Search

Polyploidy is a significant component in the evolution of many taxa, particularly plant groups. However, new polyploids face substantial fitness disadvantages due to a lack of same‐cytotype mates, and the factors promoting or preventing polyploid establishment in natural populations are often unclear. We develop spatially explicit agent‐based simulation models to test the hypothesis that a perennial life history and clonal propagation facilitate the early stages of polyploid establishment and persistence. Our models show that polyploids are more likely to establish when they have longer life spans than diploids, especially when self‐fertilization rates are high. Polyploids that combine sexual and clonal reproduction can establish across a wide range of life histories, but their success is moderated by clonal strategy. By tracking individuals and mating events, we reveal that clonal architecture has a substantial impact on the spatial structure of the mixed diploid‐polyploid population during polyploid establishment: altering patterns of mating within or between cytotypes via geitonogamous self‐fertilization, the mechanisms through which polyploid establishment proceeds, and the final composition of the polyploid population. Overall, our findings provide novel insight into the role of clonal structure in modulating the complex relationship between polyploidy, perenniality, and clonality and offer testable predictions for future empirical work. [ABSTRACT FROM AUTHOR]

In hermaphrodites, the allocation of resources to each sex function can influence fitness through mating success. A prediction that arises from sex allocation theory is that in wind‐pollinated plants, male fitness should increase linearly with investment of resources into male function but there have been few empirical tests of this prediction. In a field experiment, we experimentally manipulated allocation to male function in Ambrosia artemisiifolia (common ragweed) and measured mating success in contrasting phenotypes using genetic markers. We investigated the effects of morphological traits and flowering phenology on male siring success, and on the diversity of mates. Our results provide evidence for a linear relation between allocation to male function, mating, and fitness. We find earlier onset of male flowering time increases reproductive success, whereas later flowering increases the probability of mating with diverse individuals. Our study is among the first empirical tests of the prediction of linear male fitness returns in wind‐pollinated plants and emphasizes the importance of a large investment into male function by wind‐pollinated plants and mating consequences of temporal variation in sex allocation. [ABSTRACT FROM AUTHOR]

Species range limits often reflect niche limits, especially for ranges constrained along elevational gradients. In this study, we used elevational transplant experiments to test niche breadth and functional trait plasticity in early life stages of narrow-range Nabalus boottii and broad-range N. trifoliolatus plants to assess their climate change vulnerability and the applicability of the niche breadth-range size hypothesis to explain their range size differences. We discovered that the earliest life stage (seed germination) was the most vulnerable and the two alpine taxa, N. boottii and N. trifoliolatus var. nanus, were unable to establish at the warm low elevation site, however non-alpine N. trifoliolatus established at all three elevations, including at the high elevation (beyond-range) site. Niche limits in seed emergence may therefore contribute to range size in these taxa. In contrast, when seedlings were planted we found substantial functional trait plasticity in later life stages (average 44% across ten traits) that was highly similar for all Nabalus taxa, suggesting that differences in plasticity do not generate niche differences or restrict range size in the focal taxa. While this substantial plasticity may help buffer populations faced by climate change, the inability of the alpine taxa to establish at lower elevation sites suggests that their populations may still decline due to decreased seed recruitment under ongoing climate change. We therefore recommend monitoring alpine Nabalus populations, particularly globally rare N. boottii. [ABSTRACT FROM AUTHOR]

Imperfect historical records and complex demographic histories present challenges for reconstructing the history of biological invasions. Here, we combine historical records, extensive worldwide and genome-wide sampling, and demographic analyses to investigate the global invasion of Mimulus guttatus from North America to Europe and the Southwest Pacific. By sampling 521 plants from 158 native and introduced populations genotyped at >44,000 loci, we determined that invasive M. guttatus was first likely introduced to the British Isles from the Aleutian Islands (Alaska), followed by admixture from multiple parts of the native range. We hypothesise that populations in the British Isles then served as a bridgehead for vanguard invasions worldwide. Our results emphasise the highly admixed nature of introduced M. guttatus and demonstrate the potential of introduced populations to serve as sources of secondary admixture, producing novel hybrids. Unravelling the history of biological invasions provides a starting point to understand how invasive populations adapt to novel environments. Vallejo-Marín et al. combine historical records, extensive worldwide and genome-wide sampling, and demographic analyses to investigate the global invasion of Mimulus guttatus from North America to Europe and the Southwest Pacific. They found that M. guttatus was first likely introduced to the British Isles from the Aleutian Islands (Alaska), followed by admixture from multiple parts of the native range, and hypothesise that populations in the British Isles then served as a bridgehead for vanguard invasions worldwide. [ABSTRACT FROM AUTHOR]

