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Premise: Duplicated genes (paralogs) are abundant in plant genomes, and their retention may influence the function of genetic programs and contribute to evolutionary novelty. How gene duplication affects genetic modules and what forces contribute to paralog retention are outstanding questions. The CYCLOIDEA(CYC)‐dependent flower symmetry program is a model for understanding the evolution of gene duplication, providing multiple examples of paralog partitioning and novelty. However, a novel CYC gene lineage duplication event near the origin of higher core Lamiales (HCL) has received little attention. Methods: To understand the evolutionary fate of duplicated HCL CYC2 genes, we determined the effects on flower symmetry by suppressing MlCYC2A and MlCYC2B expression using RNA interference (RNAi). We determined the phenotypic effects on flower symmetry in single‐ and double‐silenced backgrounds and coupled our functional analyses with expression surveys of MlCYC2A, MlCYC2B, and a putative downstream RADIALIS (MlRAD5) ortholog. Results: MlCYC2A and MlCYC2B jointly contribute to bilateral flower symmetry. MlCYC2B exhibits a clear dorsal flower identity function and may additionally function in carpel development. MlCYC2A functions in establishing dorsal petal shape. Further, our results suggest an MlCYC2A–MlCYC2B regulatory interaction, which may affect pathway homeostasis. Conclusions: Our results suggest that CYC paralogs specific to higher core Lamiales may be selectively retained for their joint contribution to bilateral flower symmetry, similar to the independently derived CYC paralogs in the Lamiales model for bilateral flower symmetry research, Antirrhinum majus (snapdragon). [ABSTRACT FROM AUTHOR]

The phylogeny of the species from Phrymaceae and Mazaceae has undergone many adjustments and changes in recent years. Moreover, there is little plastome information on the Phrymaceae. In this study, we compared the plastomes of six species from the Phrymaceae and 10 species from the Mazaceae. The gene order, contents, and orientation of the 16 plastomes were found to be highly similar. A total of 13 highly variable regions were identified among the 16 species. An accelerated rate of substitution was found in the protein-coding genes, particularly cemA and matK. The combination of effective number of codons, parity rule 2, and neutrality plots revealed that the codon usage bias is affected by mutation and selection. The phylogenetic analysis strongly supported {Mazaceae [(Phrymaceae + Wightiaceae) + (Paulowniaceae + Orobanchaceae)]} relationships in the Lamiales. Our findings can provide useful information to analyze the phylogeny and molecular evolution within the Phrymaceae and Mazaceae. [ABSTRACT FROM AUTHOR]

With the disintegration of the traditionally circumscribed Scrophulariaceae, the phylogenetic placements of most genera formerly placed in that family have been resolved. However, the familial placement of the monotypic genus Mimulicalyx has not been included in any published molecular phylogenetic study. Here, we adopt a two-step approach to resolve the phylogenetic placement of Mimulicalyx using three datasets: (1) a 71 619 bp plastome alignment of Lamiales; (2) a dataset of six plastid DNA regions (atpB, matK, ndhF, rbcL, rps16 and trnL-trnF) for Phrymaceae; and (3) a dataset of the nuclear ribosomal internal and external transcribed spacer regions (nrITS, ETS) for Phrymaceae. Our analyses reveal that Mimulicalyx is a member of the tribe Mimuleae in Phrymaceae. Generic level phylogenetic relationships within Phrymaceae are further discussed, and a dichotomous key to the 15 genera currently recognized is provided. [ABSTRACT FROM AUTHOR]

Premise: Many traits covary with environmental gradients to form phenotypic clines. While local adaptation to the environment can generate phenotypic clines, other nonadaptive processes may also. If local adaptation causes phenotypic clines, then the direction of genotypic selection on traits should shift from one end of the cline to the other. Traditionally, genotypic selection on non‐Gaussian traits like germination rate have been hampered because it is challenging to measure their genetic variance. Methods: Here we used quantitative genetics and reciprocal transplants to test whether a previously discovered cline in germination rate showed additional signatures of adaptation in the scarlet monkeyflower (Mimulus cardinalis). We measured genotypic and population level covariation between germination rate and early survival, a component of fitness. We developed a novel discrete log‐normal model to estimate genetic variance in germination rate. Results: Contrary to our adaptive hypothesis, we found no evidence that genetic variation in germination rate contributed to variation in early survival. Across populations, southern populations in both gardens germinated earlier and survived more. Conclusions: Southern populations have higher early survival but it is not caused by faster germination. This pattern is consistent with nonadaptive forces driving the phenotypic cline in germination rate, but future work will need to assess whether there is selection at other life stages. This statistical framework should help expand quantitative genetic analyses for other waiting‐time traits. [ABSTRACT FROM AUTHOR]

