PEEC Graduate Student Exit Seminar
“Behavioral and genomic patterns of evolution during speciation via reproductive and agonistic character displacement”
Wednesday, March 27, 2019, 4:00 P.M.
Charles G. Miller Auditorium, B102 CLSL
Abstract: Selection to avoid hybridizing with another species can result in mating trait evolution via reproductive character displacement (RCD). Similarly, selection to avoid aggressive interactions with another species can result in agonistic character displacement (ACD). Both RCD and ACD can lead to a pattern of enhanced preferences for mating or fighting with conspecifics over heterospecifics in areas of sympatry compared to allopatry. My dissertation examined the role of RCD and ACD in driving speciation in darters. I found that male orangethroat and rainbow darters exhibit strong preferences for mating with conspecific over heterospecific females and fighting with conspecific over heterospecific males in sympatry, but such preferences are absent in allopatry. This is consistent with RCD and ACD. To investigate the selective forces promoting RCD/ACD, I measured postzygotic isolation between orangethroat and rainbow darters and found that backcross hybrids suffer from dramatic inviability. I then sequenced and assembled the orangethroat darter genome and generated a linkage map for the rainbow darter to examine the genomic basis of postzygotic isolation. My results indicate that chromosomal rearrangements and negative epistatic interactions are acting throughout the genome and result in hybrid incompatibilities. This suggests that selection to avoid hybridization has likely promoted RCD and ACD in sympatry. Furthermore, by altering traits used in species recognition, RCD and ACD between orangethroat and rainbow darters has incidentally resulted in behavioral isolation among recently diverged species of orangethroat darters via cascade RCD and cascade ACD. I showed that orangethroat males exert strong preferences for mating with females from their own species over females from another closely related orangethroat species only when they are sympatric with rainbow darters, consistent with cascade RCD and cascade ACD. Lastly, despite the presence of striking sexual dimorphism and traditional sex roles, I found that females do not exhibit preferences for varying components of male color pattern between species. Instead, male competition drives male color pattern divergence between and within species via ACD. Together, these results demonstrate that male behavior alone can drive trait divergence between and within species via RCD and ACD. This contradict the widely-accepted paradigm that female preferences promote behavioral isolation in species where males exhibit elaborate secondary sex traits.
Coffee and cookies will be served in the atrium outside the auditorium beginning at 3:30 p.m.