Publications (11) View all
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Article: Higher rates of sex evolve under K-selection.
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ABSTRACT: The geographical distribution of sexual and related asexual species has been suggested to correlate with habitat stability; sexual species tend to be in stable habitats (K-selection), whereas related asexual taxa tend to be in unstable habitats (r-selection). We test whether this broad-scale pattern can be re-created at a microevolutionary scale by experimentally evolving populations of facultatively sexual rotifers under different ecological conditions. Consistent with the pattern in nature, we find that the rate of sex evolves to lower levels in the r-selected than in K-selection environments. We consider several different explanations for these results.Journal of Evolutionary Biology 03/2013; · 3.28 Impact Factor -
Article: Different types of synchrony in chaotic and cyclic communities.
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ABSTRACT: Stability and persistence of populations is of great interest for management and conservation purposes. Spatial dynamics can have a crucial role in population stability via synchronization, and beneficial and detrimental effects on population persistence have been shown. Despite a theoretical understanding of synchronization, empirical data on synchrony of populations are restricted to systems that do not display the full spectrum of complex dynamics that may occur in nature (that is, chaos or quasiperiodicity). Here we show in experiments that the qualitative form of dynamic behaviour of chaotic and periodic oscillating communities did not change when unidirectionally coupled to oscillating driver communities. Driver and response populations were phase locked in cyclic communities, whereas chaotic communities showed only short periods of statistical coherencies. Our study provides the first empirical analysis of synchronization of chaotic communities and shows that the likelihood for chaos is not lowered in spatially explicit systems but that cyclic and chaotic systems differ in synchronization.Nature Communications 01/2013; 4:1359. · 7.40 Impact Factor -
Article: The evolution of sex is favoured during adaptation to new environments.
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ABSTRACT: Both theory and experiments have demonstrated that sex can facilitate adaptation, potentially yielding a group-level advantage to sex. However, it is unclear whether this process can help solve the more difficult problem of the maintenance of sex within populations. Using experimental populations of the facultatively sexual rotifer Brachionus calyciflorus, we show that rates of sex evolve to higher levels during adaptation but then decline as fitness plateaus. To assess the fitness consequences of genetic mixing, we directly compare the fitnesses of sexually and asexually derived genotypes that naturally occur in our experimental populations. Sexually derived genotypes are more fit than asexually derived genotypes when adaptive pressures are strong, but this pattern reverses as the pace of adaptation slows, matching the pattern of evolutionary change in the rate of sex. These fitness assays test the net effect of sex but cannot be used to disentangle whether selection on sex arises because highly sexual lineages become associated with different allele combinations or with different allele frequencies than less sexual lineages (i.e., "short-" or "long-term" effects, respectively). We infer which of these mechanisms provides an advantage to sex by performing additional manipulations to obtain fitness distributions of sexual and asexual progeny arrays from unbiased parents (rather than from naturally occurring, and thereby evolutionarily biased, parents). We find evidence that sex breaks down adaptive gene combinations, resulting in lower average fitness of sexual progeny (i.e., a short-term disadvantage to sex). As predicted by theory, the advantage to sex arises because sexually derived progeny are more variable in fitness, allowing for faster adaptation. This "long-term advantage" builds over multiple generations, eventually resulting in higher fitness of sexual types.PLoS Biology 05/2012; 10(5):e1001317. · 11.45 Impact Factor -
Article: The functional genomics of an eco-evolutionary feedback loop: linking gene expression, trait evolution, and community dynamics.
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ABSTRACT: Feedbacks between ecological and evolutionary change may play important roles in community and ecosystem functioning, but a complete eco-evolutionary feedback loop has not been demonstrated at the community level, and we know little about molecular mechanisms underlying this kind of eco-evolutionary dynamics. In predator-prey (rotifer-alga) microcosms, cyclical changes in predator abundance generated fluctuating selection for a heritable prey defence trait, cell clumping. Predator population growth was affected more by prey evolution than by changes in prey abundance, and changes in predator abundance drove further prey evolution, completing the feedback loop. Within a predator-prey cycle, genes up-regulated as clumping declined were down-regulated as clumping increased, and vice-versa. Genes changing most in expression tended to be associated with defence or its cost. Expression patterns of individual genes differed greatly between consecutive cycles (often reversing direction), suggesting that a particular phenotype may be produced by several (perhaps many) different gene transcription pathways.Ecology Letters 03/2012; 15(5):492-501. · 17.56 Impact Factor -
Article: Higher rates of sex evolve in spatially heterogeneous environments.
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ABSTRACT: The evolution and maintenance of sexual reproduction has puzzled biologists for decades. Although this field is rich in hypotheses, experimental evidence is scarce. Some important experiments have demonstrated differences in evolutionary rates between sexual and asexual populations; other experiments have documented evolutionary changes in phenomena related to genetic mixing, such as recombination and selfing. However, direct experiments of the evolution of sex within populations are extremely rare (but see ref. 12). Here we use the rotifer, Brachionus calyciflorus, which is capable of both sexual and asexual reproduction, to test recent theory predicting that there is more opportunity for sex to evolve in spatially heterogeneous environments. Replicated experimental populations of rotifers were maintained in homogeneous environments, composed of either high- or low-quality food habitats, or in heterogeneous environments that consisted of a mix of the two habitats. For populations maintained in either type of homogeneous environment, the rate of sex evolves rapidly towards zero. In contrast, higher rates of sex evolve in populations experiencing spatially heterogeneous environments. The data indicate that the higher level of sex observed under heterogeneity is not due to sex being less costly or selection against sex being less efficient; rather sex is sufficiently advantageous in heterogeneous environments to overwhelm its inherent costs. Counter to some alternative theories for the evolution of sex, there is no evidence that genetic drift plays any part in the evolution of sex in these populations.Nature 10/2010; 468(7320):89-92. · 36.28 Impact Factor