Premise: Across taxa, vegetative and floral traits that vary along a fast‐slow life‐history axis are often correlated with leaf functional traits arrayed along the leaf economics spectrum, suggesting a constrained set of adaptive trait combinations. Such broad‐scale convergence may arise from genetic constraints imposed by pleiotropy (or tight linkage) within species, or from natural selection alone. Understanding the genetic basis of trait syndromes and their components is key to distinguishing these alternatives and predicting evolution in novel environments. Methods: We used a line‐cross approach and quantitative trait locus (QTL) mapping to characterize the genetic basis of twenty leaf functional/physiological, life history, and floral traits in hybrids between annualized and perennial populations of scarlet monkeyflower (Mimulus cardinalis). Results: We mapped both single and multi‐trait QTLs for life history, leaf function and reproductive traits, but found no evidence of genetic co‐ordination across categories. A major QTL for three leaf functional traits (thickness, photosynthetic rate, and stomatal resistance) suggests that a simple shift in leaf anatomy may be key to adaptation to seasonally dry habitats. Conclusions: Our results suggest that the co‐ordination of resource‐acquisitive leaf physiological traits with a fast life‐history and more selfing mating system results from environmental selection rather than functional or genetic constraint. Independent assortment of distinct trait modules, as well as a simple genetic basis to leaf physiological traits associated with drought escape, may facilitate adaptation to changing climates. [ABSTRACT FROM AUTHOR]

PREMISE: Due to climate change, more frequent and intense periodic droughts are predicted to increasingly pose major challenges to the persistence of plant populations. When a severe drought occurs over a broad geographical region, independent responses by individual populations provide replicated natural experiments for examining the evolution of drought resistance and the potential for evolutionary rescue. METHODS: We used a resurrection approach to examine trait evolution in populations of the common monkeyflower, Mimulus guttatus, exposed to a record drought in California from 2011 to 2017. Specifically, we compared variation in traits related to drought escape and avoidance from seeds collected from 37 populations pre‐ and post‐drought in a common garden. In a parallel experiment, we evaluated fitness in two populations, one which thrived and one which was nearly extirpated during the drought, under well‐watered and dry‐down conditions. RESULTS: We observed substantial variation among populations in trait evolution. In the subset of populations where phenotypes changed significantly, divergence proceeded along trait correlations with some populations flowering rapidly with less vegetative tissue accumulation and others delaying flowering with greater vegetative tissue accumulation. The degree of trait evolution was only weakly correlated with drought intensity but strongly correlated with initial levels of standing variation. Fitness was higher in the post‐drought than pre‐drought accessions in both treatments for the thriving population, but lower in both treatments for the nearly extirpated population. CONCLUSIONS: Together, our results indicate that evolutionary responses to drought are context dependent and reflect the standing genetic variation and genetic correlations present within populations. [ABSTRACT FROM AUTHOR]

Premise: Identifying the environmental factors responsible for natural selection across different habitats is crucial for understanding the process of local adaptation in plants. Despite its importance, few studies have successfully isolated the environmental factors driving local adaptation in nature. In this study, we evaluated the agents of selection responsible for local adaptation of the monkeyflower Mimulus guttatus to California's coastal and inland habitats. Methods: We implemented a manipulative reciprocal transplant experiment at coastal and inland sites, where we excluded aboveground stressors in an effort to elucidate their role in the evolution of local adaptation. Results: Excluding aboveground stressors, most likely a combination of salt spray and herbivory, completely rescued inland annual plant fitness when transplanted to coastal habitat. The exclosures in inland habitat provided a benefit to the performance of coastal perennial plants. However, the exclosures are unlikely to provide much fitness benefit to the coastal plants at the inland site because of their general inability to flower in time to escape from the summer drought. Conclusions: Our study demonstrates that a distinct set of selective agents (aboveground vs. belowground) are responsible for local adaptation at opposite ends of an environmental gradient. [ABSTRACT FROM AUTHOR]

