift took place from bird- to butterfl y pollination in Clivia . This shift was accompanied by the evolution of trumpet-shaped fl owers, smaller nectar volume, and emission of scent, while fl ower color and nectar chemistry do not appear to have been substantially modifi ed. These results are consistent with the idea that pollinator shifts can explain major fl oral modifi cations during plant diversifi cation.
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- 2014
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38. Saurian surprise: lizards pollinate South Africa's enigmatic hidden flower
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Sandy-Lynn Steenhuisen, Timotheüs van der Niet, Ruth J. Cozien, and Steven D. Johnson
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South Africa ,Surprise ,Pollination ,Ecology ,media_common.quotation_subject ,Animals ,Ethnology ,Lizards ,General Medicine ,Flowers ,Biology ,Ecology, Evolution, Behavior and Systematics ,media_common - Published
- 2019
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39. Emasculation increases seed set in the bird-pollinated hermaphrodite Kniphofia linearifolia (Xanthorrhoeaceae): Evidence for sexual conflict?
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Steven D. Johnson, Karl J. Duffy, Kirsten L. Patrick, Duffy, Karl J., Patrick, Kirsten L., and Johnson, Steven D.
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Pollination ,Pollen Tube ,Plant Science ,Breeding ,Biology ,medicine.disease_cause ,Birds ,Hermaphroditic Organism ,Magnoliopsida ,Bird ,Hermaphrodite ,Apis mellifera scutellata ,Self-pollination ,Pollen ,Botany ,Genetics ,medicine ,Inbreeding depression ,Animals ,Hermaphroditic Organisms ,Hermaphroditism ,Ovule ,Bee ,Ecology, Evolution, Behavior and Systematics ,Seed ,Animal ,Sunbird ,Bees ,Kniphofia linearifolia ,Ecology, Evolution, Behavior and Systematic ,Microscopy, Fluorescence ,Seeds ,Emasculation ,Floral emasculation ,Pollen tube - Abstract
Hermaphroditism is the most common se xual system in plants, occurring in approximately 72% of angiosperms ( de Jong and Klinkhamer, 2006 ). Despite the success of hermaphroditism in angiosperms, hermaphrodites still need to overcome compro-mises in both the quality and quantity of seed production owing to the close spatial proximity of male and female reproductive organs ( Barrett and Harder, 1996 ). As a result, hermaphroditic plants have evolved various forms of self-incompatibility (SI) and they often separate male and female reproductive function in space and time to reduce selfi ng and promote outcrossing ( de Nettancourt 1997 ; de Jong and Klinkhamer, 2006 ). Despite this, there is still potential for interference between sex functions. The most widely studied form of reproductive interference is pollen discounting (a form of female interference with male function) which occurs in both self-compatible and self-incompatible taxa ( Kohn and Barrett, 1994 ; Harder and Barrett, 1995 ; Eckert, 2000 ; Fishman, 2000 ). A much less well-studied phenomenon is ovule discounting, a form of male interference with female function where ovules penetrated by self-pollen tubes fail to develop, thus reducing opportunities for seed production ( Aizen and Harder, 2007 ). Ovule discounting can be diffi cult to quantify in the fi eld ( Aizen and Harder, 2007 ) and has often been considered to arise solely from early acting inbreeding depression ( Eckert et al., 2010 ). However, it could also arise from ovarian (late-acting) self-incompatibility in which ovules are penetrated by tubes from self-pollen, but then fail to develop ( Seavey and Bawa, 1986 ). Compared with pollen discounting, ovule discounting has sel-dom been quantifi ed in natural populations ( Waser and Price, 1991 ; V aughton and Ramsey, 2010 ). In plants prone to ovule dis-counting, experimental removal of self-pollen by emasculation should increase seed set ( Vaughton and Ramsey, 2010 ), but the outcomes of emasculation can be complex because it can nega-tively affect the rate of pollinator visitation if pollen is used as a reward ( Duffy and Johnson, 2011 ). In this study we consider whether experimental emascula-tion affects seed production in the perennial hermaphrodite, Kniphofi a linearifolia Baker (Xanthorrhoeaceae, formerly Aspho- delaceae). Studies of related species in this lineage have shown that ovules penetrated by self-pollen tubes uniformly fail to de-velop seeds, which suggests either late-acting self-incompatibility or strong early inbreeding depression ( Naaborgh and Willemse, 1991 ; Hargreaves et al., 2012 ; S. D. Johnson, unpublished data). As
