Whether environmental effects during juvenile development can alter the ontogeny of adult mating behaviour remains largely unexplored. We evaluated the effect of diet on the early expression of conspecific recognition in spadefoot toads, Spea bombifrons. We found that juvenile toads display phonotaxis behaviour six weeks post-metamorphosis. However, preference for conspecifics versus heterospecifics emerged later and was diet dependent. Thus, the environment can affect the early development of species recognition in a way that might alter adult behaviour. Evaluating such effects is important for understanding variation in hybridization between species and the nature of species boundaries.
[Show abstract][Hide abstract] ABSTRACT: As mitochondria are inherited in a matrilinear way, an animal hybrid contains the mitochondrial DNA of its 'mother species'. Of 80 studies that analysed the mitochondrial DNA of at least five hybrid individuals, 50 showed that all hybrids contained the mitochondrial DNA of only one of the two parental species, indicating either mating of females of species A with males of species B but not vice versa (unidirectional hybridization) or the disappearance of one of the two parental mtDNA types after reciprocal hybridization. I review and discuss factors promoting unidirectional or reciprocal hybridization and present a sexual selection hypothesis for unidirectional hybridization. The inequality of the sexes in parental investment leads to the sex that invests more being the more discriminating one. In the presence of conspecific males, females reject allospecific males and, consequently, a male in an environment of both allospecific sexes is unlikely to mate, while in the absence of conspecific males, females sometimes accept fertilizations by males of other species. Thus, hybrid matings are usually between the females of a rare species and the males of a common species, but not vice versa. Copyright 1999 The Association for the Study of Animal Behaviour.
[Show abstract][Hide abstract] ABSTRACT: Character displacement has long been considered a major cause of adaptive diversification. When species compete for resources or mates, character displacement minimizes competition by promoting divergence in phenotypes associated with resource use (ecological character displacement) or mate attraction (reproductive character displacement). In this study, we investigated whether character displacement can also have pleiotropic effects that lead to fitness trade-offs between the benefits of avoiding competition and costs accrued in other fitness components. We show that both reproductive and ecological character displacement have caused spadefoot toads to evolve smaller body size in the presence of a heterospecific competitor. Although this shift in size likely arose as a by-product of character displacement acting to promote divergence between species in mating behavior and larval development, it concomitantly reduces offspring survival, female fecundity, and sexual selection on males. Thus, character displacement may represent the "best of a bad situation" in that it lessens competition, but at a cost. Individuals in sympatry with the displaced phenotype will have higher fitness than those without the displaced trait because they experience reduced competition, but they may have reduced fitness relative to individuals in allopatry. Such a fitness trade-off can limit the conditions under which character displacement evolves and may even increase the risk of "Darwinian extinction" in sympatric populations. Consequently, character displacement may not always promote diversification in the manner that is often expected.
[Show abstract][Hide abstract] ABSTRACT: The last decade has witnessed considerable theoretical and empirical investigation of how male sexual ornaments evolve. This strong male-biased perspective has resulted in the relative neglect of variation in female mate preferences and its consequences for ornament evolution. As sexual selection is a co-evolutionary process between males and females, ignoring variation in females overlooks a key aspect of this process. Here, we review the empirical evidence that female mate preferences, like male ornaments, are condition dependent. We show accumulating support for the hypothesis that high quality females show the strongest mate preference. Nonetheless, this is still an infant field, and we highlight areas in need of more research, both theoretical and empirical. We also examine some of the wider implications of condition-dependent mating decisions and their effect on the strength of sexual selection.
Current Biology 10/2006; 16(17):R755-65. DOI:10.1016/j.cub.2006.08.022 · 9.57 Impact Factor
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