Male Biases for Male Characteristics in Females in Priapella olmecae and Xiphophorus helleri (Family Poeciliidae)


Alexandra L. Basolo, School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, NE 68588–0118, USA. E-mail:


Preexisting receiver biases can affect the evolution of sexually selected traits once traits favored by such biases arise. Female guayacón olmeca, Priapella olmecae, and green swordtail, Xiphophorus helleri, possess a bias favoring sworded conspecific males, despite phylogenetic evidence that the sexually selected sword expressed by male swordtails arose in Xiphophorus after the divergence of the two genera. In this study, we investigated the state of the bias favoring a sword in male Priapella and Xiphophorus to determine whether males also possess a bias that could operate in an intersexual selection context. Male P. olmecae preferred conspecific females with swords to those without swords. Thus, males and females in this unsworded species appear to share a preexisting bias favoring individuals of the opposite sex with swords. Male X. helleri, however, did not express a bias favoring sworded females; instead, in this species in which the sword is restricted to males, males discriminated against conspecific females with swords. Previous work suggests that female mate choice and male–male competition likely contribute to the maintenance of the sword in X. helleri. The sword may also play a role in sex recognition in swordtails. The absence of a sword preference in male green swordtails could reflect the current function of the sword.