Heterosis in Cepaea

Cook, L. M.

doi:10.1111/j.1095-8312.2007.00710.x

Cited by 9 publications

(7 citation statements)

References 29 publications

(28 reference statements)

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“…The determination of shell pattern is genetic (Cain et al, 1968), and polymorphism is known to be maintained in populations over long periods of time (Silvertown et al, 2011). Evidence for the selective forces maintaining the polymorphism is mixed, with several selective factors having a role (Studies on Cepaea, 1968), including differential predation, climatic selection, heterosis (Cook, 2007) or random processes (Bellido et al, 2002). Controlled laboratory crosses indicate strong linkage between colour and pattern loci, and recent molecular analysis has used RAD-seq to examine segregation of shell colouration (Richards et al, 2013).…”

Section: Other Adaptive Colourationmentioning

confidence: 99%

Supergenes and their role in evolution

2014

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Adaptation is commonly a multidimensional problem, with changes in multiple traits required to match a complex environment. This is epitomized by balanced polymorphisms in which multiple phenotypes co-exist and are maintained in a population by a balance of selective forces. Consideration of such polymorphisms led to the concept of the supergene, where alternative phenotypes in a balanced polymorphism segregate as if controlled by a single genetic locus, resulting from tight genetic linkage between multiple functional loci. Recently, the molecular basis for several supergenes has been resolved. Thus, major chromosomal inversions have been shown to be associated with polymorphisms in butterflies, ants and birds, offering a mechanism for localised reduction in recombination. In several examples of plant self-incompatibility, the functional role of multiple elements within the supergene architecture has been demonstrated, conclusively showing that balanced polymorphism can be maintained at multiple coadapted and tightly linked elements. Despite recent criticism, we argue that the supergene concept remains relevant and is more testable than ever with modern molecular methods.

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Section: Other Adaptive Colourationmentioning

confidence: 99%

Supergenes and their role in evolution

2014

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“…The plasticity hypothesis (or a heterozygote advantage) seems to allow the maintenance of polymorphism for a wider range of species life strategies and environments; and accordingly we might expect the plasticity mechanism to be more wide-spread in trimorphic species and by extension to more complex systems with more than three alleles and more continuous and less detectable polymorphisms. In this respect, previous empirical as well as theoretical studies have shown that heterozygote advantage often underpins the maintenance of polymorphism of reproductive strategies in natural populations 1 , 24 , 36 , 45 – 47 . However, in contrast of the dominance hypothesis which benefits from experimental evidence in damselflies 17 , 28 , our plasticity hypothesis is only suggested by indirect evidence from one specific case.…”

Section: Discussionmentioning

confidence: 96%

“…Yet polymorphism is surprisingly widespread in animal and plant populations. To explain this paradox, a number of mechanisms have been proposed such as heterosis 1 , niche selection 2 , 3 or negative frequency dependent selection (FDS) 4 , 5 which are all known to allow the stable maintenance of polymorphism in natural populations 6 . Game theory suggests that multiple players competing for a resource (i.e.…”

Section: Introductionmentioning

confidence: 99%

The roles of plasticity versus dominance in maintaining polymorphism in mating strategies

Moulherat

Chaine

Mangin

et al. 2017

Sci Rep

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Although natural selection is expected to reduce variability, polymorphism is common in nature even under strong selective regimes. Discrete polymorphisms in mating strategies are widespread and offer a good opportunity to understand the genetic processes that allow the maintenance of polymorphism in relatively simple systems. Here we explored the genetic mechanism underlying the expression of discrete mating strategies in the rock-paper-scissors (RPS) game. Heterozygotes carry the genetic information for two different strategies, yet little attention has been devoted to the mechanisms underpinning heterozygote phenotype and its consequences for allele frequency dynamics. We explored the maintenance of polymorphism under 1) genetic dominance or 2) plasticity, as mechanisms driving the expression of alternative strategies in males. We developed an alternative mating strategy model and analysed allele frequency dynamics using time series analyses. Our results show that both genetic mechanisms can maintain polymorphism depending on population demographic characteristics but that plasticity can enhance the likelihood that polymorphism is maintained relative to dominance. Time series analysis on simulation outcomes show that the RPS game is mostly driven by a single strategy, but the importance of this strategy on long term dynamics is stronger when gene expression shows dominance rather than plasticity.

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“…Most studies that do find a strong selective advantage for heterozygosity involve genes in the major histocompatibility complex and other host-parasite interactions (Penn et al 2002). However, the snail Cepaea nemoralis, which is polymorphic in shell color and banding, does appear to be a strong candidate for the heterozygotic advantage model (Cook 2007). Although frequency-dependent disruptive selection from predation was once thought to drive this polymorphism (Clarke 1969), more recent work has shown that predation does not appear to be a strong selecting force on this species and that the dominant phenotypes are heterozygotic (Cook 2007).…”

Section: !mentioning

confidence: 99%

“…However, the snail Cepaea nemoralis, which is polymorphic in shell color and banding, does appear to be a strong candidate for the heterozygotic advantage model (Cook 2007). Although frequency-dependent disruptive selection from predation was once thought to drive this polymorphism (Clarke 1969), more recent work has shown that predation does not appear to be a strong selecting force on this species and that the dominant phenotypes are heterozygotic (Cook 2007). More work investigating the frequency of heterozygotic advantage is required before we can satisfactorily determine its importance as a block to sympatric speciation.…”

Section: !mentioning

confidence: 99%

The evolution and ecology of individual specializations amongst a group of dietary generalists.

Cloyed¹

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This dissertation examines individual diet specializations (IS) in a group of ecologically similar and evolutionarily related frogs and toads. Individual specialization is known to have widespread ecological and evolutionary effects.In an initial literature review (Chapter 2) I build a comprehensive theoretical framework showing how different types of population diversity can help, halt, or hinder sympatric speciation. I argue that IS can be maintained indefinitely in populations yet fail to lead to speciation because it is influenced by ecological conditions that may change.Additionally, IS can potentially aid niche partitioning among similar species, increasing species coexistence and resulting in less of the ecological opportunity required to develop more discrete polymorphisms.Stable isotopes are an increasingly common ecological tool for determining diets and habitat usage. However, to use them accurately, researchers need taxon-specific trophic discrimination factors and isotopic incorporation rates on any tissue used for stable isotope analysis. I determined these important isotope properties in adult frogs for the first time (Chapter 3), which not only allows me to use them in the following sections of v! my dissertation, but also allows other researchers to use stable isotopes to study frog and toad diets.Using stable isotope analyses, I examined how IS is influenced by ecological conditions (Chapter 4). I measured IS in five species of frogs and toads and determined which of three ecological parameters (resource diversity, intraspecific competition, and interspecific competition) affected IS in each species. I found that species differed in which ecological parameter best explained IS. Resource diversity most frequently affected IS, with conspecific density second in importance. My results showed that different ecological conditions support IS in different species.Finally, again using stable isotopes, I investigated whether intrapopulation niche variation could aid niche partitioning among the same five species of frogs and toads (Chapter 5). I found that species differed in their niches, but that subsets of individuals overlapped among species. The limited number of individuals overlapping between species decreases their interaction strength, which can contribute to niche partitioning and thus to species coexistence.vi!

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Heterosis in Cepaea

Cited by 9 publications

References 29 publications

Supergenes and their role in evolution

Supergenes and their role in evolution

The roles of plasticity versus dominance in maintaining polymorphism in mating strategies

The evolution and ecology of individual specializations amongst a group of dietary generalists.

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