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Aneil F Agrawal - One of the best experts on this subject based on the ideXlab platform.

  • Spatial Heterogeneity and the Evolution of Sex in Diploids
    The American Naturalist, 2009
    Co-Authors: Aneil F Agrawal
    Abstract:

    Abstract: Much of the theoretical work on the Evolution of Sex has focused on the effects of recombination. In diploids, segregation also occurs during Sexual reproduction. Segregation breaks down some types of genetic associations that are not affected by recombination and thus influences the Evolution of Sex in ways that are not apparent from studying the Evolution of recombination as a surrogate for Sex. Here I examine the Evolution of Sex in diploids experiencing spatially heterogeneous selection. If divergent selection causes genetic differentiation, then migration can be a powerful force generating genetic associations that may not be favored by selection. An advantage to Sex can arise from breaking down these associations. By examining modifiers of both Sex and recombination, the model allows for a direct comparison of the forces acting on these related but different processes, illuminating the role of segregation. The model also includes inbreeding, which has been shown to be important for both se...

  • Spatial heterogeneity and the Evolution of Sex in diploids.
    The American naturalist, 2009
    Co-Authors: Aneil F Agrawal
    Abstract:

    Much of the theoretical work on the Evolution of Sex has focused on the effects of recombination. In diploids, segregation also occurs during Sexual reproduction. Segregation breaks down some types of genetic associations that are not affected by recombination and thus influences the Evolution of Sex in ways that are not apparent from studying the Evolution of recombination as a surrogate for Sex. Here I examine the Evolution of Sex in diploids experiencing spatially heterogeneous selection. If divergent selection causes genetic differentiation, then migration can be a powerful force generating genetic associations that may not be favored by selection. An advantage to Sex can arise from breaking down these associations. By examining modifiers of both Sex and recombination, the model allows for a direct comparison of the forces acting on these related but different processes, illuminating the role of segregation. The model also includes inbreeding, which has been shown to be important for both segregation and recombination. I find that inbreeding affects the Evolution of Sex through segregation, not recombination. Several suggestions for empirical experiments are given.

  • Evolution of Sex why do organisms shuffle their genotypes
    Current Biology, 2006
    Co-Authors: Aneil F Agrawal
    Abstract:

    Sexual processes alter associations among alleles. To understand the Evolution of Sex, we need to know both the short-term and long-term consequences of changing these genetic associations. Ultimately, we need to identify which Evolutionary forces — for example, selection, genetic drift, migration — are responsible for building the associations affected by Sex.

  • Similarity Selection and the Evolution of Sex: Revisiting the Red Queen
    PLoS biology, 2006
    Co-Authors: Aneil F Agrawal
    Abstract:

    For over 25 years, many Evolutionary ecologists have believed that Sexual reproduction occurs because it allows hosts to change genotypes each generation and thereby evade their coevolving parasites. However, recent influential theoretical analyses suggest that, though parasites can select for Sex under some conditions, they often select against it. These models assume that encounters between hosts and parasites are completely random. Because of this assumption, the fitness of a host depends only on its own genotype (“genotypic selection”). If a host is even slightly more likely to encounter a parasite transmitted by its mother than expected by random chance, then the fitness of a host also depends on its genetic similarity to its mother (“similarity selection”). A population genetic model is presented here that includes both genotypic and similarity selection, allowing them to be directly compared in the same framework. It is shown that similarity selection is a much more potent force with respect to the Evolution of Sex than is genotypic selection. Consequently, similarity selection can drive the Evolution of Sex even if it is much weaker than genotypic selection with respect to fitness. Examination of explicit coEvolutionary models reveals that even a small degree of mother–offspring parasite transmission can cause parasites to favor Sex rather than oppose it. In contrast to previous predictions, the model shows that weakly virulent parasites are more likely to favor Sex than are highly virulent ones. Parasites have figured prominently in discussions of the Evolution of Sex, but recent models suggest that parasites often select against Sex rather than for it. With the inclusion of small and realistic exposure biases, parasites are much more likely to favor Sex. Though parasites alone may not provide a complete explanation for Sex, the results presented here expand the potential for parasites to contribute to the maintenance of Sex rather than act against it.

Sarah P. Otto - One of the best experts on this subject based on the ideXlab platform.

