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1.
BMC Ecol ; 18(1): 46, 2018 11 06.
Artigo em Inglês | MEDLINE | ID: mdl-30400870

RESUMO

BACKGROUND: Reproductive interference can mediate interference competition between species through sexual interactions that reduce the fitness of one species by another. Theory shows that the positive frequency-dependent effects of such costly errors in mate recognition can dictate species coexistence or exclusion even with countervailing resource competition differences between species. While usually framed in terms of pre-mating or post-zygotic costs, reproductive interference manifests between individual Caenorhabditis nematodes from negative interspecies gametic interactions: sperm cells from interspecies matings can migrate ectopically to induce female sterility and premature death. The potential for reproductive interference to exert population level effects on Caenorhabditis trait evolution and community structure, however, remains unknown. RESULTS: Here we test whether a species that is superior in individual-level reproductive interference (C. nigoni) can exact negative demographic effects on competitor species that are superior in resource competition (C. briggsae and C. elegans). We observe coexistence over six generations and find evidence of demographic reproductive interference even under conditions unfavorable to its influence. C. briggsae and C. elegans show distinct patterns of reproductive interference in competitive interactions with C. nigoni. CONCLUSIONS: These results affirm that individual level negative effects of reproductive interference mediated by gamete interactions can ramify to population demography, with the potential to influence patterns of species coexistence separately from the effects of direct resource competition.


Assuntos
Biota , Caenorhabditis/fisiologia , Animais , Caenorhabditis elegans/fisiologia , Dinâmica Populacional , Crescimento Demográfico , Reprodução
2.
G3 (Bethesda) ; 8(12): 3891-3902, 2018 12 10.
Artigo em Inglês | MEDLINE | ID: mdl-30327379

RESUMO

Reproductive barriers involving gametic incompatibilities can act to enhance population divergence and promote the persistence of species boundaries. Observing gametic interactions in internal fertilizing organisms, however, presents a considerable practical challenge to characterizing mechanisms of such gametic isolation. Here we exploit the transparency of Caenorhabditis nematodes to investigate gametic isolation mediated by sperm that can migrate to ectopic locations, with this sperm invasion capable of inducing female sterility and premature death. As a step toward identifying genetic factors and mechanisms associated with female susceptibility to sperm invasion, we characterized a panel of 25 C. elegans genetic mutants to test for effects on the incidence and severity of sperm invasion in both conspecific and inter-species matings. We found genetic perturbations to contribute to distinct patterns of susceptibility that identify ovulation dynamics and sperm guidance cues as modulators of ectopic sperm migration incidence and severity. Genotypes confer distinctive phenotypic sensitivities to the sperm from conspecific C. elegans males vs. heterospecific C. nigoni males, implicating evolution of functional divergence in the history of these species for components of sperm-reproductive tract interactions. Sexually-antagonistic co-evolution within species that drives divergent trait and molecular evolution between species provides a working model to explain mismatched species-specific gametic interactions that promote or mitigate ectopic sperm migration.


Assuntos
Caenorhabditis elegans/genética , Evolução Molecular , Mutação , Característica Quantitativa Herdável , Motilidade dos Espermatozoides/genética , Espermatozoides , Animais , Caenorhabditis elegans/citologia , Caenorhabditis elegans/metabolismo , Feminino , Masculino , Especificidade da Espécie
3.
PLoS Biol ; 12(7): e1001915, 2014 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-25072732

RESUMO

Conflict between the sexes over reproductive interests can drive rapid evolution of reproductive traits and promote speciation. Here we show that inter-species mating between Caenorhabditis nematodes sterilizes maternal individuals. The principal effectors of male-induced harm are sperm cells, which induce sterility and shorten lifespan by displacing conspecific sperm, invading the ovary, and sometimes breaching the gonad to infiltrate other tissues. This sperm-mediated harm is pervasive across species, but idiosyncrasies in its magnitude implicate both independent histories of sexually antagonistic coevolution within species and differences in reproductive mode (self-fertilizing hermaphrodites versus females) in determining its severity. Consistent with this conclusion, in androdioecious species the hermaphrodites are more vulnerable, the males more benign, or both. Patterns of assortative mating and a low incidence of invasive sperm occurring with conspecific mating are indicative of ongoing intra-specific sexual conflict that results in inter-species reproductive incompatibility.


Assuntos
Caenorhabditis/fisiologia , Reprodução/fisiologia , Isolamento Reprodutivo , Espermatozoides/fisiologia , Animais , Feminino , Organismos Hermafroditas/fisiologia , Infertilidade/etiologia , Inseminação , Masculino , Comportamento Sexual Animal , Especificidade da Espécie
4.
Proc Biol Sci ; 278(1721): 3116-22, 2011 Oct 22.
Artigo em Inglês | MEDLINE | ID: mdl-21367784

RESUMO

Contemporary theory predicts that the degree of mimetic similarity of mimics towards their model should increase as the mimic/model ratio increases. Thus, when the mimic/model ratio is high, then the mimic has to resemble the model very closely to still gain protection from the signal receiver. To date, empirical evidence of this effect is limited to a single example where mimicry occurs between species. Here, for the first time, we test whether mimetic fidelity varies with mimic/model ratios in an intraspecific mimicry system, in which signal receivers are the same species as the mimics and models. To this end, we studied a polymorphic damselfly with a single male phenotype and two female morphs, in which one morph resembles the male phenotype while the other does not. Phenotypic similarity of males to both female morphs was quantified using morphometric data for multiple populations with varying mimic/model ratios repeated over a 3 year period. Our results demonstrate that male-like females were overall closer in size to males than the other female morph. Furthermore, the extent of morphological similarity between male-like females and males, measured as Mahalanobis distances, was frequency-dependent in the direction predicted. Hence, this study provides direct quantitative support for the prediction that the mimetic similarity of mimics to their models increases as the mimic/model ratio increases. We suggest that the phenomenon may be widespread in a range of mimicry systems.


Assuntos
Insetos/genética , Polimorfismo Genético/genética , Adaptação Biológica , Animais , Colúmbia Britânica , Feminino , Masculino , Ontário , Fenótipo , Pigmentação , Quebeque , Seleção Genética
5.
Evolution ; 62(4): 868-78, 2008 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-18194475

RESUMO

Sexually selected traits are thought to impose survival costs on showy males. Recent empirical work found a negative relationship between male display and survival in a field cricket species (Orthoptera, Gryllidae, Gryllinae) where there is no evidence of a mating bias toward older males. In most species, however, male survival and ornamentation are positively correlated, and older males often have a mating success advantage over younger males. These findings suggest that male quality and survival are positively correlated, but more tests of this hypothesis are needed. We measured the condition dependence of male survival and calling effort in another grylline, Gryllus pennsylvanicus, where older males have previously been shown to have greater mating success. We varied condition by manipulating diet, and measured male life span and calling effort to assess the relative condition dependence of these traits. High- and medium-condition males survived longer than low-condition males, and high-condition males called more than medium- and low-condition males. Differences in calling effort among the condition treatments were not apparent early in life, but emerged as males aged. We discuss possible explanations for the differences between our study and contrasting results such as the previous grylline work.


Assuntos
Comunicação Animal , Fenômenos Fisiológicos da Nutrição Animal , Gryllidae/fisiologia , Longevidade/fisiologia , Fatores Etários , Animais , Tamanho Corporal/fisiologia , Dieta , Feminino , Masculino , Comportamento Sexual Animal/fisiologia
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