Flowering plants exhibit two principal life-history strategies: annuality (living and reproducing in one year) and perenniality (living more than one year). The advantages of either strategy depend on the relative benefits of immediate reproduction balanced against survivorship and future reproduction. This trade-off means that life-history strategies are associated with particular environments, with annuals being found more often in unpredictable habitats. Annuality and perenniality are the outcome of developmental genetic programs responding to their environment, with perennials being distinguished by their delayed competence to flower and reversion to growth after flowering. Evolutionary transitions between these strategies are frequent and have consequences for mating systems and genome evolution, with perennials being more likely to outcross with higher inbreeding depression and lower rates of molecular evolution. Integrating expectations from life-history theory with knowledge of the developmental genetics of flowering and seasonality is required to understand the mechanisms involved in the evolution of annual and perennial life histories. [ABSTRACT FROM AUTHOR]

Summary: Environmental variation affects a plant's life cycle by influencing the timing of germination and flowering, and the duration of the growing season. Yet we know little information about how environmental heterogeneity generates variation in germination schedules and the consequences for growth and fecundity through genetic and plastic responses.We use an annual population of Mimulus guttatus in which, in nature, seeds germinate in both fall and spring. We investigate whether there is a genetic basis to the timing of germination, the effect of germination timing on fecundity, and if growth and flowering respond plastically to compensate for different season lengths.Using sibling families grown in simulated seasonal conditions, we find that families do not differ in their propensity to germinate between seasons. However, the germination season affects subsequent growth and flowering time, with significant genotype‐by‐environment interactions (G × E). Most G × E is due to unequal variance between seasons, because the spring cohort harbours little genetic variance. Despite their different season lengths, the cohorts do not differ in flower number (fecundity).Heterogeneous environments with unpredictable risks may maintain promiscuous germination, which then affects flowering time. Therefore, if selection at particular life stages changes with climate change, there may be consequences for the entire life cycle. [ABSTRACT FROM AUTHOR]

Premise of the Study: The timing of major phenological transitions is critical to lifetime fitness, and life history theory predicts differences for annual and perennial plants. To correctly time these transitions, many plants rely on environmental cues such as exposure to extended periods of cold, which may occur at different stages throughout their lifetime. Methods: We studied the role of cold at different life stages, by jointly exposing seed (stratification) and rosettes (vernalization) to cold. We used 23 populations of Mimulus guttatus, which vary from annuals to perennials, and investigated how cold at one or both stages affected germination, flowering, growth, and biomass. Key Results: We found that stratification and vernalization interact to affect life cycle transitions, and that cold at either stage could synchronize flowering phenology. For perennials, either stratification or vernalization is necessary for maximum flowering. We also found that germination timing covaried with later traits. Moreover, plants from environments with dissimilar climates displayed different phenological responses to stratification or vernalization. Conclusions: In general, cold is more important for seed germination in annuals and plants from environments with warm temperatures and variable precipitation. In contrast, cold is more important for flowering in perennials: it accelerates flowering in plants from lower precipitation environments, and it increases flowering proportion in plants from cooler, more stable precipitation environments. We discuss our findings in the context of the variable environments plants experience within a population and the variation encountered across the biogeographic native range of the species. [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]

