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Deleterious genetic variation is abundant in wild populations, and understanding the ecological and conservation implications of such variation is an area of active research. Genomic methods are increasingly used to quantify the impacts of deleterious variation in natural populations; however, these approaches remain limited by an inability to accurately predict the selective and dominance effects of mutations. Computational simulations of deleterious variation offer a complementary tool that can help overcome these limitations, although such approaches have yet to be widely employed. In this perspective article, we aim to encourage ecological and conservation genomics researchers to adopt greater use of computational simulations to aid in deepening our understanding of deleterious variation in natural populations. We first provide an overview of the components of a simulation of deleterious variation, describing the key parameters involved in such models. Next, we discuss several approaches for validating simulation models. Finally, we compare and validate several recently proposed deleterious mutation models, demonstrating that models based on estimates of selection parameters from experimental systems are biased toward highly deleterious mutations. We describe a new model that is supported by multiple orthogonal lines of evidence and provide example scripts for implementing this model (https://github.com/ckyriazis/simulations_review). [ABSTRACT FROM AUTHOR]

Premise of research. Inbreeding depression is well known to contribute to the maintenance of outcrossing in flowering plants because of its direct negative impacts on germination, survival, and fertility. Yet inbreeding depression could also impact fitness indirectly by affecting traits that govern biotic interactions. Relatively little is known about inbreeding depression on traits related to pollination success. Although often associated with pollinator attraction or reward, pollination success is also determined by floral longevity. Inbreeding depression in floral longevity has not been studied but has the potential to compound pollination disadvantages confronting inbred plants. Methodology. We investigated inbreeding depression for traits related to pollination success in the mixed-mating biennial Sabatia angularis L. (Pursh) (Gentianaceae). Under controlled, pollinator-free conditions, we performed crosses to create families of selfed and outcross seed and raised these plants to flower. We compared selfed and outcrossed individuals for the following traits: flower number, flower size, corolla longevity, stigma longevity, and plant height. We also considered whether inbreeding depression was influenced by flower number–longevity trade-offs or plant size. Pivotal results. Selfed plants produced significantly smaller flowers that lived for a significantly shorter amount of time than flowers of outcrossed plants, based on corolla and stigma longevity. Consistent with prior work, we found trade-offs between floral longevity and flower number and positive relationships between longevity and plant height. However, we did not detect inbreeding depression for flower number or plant size. Conclusions. We find novel evidence that inbreeding reduces both floral longevity and flower size. Although moderate, inbreeding depression for these traits could leave selfed plants at a disadvantage in pollen-limited environments, especially where rates of pollen export outpace deposition such that plants are forced to rely on pollinators for seed production. Our work contributes to our understanding of how inbreeding depression can alter plant-pollinator interaction outcomes and raises questions about its influence on reproductive allocation. [ABSTRACT FROM AUTHOR]

When selection differs between the sexes, genes expressed by both males and females can experience sexually antagonistic (SA) selection, where beneficial alleles for one sex are deleterious for the other. Classic population genetics theory has been fundamental to understanding how and when SA genetic variation can be maintained by balancing selection, but these models have rarely considered the demographic consequences of coexisting alleles with deleterious fitness effects in each sex. In this article, we develop a stage-structured Mendelian matrix model and jointly analyze the evolutionary and demographic consequences of SA selection in obligately outcrossing (i.e., dioecious/gonochorous) and partially selfing hermaphrodite populations. We focus on identifying when SA polymorphisms are maintained by balancing selection and the population growth rate remains positive. Additionally, we analyze the effects of inbreeding depression manifesting at different life history stages and give an illustrative example of the potential for SA polymorphism in real populations using empirically estimated demographic rates for the hermaphroditic flowering plant Mimulus guttatus. Our results show that when population intrinsic growth rates approach 1, extinction occurs across large swathes of parameter space, favoring SA polymorphism or the fixation of male-beneficial alleles, and that inbreeding depression is a significant problem for maintaining SA polymorphism in partially selfing populations. Despite these demographic challenges, our example with M. guttatus appears to show that demographic rates observed in some real populations can sustain large regions of viable SA polymorphic space. [ABSTRACT FROM AUTHOR]

