Meeting Abstract

80.3  Tuesday, Jan. 6  Ecological correlates of hybridization in wood warblers (family Parulidae): a mate choice perspective WILLIS, P.M.*; SYMULA, R.E.; RYAN, M.J.; Univ. of Texas, Austin; Univ. of Texas, Austin; Univ. of Texas, Austin pmwillis@mail.utexas.edu

Variation in mate choice can arise through changes in ecological conditions, such as mate availability, that affect the cost of finding and evaluating potential mates. Little is known, however, of the role such conditions play in promoting hybridization. Hybridization is frequently recorded among the wood warblers, and a lack of conspecific mates is often implicated as a causal factor. Competition among warblers for breeding sites may also increase the cost of continued mate search and contribute to heterospecific pairing. We investigated whether hybridization among North American wood warblers correlates with various estimates of the availability of conspecific mates (e.g. population size), or the availability of suitable breeding habitat (e.g. breeding range size). We generated mtDNA-based phylogenetic trees for the family, and conducted phylogenetic comparative analyses of North American species. In contrast to earlier observations, we found hybridization to be greatest between sympatric species, and between close relatives. Results to date suggest that smaller populations produced proportionately more hybrids than larger ones, as did those with smaller breeding ranges relative to those with larger ones. While the observed correlations may arise through alternate mechanisms, our findings suggest that a low availability of either conspecific mates or breeding habitat may facilitate wood warbler hybridization by increasing permissiveness in mate choice. More generally, this study suggests that variation in environmental conditions relevant to mate choice may have important consequences for reproductive isolation between taxa, particularly where the genetic costs of hybridization are mild.