Geographical Distributions of the American Drosophila affinis Subgroup Species

Abstract

The Drosophila affinis subgroup belongs to the D. obscura group of the subgenus Sophophora Sturtevant. Except for one European species, D. helvetica Burla, 1948, the subgroup consists of eight American species: D. affinis Sturtevant, 1916; algonquin Sturtevant and Dobzhansky, 1936; athabasca Sturtevant and Dobzhansky, 1936; azteca Sturtevant and Dobzhansky, 1936; dobzhanskii Patterson, 1943; narragansett Sturtevant and Dobzhansky, 1936; seminole Sturtevant and Dobzhansky, 1936; and tolteca Patterson and Mainland, 1944. The closeness of relationship of these species is attested to not only by their morphological similarity but also by the fact that it has been possible in the laboratory to derive certain interspecific hybrids: athabasca x azteca, both reciprocal crosses (Sturtevant and Dobzhansky, 1936); algonquin 9 x athabasca d' (Miller, 1939); affinis ? x athabasca 6' (Miller, 1941); and azteca x tolteca, both reciprocal crosses (Patterson, 1954). Moreover, female algonquin-athabasca hybrids are fertile (Miller, 194L), as are both sexes of hybrids between tolteca ? 9 and azteca 6' 6' (Patterson, 1954). Since the affinis subgroup was first identified (Sturtevant and Dobzhansky, 1936), the distributions of the member species and their incidence in collections have been reported both in reports on cytological and genetic variation in the species, and in reports on Drosophila collecting and species distributionsfor example, Dobzhansky and Sokolof (1939), Miller (1939), Patterson (1943), Patterson and Wagner (1943), Dobzhansky and Epling (1944), Patterson and Mainland (1944), Novitski (1946), Spiess (1949), Patterson and Stone (1952), Williams and Miller (1952), Levitan (1954), and BuzzattiTraverso and Scossiroli (1955). These reports (and unpublished data) have not only led to extensions of previously known geographical ranges, but also have given better ideas of the limits of distribution of some of the species and of the relative frequencies of two or more of the species collected together. It is the purpose of this paper to summarize information on the distributions of the American members of the affinis subgroup, using published records and the unpublished data of the author and several other collectors.