AbstractInbreeding results from matings between relatives and often leads to a reduction in the fitness of inbred offspring, known as inbreeding depression. There is substantial variation in the magnitude of inbreeding depression among and within species, driven by differences in the biotic and abiotic environment. Recent studies in three species found that parental care has the potential to buffer against inbreeding depression in the offspring, but the generality of this pattern is still unknown. Here, we performed a meta-analysis to test whether variation in the magnitude of inbreeding depression is related to among-species differences in parental care in fishes. We synthesized 536 effect sizes across 56 studies and 18 species, spanning 47 years of research. We found that inbred offspring suffer a smaller reduction in fitness in species that provide biparental care than in species with uniparental or no care. By using a comparative approach, this study provides novel insights into the capacity of parental care to moderate inbreeding depression and suggests that these effects may currently be underappreciated. Considering the potential effects of parental care on inbreeding depression can help us understand why some species avoid inbreeding, whereas others tolerate or even prefer inbreeding, which has important implications for the maintenance of genetic variation within populations.

Pollen limitation, when inadequate pollen receipt results in a plant setting fewer seeds and fruits, can reduce plant reproductive success and promote the evolution of self-fertilization as a mechanism of reproductive assurance. However, the effect of pollen limitation on the joint evolution of mating system and seed size is not known. Using an evolutionarily stable strategy resource allocation model, we show that where moderate pollen limitation and strong inbreeding depression select for complete outcrossing, pollen limitation should also increase the optimal seed size. In contrast, pollen limitation should not affect the optimal seed size under complete selfing, in which case ovule fertilization is certain. Under intermediate conditions, a mixed mating system evolves if the probability of ovule fertilization declines as more ovules are produced, so that a selfed seed with inbreeding depression provides equal marginal fitness returns to a larger outcrossed seed that may result from pollen limitation. Under mixed mating, outcrossed seeds should be larger than selfed seeds, and pollen limitation should not affect the optimal size of either outcrossed or selfed seeds. Our results identify a novel pathway through which pollen limitation selects for mixed mating and provide an adaptive explanation as to why selfed seeds are often smaller than outcrossed seeds. [ABSTRACT FROM AUTHOR]

AbstractIncreased rates of self-fertilization offer reproductive assurance when plant populations experience pollen limitation, but self-fertilization may reduce fitness by exposing deleterious mutations. If an environmental change responsible for pollen limitation also induces plastic mating system shifts toward self-pollination, the reproductive assurance benefit and inbreeding depression cost of increased self-fertilization occur immediately, while the benefit and cost happen more gradually when increased self-fertilization occur through evolution. I built eco-evolutionary models to explore the demographic and genetic conditions in which higher self-fertilization by plasticity and/or evolution rescues populations, following deficits due to a sudden onset of pollen limitation. Rescue is most likely under an intermediate level of selfing rate increase, either through plasticity or evolution, and this critical level of selfing rate increase is higher under stronger pollen limitation. Generally, rescue is more likely through plasticity than through evolution. Under weak pollen limitation, rescue by enhanced self-fertilization may mainly occur through purging of deleterious mutations rather than reproductive assurance. The selfing rate increase conferring the highest rescue probability is lower when the initial population size is smaller. This article shows the importance of plasticity during plant population rescue and offers insights for future studies of the evolution of mating system plasticity.

There ismounting evidence that inbreeding can have complex effects on social interactions among inbred and outbred individuals. Here, we investigate effects of offspring and maternal inbreeding on parent-offspring communication in the burying beetle Nicrophorus vespilloides. We find effects of the interaction between offspring and maternal inbreeding on maternal behavior. Outbred females provided more direct care toward inbred larvae, while inbred females provided similar levels of direct care toward inbred and outbred larvae. Furthermore, we find direct and indirect effects of offspring inbreeding on offspring begging and maternal behavior, respectively. Inbred larvae spent less time begging than outbred larvae, and (outbred) females providedmore direct care and less indirect care toward inbred larvae. Finally, wefind effects of the interaction between offspring andmaternal inbreedingonlarvalbodymass. Inbredandoutbredoffspringgrewtoasimilar size when the femalewasoutbred,while inbred offspringwere of a smaller size whenthe femalewas inbred.Our results suggest thatoutbredfemalesprovidedmore care toward inbred offspring to compensate for their poor genetic quality. Our study advances our understanding of inbreeding by showing that inbreeding can have direct effects on the behavior of inbred individuals and indirect effects onthe behavior ofoutbredindividuals and that indirect effects on outbred individualsmay in turn influence the fitness of inbred individuals. [ABSTRACT FROM AUTHOR]

