Clusters of incompatible genotypes evolve with limited dispersal (original) (raw)
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Speciation by Self-organizing Barriers to Gene Flow in Simulated Populations with Localized Mating
2006
Speciation caused by intrinsically forming barriers to gene flow is demonstrated using simulated populations. Although theory predicts that underdominance would be quickly eliminated from randomly mating populations, herein it is shown that when mating interactions are localized, mild underdominance can persist for long periods, as interbreeding populations self-organize into patches of compatible types separated by viable hybrid zones. Under certain types of even mild epistasis, hybrid zones will coalesce to create intrinsic barriers to gene flow between subgroups, resulting in speciation.
BMC Evolutionary Biology, 2013
Background: Dispersal is a major factor in ecological and evolutionary dynamics. Although empirical evidence shows that the tendency to disperse varies among individuals in many organisms, the evolution of dispersal patterns is not fully understood. Previous theoretical studies have shown that condition-dependent dispersal may evolve as a means to move to a different environment when environments are heterogeneous in space or in time. However, dispersal is also a means to genetically diversify offspring, a genetic advantage that might be particularly important when the individual fitness is low. We suggest that plasticity in dispersal, in which fit individuals are less likely to disperse (Fitness-Associated Dispersal, or FAD), can evolve due to its evolutionary advantages even when the environment is homogeneous and stable, kin competition is weak, and the cost of dispersal is high. Results: Using stochastic simulations we show that throughout the parameter range, selection favors FAD over uniform dispersal (in which all individuals disperse with equal probability). FAD also has significant long-term effects on the mean fitness and genotypic variance of the population. Conclusions: We show that FAD evolves under a very wide parameter range, regardless of its effects on the population mean fitness. We predict that individuals of low quality will have an increased tendency for dispersal, even when the environment is homogeneous, there is no direct competition with neighbors, and dispersal carries significant costs.
Geography, assortative mating, and the effects of sexual selection on speciation with gene flow
Evolutionary Applications, 2015
Theoretical and empirical research on the evolution of reproductive isolation have both indicated that the effects of sexual selection on speciation with gene flow are quite complex. As part of this special issue on the contributions of women to basic and applied evolutionary biology, I discuss my work on this question in the context of a broader assessment of the patterns of sexual selection that lead to, versus inhibit, the speciation process, as derived from theoretical research. In particular, I focus on how two factors, the geographic context of speciation and the mechanism leading to assortative mating, interact to alter the effect that sexual selection through mate choice has on speciation. I concentrate on two geographic contexts: sympatry and secondary contact between two geographically separated populations that are exchanging migrants and two mechanisms of assortative mating: phenotype matching and separate preferences and traits. I show that both of these factors must be considered for the effects of sexual selection on speciation to be inferred.
Genetic isolation of fragmented populations is exacerbated by drift and selection
Journal of Evolutionary Biology, 2007
Reduced genetic variation at marker loci in small populations has been well documented, whereas the relationship between quantitative genetic variation and population size has attracted little empirical investigation. Here we demonstrate that both neutral and quantitative genetic variation are reduced in small populations of a fragmented plant metapopulation, and that both drift and selective change are enhanced in small populations. Measures of neutral genetic differentiation (F ST ) and quantitative genetic differentiation (Q ST ) in two traits were higher among small demes, and Q ST between small populations exceeded that expected from drift alone. This suggests that fragmented populations experience both enhanced genetic drift and divergent selection on phenotypic traits, and that drift affects variation in both neutral markers and quantitative traits. These results highlight the need to integrate natural selection into conservation genetic theory, and suggests that small populations may represent reservoirs of genetic variation adaptive within a wide range of environments.
Functional Ecology, 2014
1. Dispersal affects species' ability to move or adapt in response to environmental change. Successful long-distance dispersal also requires reproduction in areas with few mates, thus mating systems, especially the capacity for self-fertilization, may influence the speed and success of range shifts. 2. Here, we review: the theoretical predictions regarding dispersal and mating-system evolution at equilibrium, expanding and contracting range limits; the empirical support for these predictions; and how these geographic patterns may influence future range evolution. 3. Equilibrium range limits can arise from environmental gradients in habitat quality, temporal variation or habitat heterogeneity. Dispersal has been predicted to increase or decrease towards range edges, depending on which life-history traits respond to the ecological gradient(s). In general, spatial habitat isolation selects against dispersal, whereas temporal stochasticity favours dispersal. 4. At expanding range fronts, dispersal should increase due to spatial sorting for dispersive individuals and the benefits of colonizing vacant habitat. Dispersal evolution is likely more constrained during native range shifts than invasions. Models of expansion across environmental gradients and during climate-tracking range shifts are lacking. 5. Little theory considers evolution at contracting range margins. We suggest that increased dispersal should be selected if there is local adaptation to climate, as dispersers from warmer areas will out-compete nondispersers no longer adapted to new climatic conditions. Dispersal increases should be more pronounced in regions where local adaptation is stronger. 6. Self fertilization may be favoured at equilibrium, expanding or contracting range margins by providing reproductive assurance. However, this benefit depends on how inbreeding depression is influenced by genetic load, the severity of the abiotic environment, and the competitive milieu in edge populations. Models for the joint evolution of mating and dispersal in plants suggest that although selfing may evolve at range limits, it will not necessarily be associated with high dispersal. 7. Empirical evidence to test these predictions is scarce. Geographic surveys of dispersal traits, mating-system traits and relevant selective factors are needed, especially studies of: (i) stable range limits that identify underlying environmental gradients; (ii) moving range limits that compare traits across space and time; and (iii) contracting limits that assess variation in local adaptation towards the range edge.