Cyrtandromoea is a genus consisting of about 12 species of perennial caulescent herbs with a distribution in China, India, Myanmar, Thailand, and western Malesia. The genus has previously been associated with either Gesneriaceae or the tribe Mimuleae in Phrymaceae (in former Scrophulariaceae) with morphology in favor of the latter and molecular plastid ndhF data the former. We addressed the placement of this genus by assembling a four gene dataset (matK, ndhF, rps16, and trnL-F) comprising 270 ingroup samples representing 270 species and 51 families of the core asterids, including all families of Lamiales currently recognized. These included 111 species representing 66 genera of Gesneriaceae. We used maximum parsimony, maximum likelihood, and Bayesian inference analyses to reconstruct phylogenies that showed Cyrtandromoea to be placed in Phrymaceae. A fine-scale analysis focusing on Phrymaceae using ITS and trnL-F and 79 samples revealed that Cyrtandromoea is most closely related to a clade of genera in Phrymaceae that included Mimulus s. s. A combination of morphological synapomorphies such as cymose inflorescences, 5-angled toothed calyx, flowers with bilocular ovary with axile placentation with numerous small seeds with endosperm, and loculicidal dehiscing capsule support this placement. Our results strongly support the placement of Cyrtandromoea in Phrymaceae. [ABSTRACT FROM AUTHOR]

PREMISE OF THE STUDY: Evolutionary radiations provide excellent opportunities to study the origins of biodiversity, but rapid divergence and ongoing gene flow make inferring evolutionary relationships among taxa difficult. Consequently, combining morphological and genomic analyses will be necessary to clarify the evolutionary history of radiations. We used an integrative approach to shed light on relationships within a diverse radiation of monkeyflowers (Mimulus section Diplacus) with a controversial taxonomic history. METHODS: We used genomewide single nucleotide polymorphism data and a combination of phylogenetic and population genomic analyses to infer the evolutionary relationships within the group. Tests for hybridization were performed to reveal sources of shared variation, and multivariate analyses of floral trait data were conducted to examine the correspondence between phenotypic and phylogenetic data. KEY RESULTS: We identified four primary clades with evidence for some shared variation among them. We also detected evidence for recent gene flow between closely related subclades and populations. Strong discordance between floral trait and molecular data provides evidence for divergent and convergent phenotypic evolution. CONCLUSIONS: Mimulus section Diplacus has all the hallmarks of a rapid radiation, including diverse taxa that are at different stages of divergence, extensive shared variation among taxa, and complex patterns of phenotypic evolution. Our findings will direct future evolutionary research and have important taxonomic implications that highlight the need for a new revision of section Diplacus. [ABSTRACT FROM AUTHOR]

PREMISE OF THE STUDY:: Pollinator‐mediated selection on flower phenotypes (e.g., shape, color, scent) is key to understanding the adaptive radiation of angiosperms, many of which have evolved specialized relationships with a particular guild of animal pollinators (e.g., birds, bats, moths, bees). E‐β‐Ocimene, a monoterpene produced by OCIMENE SYNTHASE (OS) in Mimulus lewisii, is a floral scent important in attracting the species’ bumblebee pollinators. The taxa closely related to M. lewisii have evolved several different pollination syndromes, including hummingbird pollination and self pollination (autogamy). We are interested in how floral scent variation contributed to species diversification in this clade. METHODS:: We analyzed variation in E‐β‐ocimene emission within this Mimulus clade and explored its molecular basis through a combination of DNA sequencing, reverse transcriptase PCR, and enzyme functional analysis in vitro. KEY RESULTS:: We found that none of the taxa, other than M. lewisii, emitted E‐β‐ocimene from flowers. But the molecular basis underlying loss of E‐β‐ocimene emission is unique in each taxon, including deletion, missense, or frameshift mutations in the OS gene, and potential posttranscriptional downregulation. CONCLUSIONS:: The molecular evidence suggests that parallel loss‐of‐function in OS is the best explanation for the observed pattern of E‐β‐ocimene emission, likely as the result of natural selection. [ABSTRACT FROM AUTHOR]