Organisms exhibit an incredible diversity of life history strategies as adaptive responses to environmental variation. The establishment of novel life history strategies involves multilocus polymorphisms, which will be challenging to establish in the face of gene flow and recombination. Theory predicts that adaptive allelic combinations may be maintained and spread if they occur in genomic regions of reduced recombination, such as chromosomal inversion polymorphisms, yet empirical support for this prediction is lacking. Here, we use genomic data to investigate the evolution of divergent adaptive ecotypes of the yellow monkey flower Mimulus guttatus. We show that a large chromosomal inversion polymorphism is the major region of divergence between geographically widespread annual and perennial ecotypes. In contrast, ∼40,000 single nucleotide polymorphisms in collinear regions of the genome show no signal of life history, revealing genomic patterns of diversity have been shaped by localized homogenizing gene flow and large-scale Pleistocene range expansion. Our results provide evidence for an inversion capturing and protecting loci involved in local adaptation, while also explaining how adaptive divergence can occur with gene flow. [ABSTRACT FROM AUTHOR]

Premise: Variation in seed traits is common within and among populations of plant species and often has ecological and evolutionary implications. However, due to the time‐consuming nature of manual seed measurements and the level of variability in imaging techniques, quantifying and interpreting the extent of seed variation can be challenging. Methods: We developed a standardized high‐throughput technique to measure seed number, as well as individual seed area and color, using a derived empirical scale to constrain area in Arabidopsis thaliana, Brassica rapa, and Mimulus guttatus. We develop a specific rational model using seed area measured at various spatial scales relative to the pixel count, observing the asymptotic value of the seed area as the modeled number of pixels approaches infinity. Results: We found that our model has high reliability in estimating seed traits and efficiently processes large numbers of images, facilitating the quantification of seed traits in studies with large sample sizes. Discussion: This technique facilitates consistency between imaging sessions and standardizes the measurement of seed traits. These novel advances allow researchers to directly and reliably measure seed traits, which will enable tests of the ecological and evolutionary causes of their variation. [ABSTRACT FROM AUTHOR]

The diversity of life history strategies within the angiosperms illustrates the evolutionary flexibility of reproductive characteristics. The number of times an individual reproduces is a key life history trait, and transitions from iteroparous perennials to semelparous annuals have occurred frequently in the flowering plants. Despite the frequency of this evolutionary transition, and the importance of annuality versus perenniality to both agriculture and ecology, understanding the molecular and genetic mechanisms involved in perennial flowering is in their infancy. In this issue of Molecular Ecology, Kiefer et al. () make significant progress towards understanding divergence in seasonal flowering between annual and perennial species in the Arabideae tribe of Brassicaceae. By combining a comparative approach with gene expression and sequence comparisons, they show that transcriptional differences in FLC orthologs, a floral inhibitor in Arabidopsis thaliana, have occurred repeatedly and underlie differences in flowering between annuals and perennials. [ABSTRACT FROM AUTHOR]

Differential natural selection acting on populations in contrasting environments often results in adaptive divergence in multivariate phenotypes. Multivariate trait divergence across populations could be caused by selection on pleiotropic alleles or through many independent loci with trait-specific effects. Here, we assess patterns of association between a suite of traits contributing to life history divergence in the common monkey flower, Mimulus guttatus, and examine the genetic architecture underlying these correlations. A common garden survey of 74 populations representing annual and perennial strategies from across the native range revealed strong correlations between vegetative and reproductive traits. To determine whether these multitrait patterns arise from pleiotropic or independent loci, we mapped QTLs using an approach combining high-throughput sequencing with bulk segregant analysis on a cross between populations with divergent life histories. We find extensive pleiotropy for QTLs related to flowering time and stolon production, a key feature of the perennial strategy. Candidate genes related to axillary meristem development colocalize with the QTLs in a manner consistent with either pleiotropic or independent QTL effects. Further, these results are analogous to previous work showing pleiotropy-mediated genetic correlations within a single population of M. guttatus experiencing heterogeneous selection. Our findings of strong multivariate trait associations and pleiotropic QTLs suggest that patterns of genetic variation may determine the trajectory of adaptive divergence. [ABSTRACT FROM AUTHOR]