The evolution of partial reproductive isolation as an adaptive optimum
Evolution, 2019
Decades of theoretical work on the evolution of adaptive prezygotic isolation have led to an interesting finding-namely that stable partial reproductive isolation is a relatively common outcome. This conclusion is generally lost, however, in the desire to pinpoint when exactly speciation occurs. Here we argue that the evolution of partial reproductive isolation is of great interest in its own right, and matches empirical findings that ongoing hybridization is taxonomically widespread. We present the mechanisms by which partial reproductive isolation can be a stable evolutionary endpoint, concentrating on insights from theoretical studies. We focus not on cases in which hybridization results from constraints imposed by ongoing migration or mutation, but on the intriguing idea that partial reproductive isolation may instead be an adaptive optimum. We identify three general categories of selective mechanisms that can lead to partial reproductive isolation: context-dependent hybrid advantage, indirect selection due to the varying actions of sexual selection in different geographic contexts, and a balance of costs of choosiness with indirect selection for stronger mating preferences. By any of these mechanisms, stable partial reproductive isolation can potentially provide a robust evolutionary alternative to either complete speciation or population fusion.
The genetic consequences of long distance dispersal during colonization
Heredity, 1994
Rare long distance dispersal may have little impact on gene frequencies in established populations but it can dramatically increase gene flow during episodes of range expansion. We model the invasion of new territory by genetically distinct populations of the same species to investigate the dynamics of such episodes. If long distance dispersal is sufficiently frequent, the populations do not spread as a wave of advance but instead found intermingled isolates. We argue that this process can explain many otherwise puzzling patterns in the geographical distribution of alleles.
On some genetic consequences of social structure, mating systems, dispersal, and sampling
Proceedings of the National Academy of Sciences, 2015
Significance Many species live in socially structured populations, forming cohesive units with kin structure. Yet, sociality has been neglected by population geneticists under the assumption that social groups can be seen as small demes subjected to significant genetic drift. Such demes are usually considered to be susceptible to inbreeding, with inbreeding avoidance becoming a major force explaining dispersal strategies. We find that social structure is highly effective in maintaining high genotypic and genetic diversity levels, without invoking sex-biased dispersal or inbreeding avoidance mechanisms. These findings should change the way we perceive social groups.
Sensitivity of Self-Organized Speciation to Long-Disctance Dispersal
2007 IEEE Symposium on Artificial Life, 2007
Previous work has shown that speciation can result from the self-organized accumulation of multiple mildly underdominant (nearly neutral) loci in a continuous population, when mating is spatially localized. In contrast, when mating is panmictic, underdominance is quickly eliminated and the population always converges on a single genotype, as predicted by mean-field approximations. The focus of this work is to examine the sensitivity of selforganizing speciation to the assumption of purely localized interactions. We alter the interaction topology from nearest neighbor interactions to panmictic interactions in two ways: (i) by increasing the size of the contiguous mating neighborhoods and (ii) by allowing for long-distance dispersal of individuals with increasing probability. Our results show self-organized speciation to be robust to mating neighborhood sizes significantly larger than nearest neighbor interactions and to probabilities of long-distance dispersal that fall well into the range of so called "small-world" interaction topologies.
The effects of sexual selection on trait divergence in a peripheral population with gene flow
Evolution, 2015
The unique aspects of speciation and divergence in peripheral populations have long sparked much research. Unidirectional migration, received by some peripheral populations, can hinder the evolution of distinct differences from their founding populations. Here, we explore the effects that sexual selection, long hypothesized to drive the divergence of distinct traits used in mate choice, can play in the evolution of such traits in a partially isolated peripheral population. Using population genetic continent-island models, we show that with phenotype matching, sexual selection increases the frequency of an island-specific mating trait only when female preferences are of intermediate strength. We identify regions of preference strength for which sexual selection can instead cause an island-specific trait to be lost, even when it would have otherwise been maintained at migration-selection balance. When there are instead separate preference and trait loci, we find that sexual selection can lead to low trait frequencies or trait loss when female preferences are weak to intermediate, but that sexual selection can increase trait frequencies when preferences are strong. We also show that novel preference strengths almost universally cannot increase, under either mating mechanism, precluding the evolution of premating isolation in peripheral populations at the early stages of species divergence.