Drosophila limpiensis Mainland, 1941

Grimaldi, David A., 2022, The Drosophila funebris Species Group in North America (Diptera: Drosophilidae), American Museum Novitates 2022 (3988), pp. 1-28 : 13-17

Drosophila limpiensis Mainland, 1941 , new status

Figures 1A , 2A , 4A , 5A ; 6A, B, H ; 7C ; 8A ; 9B

Drosophila macrospina limpiensis Mainland, 1941: 160 . Mainland, 1942 (hybrid sterility); Patterson and Wheeler, 1942 (redescription, immature stages, internal reproductive organs, chromosomes); Patterson and Stone, 1952 (distribution); Ewing, 1979 (mating behavior)

DIAGNOSIS: Very similar to macrospina , with differences as noted. Postocellar setae parallel to very slightly convergent (vs. usually strongly convergent to crossing in macrospina ); male with lateral lobes of distiphallus in D. limpiensis thinner (especially at the apex), less protruding than in macrospina ; apical lobes with fewer lateral serrations; gap between cercal spines 2 and 3 slightly less than width of spine 2 (gap is substantially larger than width of spine 2 in macrospina ). Female: oviscapt dark, sclerotized as in macrospina . No distinction between the two species is apparent in the surstyli or female terminalia.

DESCRIPTION: A description was provided by Patterson and Wheeler (1942), to which the following details of the adults are added (N = 4 specimens measured, all from type locality [Limpia Canyon, TX]): Body size: ThL 1.38 mm (1.35–1.44); wing length, 2.21 mm (2.15–2.35).

HEAD: proportions HW/HD 1.38 (1.35–1.44); frons short, FL/LFW 0.71 (0.69–0.75), broadened dorsally, UFW/LFW 1.35 (1.30–1.38); vertical setae equal in size, VT-index 0.98 (0.96– 1.03); vibrissa slightly larger than subvibrissa, vibrissa index 0.85 (0.65–1.05); ocellar setae significantly longer than postocellars. Eye shape ovoid, ED/EW 1.32 (1.28–1.37); cheek short, ED/CD 7.90 (7.1–8.3); proclinate seta twice the length of anteriorreclinate, OR 1 /OR 2 2.09 (2.0– 2.25), proclinate significantly shorter than posterior reclinate, OR 1 /OR 3 0.68 (0.58–0.75); carina narrow, CL/CW 5.3 (4.6–5.8).

THORAX: Postpronotal setae very similar in size, h-index 0.89 0.81–0.95); ant. dorsocentral seta shorter than post. dc, DC-index 0.68; post. katepisternal seta significantly larger than anterior one, S-index 0.59 (0.55–0.68); post. scutellar seta larger than ant. scutellar, Scut-index 0.85. WING of moderate length, WL/ThL 2.02 (1.94–2.09), relatively broad WL/WW 2.14 (2.01–2.21); C-index 2.82 (2.75–2.96); hb-index 1.93 (1.78–2.04); 4V-index 1.54 (1.51–1.60); dm-cu distant from wing margin, 5X-index 1.32 (1.08–1.42).

TYPES: Holotype, male (label typed): D. macrospina /limpiensis M/ Limpia Canyon ,/ Texas 1939/ J.T. Patterson, col./Type. In AMNH.

SPECIMENS EXAMINED: MEXICO: Sonora, DSC stock no. 15120-1931.02 (4M, 4 F, 2 of each dissected) (no further locality data). United States: Arizona: Patagonia, ex DSC stock no. 15120- 1921.00 (4M, 4F, 2 of each dissected); Texas: Ft. Davis /Limpia Canyon/MR Wheeler, WK Baker June 1947 /1704.5 (3M, 3F; 1 dissected). Field notebooks from the former UT collection contain more detailed locality information for collection lot 1704.5, (recorded as macrospina ): “Limpia Canyon, 10 mi W of junction of state highways #17 and #118 near Ft. Davis, Texas and 6.6 mi from Lot 1703. 4 traps.” Coordinates are 30.7775°, -103.7412°. All in AMNH .

DISTRIBUTION: Patterson and Wagner (1943) mapped 22 records of limpiensis , which was updated by Patterson and Stone (1952). They describe a distribution from northern Mexico (Sonora, central Chihuahua [Loredo]) north to western Texas (Davis Mountains) and portions of New Mexico, most of Arizona and the southwestern corner of Utah. There is a gap in central Texas and northward—in an area that the University of Texas lab sampled very well—where limpiensis ends and macrospina begins more eastward. Regrettably, most of the specimens from these localities were not saved.

Besides the specimens examined and Patterson records cited above, Mainland (1942) used stocks of limpiensis for his crossing experiments from the following localities: MEXICO: Sonora: Hermosillo (29.0745°, -110.9594°), Magdalena (30.6303°, -110.9699°), Punta del Agua (28.4258°, -110.4067°). United States: Arizona: Patagonia (31.5410°, -110.7531°); New Mexico: Silver City (32.7865°, -108.2652°), Radium Springs (32.4819°, -106.9072°); Texas: Limpia Canyon (30.7774°, -103.7412°); Utah: Zion National Park (~37.2550°, -112.9797°). This material was also the basis for the description by Patterson and Wheeler (1942).