Understanding the genetic basis of complex quantitative traits is a central problem in evolutionary biology, particularly for traits that may lead to adaptations in natural populations. The annual and perennial ecotypes of Mimulus guttatus provide an excellent experimental system for characterizing the genetic components of population divergence. The 2 life history ecotypes coexist throughout the geographic range. Focusing on population differences in life history traits, I examined the strength and direction of pairwise epistatic interactions between 2 target chromosomal regions (DIV1 and DIV2) when singly and cointrogressed into the alternate population’s genetic background. I measured a suite of flowering and vegetative traits related to life history divergence in 804 plants from 18 reciprocal near-isogenic lines. I detected pleiotropic main effects for the DIV1 QTL in both genetic backgrounds and weaker main effects of the DIV2 QTL, primarily in the perennial background. Many of the traits showed epistatic interactions between alleles at the DIV1 and DIV2 QTL. Finally, for many traits, the magnitude of effect size was greater in the perennial background. I evaluate these results in the context of their potential role in population divergence in M. guttatus and adaptive evolution in natural populations. [ABSTRACT FROM PUBLISHER]

Species with extensive ranges experience highly variable environments with respect to temperature, light and soil moisture. Synchronizing the transition from vegetative to floral growth is important to employ favorable conditions for reproduction. Optimal timing of this transition might be different for semelparous annual plants and iteroparous perennial plants., We studied variation in the critical photoperiod necessary for floral induction and the requirement for a period of cold-chilling (vernalization) in 46 populations of annuals and perennials in the Mimulus guttatus species complex. We then examined critical photoperiod and vernalization QTLs in growth chambers using F2 progeny from annual and perennial parents that differed in their requirements for flowering., We identify extensive variation in critical photoperiod, with most annual populations requiring substantially shorter day lengths to initiate flowering than perennial populations. We discover a novel type of vernalization requirement in perennial populations that is contingent on plants experiencing short days first. QTL analyses identify two large-effect QTLs which influence critical photoperiod. In two separate vernalization experiments we discover each set of crosses contain different large-effect QTLs for vernalization., Mimulus guttatus harbors extensive variation in critical photoperiod and vernalization that may be a consequence of local adaptation. [ABSTRACT FROM AUTHOR]

Sex allocation in hermaphrodites can be affected by spatial and temporal variation in resources, especially in plants where size dependent gender modification is commonplace. The evolution of sex allocation will depend on the relative importance of genetic and environmental factors governing patterns of investment in female and male function. In wind-pollinated plants, theoretical models predict a positive relation between size and male investment because of the fitness advantages associated with more effective pollen dispersal. Theory also predicts that the timing and allocation to each sex function should depend on available resources. We grew maternal half-sibling families of annual, wind-pollinated, Ambrosia artemisiifolia in sun and shade treatments to investigate these predictions. There was significant genetic variation for female and male flower production in both sun and shade treatments. Size-dependent sex allocation occurred in the direction predicted by theory, with male flower production increasing more rapidly in larger plants. The timing of sex function also varied, with significant genetic variation for dichogamy within environments and plasticity of this trait between environments. Protandry was expressed more commonly in the sun and protogyny in the shade. The occurrence of dynamic sex allocation with changing size and experimental treatment indicates the potential for adaptive responses under different ecological conditions. [ABSTRACT FROM AUTHOR]

In angiosperms, ovules are "packaged" within individual flowers, and an optimal strategy should occur depending on pollination and resource conditions. In animal-pollinated species, wide variation in ovule number per flower occurs, and this contrasts with wind-pollinated plants, where most species possess uniovulate flowers. This pattern is usually explained as an adaptive response to low pollen receipt in wind-pollinated species. Here, we develop a phenotypic model for the evolution of ovule number per flower that incorporates the aerodynamics of pollen capture and a fixed resource pool for provisioning of flowers, ovules, and seeds. Our results challenge the prevailing explanation for the association between uniovulate flowers and wind pollination. We demonstrate that when flowers are small and inexpensive, as they are in wind-pollinated species, ovule number should be minimized and lower than the average number of pollen tubes per style, even under stochastic pollination and fertilization regimes. The model predicts that plants benefit from producing many small inexpensive flowers, even though some flowers capture too few pollen grains to fertilize their ovules. Wind-pollinated plants with numerous flowers distributed through- out the inflorescence, each with a single ovule or a few ovules, sample more of the airstream, and this should maximize pollen capture and seed production. [ABSTRACT FROM AUTHOR]

