title: The search for causal traits of speciation: Divergent female mate preferences target male courtship song, not pheromones, in Drosophila athabasca species complex.
abstract: Understanding speciation requires the identification of traits that cause reproductive isolation. This remains a major challenge since it is difficult to determine which of the many divergent traits actually caused speciation. To overcome this difficulty, we studied the sexual cue traits and behaviors associated with rapid speciation between EA and WN sympatric behavioral races of Drosophila athabasca that diverged only 16,000-20,000 years ago. First, we found that sexual isolation was essentially complete and driven primarily by divergent female mating preferences. To determine the target of female mate choice, we found that, unlike cuticular hydrocarbons (CHCs), male courtship song is highly divergent between EA and WN in both allopatry and sympatry and is not affected by latitudinal variation. We then used pheromone rub-off experiments to show no effect of CHCs on divergent female mate choice. In contrast, both male song differences and male mating success in hybrids exhibited a large X-effect and playback song experiments confirmed that male courtship song is indeed the target of sexual isolation. These results show that a single secondary sexual trait is a major driver of speciation and suggest that we may be overestimating the number of traits involved in speciation when we study older taxa.
authors.affiliation: Department of Biology, Union College, Schenectady, New York, 12308. yukilevr@union.edu.
authors.forename: Roman
authors.initials: R
authors.lastname: Yukilevich
authors.affiliation: Department of Biology, Union College, Schenectady, New York, 12308.
authors.forename: Taylor
authors.initials: T
authors.lastname: Harvey
authors.affiliation: Department of Biology, Union College, Schenectady, New York, 12308.
authors.forename: Son
authors.initials: S
authors.lastname: Nguyen
authors.affiliation: Department of Biology, Union College, Schenectady, New York, 12308.
authors.forename: Joanne
authors.initials: J
authors.lastname: Kehlbeck
authors.affiliation: Department of Biology, Union College, Schenectady, New York, 12308.
authors.forename: Agnes
authors.initials: A
authors.lastname: Park
mesh_terms: D000818:Animals; D003380:Courtship; D004330:Drosophila / Q000145:classification* / Q000235:genetics* / Q000502:physiology; D005260:Female; D049810:Genetic Speciation; D008297:Male; D052586:Mating Preference, Animal; D010675:Pheromones / Q000378:metabolism; D060047:Reproductive Isolation; D014481:United States; D014828:Vocalization, Animal
chemical_list: D010675:Pheromones
keywords: Cuticular hydrocarbons; ecological speciation; female mating preference; large X-effect; magic traits; male courtship song; sexual isolation; sexual selection; speciation phenotypes