- Published
- 2013
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40. Generalised pollination systems for three invasive milkweeds in Australia
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Steven D. Johnson and Megan Ward
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Asclepias curassavica ,Plant Nectar ,Pollination ,Wasps ,Introduced species ,Flowers ,Plant Science ,Gomphocarpus ,Gomphocarpus fruticosus ,Pollinator ,Animals ,Nectar ,Zoophily ,Asclepias ,Ecosystem ,Ecology, Evolution, Behavior and Systematics ,biology ,Ecology ,General Medicine ,biology.organism_classification ,Apocynaceae ,Lepidoptera ,Queensland ,Introduced Species ,Butterflies - Abstract
Because most plants require pollinator visits for seed production, the ability of an introduced plant species to establish pollinator relationships in a new ecosystem may have a central role in determining its success or failure as an invader. We investigated the pollination ecology of three milkweed species - Asclepias curassavica, Gomphocarpus fruticosus and G. physocarpus - in their invaded range in southeast Queensland, Australia. The complex floral morphology of milkweeds has often been interpreted as a general trend towards specialised pollination requirements. Based on this interpretation, invasion by milkweeds contradicts the expectation than plant species with specialised pollination systems are less likely to become invasive that those with more generalised pollination requirements. However, observations of flower visitors in natural populations of the three study species revealed that their pollination systems are essentially specialised at the taxonomic level of the order, but generalised at the species level. Specifically, pollinators of the two Gomphocarpus species included various species of Hymenoptera (particularly vespid wasps), while pollinators of A. curassavica were primarily Lepidoptera (particularly nymphalid butterflies). Pollinators of all three species are rewarded with copious amounts of highly concentrated nectar. It is likely that successful invasion by these three milkweed species is attributable, at least in part, to their generalised pollinator requirements. The results of this study are discussed in terms of how data from the native range may be useful in predicting pollination success of species in a new environment.
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- 2012
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41. The evolution of floral mimicry: identifying traits that visually attract pollinators
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Petr Šmilauer, Steven D. Johnson, Andreas Jürgens, and Jana Jersáková
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Forage (honey bee) ,Inflorescence ,Pollinator ,Watsonia ,Botany ,Mimicry ,Nectar guide ,Biology ,biology.organism_classification ,Attraction ,Ecology, Evolution, Behavior and Systematics ,Batesian mimicry - Abstract
Summary Some orchids have been proposed to be Batesian floral mimics imitating flowers of sympatric rewarding species to attract pollinators. It is not yet well understood which traits are critical for pollinator attraction, although colour, shape and scent have all been implicated. We conducted field-based behavioural experiments using pairwise combinations of plastic flowers differing in spectral and shape properties offered to long-proboscid tabanid flies (Philoliche aethiopica) at two sites – one where the fly-pollinated orchid mimic Disa pulchra occurs with its pink-flowered model, the iris Watsonia lepida and another where the flies forage on a blue-flowered rewarding plant Agapanthus campanulatus. Flies intensively visited and probed plastic flowers of colours indistinguishable in a fly vision model from those of the rewarding plants. Inflorescence architecture and brightness of plastic flowers made little difference to fly attraction, but those that matched the shape and nectar guides of Watsonia flowers were significantly more attractive. Flowers of the three focal plant species are weakly scented and divergent in scent chemistry. This study shows that traits that mimic, in order of importance, the spectra, shape and nectar guide patterns of flowers of rewarding plants would be under strong selection in food-deceptive orchids as they maximize attractiveness to their pollinators. Our experiments also help to explain why deceptive orchids in general often seem to match the flowers of sympatric rewarding plants more in visual attributes than in scent chemistry.