Background: The rich literature that characterizes the field of pollination biology has focused largely on animal-pollinated plants. At least 10 % of angiosperms are wind pollinated, and this mode of pollination has evolved on multiple occasions among unrelated lineages, and hence this discrepancy in research interest is surprising. Here, the evolution and functional ecology of pollination and mating in wind-pollinated plants are discussed, a theoretical framework for modelling the selection of wind pollination is outlined, and pollen capture and the occurrence of pollen limitation in diverse wind-pollinated herbs are investigated experimentally. [ABSTRACT FROM PUBLISHER]

• Monoecy and protogyny are widespread in wind-pollinated plants and have been interpreted as outcrossing mechanisms, though few studies have investigated their function. Carex, a large genus of anemophilous herbs, is predominantly monoecious and many species are protogynous. We investigated whether monoecy and protogyny limit self-pollination in seven Carex species. • We conducted field experiments comparing stigmatic pollen loads and seed set between intact and emasculated stems. We tested for self-compatibility and evaluated pollen limitation of seed set by supplemental pollination. Finally, we measured outcrossing rates in open-pollinated and emasculated stems using allozyme markers. • Emasculated stems captured significantly less pollen than open-pollinated stems and set less seed. Pollen deposition during the female-only phase for intact stems was only 12% of the total captured. Outcrossing rates for three species indicated high selfing (range t = 0.03–0.39). Allozyme loci in the remaining species were monomorphic also suggesting high selfing. These results demonstrate that neither monoecy nor protogyny is particularly effective at limiting self-fertilization. • Selection for the avoidance of selfing is unlikely to maintain monoecy in many Carex species although protogyny may provide limited opportunities for outcrossing. We propose that geitonogamy in self-compatible wind-pollinated species with unisexual flowers may be widespread and provides reproductive assurance. [ABSTRACT FROM AUTHOR]

The proximity of mates can influence mating opportunities and the quantity and quality of offspring, especially in dioecious plant species. Progeny sex ratios modulated by environmental conditions is one of the most radical ways in which offspring quality may be influenced, yet it has rarely been reported in plants. A mechanism proposed to influence progeny sex ratios in dioecious plants involves competition between female- and male-determining microgametophytes (certation) as a result of variation in pollination intensity. However, the role of selective fertilization in dioecious plants is controversial and has not been demonstrated under field conditions. Here we investigate whether natural variation in the spatial arrangement of females and males influences pollination intensity and progeny sex ratios in the wind-pollinated herb Rumex nivalis. Based on previous experimental manipulation of pollination intensity in this species, we predicted that maternal parents in close proximity to males would produce more strongly female-biased progeny sex ratios. We tested this prediction in six alpine populations in Switzerland by measuring the distance between focal females and neighboring males and assessing pollen loads and seed sex ratios of maternal parents. In four of the six populations, females positioned in close proximity to males captured more pollen and exhibited more female-biased sex ratios. Our results demonstrate that demographic aspects of the maternal mating environment can influence progeny sex ratios. The most probable explanation for biased primary sex ratios in Rumex is selective fertilization resulting from pollen tube competition. [ABSTRACT FROM AUTHOR]

Wind pollination is predominantly a derived condition in angiosperms and is thought to evolve in response to ecological conditions that render animal pollination less advantageous. However, the specific ecological and evolutionary mechanisms responsible for transitions from animal to wind pollination are poorly understood in comparison with other major reproductive transitions in angiosperms, including the evolution of selfing from outcrossing and dioecy from hermaphroditism. To investigate correlations between wind pollination and a range of characters including habitat type, sexual system, floral display size, floral showiness, and ovule number, we used a large-scale molecular phylogeny of the angiosperms and maximum likelihood methods to infer historical patterns of evolution. This approach enabled us to detect correlated evolution and the order of trait acquisition between pollination mode and each of nine characters. Log likelihood ratio tests supported a model of correlated evolution for wind pollination and habitat type, floral sexuality, sexual system, flower size, flower showiness, presence versus absence of nectar, and ovule number. In contrast, wind pollination and geographical distribution and number of flowers per inflorescence evolve independently. We found that in wind-pollinated taxa, nectar is lost more often and ovule number is reduced to one. We also found that wind pollination evolves more frequently in lineages already possessing unisexual flowers and/or unisexual plants. An understanding of the ecological and life-history context in which wind pollination originates is fundamental to further investigation of the microevolutionary forces causing transitions from animal to wind pollination. [ABSTRACT FROM AUTHOR]

