JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. The evolution of female mating preferences has received considerable attention in sexual selection theory (Andersson 1994), but the importance of male mating preferences and how they differ from female mating preferences remain unclear. In some species both males and females are choosy, indicating potential for each sex to gain direct and/ or indirect benefits from their choice of mating partner.There are now many species in which mutual mate choice has been demonstrated (Hill 1993;Jones and Hunter 1993;Monaghan et al. 1996;Hunt et al. 1999;Sandvik et al. 2000;Velando et al. 2001;Chenoweth and Blows 2003). When mutual mate choice occurs on homologous signal traits, any intersexual differences in the strength or form of sexual selection generated by mate choice will have consequences for the expected level of sexual dimorphism. A net selection differential among the sexes is a prerequisite for the evolution of sexual dimorphism (Lande 1980). This net selection differential is often thought to be a result of directional sexual selection acting on males. However, in species in which male choice also occurs on the same trait, the opportunity for sexual selection on female as well as male traits means that the net selection differential among the sexes cannot be fully understood without an analysis of sexual selection on each of the sexes. Importantly, the link between choosiness per se and the type of sexual selection that it generates (directional, stabilizing, or disruptive) needs to be quantified.The presence of male mating preferences for female signal traits in species with conventional sex roles provides a challenge for sexual selection theory (Amundsen 2000) because of the limited conditions under which such behavior might evolve (Kokko and Johnstone 2002). Theoretically, male choice may be adaptive when male parental investment is high and/or the cost of searching for a mate is low and/or the variance in female quality is high (Burley 1977;Parker 1983;Owens and Thompson 1994;Johnstone et al. 1996;Kokko and Monaghan 2001). In insects, male choice has been found to be strongly associated with female traits that are indicators of fecundity such as body mass or body size (Bonduriansky 2001), although there is less evidence for sexual selection on female signal traits.The impact of mating preferences on trait values in the opposite sex can be investigated in two ways (Wagner 1998). First, the distribution of individual preference functions in one sex can be measured and compared to the distribution of trait values in the other sex (Ritchie 1996). This approach provides information on whether different types of mating preferences exist within a population (Wagner 1998). Second, a ...

If sexual selection is to result in speciation, traits involved in mate choice within species need to be capable of producing sexual isolation between species. We investigated the association between mate choice and sexual isolation using interspecific hybrids between two sibling species, Drosophila serrata and Drosophila birchii. A perfuming experiment demonstrated that olfaction was involved in the sexual isolation between the two species. A quantitative genetic analysis using 30 populations of hybrids between the two species indicated that mating success in hybrid individuals was predominately determined by cuticular hydrocarbons; the average genetic correlation between mating success and cuticular hydrocarbon profile was 0.84, and in some instances exceeded 0.95. Multivariate analysis of the cuticular hydrocarbons of the two species revealed that there were three independent blends of cuticular hydrocarbons that separated three levels of organization: species, sex, and sex within species. The hydrocarbons used by hybrids in mate choice included those that separated the two species, demonstrating that species-specific characters may be used in mate choice within populations. The interspecific reciprocal cross had major effect on which cuticular hydrocarbons were associated with mating success, indicating that the expression of the cuticular hydrocarbons was strongly sex linked.

Natural populations inhabiting the same environment often independently evolve the same phenotype. Is this replicated evolution a result of genetic constraints imposed by patterns of genetic covariation? We looked for associations between directions of morphological divergence and the orientation of the genetic variance-covariance matrix (G) by using an experimental system of morphological evolution in two allopatric nonsister species of rainbow fish. Replicate populations of both Melanotaenia eachamensis and Melanotaenia duboulayi have independently adapted to lake versus stream hydrodynamic environments. The major axis of divergence (z) among all eight study populations was closely associated with the direction of greatest genetic variance (gmax), suggesting directional genetic constraint on evolution. However, the direction of hydrodynamic adaptation was strongly associated with vectors of G describing relatively small proportions of the total genetic variance, and was only weakly associated with gmax. In contrast, divergence between replicate populations within each habitat was approximately proportional to the level of genetic variance, a result consistent with theoretical predictions for neutral phenotypic divergence. Divergence between the two species was also primarily along major eigenvectors of G. Our results therefore suggest that hydrodynamic adaptation in rainbow fish was not directionally constrained by the dominant eigenvector of G. Without partitioning divergence as a consequence of the adaptation of interest (here, hydrodynamic adaptation) from divergence due to other processes, empirical studies are likely to overestimate the potential for the major eigenvectors of G to directionally constrain adaptive evolution.

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org..

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org..