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- 2012
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42. Persistence of flower visitors and pollination services of a generalist tree in modified forests
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Nina Farwig, Ingo Grass, Eike Lena Neuschulz, Steven D. Johnson, and Alexandra Botzat
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Ecology ,Disturbance (ecology) ,biology ,Pollination ,Land use ,Abundance (ecology) ,Celtis africana ,Ecosystem ,biology.organism_classification ,Generalist and specialist species ,Ecology, Evolution, Behavior and Systematics ,Woody plant - Abstract
Flower-visiting insects provide essential pollination services to many plant species. It is thus of critical importance to understand the effects of anthropogenic landscape modification on these animals. Particularly at the landscape scale, we still lack information on how flower visitors are affected by different intensities of human disturbance. In this study, we chose six representative types of forest modification across a heterogeneous South African landscape. At 36 study sites we observed insect visitation to Celtis africana flowers in two consecutive years. This generalist tree species has small unspecialized flowers which we found to be pollinated by a diverse array of insects as well as by wind. Visitation rates to flowers of C. africana differed significantly among the six forest types and between two study years. Visitation rates were enhanced in modified forests, facilitated by a high abundance of feral honeybees (Apis mellifera). Fruit set in C. africana showed significant positive associations with insect visitation and with the diversity of flower visitors, but was only weakly predicted by forest type. Our findings imply that even though forest modification can strongly alter flower visitors, pollination services for trees with unspecialized flowers may persist at a landscape scale. We advise conservation managers to maintain modified forest fragments in addition to natural forests as these may contribute to sustain pollination services in human-modified landscapes.
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- 2012
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43. The relative contributions of insect and bird pollinators to outcrossing in an African Protea (Proteaceae)
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Steven D. Johnson, Herman van der Bank, and Sandy-Lynn Steenhuisen
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Insecta ,Pollination ,Outcrossing ,Flowers ,Plant Science ,Protea ,medicine.disease_cause ,Proteaceae ,Birds ,Pollinator ,Pollen ,Botany ,Genetics ,Inbreeding depression ,medicine ,Animals ,Alleles ,Crosses, Genetic ,Ecology, Evolution, Behavior and Systematics ,Plant Proteins ,biology ,fungi ,food and beverages ,biology.organism_classification ,Mating system ,Protea caffra ,Seedlings ,Seeds ,Regression Analysis - Abstract
Premise of the study: A useful, but seldom applied, measure of the effectiveness of different pollinators is their contribution to the rate of outcrossing. This measure is particularly useful in facultatively autogamous plants for which seed set cannot be used as a direct measure of pollinator effectiveness. We used selective exclusion experiments to assess the importance of insects for outcrossing in Protea caffra , a facultatively autogamous shrub with scented fl owers that are visited frequently by both birds and insects (mainly beetles). Methods and results: Pollen loads on stigmas, pollen tube growth, seed set, seed mass, germination, and early seedling survivorship were similar for vertebrate-excluded and open-pollinated infl orescences. Pollen-supplementation mostly did not increase seed set, revealing resource limitation. Mean multilocus outcrossing rates, estimated using eight polymorphic allozyme loci, were similar for progeny from infl orescences excluded from bird visitors (0.65) and for those visited by both birds and insects (0.59). Wright’s fi xation indices indicated that the adult population is near Hardy–Weinberg equilibrium but differed markedly for maternal plants ( F IS = –0.187 ± 0.065) and their early stage progeny ( F IS = 0.258 ± 0.002). Since seed from self and cross hand-pollinations were equally viable in terms of germination, this discrepancy in F IS could be explained by inbreeding depression that occurs between germination and reproductive maturity. Conclusions: Since outcrossing rates were not reduced when birds were excluded, we infer that insects are effective agents of cross pollination in P. caffra . This helps to explain the evolution of traits associated with insect pollination, such as fruity fl oral scent, in this species.