  • Evolution of Sex: Using experimental genomics to select among competing theories.
    BioEssays : news and reviews in molecular cellular and developmental biology, 2016
    Co-Authors: Nathaniel P. Sharp, Sarah P. Otto
    Abstract:

    Few topics have intrigued biologists as much as the Evolution of Sex. Understanding why Sex persists despite its costs requires not just rigorous theoretical study, but also empirical data on related fundamental issues, including the nature of genetic variance for fitness, patterns of genetic interactions, and the dynamics of adaptation. The increasing feasibility of examining genomes in an experimental context is now shedding new light on these problems. Using this approach, McDonald et al. recently demonstrated that Sex uncouples beneficial and deleterious mutations, allowing selection to proceed more effectively with Sex than without. Here we discuss the insights provided by this study, along with other recent empirical work, in the context of the major theoretical models for the Evolution of Sex.

  • the red queen coupled with directional selection favours the Evolution of Sex
    Journal of Evolutionary Biology, 2012
    Co-Authors: Emma E Hodgson, Sarah P. Otto
    Abstract:

    Why Sexual reproduction has evolved to be such a widespread mode of reproduction remains a major question in Evolutionary biology. Although previous studies have shown that increased Sex and recombination can evolve in the presence of host–parasite interactions (the ‘Red Queen hypothesis’ for Sex), many of these studies have assumed that multiple loci mediate infection vs. resistance. Data suggest, however, that a major locus is typically involved in antigen presentation and recognition. Here, we explore a model where only one locus mediates host–parasite interactions, but a second locus is subject to directional selection. Even though the effects of these genes on fitness are independent, we show that increased rates of Sex and recombination are favoured at a modifier gene that alters the rate of genetic mixing. This result occurs because of selective interference in finite populations (the ‘Hill– Robertson effect’), which also favours Sex. These results suggest that the Red Queen hypothesis may help to explain the Evolution of Sex by contributing a form of persistent selection, which interferes with directional selection at other loci and thereby favours Sex and recombination.

  • The Evolution of Sex and recombination in response to abiotic or coEvolutionary fluctuations in epistasis
    Genetics, 2007
    Co-Authors: Sarah P. Otto
    Abstract:

    Evolutionary biologists have identified several factors that could explain the widespread phenomena of Sex and recombination. One hypothesis is that host-parasite interactions favor Sex and recombination because they favor the production of rare genotypes. A problem with many of the early models of this so-called Red Queen hypothesis is that several factors are acting together: directional selection, fluctuating epistasis, and drift. It is thus difficult to identify what exactly is selecting for Sex in these models. Is one factor more important than the others or is it the synergistic action of these different factors that really matters? Here we focus on the analysis of a simple model with a single mechanism that might select for Sex: fluctuating epistasis. We first analyze the Evolution of Sex and recombination when the temporal fluctuations are driven by the abiotic environment. We then analyze the Evolution of Sex and recombination in a two-species coEvolutionary model, where directional selection is absent (allele frequencies remain fixed) and temporal variation in epistasis is induced by coEvolution with the antagonist species. In both cases we contrast situations with weak and strong selection and derive the Evolutionarily stable (ES) recombination rate. The ES recombination rate is most sensitive to the period of the cycles, which in turn depends on the strength of epistasis. In particular, more virulent parasites cause more rapid cycles and consequently increase the ES recombination rate of the host. Although the ES strategy is maximized at an intermediate period, some recombination is favored even when fluctuations are very slow. By contrast, the amplitude of the cycles has no effect on the ES level of Sex and recombination, unless Sex and recombination are costly, in which case higher-amplitude cycles allow the Evolution of higher rates of Sex and recombination. In the coEvolutionary model, the amount of recombination in the interacting species also has a large effect on the ES, with Evolution favoring higher rates of Sex and recombination than in the interacting species. In general, the ES recombination rate is less than or equal to the recombination rate that would maximize mean fitness. We also discuss the effect of migration when Sex and recombination evolve in a metapopulation. We find that intermediate parasite migration rates maximize the degree of local adaptation of the parasite and lead to a higher ES recombination rate in the host.

  • Species interactions and the Evolution of Sex.
    Science (New York N.Y.), 2004
    Co-Authors: Sarah P. Otto, Scott L. Nuismer
    Abstract:

    The Red Queen hypothesis posits that Sex has evolved in response to the shifting adaptive landscape generated by the Evolution of interacting species. Previous studies supporting the Red Queen hypothesis have considered a narrow region of parameter space and only a subset of ecological and genetic interactions. Here, we develop a population genetics model that circumscribes a broad array of ecological and genetic interactions among species and derive the first general analytical conditions for the impact of species interactions on the Evolution of Sex. Our results show that species interactions typically select against Sex. We conclude that, although the Red Queen favors Sex under certain circumstances, it alone does not account for the ubiquity of Sex.