PREMISE OF THE STUDY: The stigmas of several species are touch sensitive and respond to pressure by closing. Previous research suggests that stigma closure could prevent self pollination within a flower during a pollinator's visit or enhance male function by increasing pollen export. Both factors could be favored in outcrossers, and neither would be beneficial in selfers. METHODS: We investigated variation in stigma-closing and the duration of closure in annual and perennial populations of the variable species Mimulus guttatus and whether four closely related selfing species (M. cupriphilus, M. laciniatus, M. nasutus, and M. pardalis) have lost their touch sensitivity. We grew plants in a controlled environment and performed experiments with and without the addition of pollen to the stigma. KEY RESULTS: In M. guttatus, the speed of stigma-closing was rapid and unaffected by the deposition of pollen. Populations varied significantly in closing speed, which may reflect their geographic location. For annual populations only, anther-stigma separation significantly affected closing speed. Also, stigmas that closed quickly stayed closed longer, and stigmas that received pollen remained closed longer. Finally, in the selfing species, stigma-closing was more variable; some populations have entirely lost the ability to respond to touch. CONCLUSIONS: We discuss our results in the context of traits that promote outcrossing and traits that are under selection during the evolution of selfing. This is the first characterization of variation in touch responses across multiple populations within a species and the first to demonstrate the loss of touch sensitivity in selfing lineages. [ABSTRACT FROM AUTHOR]

PREMISE OF THE STUDY: Reproductive isolation between sympatric species pairs may be maintained by both pre- and postmating barriers. Here we evaluate potential barriers to mating between the outcrossing Mimulus luteus and its more highly selfing sympatric congener, M. cupreus, two members of the South American luteus complex of Mimulus. METHODS: Seed set was compared following autonomous self-pollination, manual pollination, conspecific outcrossing, and sympatric and allopatric hybridization, for laboratory-maintained inbred lines and wild-collected accessions. Survival and reproductive fitness of hybrids relative to parental species were examined across environments that differed with respect to temperature and soil nutrients, two factors that vary across the ranges of M. luteus and M. cupreus. KEY RESULTS: Mimulus luteus was minimally capable of autonomous self-fertilization, consistent with reliance on an animal pollinator, whereas M. cupreus was a successful selfer across all tested accessions. Postmating barriers to hybridization are negligible, in both low- and high-stress environments, across multiple sympatric and allopatric populations. CONCLUSION: As in the North American M. guttatus-M. nasutus species pair, postmating barriers contribute little to isolation between M. luteus and M. cupreus. This result reinforces the importance of premating barriers, specifically species differences in reliance on, and accessibility to, animal pollinators. A unique aspect of the M. luteus-M. cupreus pair is the recent gain of red floral anthocyanin pigmentation in M. cupreus. On the basis of species differences in vegetative anthocyanin production, a facultative stress-protective response, we propose a potential stress-protective role for the constitutive floral anthocyanins of M. cupreus. [ABSTRACT FROM AUTHOR]

An update of the Angiosperm Phylogeny Group ( APG) classification of the orders and families of angiosperms is presented. Several new orders are recognized: Boraginales, Dilleniales, Icacinales, Metteniusiales and Vahliales. This brings the total number of orders and families recognized in the APG system to 64 and 416, respectively. We propose two additional informal major clades, superrosids and superasterids, that each comprise the additional orders that are included in the larger clades dominated by the rosids and asterids. Families that made up potentially monofamilial orders, Dasypogonaceae and Sabiaceae, are instead referred to Arecales and Proteales, respectively. Two parasitic families formerly of uncertain positions are now placed: Cynomoriaceae in Saxifragales and Apodanthaceae in Cucurbitales. Although there is evidence that some families recognized in APG III are not monophyletic, we make no changes in Dioscoreales and Santalales relative to APG III and leave some genera in Lamiales unplaced (e.g. Peltanthera). These changes in familial circumscription and recognition have all resulted from new results published since APG III, except for some changes simply due to nomenclatural issues, which include substituting Asphodelaceae for Xanthorrhoeaceae (Asparagales) and Francoaceae for Melianthaceae (Geraniales); however, in Francoaceae we also include Bersamaceae, Ledocarpaceae, Rhynchothecaceae and Vivianiaceae. Other changes to family limits are not drastic or numerous and are mostly focused on some members of the lamiids, especially the former Icacinaceae that have long been problematic with several genera moved to the formerly monogeneric Metteniusaceae, but minor changes in circumscription include Aristolochiaceae (now including Lactoridaceae and Hydnoraceae; Aristolochiales), Maundiaceae (removed from Juncaginaceae; Alismatales), Restionaceae (now re-including Anarthriaceae and Centrolepidaceae; Poales), Buxaceae (now including Haptanthaceae; Buxales), Peraceae (split from Euphorbiaceae; Malpighiales), recognition of Petenaeaceae (Huerteales), Kewaceae, Limeaceae, Macarthuriaceae and Microteaceae (all Caryophyllales), Petiveriaceae split from Phytolaccaceae (Caryophyllales), changes to the generic composition of Ixonanthaceae and Irvingiaceae (with transfer of Allantospermum from the former to the latter; Malpighiales), transfer of Pakaraimaea (formerly Dipterocarpaceae) to Cistaceae (Malvales), transfer of Borthwickia, Forchhammeria, Stixis and Tirania (formerly all Capparaceae) to Resedaceae (Brassicales), Nyssaceae split from Cornaceae (Cornales), Pteleocarpa moved to Gelsemiaceae (Gentianales), changes to the generic composition of Gesneriaceae ( Sanango moved from Loganiaceae) and Orobanchaceae (now including Lindenbergiaceae and Rehmanniaceae) and recognition of Mazaceae distinct from Phrymaceae (all Lamiales). [ABSTRACT FROM AUTHOR]