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- 2012
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44. Competition versus facilitation: conspecific effects on pollinator visitation and seed set in the iris Lapeirousia oreogena
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Steven D. Johnson, Michael Kuhlmann, and Hilke Hollens
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Pollination ,Ecology ,Range (biology) ,media_common.quotation_subject ,fungi ,food and beverages ,Biology ,Fecundity ,Competition (biology) ,Agronomy ,Pollinator ,Abundance (ecology) ,Facilitation ,Set (psychology) ,Ecology, Evolution, Behavior and Systematics ,media_common - Abstract
Ecological interactions between conspecific plants can range from facilitative to competitive depending on the spacing and abundance of individuals. Competitive interactions are expected when plants flower en-masse and availability of pollinators is limited. We tested this prediction using Lapeirousia oreogena, a mass-flowering South African iris that is pollinated by a single species of long-proboscid fly. Controlled hand-pollination experiments showed that L. oreogena is self-compatible, but reliant on pollinator visits for seed set. Seed production per flower showed a significant negative relationship with patch size (and the correlated measure of number of individuals per patch), but was not affected by flower density or distance to neighbouring patches. There was a tendency for fly abundance to increase with patch size, but the rate of visits to individual flowers by flies was not affected by patch size. Seed set of hand-pollinated flowers did not differ for plants in and out of dense patches, indicating that the large differences in seed set among patches were likely to reflect pollinator visits, rather than the genetic or physiological capacity of plants to produce seeds. The reduced fecundity of L. oreogena in large patches with a greater numbers of flowers is consistent with the idea that plants with highly specialized pollination systems can experience intra-specific competition for pollination.
- Published
- 2011
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45. Digestion of fruit of invasive alien plants by three southern African avian frugivores
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Colleen T. Downs, Steven D. Johnson, and Lorinda A. Jordaan
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Speckled mousebird ,biology ,Seed dispersal ,Lantana camara ,food and beverages ,Introduced species ,biology.organism_classification ,Generalist and specialist species ,Bulbul ,Solanum mauritianum ,Frugivore ,Botany ,Animal Science and Zoology ,Ecology, Evolution, Behavior and Systematics - Abstract
Many highly invasive plants are fleshy-fruited and owe their invasiveness largely to mutualisms formed with local dispersers. The energetic benefits gained by frugivores from ingestion of fruits of invasive alien plants remain poorly documented. We assess whether avian frugivores process fruits of invasive alien plants effectively to meet their daily energetic requirements. Four fleshy-fruited plant species that are invasive in southern Africa were considered –Solanum mauritianum, Cinnamomum camphora, Lantana camara and Psidium guajava. Their fruits were fed to three common generalist frugivores – Red-winged Starling Onychognathus morio, Speckled Mousebird Colius striatus and Dark-capped Bulbul Pycnonotus tricolor– to determine the efficiency of digestion. Energetic parameters calculated for all fruit diets varied significantly between frugivore species. Speckled Mousebirds and Dark-capped Bulbuls maintained body mass and efficiently processed all four fruit types, whereas Red-winged Starlings only did so on C. camphora and S. mauritianum diets. These results explain why these fruits are attractive to local avian frugivores. Furthermore, these avian frugivores processed large quantities of invasive fruits, thereby serving as potentially efficient dispersers.
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- 2011
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46. Reproductive biology of Australian acacias: important mediator of invasiveness?
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Andres Fuentes-Ramirez, David M. Richardson, James G. Rodger, Carla J. Harris, Johannes J. Le Roux, Elizabete Marchante, Steven D. Johnson, Nicholas George, Joseph T. Miller, John R. U. Wilson, Hélia Marchante, Graham N. Stone, Daniel J. Murphy, Elizabeth M. Wandrag, Matthew Prescott, Margaret Byrne, Anton Pauw, and Michelle R. Gibson
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Modes of reproduction ,Pollination ,Ecology ,Seed dispersal ,Reproductive biology ,Trait ,Introduced species ,Biology ,Generalist and specialist species ,Ecology, Evolution, Behavior and Systematics ,Invasive species - Abstract
Aim Reproductive traits are important mediators of establishment and spread of introduced species, both directly and through interactions with other life-history traits and extrinsic factors. We identify features of the reproductive biology of Australian acacias associated with invasiveness. Location Global. Methods We reviewed the pollination biology, seed biology and alternative modes of reproduction of Australian acacias using primary literature, online searches and unpublished data. We used comparative analyses incorporating an Acacia phylogeny to test for associations between invasiveness and eight reproductive traits in a group of introduced and invasive (23) and non-invasive (129) species. We also explore the distribution of groups of trait ‘syndromes’ between invasive and non-invasive species. Results Reproductive trait data were only available for 126 of 152 introduced species in our data set, representing 23/23 invasive and 103/129 non-invasive species. These data suggest that invasives reach reproductive maturity earlier (10/13 within 2 years vs. 7/26 for non-invasives) and are more commonly able to resprout (11/21 vs. 13/54), although only time to reproductive maturity was significant when phylogenetic relationships were controlled for. Our qualitative survey of the literature suggests that invasive species in general tend to have generalist pollination systems, prolific seed production, efficient seed dispersal and the accumulation of large and persistent seed banks that often have fire-, heat- or disturbance-triggered germination cues. Conclusions Invasive species respond quicker to disturbance than non-invasive taxa. Traits found to be significant in our study require more in-depth analysis involving data for a broader array of species given how little is known of the reproductive biology of so many taxa in this species-rich genus. Sets of reproductive traits characteristic of invasive species and a general ability to reproduce effectively in new locations are widespread in Australian acacias. Unless there is substantial evidence to the contrary, care should be taken with all introductions.
