It has been hypothesized that morphological diversity within clades can be generated by
simple alterations of shared developmental programs. However, few studies have examined …

In a natural population, we document changes in the frequencies of alleles influencing body
size and size-correlated alternative male reproductive tactics, and we examine the possible …

Natural and sexual selection can have either opposing or synergistic effects on the evolution
of traits. In the green swordtail Xiphophorus helleri, sexual selection arising from female …

When a genetically determined polymorphism is selectively maintained in a population, the
different morphs should have equal fitnesses at equilibrium. We empirically examined this …

The heritabilities of body length of male, green swordtails were estimated at five ages and at
maturity by full-sib analyses. Male offspring from each of 32 maternal families were reared …

Recent years have seen increasing awareness of the utility of comparative studies using
phylogenies to test hypotheses of evolutionary process (eg, Felsenstein 1985; Donoghue …

Hybridization is increasingly being recognized as a widespread process, even between
ecologically and behaviorally divergent animal species. Determining phylogenetic …

Responses to sexually antagonistic selection are thought to be constrained by the shared
genetic architecture of homologous male and female traits. Accordingly, adaptive sexual …

Sexual selection can increase morphological diversity within and among species. Little is
known regarding how interspecific variation produced through sexual selection affects other …

The swordlike exaggerated caudal fin extensions of male swordtails are conspicuous traits
that are selected for through female choice. Swords are one of only few examples where the …