David Laloi - One of the best experts on this subject based on the ideXlab platform.

  • The Sex chromosome system can influence the Evolution of Sex-biased dispersal.
    Journal of evolutionary biology, 2018
    Co-Authors: Thomas Brom, Manuel Massot, David Laloi
    Abstract:

    Sex-biased dispersal is a much-discussed feature in literature on dispersal. Diverse hypotheses have been proposed to explain the Evolution of Sex-biased dispersal, a difference in dispersal rate or dispersal distance between males and females. An early hypothesis has indicated that it may rely on the difference in Sex chromosomes between males and females. However, this proposal was quickly rejected without a real assessment. We propose a new perspective on this hypothesis by investigating the Evolution of Sex-biased dispersal when dispersal genes are Sex-linked, that is when they are located on the Sex chromosomes. We show that individuals of the heterogametic Sex disperse relatively more than do individuals of the homogametic Sex when dispersal genes are Sex-linked rather than autosomal. Although such a Sex-biased dispersal towards the heterogametic Sex is always observed in monogamous species, the mating system and the location of dispersal genes interact to modulate Sex-biased dispersal in monandry and polyandry. In the context of the multicausality of dispersal, we suggest that Sex-linked dispersal genes can influence the Evolution of Sex-biased dispersal.

  • Kin competition drives the Evolution of Sex-biased dispersal under monandry and polyandry, not under monogamy
    Animal Behaviour, 2016
    Co-Authors: Thomas Brom, Manuel Massot, Stéphane Legendre, David Laloi
    Abstract:

    The relation between mating system and Sex-biased dispersal has been debated for three decades. However, the relative importance of the processes involved in this relation remains poorly known. In this study, we paid special attention to kin competition. We built an adaptive individual-based model fixing three mating systems (monandry, polyandry, monogamy) in a metapopulation, and allowing dispersal across patches to evolve independently for males and females. Our simulations showed that a difference in the number of mates can determine the Evolution of Sex-biased dispersal. Dispersal appears male biased under monandry and polyandry, but balanced under monogamy. By contrast, we showed that inbreeding can influence but does not promote Sex-biased dispersal, and that the primary Sex ratio does not qualitatively affect the Evolution of Sex-biased dispersal under monandry and polyandry. These results are driven by the interaction of two factors: the variation in reproductive success between patches in the metapopulation and kin competition. These two factors are influenced by the mating system, which modifies both the competition for access to partners and the mean relatedness between individuals. To ascertain that kin competition actually drives Sex-biased dispersal, we made simulations with destruction of any genetic structure in the metapopulation, and we found that in this case dispersal was not Sex biased.

Diogo Cavalcanti Cabraldemello - One of the best experts on this subject based on the ideXlab platform.

  • tracking the Evolution of Sex chromosome systems in melanoplinae grasshoppers through chromosomal mapping of repetitive dna sequences
    BMC Evolutionary Biology, 2013
    Co-Authors: Octavio M Palaciosgimenez, Elio Rodrigo Daniel Castillo, Dardo A Marti, Diogo Cavalcanti Cabraldemello
    Abstract:

    Background The accumulation of repetitive DNA during Sex chromosome differentiation is a common feature of many eukaryotes and becomes more evident after recombination has been restricted or abolished. The accumulated repetitive sequences include multigene families, microsatellites, satellite DNAs and mobile elements, all of which are important for the structural remodeling of heterochromatin. In grasshoppers, derived Sex chromosome systems, such as neo-XY♂/XX♀ and neo-X1X2Y♂/X1X1X2X2♀, are frequently observed in the Melanoplinae subfamily. However, no studies concerning the Evolution of Sex chromosomes in Melanoplinae have addressed the role of the repetitive DNA sequences. To further investigate the Evolution of Sex chromosomes in grasshoppers, we used classical cytogenetic and FISH analyses to examine the repetitive DNA sequences in six phylogenetically related Melanoplinae species with X0♂/XX♀, neo-XY♂/XX♀ and neo-X1X2Y♂/X1X1X2X2♀ Sex chromosome systems.