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- 2011
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47. Characterization of Influenza A Outbreaks in Minnesota Swine Herds and Measures Taken to Reduce the Risk of Zoonotic Transmission
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Steven V. Johnson, Amanda Beaudoin, Jeff B. Bender, Marie Gramer, and Peter R. Davies
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Veterinary medicine ,education.field_of_study ,General Veterinary ,General Immunology and Microbiology ,Epidemiology ,Transmission (medicine) ,business.industry ,animal diseases ,Biosecurity ,Population ,Public Health, Environmental and Occupational Health ,Outbreak ,medicine.disease_cause ,Vaccination ,Infectious Diseases ,Public health surveillance ,Herd ,Influenza A virus ,medicine ,business ,education - Abstract
Influenza A virus infections commonly cause respiratory disease in swine and can be transmitted between people and pigs, with potentially novel strains introduced into herds and spilling back into the human population. The goals of this study were to characterize influenza infections in Minnesota pigs and assess biosecurity measures used by swine workers. Veterinarians submitting influenza-positive swine samples to the University of Minnesota Veterinary Diagnostic Laboratory between October 2007 and April 2009 were surveyed regarding disease-related information and biosecurity procedures at each farm. Influenza-positive samples were submitted year-round, peaking in spring and fall. H1N1 was the most commonly detected subtype (56%), followed by H3N2 (14%) and H1N2 (12%). Most positive submissions were associated with illness in growing pigs (median age 8.8 weeks, IQR 5-15). Median morbidity and mortality were 25% (IQR 10-48) and 2% (IQR 0.5-3.5), respectively. Vaccination of sows and growing pigs was conducted at 71% and 7.9% of the swine farms, respectively. Specialized footwear was reported as the most common form of protective equipment used by workers. Employee vaccination for seasonal influenza was 19%. The sow vaccination rate in this study is consistent with national data, although growing pig vaccination is lower than the national average. Seasonal and age trends identified here may provide diagnostic guidance when growing pigs experience respiratory disease. Inconsistent use of protective equipment and employee vaccination at swine farms indicates the need for further discussion and research of approaches to minimize interspecies influenza transmission on swine farms.