Selection on floral traits in hermaphroditic plants is determined by both male and female reproductive success. However, predictions regarding floral trait and mating system evolution are often based solely on female fitness. Selection viamale fitness has the potential to affect the outcomes of floral evolution. In this study, we used paternity analysis to assess individual selfing rates and selection on floral traits via male and female fitness in an experimental population of Clarkia xantiana where pollen limitation of seed set was strong. We detected selection through both female and male fitness with reinforcing or noninterfering patterns of selection through the two sex functions. For female fitness, selection favored reduced herkogamy and protandry, traits that promote increased autonomous selfing. For male fitness, selection on petal area was disruptive, with higher trait values conferring greater pollinator attraction and outcross siring success and smaller trait values leading to higher selfed siring success. Combining both female and male fitness, selection on petal area and protandry was disruptive because intermediate phenotypes were less successful as both males and females. Finally, functional relationships among male and female fertility components indicated that selfing resulted in seed discounting and pollen discounting. Under these functional relationships, the evolutionarily stable selfing rate can be intermediate or predominantly selfing or outcrossing, depending on the segregating load of deleterious mutations. [ABSTRACT FROM AUTHOR]

Reinforcement can contribute to speciation by increasing the strength of prezygotic isolating mechanisms. Theoretical analyses over the past two decades have demonstrated that conditions for reinforcement are not unduly restrictive, and empirical investigations have documented over a dozen likely cases, indicating that it may be a reasonably common phenomenon in nature. Largely uncharacterized, however, is the diversity of biological scenarios that can create the reduced hybrid fitness that drives reinforcement. Here I examine one such scenario-the evolution of the "selfing syndrome" (a suite of characters including reductions in flower size and in nectar, pollen, and scent production) in highly selfing plant species. Using a fourlocus model, where the loci are (1) a discrimination locus, (2) a targetof- discimination locus, (3) a pollen-production locus, and (4) a selfing-rate locus, I determine the conditions under which this syndrome can favor reinforcement, an increase in discrimination through change at locus 1, in an outcrossing species that experiences gene flow from a highly selfing species. In the absence of both linkage disequilibrium between loci and pollen discounting, reinforcement can occur, but only in a very small fraction of the parameter combinations examined. Moderate linkage (r = 0:1) between one pair of loci increases this fraction moderately, depending on which two loci are linked. Pollen discounting (a reduction in pollen exported to other plants due to increased selfing), by contrast, can increase the fraction of parameter combinations that result in reinforcement substantially. The evolution of reduced pollen production in highly selfing species thus facilitates reinforcement, especially if substantial pollen discounting is associated with selfing. [ABSTRACT FROM AUTHOR]

Premise of research. The mating systems of introduced plant species are important components of their invasive success because they can favor reproductive assurance during the colonization process. The hypothesis known as Baker's rule implies that colonizing species should evolve toward a lower dependence on pollinators, a higher self-fertility, and a lower inbreeding depression. Here, we test these predictions by comparing the mating system of the perennial shrub Ulex europaeus (Fabaceae) in regions from its native and invaded ranges. Methodology. We performed controlled pollinations on plants from two regions of origin (Brittany and Scotland) and two invaded regions (New Zealand and Reunion) grown in a common garden. We tested the possibility of autonomous pollination; estimated the relative seed set of selfing versus outcrossing; and recorded the viability, mass, and germination capacity of the seeds produced. Pivotal results. Ulex europaeus cannot set seeds in the absence of active pollination. Seed set after selfing was lower than seed set after outcrossing, indicating that the species is partly self-incompatible. The level of self-compatibility was highly variable depending on the individuals, but native and invaded regions exhibited similar levels of self-fertility. Early inbreeding depression was very low in both native and invaded regions. Seed mass and germination velocity were higher in the invaded regions than in the native regions. Conclusions. Reproductive traits linked with reproductive assurance (autonomous pollination, self-fertility, inbreeding depression) were similar in native and in introduced regions, which does not support the predictions of Baker's rule. The study, however, reveals that plants from the invaded regions exhibit higher values for seed traits related to competitive ability at early stages. These results can be explained by the life history of gorse and by the history of its introduction in the invaded regions. [ABSTRACT FROM AUTHOR]

