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To meet the demand for more and larger tallgrass prairie restorations, seed is frequently collected en-masse from remnant native plant populations. Overharvesting of seed may lead to population extinctions, but these risks are not well studied. Species' reproductive strategies may provide a basis for risk assessment. We assessed extinction risks associated with seed harvest for grassland plant species with different reproductive strategies (clonal vs. non-clonal). Using stage-based matrix models, we projected the extinction risk for two clonal and four non-clonal prairie species subjected to five harvest scenarios: ( i) no harvest, ( ii and iii) annual harvest at low/high intensity (50% and 75% seeds removed), and ( iv and v) triennial harvest at low/high intensity. We compared the magnitude of growth or decline ( λ) and mean extinction risk among populations during a 25-year modeling period. Non-clonal species were robust to triennial and low-intensity harvest, but susceptible to decreases in population growth ( λ) up to 0.5 and elevated extinction risks up to 95% with high intensity annual harvest. Clonal species were unaffected by seed harvest, owing to a compensatory effect of vegetative propagation on growth rates. To maintain populations of non-clonal species in remnant grasslands, high intensity annual harvest should be avoided. [ABSTRACT FROM AUTHOR]

Gene expression profiles are important data to reveal the functions of genes putatively involved in crucial biological processes. RNA arbitrarily primed polymerase chain reaction (RAP-PCR) and specifically primed reverse transcription polymerase chain reaction (RT-PCR) were combined to screen differentially expressed genes following development of a commercial Bacillus thuringiensis subsp. kurstaki strain 8010 (serotype 3a3b). Six differentially expressed transcripts (RAP1 to RAP6) were obtained. RAP1 encoded a putative triple helix repeat-containing collagen or an exosporium protein H related to spore pathogenicity. RAP2 was homologous to a ClpX protease and an ATP-dependent protease La (LonB), which likely acted as virulence factors. RAP3 was homologous to a beta subunit of propionyl-CoA carboxylase required for the development of Myxococcus xanthus. RAP4 had homology to a quinone oxidoreductase involved in electron transport and ATP formation. RAP5 showed significant homology to a uridine kinase that mediates phosphorylation of uridine and azauridine. RAP6 shared high sequence identity with 3-methyl-2-oxobutanoate-hydroxymethyltransferase (also known as ketopantoate hydroxymethyltransferase or PanB) involved in the operation of the tricarboxylic acid cycle. The findings described here would help to elucidate the molecular mechanisms underlying the differentiation process of B. thuringiensis and unravel novel pathogenic genes. Les profils d'expression génique fournissent d'importants éléments révélant les fonctions de gènes potentiellement impliqués dans des processus biologiques déterminants. On a combiné des réactions de polymérisation en chaîne de l'ARN utilisant des amorces arbitraires (RAR-PCR) et de PCR á transcription inverse (RT-PCR) á amorces spécifiques afin de rechercher des gènes exprimés de manière différentielle lors du développement de Bacillus thuringiensis subsp. kurstaki souche 8010 (sérotype 3a3b). On a obtenu 6 transcrits exprimés différentiellement (RAP1 á RAP6). RAP1 codait un collagène putatif á répétition trihélicoïdale ou une protéine H d'exine liée á la pathogénicité de la spore. RAP2 était homologue á une protéase ClpX et á une protéase La dépendante de l'ATP (LonB) dont la fonction était probablement liée á la virulence. RAP3 était homologue á une sous-unité bêta de la propionyl-CoA carboxylase nécessaire au développement de Myxococcus xanthus. RAP4 était homologue á une quinone oxydoréductase participant au transport d'électrons et á la formation d'ATP. RAP5 présentait une forte homologie á une uridine kinase responsable de la phosphorylation de l'uridine et de l'azauridine. RAP6 partageait une identité de séquence élevée avec la 3-méthyl-2-oxobutanoate-hydroxyméthyltransférase (aussi connue comme la kétopantoate hydroxyméthyltransférase ou PanB) impliquée dans le cycle de Krebs. Ces trouvailles permettraient d'élucider les mécanismes moléculaires sous-tendant le processus de différenciation de B. thuringiensis et de mettre au jour de nouveaux gènes pathogènes. [ABSTRACT FROM AUTHOR]

This study tested the hypothesis that sea lampreys ( Petromyzon marinus L., 1758) undergo a reduction in the photosensitivity of photoreceptors in the tail after metamorphosing from burrow-dwelling, filter-feeding larval sea lampreys (ammocoetes) into open-water, parasitic juvenile phase animals that attach themselves to and feed on the blood of marine and freshwater fishes. Using a photo-illumination apparatus, ammocoetes and juvenile sea lampreys were exposed to white light at an intensity of 10 lx and the photokinetic response (time to movement) was measured in individual animals. The median latency of the response of juvenile lampreys was 5.4 times longer (i.e., slower response time) than observed in ammocoetes, and only 61% of the juvenile animals responded to the light compared with 95% of ammocoetes. It is concluded that the greater photosensitivity of tail photoreceptors in ammocoetes helps ensure that the animals are totally concealed from potential predators while burrowing. Decreased photosensitivity following metamorphosis is likely related to the transition to an open water, parasitic life style in which tail photoreception would have little selective advantage. [ABSTRACT FROM AUTHOR]