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- 2011
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48. Effects of pollen reward removal on fecundity in a self-incompatible hermaphrodite plant
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Steven D. Johnson and Karl J. Duffy
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Pollen source ,Plant Science ,General Medicine ,Biology ,medicine.disease_cause ,biology.organism_classification ,Attraction ,Hermaphrodite ,Pollinator ,Pollen ,Botany ,medicine ,Nectar guide ,Nectar ,Aloe maculata ,Ecology, Evolution, Behavior and Systematics - Abstract
The pollen of hermaphrodite plants is often utilised by flower-visiting animals. While pollen production has obvious benefits for plant male fitness, its consequences for plant female fitness, especially in self-incompatible hermaphrodite species, are less certain. Pollen production could either enhance seed production though increased pollinator attraction, or reduce it if ovules are discounted by deposition of self pollen, as can occur in species with late-acting self-incompatibility. To test the effects of pollen reward provision on female fitness, we artificially emasculated flowers in two populations of the succulent Aloe maculata (Asphodelaceae), which has a late-acting self-incompatibility system, over the course of its flowering period. Flowers of this species are visited by sunbirds (for nectar) and native bees (for pollen and nectar). We measured floral visitation rates, floral rejection rates, pollen deposition on stigmas and fruit and seed set in both emasculated and non-emasculated plants. We found that flowers of emasculated plants suffered reduced visitation and increased rejection (arrival without visitation) by bees, but not by sunbirds; had fewer pollen grains deposited on stigmas and showed an overall decrease in fruit set and seed set. Rates of seed abortion were, however, greatly reduced in emasculated flowers. This study shows that pollen rewards can be important for seed set, even in self-incompatible plants, which have been assumed to rely on nectar rewards for pollinator attraction. Seed abortion was, however, increased by pollen production, a result that highlights the complexity of selection on pollen production in hermaphrodite flowers.
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- 2011
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49. A Comparison of the Survival and Migratory Behavior of Hatchery-Reared and Naturally Reared Steelhead Smolts in the Alsea River and Estuary, Oregon, using Acoustic Telemetry
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James H. Power, James Ray, Derek R. Wilson, and Steven L. Johnson
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geography ,geography.geographical_feature_category ,Ecology ,Estuary ,Broodstock ,Management, Monitoring, Policy and Law ,Aquatic Science ,Biology ,Brood ,Hatchery ,Fishery ,Telemetry ,Tributary ,Juvenile ,Rainbow trout ,Ecology, Evolution, Behavior and Systematics - Abstract
We tracked three groups of steelhead Oncorhynchus mykiss smolts implanted with acoustic transmitters to determine whether the degree of hatchery domestication or the juvenile rearing environment (hatchery raceway versus natural stream) influenced migration timing and survival in the Alsea River and estuary, Oregon. Two groups consisted of age-1 smolts reared in concrete raceways. One hatchery-reared group (traditional brood group) was derived from the traditional Alsea River broodstock initially developed in the 1950s. The second hatchery-reared group (new brood group) was derived from naturally reared Alsea River adult steelhead that were captured and spawned at the hatchery beginning in the winter of 2000–2001. The third group (naturally reared group) consisted of age-2 naturally reared smolts captured in a downstream migrant trap located in a tributary stream near the hatchery. We placed transmitters in 74 traditional brood smolts, 76 new brood smolts, and 72 naturally reared smolts. Thirty-on...
- Published
- 2010
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50. EVOLUTION AND COEXISTENCE OF POLLINATION ECOTYPES IN AN AFRICAN GLADIOLUS (IRIDACEAE)
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Ronny Alexandersson, Bruce Anderson, and Steven D. Johnson
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Iridaceae ,Pollination ,Ecotype ,Pollinator ,Directional selection ,Sympatric speciation ,Foraging ,Botany ,Genetics ,Allopatric speciation ,Biology ,General Agricultural and Biological Sciences ,Ecology, Evolution, Behavior and Systematics - Abstract
Pollinator-mediated selection has been suggested as a key driver of speciation in plants. We examined the potential role of hawkmoth pollinators in driving allopatric divergence and maintaining sympatric coexistence of morphotypes in the African iris Gladiolus longicollis. Floral tube length in this species varies from 35 mm to 130 mm across its geographic range and reflects the prevailing tongue lengths of local hawkmoth assemblages. The distribution of floral tube lengths is bimodal with two relatively discrete categories—long (about 90 mm) or short (about 50 mm)—that match the bimodal distribution of hawkmoth tongue lengths in eastern South Africa. At a contact site between these two floral morphs, we found few individuals of intermediate length, suggesting limited gene flow between morphs despite their interfertility. A difference in flowering phenology appears to be the main isolating barrier between morphs at this site. Long- and short-tubed morphs differed markedly in the chemical composition of their floral fragrance, a trait that could be used as a cue for morph-specific foraging by hawkmoths. Positive directional selection on tube length was found to occur in both morphs.
- Published
- 2009
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