Meeting Abstract

P1.163  Saturday, Jan. 4 15:30  Sexual selection and trait introgression across replicated natural hybrid zones in swordtail fish (Teleostei:Xiphophorus) JOFRE-RODRIGUEZ, GI*; ROSENTHAL, GG; Texas A&M University; Texas A&M University gjofre@bio.tamu.edu

Clinal hybrid zones, where one species transitions to another over a spatial gradient, are amenable to powerful tests of evolutionary hypotheses by comparing cline widths among traits and genetic markers. Gene flow in hybrid zones can generate introgression of specific genes; sexual selection by mate choice can drive both the loss of novel traits or the loss of an existing one. We will study how these two processes affect specific traits in natural hybrid zones between the livebearing fish Xiphophorus malinche and X. birchmanni along three independent altitudinal gradients in the foothills of the Sierra Madre Oriental of Hidalgo state, Mexico. I will characterize phenotypic clines by quantifying both male sexually-dimorphic morphology and female mating preferences for morphological traits upstream to downstream in at least seven localities per cline. To estimate genome-wide genotypic clines, I will use Multiplexed Shotgun Genotyping (MSG) to identify soft ancestry calls in sampled individuals, corresponding to X. malinche or X. birchmanni. By comparing cline width in morphological traits relative to cline width in genome-wide ancestry, I can estimate the magnitude and direction of selection on these traits across the hybrid zone. I can then compare this estimate of selection with that predicted by clinal data on mating preferences. I can also compare cline width for morphological traits with that for candidate gene regions associated with these traits.