Growth and maturity of two sympatric gadids were examined from 48 Atlantic ( Gadus morhua L., 1758) and 42 Greenland ( Gadus ogac Richardson, 1836) cod ranging from 17 to 74 cm in length collected from an inshore area of Trinity Bay, Newfoundland, Canada, during 2009 and 2010. Ages estimated from otolith readings ranged from 2 to 7 for both species. Age and size at 50% maturity differed between species, being 2.3 years and 28.2 cm for G. ogac and 4.6 years and 48.8 cm for G. morhua. von Bertalanffy growth models did not differ between species with parameters L∞ = 91 cm, k = 0.16 year−1, t0 = -0.02 years for G. ogac and L∞ = 112 cm, k = 0.13 year−1, t0 = 0.18 years for G. morhua. Length ( L) - mass ( W) relationships differed; W = 0.000005 kg·cm− b × L3.17 for G. ogac and W = 0.000011 kg·cm− b × L2.91 for G. morhua suggested slightly positive and negative allometric growth, respectively. For G. morhua, growth curves, length-mass relationships, and maturity rates did not differ between fish collected during this and earlier studies. Differences in maturity schedules and growth may decrease resource competition and help facilitate coexistence of these species. [ABSTRACT FROM AUTHOR]

Short-lived annuals should allocate more resources towards reproduction, whereas long-lived perennials should allocate more resources towards tissue maintenance. Although ecological data support this hypothesis, no studies have examined the physiological basis for lifespan differences between annuals and perennials. Based on the oxidative theory of aging, hydrogen peroxide (H2O2) levels should be lower in perennating tissues (e.g., basal roots) - but not nonperennating tissues (e.g., cotyledons) - from perennials compared with annuals. We tested this prediction using two annual and two perennial species of flax ( Linum). As predicted, H2O2 concentrations were lower in roots from perennials than from annuals, reflecting higher catalase activity in roots from perennials. In cotyledons, contrary to our predictions, H2O2 concentrations were actually higher in perennials than in annuals, despite higher catalase activity in perennials as well, likely reflecting higher H2O2 production via peroxisomes and chloroplasts. Therefore, we propose that, consistent with the oxidative theory of aging, perennial flax species have a lower oxidative burden in their roots, but this comes at the cost of a greater oxidative burden in their shoots. As we demonstrate, perenniality is ancestral in Linum, and so derivation of the annual condition likely involved a physiological shift towards a more equitable oxidative burden between roots and shoots. [ABSTRACT FROM AUTHOR]

Excessively high rates of fishing mortality have led to rapid declines of several commercially important fish stocks. To harvest fish stocks sustainably, fisheries management requires accurate information about population dynamics, but the generation of this information, known as fisheries stock assessment, traditionally relies on conservative and rather narrowly data-driven modelling approaches. To improve the information available for fisheries management, there is a demand to increase the biological realism of stock-assessment practices and to better incorporate the available biological knowledge and theory. Here, we explore the development of fisheries stock-assessment models with an aim to increasing their biological realism, and focus particular attention on the possibilities provided by the hierarchical Bayesian modelling framework and ways to develop this approach as a means of efficiently incorporating different sources of information to construct more biologically realistic stock-assessment models. The main message emerging from our review is that to be able to efficiently improve the biological realism of stock-assessment models, fisheries scientists must go beyond the traditional stock-assessment data and explore the resources available in other fields of biological research, such as ecology, life-history theory and evolutionary biology, in addition to utilizing data available from other stocks of the same or comparable species. The hierarchical Bayesian framework provides a way of formally integrating these sources of knowledge into the stock-assessment protocol and to accumulate information from multiple sources and over time. [ABSTRACT FROM AUTHOR]

For the first time, the phenotypes formed in the reduced mycorrhizal colonization (rmc) Solanum lycopersicum L. (tomato) mutant with different arbuscular mycorrhizal (AM) fungi were used to explore the potential of different fungal structures to support development of external fungal mycelium and spores. The life cycle of AM fungi with rmc was followed for up to 24 weeks. Results showed that production of external mycelium was slight and transitory for those fungi that did not penetrate the roots of rmc (Pen–) (Glomus intraradices DAOM181602 and Glomus etunicatum). For fungi that penetrated the root epidermis and hypodermis (Coi–, Glomus coronatum and Scutellospora calospora) the mycelium produced varied in size, but was always smaller than with the wild-type 76R. Spores were formed by these fungi with 76R but not with rmc. The only fungus forming a Myc+ phenotype with rmc, G. intraradices WFVAM23, produced as much mycelium with rmc as with 76R. We observed lipid accumulation in hyphae and vesicles in both plant genotypes with this fungus. Mature spores were formed with 76R. However, with rmc, spores remained small and (presumably) immature for up to 24 weeks. We conclude that significant carbon transfer from plant to fungus can occur in Coi– interactions with rmc in which no cortical colonization occurs. We speculate that both carbon transfer and root signals are required for mature spores to be produced. [ABSTRACT FROM AUTHOR]

Genome size (C value, the haploid DNA content of the nucleus) varies widely among eukaryotes, increasing through duplication or insertion of transposable elements and decreasing through deletions. Here, we investigate relationships between genome size and life-history attributes potentially related to fitness, including body mass, brain mass, gestation time, age at sexual maturity, and longevity, in 42 species of primates. Using multivariate and phylogenetically informed analyses, we show that genome size is unrelated to any of these traits. Genome size exhibits little variation within primates and its evolution does not appear to be correlated with changes in life-history traits. This further indicates that the phenotypic consequences of variation in genome size are dependent on the particular biology of the group in question. [ABSTRACT FROM AUTHOR]