Premise of research. Aulonemia aristulata (Doll) McClure--an endemic Brazilian species--flowers, sets seed, and subsequently dies after many years of vegetative growth. After it has died, plants regenerate by seed germination on the forest floor. Because of the sporadic and unusual records of the flowering cycle and the difficulty of identifying individuals, few studies of the genetic structure of bamboo populations have been published. In this study, we investigated how the flowering event affects the genetic diversity among different populations and evaluated the genetic variability between two ontogenic stages. Methodology. We collected seedlings in July 2009 and saplings in February 2010 in two study areas. We investigated the genetic diversity using markers with different modes of inheritance: nuclear simple sequence repeats (SSRs) and chloroplast SSRs. Pivotal results. The nuclear genetic diversity of the study populations was higher than in other bamboo species. All populations had high and significant inbreeding values, indicating a deficiency of heterozygotes. In general, saplings exhibited less inbreeding than seedlings. Moreover, chloroplast genetic diversity was low, which may indicate that individuals share maternal ancestors. Conclusions. This study demonstrates that sexual reproduction, demographic history, and colonization patterns may contribute to population diversity. The decrease in plant density between ontogenetic stages (i.e., from seedling to sapling) was associated with a higher frequency of homozygotes in seedlings compared with saplings and could indicate intraspecific competition coupled with inbreeding depression as the main factor reducing plant density in bamboos. [ABSTRACT FROM AUTHOR]

Inbreeding depression varies considerably among populations, but only some aspects of this variation have been thoroughly studied. Because inbreeding depression requires genetic variation, factors that influence the amount of standing variation can affect the magnitude of inbreeding depression. Environmental heterogeneity has long been considered an important contributor to the maintenance of genetic variation, but its effects on inbreeding depression have been largely ignored by empiricists. Here we compare inbreeding depression, measured in two environments, for 20 experimental populations of Drosophila melanogaster that have been maintained under four different selection regimes, including two types of environmentally homogeneous selection and two types environmentally heterogeneous selection. In line with theory, we find considerably higher inbreeding depression in populations from heterogeneous selection regimes. We also use our data set to test whether inbreeding depression is correlated with either stress or the phenotypic coefficient of variation (CV), as suggested by some recent studies. Though both of these factors are significant predictors of inbreeding depression in our study, there is an effect of assay environment on inbreeding depression that cannot be explained by either stress or CV. [ABSTRACT FROM AUTHOR]

Populations of the moss Atrichum undulatum contain females, males, and hermaphrodites, and hermaphrodites can have sex organs in close proximity or spatially separated across branches. Here we ask whether differences in gender influence selfing rates or progeny fitness. We used allozyme electrophoresis to measure selfing rates of female and hermaphrodite gametophytes. We measured size and spore number of sporophytes from females and hermaphrodites and germination, survival, and photosynthetic capacity of their gametophytes grown on medium with supplemental nutrients or only with tap water to simulate a harsher environment. Females showed no significant selfing between sibling gametophytes. Significant within-gametophyte selfing was found in hermaphrodites with minimal spatial separation of male and female sex organs. Parental gender did not influence sporophyte size, but sporophytes from females contained slightly more spores. After 6 mo, only progeny from females survived on tap water media. When progeny were transplanted onto tap water media, progeny of females had greater photosynthetic capacity but also higher nonphotochemical quenching than that of hermaphrodites, resulting in realized photosynthetic rates similar to those of hermaphrodites. While the observed fitness differences are small, they suggest that there may be selection on sexual systems in A. undulatum, perhaps through either increased provisioning of resources to progeny by females or gametophytic inbreeding depression following selfing in hermaphrodites. [ABSTRACT FROM AUTHOR]

