Drosophila (Sophophora) athabasca Sturtevant and Dobzhansky

Grimaldi, David A., 2024, The Drosophila (Sophophora) obscura species group in the Americas (Diptera: Drosophilidae): review, revisions, and three new species, American Museum Novitates 2024 (4015), pp. 1-44 : 15-16

publication ID	https://doi.org/ 10.1206/4015.1
persistent identifier	https://treatment.plazi.org/id/0387351B-FFF3-FFA9-F62A-58E8FBCDFAFC
treatment provided by	Felipe
scientific name	Drosophila (Sophophora) athabasca Sturtevant and Dobzhansky
status

Treatment

Drosophila (Sophophora) athabasca Sturtevant and Dobzhansky View in CoL

Figures 7B View FIG , 9C View FIG , 14B View FIG

Drosophila (Sophophora) athabasca Sturtevant and Dobzhansky, 1936: 576 ; D. athabasca mahican Sturtevant and Dobzhansky, 1936 .

DIAGNOSIS: Like affinis and algonquin , thorax color varying from light brown to deep black-brown. Carina very narrow, short; male sex comb on ta 1 typically with 4 teeth (ranging from 3–5; Sulerud and Miller, 1966), ta 2 with 1 tooth; male ta 1 noticeably longer than (1.23×) ta 2; base of inner ventral epandrial lobe with furrows, no microtrichia; surstylus with row of 8–10 prensisetae; spermatheca very flattened, squat, width 2× the height (vs. 1.7× or less).

TYPE: Lectotype, ♂, selected from series of 7 specimens all labeled as “Grav [i.e., Gravina Island , Alaska: handwritten] / A.H. Sturtevant Collection 1970 [printed].” The male specimen to which Steyskal attached a penciled note “athabasca type” was labeled 12 June 2023 by me as the lectotype. In the USNM.

SPECIMENS EXAMINED: Besides type series (above), the following specimens: CANADA: Northwest Territories, Aklavik, May 24–July 25, 1931, Bryant [coll.] [68.24438, -134.97486], based on a series of six specimens caught on different days during May and July. UNITED GoogleMaps

STATES: NEW JERSEY: Bergen Co., Ridgewood, IV /87, Anne Soll / bred: spadices ( ASG 30 ♀, ASG 31♂) ( AMNH). NEW YORK: Sullivan Co. , Mongaup Lake , 3 mi N Debruce, 1/VI/68, hillside hardwood forest, carrion trap #316, S. Peck (9♂, 23♀) .

DISTRIBUTION: Northern North America, extending further southward in the east along the Appalachians, in central North America along the Rockies, and in the west along the Cascades. A new, very northern record for the species is the record given above from Aklavik, Northwest Territories. The species had previously been recorded from nearby Inuvik, NWT and Tuktoyaktuk, NWT, on the Arctic coast ( Toda, 1981; Takada and Toda, 1982). The flies are clearly resident in this tundra, where the only woody plants are shrubby birches ( Betula papyrifera : Betlulaceae) and some willows ( Salix spp. : Salicaceae ); this is not too surprising given their attraction to such varied substrates as skunk cabbage and even carrion.

COMMENTS: Three “semispecies” have been circumscribed for D. athabasca : western-northern (to which the type locality of the species belongs; distributed in the northern portions of eastern North America and northwestern N. America), and “semispecies” eastern A (northeastern North America) and eastern B (some coastal areas within northeastern U.S.). Their existence was originally based on significant differences in male courtship songs ( Miller, 1958; Miller et al., 1975; Chang and Miller, 1978), then confirmed with isozymes ( Jaenike et al., 1978), mtDNA sequences ( Yoon and Aquadro, 1994), and genomes ( Wong Miller et al., 2017). The “typical” form of athabasca reported by Sturtevant and Dobzhansky (1936)—the nominal subspecies—corresponds to flies from the western-northern “semispecies”; their subspecies mahican corresponds to “semispecies” eastern A and/or B. Sturtevant and Dobzhansky (1936) reported that D. athabasca mahican Sturtevant and Dobzhansky is somewhat lighter (thorax, legs, frons) than athabasca athabasca , but I have not found this to be consistent, and think that more northern or higher elevation populations may be darker in general because of cooler temperatures.

Though hybrids among “semispecies” are fully viable and fertile they rarely interbreed even in areas of sympatry, a separation reinforced by female mating preference toward male courtship (Yukilevich et al 2016). Not surprisingly, much of the genomic divergence is on the X chromosome, estimated to have originated only about 20,000 years ago (ca. 4 × 104 generations) ( Wong Miller et al., 2017). I was unable to detect morphological differences among semispecies in a blind test using cultures from each of them, which were provided years ago by Carol Yoon ( Yoon and Aquadro, 1994). Given that the semispecies, or subspecies, are not morphologically distinguishable they should continue to be classified as one species despite the behavioral and genetic differences. This is a compelling example of incipient speciation.