Meeting Abstract

P2.61  Jan. 5  Behavioral thermoregulatory adaptations in Drosophila santomea and Drosophila yakuba larvae as hybridization barriers WANG, G*; KIM, GC; Univ of Washington, Seattle; Univ of Washington, Seattle gw0@u.washington.edu

Drosophila santomea is a recently discovered sister species of Drosophila yakuba found on the island of Sao Tom�. D. santomea resides at higher altitudes than D. yakuba and the two species overlap over a narrow range at intermediate altitudes. Hybridization is minimal between the two species with hybrids making up only 1% of all flies in the overlapping zone. Though some work has suggested explored pre-zygotic isolating mechanisms, no study had investigated potential post-zygotic barriers to hybridization in these species. Given the disjunct altitudinal distributions of the two species and the strong correlation of temperature with altitude, we predicted that heritable thermoregulatory behaviors could act as post-zygotic barriers to hybridization. We measured larval preferred (T_pref) by recording larval positions after 45 minutes on a laboratory thermal gradient. We measured T_MVT and T_VW temperatures by gradually heating plates of media containing larvae and recording the temperatures at which larvae left the food (T_MVT ) and at which larvae vertically waved(T_VW). D. santomea had significantly lower T_MVT, T_VW, and T_pref than D. yakuba. Hybrid thermoregulatory behaviors were intermediate between the parent species but strongly biased towards D. yakuba. If the parent species lay their eggs in different microclimates, hybrid larvae with D. santomea mothers and the thermoregulatory behaviors inherited from D. yakuba fathers might suffer reduced survivorship. These data support the hypothesis that thermoregulatory behaviors prevent hybridization in these species, however more work investigating the larval microclimates of the parent species is necessary.