PREMISE OF THE STUDY: Coflowering plants often share pollinators and may receive mixed species pollen loads. Although detrimental effects of heterospecific pollen receipt have been documented, trait-based modifiers of interactions on the stigma remain largely unknown. Chemicals that mediate interactions between sporophytes could also influence pollen-pollen or pollen-style interactions. We test for the first time whether nickel (Ni) accumulation in pollen can lead to "elemental allelopathy" and intensify the fitness consequences of heterospecific pollen receipt. METHODS: We grew Ni-hyperaccumulator Streptanthus polygaloides in soils augmented with three concentrations of Ni, measured pollen Ni concentration, and hand-pollinated non-Ni hyperaccumulator Mimulus guttatus. We assayed pollen germination, tube gro th and seeds of M. guttatus after pure and mixed species pollinations. KEY RESULTS: Streptanthus polygaloides pollen accumulated Ni in proportion to soil availability and at levels significantly greater than M. guttatus pollen. Altho ug h receipt of 5. polygaloides pollen increased M. guttatus pollen germination, it decreased the proportion of pollen tubes reaching the ovary and seed number. Increased Ni in pollen, however, did not significantly intensify the e ffect of S. polygaloides pollen receipt on M. guttatus seed production. CONCLUSIONS: Different levels of Ni in the pollen of S. polygaloides achieved in the greenhouse did not significantly reduce the fitness of M. guttatus. Stigma tolerance to Ni may also have contributed to the lack of response to increased Ni in heterospecific pollen. This study paves the way for additional tests in other metal hyperaccumulators and recipients, and to identify mechanisms of interactions on the stigma. [ABSTRACT FROM AUTHOR]

* Premise of the study: Ultraviolet (UV) floral patterns are common in angiosperms and mediate pollinator attraction, efficiency, and constancy. UV patterns may vary within species, yet are cryptic to human observers. Thus, few studies have explicitly described the distribution or ecological significance of intraspecific variation in UV floral patterning. Here, we describe the geographic distribution and pattern of inheritance of a UV polymorphism in the model plant species Mimulus guttatus (Phrymaceae). We then test whether naturally occurring UV phenotypes influence pollinator interactions within M. guttatus. * Methods: We document UV patterns in 18 annual and 19 perennial populations and test whether UV pattern is associated with life history. To examine the pattern of inheritance, we conducted crosses within and between UV phenotypes. Finally, we tested whether bee pollinators discriminate among naturally occurring UV phenotypes in two settings: wild bee communities and captive Bombus impatiens. * Key results: Within M. guttatus, perennial populations exhibit a small bulls-eye pattern, whereas a bilaterally symmetric runway pattern occurs mainly in annual populations. Inheritance of UV patterning is consistent with a single-locus Mendelian model in which the runway phenotype is dominant. Bee pollinators discriminate against unfamiliar UV patterns in both natural and controlled settings. * Conclusions: We describe a widespread UV polymorphism associated with life history divergence within Mimulus guttatus. UV pattern influences pollinator visitation and should be considered when estimating reproductive barriers between life history ecotypes. This work develops a new system to investigate the ecology and evolution of UV floral patterning in a species with extensive genomic resources. [ABSTRACT FROM AUTHOR]