  • tracking the Evolution of Sex chromosome systems in melanoplinae grasshoppers through chromosomal mapping of repetitive dna sequences
    BMC Evolutionary Biology, 2013
    Co-Authors: Octavio M Palaciosgimenez, Elio Rodrigo Daniel Castillo, Dardo A Marti, Diogo Cavalcanti Cabraldemello
    Abstract:

    The accumulation of repetitive DNA during Sex chromosome differentiation is a common feature of many eukaryotes and becomes more evident after recombination has been restricted or abolished. The accumulated repetitive sequences include multigene families, microsatellites, satellite DNAs and mobile elements, all of which are important for the structural remodeling of heterochromatin. In grasshoppers, derived Sex chromosome systems, such as neo-XY♂/XX♀ and neo-X1X2Y♂/X1X1X2X2♀, are frequently observed in the Melanoplinae subfamily. However, no studies concerning the Evolution of Sex chromosomes in Melanoplinae have addressed the role of the repetitive DNA sequences. To further investigate the Evolution of Sex chromosomes in grasshoppers, we used classical cytogenetic and FISH analyses to examine the repetitive DNA sequences in six phylogenetically related Melanoplinae species with X0♂/XX♀, neo-XY♂/XX♀ and neo-X1X2Y♂/X1X1X2X2♀ Sex chromosome systems. Our data indicate a non-spreading of heterochromatic blocks and pool of repetitive DNAs (C 0 t-1 DNA) in the Sex chromosomes; however, the spreading of multigene families among the neo-Sex chromosomes of Eurotettix and Dichromatos was remarkable, particularly for 5S rDNA. In autosomes, FISH mapping of multigene families revealed distinct patterns of chromosomal organization at the intra- and intergenomic levels. These results suggest a common origin and subsequent differential accumulation of repetitive DNAs in the Sex chromosomes of Dichromatos and an independent origin of the Sex chromosomes of the neo-XY and neo-X1X2Y systems. Our data indicate a possible role for repetitive DNAs in the diversification of Sex chromosome systems in grasshoppers.

Thomas Brom - One of the best experts on this subject based on the ideXlab platform.

  • The Sex chromosome system can influence the Evolution of Sex-biased dispersal.
    Journal of evolutionary biology, 2018
    Co-Authors: Thomas Brom, Manuel Massot, David Laloi
    Abstract:

    Sex-biased dispersal is a much-discussed feature in literature on dispersal. Diverse hypotheses have been proposed to explain the Evolution of Sex-biased dispersal, a difference in dispersal rate or dispersal distance between males and females. An early hypothesis has indicated that it may rely on the difference in Sex chromosomes between males and females. However, this proposal was quickly rejected without a real assessment. We propose a new perspective on this hypothesis by investigating the Evolution of Sex-biased dispersal when dispersal genes are Sex-linked, that is when they are located on the Sex chromosomes. We show that individuals of the heterogametic Sex disperse relatively more than do individuals of the homogametic Sex when dispersal genes are Sex-linked rather than autosomal. Although such a Sex-biased dispersal towards the heterogametic Sex is always observed in monogamous species, the mating system and the location of dispersal genes interact to modulate Sex-biased dispersal in monandry and polyandry. In the context of the multicausality of dispersal, we suggest that Sex-linked dispersal genes can influence the Evolution of Sex-biased dispersal.

  • Kin competition drives the Evolution of Sex-biased dispersal under monandry and polyandry, not under monogamy
    Animal Behaviour, 2016
    Co-Authors: Thomas Brom, Manuel Massot, Stéphane Legendre, David Laloi
    Abstract:

    The relation between mating system and Sex-biased dispersal has been debated for three decades. However, the relative importance of the processes involved in this relation remains poorly known. In this study, we paid special attention to kin competition. We built an adaptive individual-based model fixing three mating systems (monandry, polyandry, monogamy) in a metapopulation, and allowing dispersal across patches to evolve independently for males and females. Our simulations showed that a difference in the number of mates can determine the Evolution of Sex-biased dispersal. Dispersal appears male biased under monandry and polyandry, but balanced under monogamy. By contrast, we showed that inbreeding can influence but does not promote Sex-biased dispersal, and that the primary Sex ratio does not qualitatively affect the Evolution of Sex-biased dispersal under monandry and polyandry. These results are driven by the interaction of two factors: the variation in reproductive success between patches in the metapopulation and kin competition. These two factors are influenced by the mating system, which modifies both the competition for access to partners and the mean relatedness between individuals. To ascertain that kin competition actually drives Sex-biased dispersal, we made simulations with destruction of any genetic structure in the metapopulation, and we found that in this case dispersal was not Sex biased.