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When does female multiple mating evolve to adjust inbreeding? Effects of inbreeding depression, direct costs, mating constraints, and polyandry as a threshold trait.

ABSTRACT: Polyandry is often hypothesized to evolve to allow females to adjust the degree to which they inbreed. Multiple factors might affect such evolution, including inbreeding depression, direct costs, constraints on male availability, and the nature of polyandry as a threshold trait. Complex models are required to evaluate when evolution of polyandry to adjust inbreeding is predicted to arise. We used a genetically explicit individual-based model to track the joint evolution of inbreeding strategy and polyandry defined as a polygenic threshold trait. Evolution of polyandry to avoid inbreeding only occurred given strong inbreeding depression, low direct costs, and severe restrictions on initial versus additional male availability. Evolution of polyandry to prefer inbreeding only occurred given zero inbreeding depression and direct costs, and given similarly severe restrictions on male availability. However, due to its threshold nature, phenotypic polyandry was frequently expressed even when strongly selected against and hence maladaptive. Further, the degree to which females adjusted inbreeding through polyandry was typically very small, and often reflected constraints on male availability rather than adaptive reproductive strategy. Evolution of polyandry solely to adjust inbreeding might consequently be highly restricted in nature, and such evolution cannot necessarily be directly inferred from observed magnitudes of inbreeding adjustment.

SUBMITTER: Duthie AB

PROVIDER: S-EPMC5053304 | biostudies-other | 2016 Sep

REPOSITORIES: biostudies-other

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When does female multiple mating evolve to adjust inbreeding? Effects of inbreeding depression, direct costs, mating constraints, and polyandry as a threshold trait.

Duthie A Bradley AB Bocedi Greta G Reid Jane M JM

Evolution; international journal of organic evolution 20160821 9

Polyandry is often hypothesized to evolve to allow females to adjust the degree to which they inbreed. Multiple factors might affect such evolution, including inbreeding depression, direct costs, constraints on male availability, and the nature of polyandry as a threshold trait. Complex models are required to evaluate when evolution of polyandry to adjust inbreeding is predicted to arise. We used a genetically explicit individual-based model to track the joint evolution of inbreeding strategy an ...[more]

PMID: 27464756

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Project description:Background and aimsVariation in inbreeding depression (?) among individual plants is considered to play a central role in mating system evolution and population genetics. Moreover, such variation could be linked to individual susceptibility to pollen limitation (PL) because those individuals strongly affected by ? for seed production will require more outcross pollen for setting a given number of fruits or seeds. However, no study has tested explicitly for associations between PL and ? at the individual plant level. This study assesses the extent of among-individual variation in PL and ?, the consistency of ? across life stages, and the relationships between individual PL and ? in the mixed-mating shrub Myrtus communis.MethodsControlled hand-pollinations were performed in a natural M. communis population. Marked flowers were monitored until fruit production and a greenhouse experiment was conducted with the seeds produced.Key resultsCompared with selfing, outcross-pollination enhanced seed number per fruit, germination rate and seedling growth, but did not enhance fruit-set. Only seed number per fruit was pollen limited and, thus, cumulative pollen limitation depended more on pollen quality (outcross pollen) than on quantity. The effects of ? varied considerably across life stages and individual plants. Cumulative ? was high across individuals (mean ? = 0·65), although there were no positive correlations between ? values at different life stages. Interestingly, maternal plants showing stronger ? for seed production were more pollen limited, but they were also less affected by ? for seedling growth because of a seed size/number trade-off.ConclusionsResults show a general inconsistency in ? across life stages and individuals, suggesting that different deleterious loci are acting at different stages. The association between ? and PL at the individual level corroborates the idea that pollen limitation may be 'genotype-dependent' regardless of other factors.

Project description:BackgroundUnderstanding the mechanisms that control species genetic structure has always been a major objective in evolutionary studies. The association between genetic structure and species attributes has received special attention. As species attributes are highly taxonomically constrained, phylogenetically controlled methods are necessary to infer causal relationships. In plants, a previous study controlling for phylogenetic signal has demonstrated that Wright's FST, a measure of genetic differentiation among populations, is best predicted by the mating system (outcrossing, mixed-mating or selfing) and that plant traits such as perenniality and growth form have only an indirect influence on FST via their association with the mating system. The objective of this study is to further outline the determinants of plant genetic structure by distinguishing the effects of mating system on gene flow and on genetic drift. The association of biparental inbreeding and inbreeding depression with population genetic structure, mating system and plant traits are also investigated.ResultsBased on data from 263 plant species for which estimates of FST, inbreeding (FIS) and outcrossing rate (tm) are available, we confirm that mating system is the main influencing factor of FST. Moreover, using an alternative measure of FST unaffected by the impact of inbreeding on effective population size, we show that the influence of tm on FST is due to its impact on gene flow (reduced pollen flow under selfing) and on genetic drift (higher drift under selfing due to inbreeding). Plant traits, in particular perenniality, influence FST mostly via their effect on the mating system but also via their association with the magnitude of selection against inbred individuals: the mean inbreeding depression increases from short-lived herbaceous to long-lived herbaceous and then to woody species. The influence of perenniality on mating system does not seem to be related to differences in stature, as proposed earlier, but rather to differences in generation time.ConclusionPlant traits correlated with generation time affect both inbreeding depression and mating system. These in turn modify genetic drift and gene flow and ultimately genetic structure.

Dataset Information

When does female multiple mating evolve to adjust inbreeding? Effects of inbreeding depression, direct costs, mating constraints, and polyandry as a threshold trait.

Publications

When does female multiple mating evolve to adjust inbreeding? Effects of inbreeding depression, direct costs, mating constraints, and polyandry as a threshold trait.

Similar Datasets

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