Premise of study: Botanists have long been interested in the reasons for genetic variation among individuals, populations, and species of plants. The anthocyanin pathway is ideal for studying the evolution of such phenotypic variation. Methods: We used a combination of quantitative trait loci mapping and association studies to understand the genetic basis of variation in five anthocyanin phenotypes including calyx, corolla, and leaf coloration patterns that vary within and among populations of Mimulus guttatus. We then examined what genes might be responsible for this phenotypic variation and whether one of the traits, calyx spotting, is randomly distributed across the geographic range of the species. Key results: All five phenotypes in M. guttatus were primarily controlled by the same major locus (PLA/), which contains a tandem array of three R2R3-MYB genes known to be involved in the evolution of flower color in a related species of Mimulus. Calyx spotting was nonrandomly distributed across the range of M. guttatus and correlated with multiple climate variables. Conclusions: The results of this study suggest that variation in R2R3-MYB genes is the primary cause of potentially important anthocyanin phenotypic variation within and among populations of M. guttatus, a finding consistent with recent theoretical and empirical research on flower color evolution. [ABSTRACT FROM AUTHOR]

Context: Methanol extracts obtained from eight species belonging to four families of the Lamiales order native to Mexico were investigated for biological action. Objective: Cytotoxicity and antioxidant activity of methanol extracts have been investigated. Materials and methods: Cytotoxic activity was evaluated by the sulphorhodamine B protein staining assay against KB (nasopharyngeal), HEp-2 (larynx), HF-6 (colon), MCF7 (breast), PC-3 (prostate), and Ca Ski (cervix) carcinoma cell lines. To analyze the antioxidant activity, common stable radicals chromogens, 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid (ABTS·++) and DPPH (1,1-diphenyl-2-picrylhydrazyl) were used. The ferric reducing antioxidant power (FRAP) and the total phenolic content of the samples were also determined. Results: Some of the extracts, such as Limosella aquatica L. (Scrophulariaceae), Mimulus glabratus Kunth. (Phrymaceae), Pedicularis mexicana Zucc. ex Benth. (Orobanchaceae), and Penstemon campanulatus (Cav.) Willd. (Plantaginaceae) displayed remarkably selective cytotoxic activity. However, the extract from Veronica americana (Raf.) Schwein (Plantaginaceae) showed the highest activity with IC50 values of 1.46 and 0.169 μg/mL on PC-3 and HF-6 cells, respectively. With the exception of M. glabratus, all the extracts showed different degrees of antioxidant activity with IC50 values from 0.89 up to 1.8 in the ABTS assay; from 0.49 up to 1.25 mg/mL in the DPPH assay and with the FRAP evaluation, 36 to 68 equivalents in mM of FeSO4. V. americana also showed the highest antoxidant activity with IC50 values from 0.491 and 0.892 mg/mL, on DPPH and ABTS assays, respectively. Discussion and conclusion: These findings demonstrated that the species studied have great potential cytotoxic and antioxidant activity. [ABSTRACT FROM AUTHOR]

Mimulus minimus is described and illustrated as a new species based on plants collected in the northeastern mountains of Michoacan state, Mexico. It grows in wet sites in the Pinus-Quercus-Cupressus forest. The new species is included in the section Simiolus Greene (subgenus Synplacus Grant). Its similarities and differences with morphologically more closely related species such as Mimulus calciphilus Gentry, M. depressus Phil., M. glabratus Kunth, M. minutiflorus Vickery, M. Wiensii Vickery and M. yecorensis Vickeri and M. guttatus DC. are discussed. [ABSTRACT FROM AUTHOR]

Movement of pollinators between coflowering plant species may influence conspecific pollen deposition and seed set. Interspecific pollinator movements between native and showy invasive plants may be particularly detrimental to the pollination and reproductive success of native species. We explored the effects of invasive Lythrum salicaria on the reproductive success of Mi,nulus ringens, a wetland plant native to eastern North America. Pollinator flights between these species significantly reduced the amount of conspecific pollen deposited on Mi,nulus stigmas and the number of seeds in Mi,nulus fruits, suggesting that pollen loss is an important mechanism of competition for pollination. Although pollen loss is often attributed to pollen wastage on heterospecific floral structures, our novel findings suggest that grooming by bees as they forage on a competitor may also significantly reduce outcross pollen export and seed set in Mimulus ringens. [ABSTRACT FROM AUTHOR]

