Female Associative Behavior Accompanies Morphological Distinction in Two Panamanian Populations of the MollyPoecilia gilli(Kner)

We investigated the associative behavior of the female molly (Pisces: Poeciliidae), Poecilia gilli (Kner), collected from two Panamanian populations—one from a clear running forest stream and the other from an impacted suburban stream. We tested the hypotheses that females would preferentially associate with males and females of their local population versus the foreign population and that males would prefer local females. We also tested the hypothesis that morphological distinctions between the two populations can be made. We found that females preferentially associated with local males but preferred neither local nor foreign females. Males exhibited no preference for females based on stream of origin. Dorsal fin height differed between populations but sex had no effect on this trait. Ecological factors or female preference could be responsible for this divergence, which could be reinforced by female preference for local males.