The organization of neutral genetic variation has long been used as a diagnostic tool to infer demographic properties of populations, and recently it has been shown that this information can also be used to estimate the magnitude of genetic deterioration in small or fragmented populations. A further step of this research is to assess whether neutral genetic indicators can serve to predict and compare the viabilities of endangered species. I use modeling to explore how ecological metapopulation settings are related to neutral genetic indicators (such as the fixation index ∣FST∣), changes in genetic load, and metapopulation viability. The analysis indicates that genetic indicators are generally strongly and consistently correlated with the genetic load, population size and structure, and time of extinction but identifies two potential limitations for their use in viability assessments. First, the regime of environmental perturbations is not accurately reflected by neutral indicators, so that their predictive power may be reduced in variable environments. Second, many species are threatened by recent human-induced changes of their habitat configuration. In most cases, genetic indicators may not have reached their equilibrium value in the altered habitat, which limits their ability to compare species with heterogeneous histories and life-history traits. [ABSTRACT FROM AUTHOR]

Gynodioecy involves the stable co-occurrence of females and hermaphrodites. Its maintenance theoretically depends on differences in female and male reproductive success among gender morphs. Although many gynodioecious species also include gynomonoecious individuals that carry a mixture of female and perfect flowers, little is known about the male and female fitness of this third morph. Here, we present the first study of the reproductive system of Silene nutans, including females, gynomonoecious plants, and hermaphrodites. By measuring 10 floral traits in controlled conditions, we showed that females bear smaller and lighter flowers than hermaphrodites, with female and perfect flowers of gynomonoecious plants being intermediates. By measuring pollen quantity and quality, we showed that gynomonoecious plants had a lower potential male fitness than hermaphrodites at the level of both flowers and individuals. In addition, gynomonoecious plants were shown to widely vary their proportion of female flowers (0.03-0.9) and their floral traits, suggesting a quantitative restoration of male fertility. Finally, controlled pollinations showed evidence for inbreeding depression (δ = 0:3) in progeny of hermaphrodites and gynomonoecious individuals, affecting both pre- and postdispersal traits; this could provide a selective advantage for females. [ABSTRACT FROM AUTHOR]

Classical models studying the evolution of self-fertilization in plants conclude that only complete selfing and complete outcrossing are evolutionarily stable. In contrast with this prediction, 42% of seed-plant species are reported to have rates of self-fertilization between 0.2 and 0.8. We propose that many previous models fail to predict intermediate selfing rates because they do not allow for functional relationships among three components of reproductive fitness: self-fertilized ovules, outcrossed ovules, and ovules sired by successful pollen export. Because the optimal design for fertility components may differ, conflicts among the alternative pathways to fitness are possible, and the greatest fertility may be achieved with some self-fertilization. Here we develop and analyze a model to predict optimal selfing rates that includes a range of possible relationships among the three components of reproductive fitness, as well as the effects of evolving inbreeding depression caused by deleterious mutations and of selection on total seed number. We demonstrate that intermediate selfing is optimal for a wide variety of relationships among fitness components and that inbreeding depression is not a good predictor of selfing-rate evolution. Functional relationships subsume the myriad effects of individual plant traits and thus offer a more general and simpler perspective on mating system evolution. [ABSTRACT FROM AUTHOR]

Several aspects of the reproductive biology of Fumana juniperina were analyzed to find out whether delayed selfing occurs within a representative natural population in southwest Sardinia. Similar fruit set was obtained after autonomous, within-flower, and between-flower self-pollination (0.35, 0.53, and 0.46, respectively), crosspollination (0.45), and control (0.39). Seed set and seed mass did not differ significantly between pollination treatments (P > 0.05). Autonomous self-pollination was favored at the end of floral anthesis, when the petals fell and the sepals closed and pushed the anthers onto the stigma, making contact. No pollinators were seen visiting the flowers during the 42-h observation period, and the stigmatic pollen load on open-pollinated flowers, collected after the petals had fallen and before anther and stigma contact had occurred, was not enough to fertilize all the ovules. Low levels of inbreeding depression were found for fruit set (δ = -0.167), seed set (δ = -0.086), seed mass (δ = 0.008), and seed germination (d δ = -0.052). These results support the idea that F. juniperina is selfcompatible and capable of autonomous self-pollination through changes in the position of the stigma and anthers at the end of floral anthesis. This is a case of how delayed selfing can be an efficient mating strategy that ensures reproduction in this plant when pollinators are scarce. This is the first time that a mechanism of delayed selfing has been described within the family Cistaceae. [ABSTRACT FROM AUTHOR]

