SEMISPECIES OF DROSOPHILA ATHABASCA DISTINGUISHABLE BY MALE COURTSHIP SOUNDS.

Abstract

During the past twenty years there has accumulated evidence that the widespread North American species, Drosophila athabasca Sturtevant and Dobzhansky 1936, consists of reproductively isolated, genetically divergent parts that warrant recognition as semispecies (Miller, 1958; Miller and Westphal, 1967; Miller and Voelker, 1972). Although no dependable phenotypic characteristics are known to distinguish these divisions of D. athabasca, ethological isolation between laboratory strains is sometimes strong (but usually incomplete, and hybrids are fertile), and chromosomal differences between the reproductively isolated divisions of the species appear substantial. Recently one of us (R. A. P.) discovered that amplified male courtship sounds are strikingly different from one kind of athabasca to another (Patty et al., 1973). We now present the results of a survey of male courtship sounds in seventy-two laboratory strains of D. athabasca interpreted as representing three semispecies-eastern A, B, and western-northern. The existence of three ethologically isolated kinds of D. athabasca was reported by Miller (1958), who found low frequencies of mating between Wyoming (and other western), Michigan, and New York strains. Miller and Westphal (1967) presented data from ethological isolation tests showing a consistent difference between fifteen western strains, with a Type I or Type V Y Chromosome, and nine eastern