Mimulus verbenaceus has successfully invaded and/or competed for the very specialized habitats of desert seeps and springs characterized by scarce or no pollinators (personal observation). It has done so by evolving an ingenious mechanism of reproductive assurance in which the senescing epipetalous corolla bends down, abscisses and slides down its style dragging its anthers over the stigma lobes, resulting in self-pollination. This dragging mechanism both depends on the plants ability to self-pollinate and presumably promotes the evolution of self-pollination by providing an advantage—invasion of new habitats—to counter-balance the disadvantages of selfing. M. verbenaceus has evolved a second means of reproductive assurance that depends on the nearness of the anthers to the stigma lobes. They are close, even touching, in the red flowers, leading to much self-pollination and are well separated in the yellow flowers leading to little self-pollination. This advantage of the red-flowered plants likely explains the relative abundance of the red morph and the rarity of the yellow morph in nature as well as the greater seed set of the red-flowered morph than that of the yellow-flowered morph. [ABSTRACT FROM AUTHOR]

Speciation often involves the evolution of numerous prezygotic and postzygotic isolating barriers between divergent populations. Detailed knowledge of the strength and nature of those barriers provides insight into ecological and genetic factors that directly or indirectly influenced their origin, and may help predict whether they will be maintained in the face of sympatric hybridization and introgression. We estimated the magnitude of pre- and postzygotic barriers between naturally occurring sympatric populations of Mimulus guttatus and M. nasutus. Prezygotic barriers, including divergent flowering phenologies, differential pollen production, mating system isolation, and conspecific pollen precedence, act asymmetrically to completely prevent the formation of F1 hybrids among seeds produced by M. guttatus (F1g), and reduce F1 hybrid production among seeds produced by M. nasutus (F1n) to only about 1%. Postzygotic isolation is also asymmetric: in field experiments, F1g but not F1n hybrids had significantly reduced germination rates and survivorship compared to parental species. Both hybrid classes had flower, pollen, and seed production values within the range of parental values. Despite the moderate degree of F1g hybrid inviability, postzygotic isolation contributes very little to the total isolation between these species in the wild. We also found that F1 hybrid flowering phenology overlapped more with M. guttatus than M. nasutus. These results, taken together, suggest greater potential for introgression from Mo nasutus to M. guttatus than for the reverse direction. We also address problems with commonly used indices of isolation, discuss difficulties in calculating meaningful measures of reproductive isolation when barriers are asymmetric, and propose novel measures of prezygotic isolation that are consistent with postzygotic measures. [ABSTRACT FROM AUTHOR]

Thermonasty-like responses were observed on some main stems of Phryma leptostachya (Phrymaceae) plants cultivated in the open. To confirm the thermonastic nature of these responses, the plants were moved into an artificially illuminated chamber and observed under controlled conditions. At low temperatures (about 12°C) and in the dark, slanted terrestrial young main stems of P. leptostachya became prostrate. At higher temperatures (about 25°C) and in the dark, the prostrate stems became slanted. Their movement was confirmed under controlled conditions and is therefore considered to be thermonastic in nature. [ABSTRACT FROM AUTHOR]

This study examines molecular and morphological differentiation in Phryma L., which has only one species with a well-known classic intercontinental disjunct distribution between eastern Asia (EA) and eastern North America (ENA). Phylogenetic analysis of nuclear ribosomal ITS and chloroplast rps16 and trnL-F sequences revealed two highly distinct clades corresponding to EA and ENA. The divergence time between th! intercontinental populations was estimated to be 3.68 ± 2.25 to 5.23 ± 1.37 million years ago (mya) based on combined chloroplast data using Bayesian and penalized likelihood methods. Phylogeographic and dispersal-vicariance (DIVA) analysis suggest a North American origin of Phryma and its migration into EA via the Bering land bridge. Multivariate analysis based on 23 quantitative morphological characters detected no geographic groups at the intercontinental level. The intercontinental populations of Phryma thus show distinct molecular divergence with little morphological differentiation. The discordance of the molecular and morphological patterns may be explained by morphological stasis due to ecological similarity in both continents. The divergence of Phryma from its close relatives in the Phrymaceae was estimated to be at least 32.32 ± 4.46 to 4!.35 ± 3.18 mya. [ABSTRACT FROM AUTHOR]