The evolutionary transition from diploidy to polyploidy is prevalent in flowering plants and may result in correlated changes in mating system (outcrossing rate). Most theory predicts a shift toward self-fertilization (decrease in outcrossing) in polyploids, but empirical evidence for this pattern and its underlying mechanisms is inconclusive or restricted to a few cases. In an analysis of variation in outcrossing rates among diploidpolyploid species pairs from the literature, polyploids had lower outcrossing rates (higher selfing; t = 0:23, SE = 0:09) than diploids (t = 0:52, SE = 0:12). Among polyploids, however, allopolyploids were predominantly selfing (t = 0:20, SE = 0:099), whereas autopolyploids had significantly higher outcrossing rates (t = 0:64, SE = 0:087), raising the question of what limits the evolution of selfing in autopolyploids. To address this, we examined the magnitude of inbreeding depression in synthetic polyploids of the plant Chamerion angustifolium. The intrinsic cost of selfing in newly formed polyploids was negligible compared with extant polyploids, thus promoting the spread of selfing. However, there was weak evidence that inbreeding depression increases with history of inbreeding, suggesting that the rise in selfing may be ephemeral and that selection ultimately favors mixed or outcrossed mating systems in autopolyploids. Such constraints on selfing have some theoretical support, but additional research on patterns of variation and genetic mechanisms governing polyploid mating systems are needed. [ABSTRACT FROM AUTHOR]

Nymphaea is the most speciose, phenotypically diverse, and geographically widespread (nearly global) genus of Nymphaeales. Phylogenetic relationships among 35 of an estimated 45-50 species of Nymphaea are presented based on an analysis of the chloroplast trnT-trnF region. Because this is the first phylogenetic analysis of Nymphaea, monophyly of the genus had to be tested, and its status in Nymphaeales had to be inferred. Rooting was therefore extended to more distant outgroups (Amborella, Austrobaileyales). Monophyly of Nymphaea received weak support, with a Euryale-Victoria clade appearing as sister. The three major lineages within Nymphaea are constituted by the northern temperate subg. Nymphaea that is sister to all remaining species, a subgg. Hydrocallis-Lotos clade, and a subgg. Anecphya-Brachyceras clade. The Australian genus Ondinea was nested at species level within Nymphaea subg. Anecphya. The pantropical subg. Brachyceras as currently circumscribed does not appear natural, with Nymphaea petersiana belonging to subg. Lotos. Microstructural changes are frequent and highly informative, exhibiting lower levels of homoplasy than substitutions. Reconstructing the evolution of microstructural changes shows a strong insertion bias in simple sequence repeats. Complex indels are often explained by mutational events that occurred independently in different parts of the tree rather than being the result of stepwise events at subsequent nodes. AT-rich, satellite-like sequence parts have evolved independently in the P8 stem loop of the trnL group I intron inNuphar and inmajor lineages of Nymphaea. They seem to be conserved in sequence within species but are highly variable among species. Moreover, the trnT-trnF region provides a signal that allows recognition (bar coding) of most species analyzed so far. [ABSTRACT FROM AUTHOR]

The distribution of infectious diseases within populations can be characterized in terms of variation in the susceptibility and exposure of individual hosts. In general, selfing has been associated with an increase in susceptibility to pathogens, though selfing effects on plant quality may further affect pathogen exposure due to foraging insects. We observed lower incidence of a beetle-vectored bacterium, Erwinia tracheiphila, in self-fertilized wild gourds (Cucurbita pepo ssp. texana) over 2 yr of field-scale epidemics in 50 : 50 mixtures of selfed and outcrossed wild gourds. Subsequent inoculation experiments revealed no significant association between inbreeding and susceptibility, suggesting differential exposure in selfed and outcrossed plants as an explanation for the observed pattern of incidence. Selfed C. pepo tend to be smaller and produce fewer flowers and fruits, which are attractive to the specialist beetles that vector Erwinia. We experimentally manipulated plant size by transplanting first-generation selfed and outcrossed seedlings to the field on three staggered dates and found that larger plants had higher incidence of Erwinia regardless of inbreeding. We conclude that vector selection of larger plants leads to increased exposure of outcrossed plants. Thus, disease mortality risk due to vector behavior is a potential cost to outcrossed plants. [ABSTRACT FROM AUTHOR]