The aerodynamics of wind pollination selects for an intimate relation between form and function in anemophilous plants. Inflorescence architecture and floral morphology vary extensively within the Poaceae, but the functional implication of this variation remains largely unknown. Here we quantify associations between floret, culm, and inflorescence characteristics for 25 grass species in Kananaskis, Alberta, Canada, and consider whether different architectures may implement unique mechanisms to aid pollination, The species cluster into four categories defined by all combinations of floret size (small vs. large) and inflorescence architecture (compact vs. diffuse). Species differed significantly for all 18 traits that we measured, with 12 traits differing only between floret-size classes, three differing only between inflorescence types, and three differing among both (independently or by an interaction). Based on these morphological associations, we discuss the aerodynamic and functional consequences of each category for wind pollination. The independence of inflorescence and floral traits has probably allowed exploration of all possible combinations of inflorescence architecture and floret size during the evolution of the Poaceae. [ABSTRACT FROM AUTHOR]

1. Inflorescence architecture and floral morphology vary extensively within the Poaceae, but the functional significance of this variation remains largely unknown. As grasses are wind-pollinated, their inflorescence diversity probably reflects alternate solutions to manipulating airstreams to enhance pollen export and import. We tested this hypothesis with two field experiments that contrasted pollen removal and receipt by compact and diffuse inflorescences.2. In the‘aggregation’ experiment, we tied together panicle branches of two species with diffuse inflorescences, creating more compact inflorescences. Aggregation reduced pollen removal from both species, probably by increasing boundary-layer thickness. The effects of inflorescence aggregation differed between the two species in a manner that is consistent with pollen-size differences, which could affect the ability of pollen grains to pass through the thickened boundary layer around stigmas.3. The‘staking’ experiment constrained inflorescence motion and revealed that culm characteristics contribute to the interaction between grass inflorescences and airstreams. In particular, inflorescence oscillation principally serves pollen removal for species with compact inflorescences, but is of primary importance in pollen receipt for species with diffuse architectures.4. These results suggest that inflorescence architecture interacts with wind in a complex manner to facilitate pollination and supports the hypothesis that the extensive diversity of inflorescence architecture within the Poaceae represents evolutionary solutions to the physical constraints of wind pollination.Functional Ecology(2004)18, 851–860 [ABSTRACT FROM AUTHOR]

Focuses on a study which investigated the consequences of combined versus separate sex function on mating patterns and genetic variation in monoecious and dioecious population of Sagittaria latifolia. Estimates of mating patterns; Discussion on reproductive isolation between monoecious and dioecious populations; Implications for the evolution of dioecy.

The article discusses annual and perennial reproductive strategies in plants. Topics discussed include evolutionary transitions between perenniality and annuality in angiosperms, genetic control of flowering and the need for field experiments to understand evolutionary transitions betweeen strategies and selection in perennial plants.

In this article the author comments on the evolution of animal pollination of the angiosperms. The author mentions that insects play a vital role in collecting pollens and transporting them from one plant to another. Moreover, he adds that pollination provides clear picture of the transition beteen wind pollination and animal pollination.

