Phylogenetic Evidence for the Gain and Loss of a Sexually Selected Trait in Sailfin Mollies

Abstract

A phylogenetic comparative approach was used to examine the evolution of the enlarged “sailfin,” characteristic of the monophyletic lineage of sailfin mollies ( Poecilia : Mollienesia ), but absent in one of its species, P . latipunctata . Ancestral character state reconstructions demonstrated that the ancestral sailfin molly possessed the enlarged sailfin, and, thus, males of P . latipunctata have secondarily lost this trait. The strength of female mating preference was measured in P . latipunctata for two known targets of sexual selection, large male size, and sailfin male phenotype. Females of P . latipunctata preferred conspecific males of larger body size to those of smaller body size, but showed no preference for sailfin males of a related species, P . velifera , when compared with males of the shortfin species, P . mexicana . Taken together, these results suggest that the targets of sexual selection may have shifted in this species and that reduction in female preference for sailfin males may have played a role in the loss of this ornament.