The timing and effectiveness of pollinator visitation to flowers is an Important factor influencing mating patterns and reproductive success. Multiple pollinator probes to a flower may increase both the quantity and genetic diversity of progeny, especially if single probes deposit insufficient pollen for maximal seed set or if the interval between probes is brief. When pollen carryover is limited, sequential pollen loads may also differ markedly in sire representation. We hypothesized that these conditions help explain high levels of multiple paternity in Mimulus ringens fruits. We documented all bee visits to individual flowers, quantified resulting seed set, and determined paternity for 20 seeds per fruit. Most (76%) flowers received multiple probes, and the interval between probes was usually <30 mm. Flowers probed multiple times produced 44% more seeds than flowers probed once. All fruits were multiply sired. Flowers receiving a single probe averaged 3.12 outcross sires per fruit, indicating that single probes deposit pollen from several donors. Multiple paternity was even greater after three or more probes (4.92 outcross sires), demonstrating that sequential visits bring pollen from donors not represented in the initial probe. [ABSTRACT FROM AUTHOR]

Field surveys in eastern North America confirm the naturalization of Glossostigma plants at 19 localities in four states: Connecticut, New Jersey, Pennsylvania, and Rhode Island. DNA sequence analysis of individuals from 14 sampled populations identifies these nonindigenous plants as Glossostigma cleistanthum, a species native to Australia and New Zealand. These results correct prior misidentifications of North American plants as G. diandrum. The earliest North American record of G. cleistanthum (1992) is from a Ramsar tidal wetland in Connecticut. Morphological analyses demonstrate that G. cleistanthum differs from G. diandrum by its longer leaves and ability to produce both cleistogamous and chasmogamous flowers in response to ecological conditions. Glossostigma cleistanthum has a high reproductive potential and spreads rapidly within and between both artificial and natural habitats. A survey of more than 100 lakes indicated that G. cleistanthum occurs most often in waters with high clarity and low pH, alkalinity, conductivity, and phosphorous. Because of its affinity for oligotrophic conditions, this species is a particular threat to pristine natural aquatic communities, which often contain imperiled plants. [ABSTRACT FROM AUTHOR]

Most models of mating system evolution predict mixed mating to be unstable, although it is commonly reported from nature. Ecological interactions with mutualistic pollinators can help account for this discrepancy, but antagonists such as herbivores are also likely to play a role. In addition, inbreeding can alter ecological interactions and directly affect selfing rates, which may also contribute to maintaining mating system variation. We explored herbivore and inbreeding effects on pollinator behavior and selfing rates in Mimulus guttatus. First, individual spittlebug (Philaenus spumarius) herbivores were applied to native plants in two populations. Spittlebugs reduced flower size, increased anther-stigma distance, and increased selfing rates. A second experiment factorially crossed spittlebug treatment with inbreeding history (self- vs. cross-fertilized), using potted plants in arrays. Spittlebugs did not affect pollinator behavior, but they reduced flower size and nearly doubled the selfing rate. Inbreeding reduced the frequency of pollinator visits and increased flower-handling time, and this may be the first report that inbreeding affects pollinator behavior. Selfing rates of inbred plants were reduced by one hall which may reflect early inbreeding depression or altered pollinator behavior. The contrasting effects of herbivory and inbreeding on selfing rates may help maintain mating system variation in M. guttatus. [ABSTRACT FROM AUTHOR]

A well-supported phylogeny is presented from both chloroplast DNA (the trnL/F region) and two regions of nuclear rDNA (ITS [internal transcribed spacer] and ETS [external transcribed spacer]) with nearly complete sampling for Mimulus (Phrymaceae) in western North America. Three separate genera are derived from within the clade that contains all the Mimulus species in western North America. The taxonomic status of the proposed sections of Mimulus and the relationships of many taxonomically difficult species are considered with observations on morphological evolution. Discordance between data sources provides support for the hypothesis that M. evanescens is a hybrid between M. latidens and M. breviflorus. In two major clades (Eunanus and Diplacus), patterns of genetic variation do not match the current taxonomy. The clustering of taxa in Eunanus is strongly associated with geographic distributions. Mimulus aurantiacus sensu Thompson, M. nanus, and M. floribundus are found to be progenitor species to other species that appear to be derived from within them. Polyploidy and aneuploidy events are clustered near the tips of the phylogeny. Thus, these two mechanisms are concluded to have played a relatively small role in the evolution of persistent lineages in Mimulus. The phylogenetic distribution of rare taxa is also examined. [ABSTRACT FROM AUTHOR]