Reproductive timing is a key life‐history trait that impacts the pool of available mates, the environment experienced during flowering, and the expression of other traits through genetic covariation. Selection on phenology, and its consequences on other life‐history traits, has considerable implications in the context of ongoing climate change and shifting growing seasons. To test this, we grew field‐collected seed from the wildflower Mimulus guttatus in a greenhouse to assess the standing genetic variation for flowering time and covariation with other traits. We then created full‐sib families through phenological assortative mating and grew offspring in three photoperiod treatments representing seasonal variation in daylength. We find substantial quantitative genetic variation for the onset of flowering time, which covaried with vegetative traits. The assortatively‐mated offspring varied in their critical photoperiod by over two hours, so that families differed in their probability of flowering across treatments Allocation to flowering and vegetative growth changed across the daylength treatments, with consistent direction and magnitude of covariation among flowering time and other traits. Our results suggest that future studies of flowering time evolution should consider the joint evolution of correlated traits and shifting seasonal selection to understand how environmental variation influences life histories. Reproductive timing is a key life‐history trait that affects the pool of available mates, the environment experienced during flowering, and the expression of other traits through genetic covariation. We found a broad distribution of heritable variation in flowering time and correlated traits, providing the potential for assortative mating. Next we grew assortatively mated offspring in daylengths representing seasonal variation and found the probability and timing of flowering changed across daylengths, with consistent direction and magnitude of traits correlations. [ABSTRACT FROM AUTHOR]

Color polymorphisms have long been of evolutionary interest for their diverse roles, including mate choice, predator avoidance, and pollinator attraction. While color variation is often under strong selection, some taxa demonstrate unexpectedly high frequencies of presumed deleterious color forms. Here we show that a genetic variant underlying complete loss of anthocyanin pigmentation has risen to an unexpectedly high frequency of 10.2 in a natural population of the plant Mimulus guttatus. Decreased expression of MYB5 transcription factor is associated with unpigmentedmorphs. While the allele was found only in heterozygote adults in the wild, suggesting negative selection, experiments were unable to demonstrate a fitness cost for unpigmented plants, suggesting a cryptic selection pressure in the wild. However, life-history differences among morphs suggests that unpigmented individuals benefit fromlater flowering and clonal growth. Overall, our study highlights the complex interplay of factors maintaining variation in nature, even for genes of major effect. [ABSTRACT FROM AUTHOR]

The timing of reproduction in response to variable environmental conditions is critical to plant fitness, and is a major driver of taxon differentiation. In the yellow monkey flower, Mimulus guttatus, geographically distinct North American populations vary in their photoperiod and chilling (vernalization) requirements for flowering, suggesting strong local adaptation to their surroundings. Previous analyses revealed quantitative trait loci (QTL) underlying short-day mediated vernalization responsiveness using two annual M. guttatus populations that differed in their vernalization response. To narrow down candidate genes responsible for this variation, and to reveal potential downstream genes, we conducted comparative transcriptomics and quantitative PCR (qPCR) in shoot apices of parental vernalization responsive IM62, and unresponsive LMC24 inbred lines grown under different photoperiods and temperatures. Our study identified several metabolic, hormone signaling, photosynthetic, stress response, and flowering time genes that are differentially expressed between treatments, suggesting a role for their protein products in short-day-mediated vernalization responsiveness. Only a small subset of these genes intersected with candidate genes from the previous QTL study, and, of the main candidates tested with qPCR under nonpermissive conditions, only SHORT VEGETATIVE PHASE (SVP) gene expression met predictions for a population-specific short-day-repressor of flowering that is repressed by cold. [ABSTRACT FROM AUTHOR]

Evolutionary biology is in an exciting era, in which powerful genomic tools make the answers accessible to long-standing questions about variation, adaptation and speciation. The availability of a suite of genomic resources, a shared knowledge base and a long history of study have made the phenotypically diverse plant genus Mimulus an important system for understanding ecological and evolutionary processes. An international Mimulus Research Meeting was held at Duke University in June 2014 to discuss developments in ecological and evolutionary genetic studies in Mimulus. Here, we report major recent discoveries presented at the meeting that use genomic approaches to advance our understanding of three major themes: the parallel genetic basis of adaptation; the ecological genomics of speciation; and the evolutionary significance of structural genetic variation. We also suggest future research directions for studies of Mimulus and highlight challenges faced when developing new ecological and evolutionary model systems. [ABSTRACT FROM AUTHOR]