Meeting Abstract

P2.138  Tuesday, Jan. 5  Predation risk and encounter rates with conspecific males influence female mate choice in hybridizing swordtail fishes WILLIS, P.M.*; RYAN, M.J.; ROSENTHAL, G.G; Univ. of Texas at Austin; Univ. of Texas at Austin; Texas A&M Univ. pmwillis@mail.utexas.edu

Direct costs and benefits (i.e., those that affect the chooser’s survival or fecundity) have prominent effects on mate choice within species. Where mate sampling is costly (e.g., where predation risk is high, or mate densities low), choosiness tends to decline. Although direct costs and benefits of choice within species are well-understood, little is known of their role in hybridizing taxa. We investigated the influence of variation in a) predation risk and b) encounter rates with male conspecifics on female mate choice in the naturally-hybridizing species pair Xiphophorus birchmanni – X. malinche. We presented female X. birchmanni with conspecific and heterospecific males, varying a) the distance to shelter (our proxy for predation risk), or b) the time elapsed since conspecific males were encountered. When shelter was equidistant from either species, females preferred to associate with conspecifics; however, this pattern was reversed when shelter was in closer proximity to heterospecifics. Similarly, females isolated from conspecific males for 24 hrs spent significantly more time associating with heterospecifics than they did when conspecific males were encountered immediately prior. These findings suggest that, despite preferences for conspecifics, females reduce their discrimination against heterospecifics in the face of increasing survival or search costs. As seasonal flooding and drought likely contribute to variation in both predation pressure and conspecific mate densities, one or both may be facilitating hybridization in the wild. More generally, these findings highlight the potential for direct costs and benefits of choice to promote or inhibit hybridization and reproductive isolation.