An understanding of how selfing occurs and whether selfing incurs costs relative to outcrossing is necessary for an evolutionary analysis of self-fertilization. We used glasshouse and field experiments to address these questions in the perennial herb Bulbine bulbosa. Flowers did not autonomously self-pollinate, and geitonogamy was unlikely because plants opened only one short-lived flower per day on average. Instead, selfing occurred via facilitated autogamy. We manipulated selfing rate and showed that seed set was negatively related to levels of selfing because many selfed zygotes aborted. Selfed seedlings were smaller and fewer survived compared with crossed seedlings, resulting in high cumulative inbreeding depression (0.85). Naturally pollinated plants had high ovule fertilization similar to that of experimentally cross-pollinated and self-pollinated plants. However, naturally pollinated plants produced fewer fruits and seeds than did cross-pollinated plants but similar numbers as self-pollinated plants, indicating that pollinators deposited mostly self pollen. We conclude that in B. bulbosa, facilitated autogamy was the dominant form of self-fertilization and that selfing incurred severe costs. [ABSTRACT FROM AUTHOR]

In a gynodioecious plant population, where female and hermaphroditic plants co-occur, females must produce more seeds or better-quality offspring than hermaphrodites to be maintained. Further, differences in the magnitude of pollen limitation and inbreeding depression between females and hermaphrodites may affect the relative fitness of the gender morphs and consequently population dynamics. We integrated demographic data into data on pollen limitation and inbreeding depression in a gynodioecious herb. Using a matrix model approach, we then examined the effects of pollen limitation and inbreeding depression on population growth rate and sex ratio. Hermaphrodites tended to contribute more to population growth rates than females. Because of the insensitivity of population growth rates to variation in annual fecundity, pollen limitation of either females or hermaphrodites had a negligible effect on population sex ratio. Inbreeding depression expressed simultaneously in three fitness components of the offspring produced by hermaphrodites reduced stochastic population growth rate and increased female frequency. Given that population growth rates are insensitive to fecundity transitions and that hermaphrodites have moderate selfing rates, our results suggest that inbreeding depression plays a larger role in the maintenance of females in gynodioecious populations than pollen limitation. [ABSTRACT FROM AUTHOR]

The extent to which offspring resemble their parents in genotype and phenotype underpins patterns of genetic and phenotypic variation, selection, and evolution in natural populations. Genetic and phenotypic resemblance can clearly result from additive genetic variance and can be shaped by nongenetic parental and common environmental influences. In contrast, there is no straightforward expectation that inbreeding coefficient (f ), a nonadditive component of genetic ‘quality,’ should be correlated across parents and offspring in sexually reproducing species or consequently cause resemblance across generations. Here, we report a significant parent f-offspring f correlation within a free-living pedigreed population of song sparrows (Melospiza melodia) on Mandarte Island, Canada. Across 15 years, relatively inbred parents had relatively inbred offspring on average. We show that rather than requiring nonrandom pairing with respect to f and kinship, parent f-offspring f correlations arise as an intrinsic consequence of random pairing within Mandarte's open population, where immigrants interbreed with Mandarte-hatched natives. However, on Mandarte, parent f-offspring f correlations may have been exacerbated because relatively inbred individuals paired with more closely related mates than expected by chance. Such intrinsic parent f-offspring f correlations have major implications for the understanding of resemblance, selection, and evolution in natural populations. [ABSTRACT FROM AUTHOR]

Inbreeding depression is one of the possible reasons organisms disperse. In this article, we present a two-locus model for the evolution of dispersal in the presence of inbreeding depression. The first locus codes for a modifier of the migration rate, while the second locus is a selected locus generating inbreeding depression. We express the change in frequency of the migration modifier as a function of allele frequencies and genetic associations and then use a quasi-equilibrium assumption to express genetic associations as functions of allele frequencies. Our model disentangles two effects of inbreeding depression: it gives an advantage to migrant individuals because their offspring are on average less homozygous, but it also decreases the degree of population structure, thus decreasing the strength of kin selection for dispersal. We then extend our model to include an infinite number of selected loci. When the cost of dispersal is not too high, the model predictions are confirmed by multilocus simulation results and show that inbreeding depression can have a substantial effect on the dispersal rate. For high costs of dispersal, we observe discrepancies between the model and the simulations, probably caused by associations among selected loci, which are neglected in the analysis. [ABSTRACT FROM AUTHOR]

