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

摘要

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 ofP.latipunctatahave secondarily lost this trait. The strength of female mating preference was measured inP.latipunctatafor two known targets of sexual selection, large male size, and sailfin male phenotype. Females ofP.latipunctatapreferred 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.