We have compared selfed and outbred offspring from individual plants of the annual plant Nigella degenii to examine patterns of inbreeding depression in two direct components of fitness (flower number and pollen viability) and a number of morphological or phenological characters for which the optimal phenotype may be habitat specific. Selfing lowered flower number, plant height, flower size, and pollen viability and caused a shift toward later germination and flowering dates. There was no significant difference in inbreeding depression between fitness components and characters reflecting morphology or phenology regardless of how inbreeding response was estimated. Family-level analyses revealed moderately strong correlated responses involving flower number and each of the nonfitness characters, whereas pollen viability showed an independent response to inbreeding. On the basis of these observations, we hypothesize that morphology and phenology could make a significant contribution to lifetime inbreeding depression in N. degenii, that inbreeding responses in different types of characters involve loci with both general and specific effects on the phenotype, and that morphological inbreeding depression has contributed to the evolutionary reduction of floral structures so prevalent in the Nigella arvensis complex. [ABSTRACT FROM AUTHOR]

We conducted a greenhouse study on Vaccinium myrtillus (a perennial species with a mixed mating system) to compare the fertility parameters following self-, cross-, and mixed-pollinations. Using an isozyme polymorphism, we also determined the proportion of selfed offspring in progenies obtained after mixed- pollinations. A high level of early inbreeding depression was observed (δ = 0.67), and a bias in the genetic representation of self and outcross markers in progenies from mixed-pollinations was detected. Offspring from mixed-pollinations were sired mainly (84.1 %) by cross-pollen. The proportion of selfed offspring was correlated with the inbreeding depression estimates. However, those proportions were higher than the proportions expected on the basis of the individual inbreeding depression estimates. This might be explained by selective abortion of selfed embryos rather than prezygotic selection against self-pollen tubes. [ABSTRACT FROM AUTHOR]

AbstractInbreeding depression is often found in small, inbred populations, but whether it can be detected in and have evolutionary consequences for large, wide-ranging populations is poorly known. Here, we investigate the possibility of inbreeding in a large population to determine whether mild levels of inbreeding can still have genetic and phenotypic consequences and how genomically widespread these effects can be. We apply genome-wide methods to investigate whether individual and parental heterozygosity is related to morphological, growth, or life-history traits in a pelagic seabird, Leach's storm-petrel ( Oceanodroma leucorhoa ). Examining 560 individuals as part of a multiyear study, we found a substantial effect of maternal heterozygosity on chick traits: chicks from less heterozygous (relatively inbred) mothers were significantly smaller than chicks from more heterozygous (noninbred) mothers. We show that these heterozygosity-fitness correlations were due to general genome-wide effects and demonstrate a correlation between heterozygosity and inbreeding, suggesting inbreeding depression. We used population genetic models to further show that the variance in inbreeding was probably due to past demographic events rather than the current mating system and ongoing mate choice. Our findings demonstrate that inbreeding depression can be observed in large populations and illustrate how the integration of genomic techniques and fieldwork can elucidate its underlying causes.

AbstractIn angiosperms, perennials typically present much higher levels of inbreeding depression than annuals. One hypothesis to explain this pattern stems from the observation that inbreeding depression is expressed across multiple life stages in angiosperms. It posits that increased inbreeding depression in more long-lived species could be explained by differences in the way mutations affect fitness, through the life stages at which they are expressed. In this study, we investigate this hypothesis. We combine a physiological growth model and multilocus population genetics approaches to describe a full genotype-to-phenotype-to-fitness map. We study the behavior of mutations affecting growth or survival and explore their consequences in terms of inbreeding depression and mutation load. Although our results agree with empirical data only within a narrow range of conditions, we argue that they may point us toward the type of traits capable of generating high inbreeding depression in long-lived species-that is, traits under sufficiently strong selection, on which selection decreases sharply as life expectancy increases. Then we study the role deleterious mutations maintained at mutation-selection balance may play in the joint evolution of growth and survival strategies.