COMMENTS: What were considered eastern and southwestern populations/subspecies of macrospina are now separated into two species, macrospina and limpiensis , respectively.

While the morphological evidence for separating limpiensis from macrospina is subtle, it is consistent as diagnosed above. Also, evidence from Mainland (1941, 1942) indicates substantial hybrid infertility between Drosophila macrospina and D. limpiensis . Flies of the two species readily mate but the F 1 hybrids of limpiensis female and macrospina male crosses were “sterile to slightly fertile” ( Mainland, 1942). Patterson and Stone (1952) mentioned an east-west gradient in hybrid sterility between macrospina X limpiensis , which may reflect the apparent geographical separation between these species in western Texas and Oklahoma. COII sequences of DSC stocks of macrospina and limpiensis in GenBank (National Center for Biotechnology Information, 2020) have 99% similarity based on BLAST analyses. Assuming the online sequences are correct, this is typically considered minimal identity for species separation (e.g., the sister species Drosophila sechellia and D. simulans have 97% similarity in the COI region). However, and for larger context, COII sequences between D. macrospina and Zaprionus tuberculatus , for example, and species in the Drosophila cardini group have 90% similarity. The close genetic similarity between D. macrospina and limpiensis no doubt reflects the subtle phenotypic differences between the species.

Spieth (1952: 434) mentioned that the mating behavior of macrospina and limpiensis is “identical in all respects,” but this was based on visual observation. He studied two cultures: no. 1897 from Alleghany State Park, New York ( macrospina ), and no. 1248.1b from San Bernardino, Arizona ( limpiensis ); specimens from the latter culture were morphologically studied here. Ewing (1979) reported significant differences in the male mating songs, based on two other cultures (numbers were not reported): one from Patagonia, Arizona (for limpiensis , presumably same material studied morphologically here), and one from Albuquerque, New Mexico (for macrospina , material not studied here). According to Ewing (1979) Drosophila limpiensis and macrospina differ in both the primary and secondary songs, limpiensis having longer interburst intervals, greater amplitude of sound pulses, and, in the secondary song, the pulses are more condensed.

In addition to morphological, genetic, and behavioral distinctions, Drosophila limpiensis and D. macrospina also appear to be ecologically distinct, the former occurring in hot, dry areas in western Texas, New Mexico, Arizona, and northwestern Mexico. Drosophila macrospina is a resident of forested areas with humid climates from eastern Texas to Florida, north to New England; northernmost records are in Michigan; Rochester, New York; and southern Ontario, Canada ( Miller et al., 2017).

Figures

FIG. 1. Heads, frontal views, of native North American species of the Drosophila funebris group. A. D. limpiensis (ex: type locality: Limpia Canyon, Texas). B. D. macrospina (ex: Rochester, NY). C. D. subfunebris (ex: type series: Pasadena, CA). D. D. trispina (ex: type series: Earp, CA). To the same scale.

FIG. 2. Heads, lateral views, of native North American species of the Drosophila funebris group. A. D. limpiensis (ex: Limpia Canyon, TX). B. D. macrospina (ex: Piqua, OH). C. D. subfunebris (ex: Pasadena, CA). D. D. trispina (ex: Earp, CA). To the same scale.

FIG. 4. Epandria (male) of native North American species of the Drosophila funebris group; posterolateral views (to same scale). A. D. limpiensis (ex: Limpia Canyon, TX). B. D. macrospina (ex: Magazine Mtn., AR). C. D. subfunebris (ex: Pasadena, CA). D. D. trispina (ex: Earp, CA).

FIG. 5. Male genitalia of native North American species of the Drosophila funebris group, ventral views (to same scale). A. D. limpiensis (ex: Limpia Canyon, TX). B. D. macrospina (ex: St. Catherine’s Island, GA). C. D. macrospina (ex: Rochester, NY). D. D. subfunebris (ex: Pasadena, CA). E. D. trispina (ex: Earp, CA).

FIG. 6. External details of male terminalia, A–G: Cercal spines, right lateral views; H–K: Surstyli, lateral views. All to same scale. A. D. limpiensis (ex: Limpia Canyon, TX). B. D. limpiensis (ex: Patagonia, Arizona). C. D. macrospina (ex: New Orleans, LA). D. D. macrospina (ex: Piqua, OH), dashed line indicates spine sometimes missing. E. D. subfunebris ex: Pasadena, CA). F. G. D. trispina (ex: Earp, CA), G. showing right cercus with one less spine. H. D. limpiensis (ex: Limpia Canyon, TX). I. D. macrospina (ex: New Orleans, LA). J. D. subfunebris (ex: Pasadena, CA). K. D. trispina (ex: Earp, CA).

FIG. 7. Aedeagi with aedeagal apodemes, ejaculatory apodemes (B, D, E), lateral views (all to same scale). A. D. macrospina (ex: Magazine Mtn., AR). B. D. macrospina (ex: Rochester, NY). C. D. limpiensis (Limpia Canyon, TX). D. D. trispina. E. D. subfunebris.

FIG. 8. Detail of apices of aedeagi (ventral views) of native North American species of the D. funebris group (all to the same scale). A. D. limpiensis. B. D. macrospina (ex: New Orleans, LA). C. D. macrospina (ex: Piqua, OH). D. D. macrospina (ex: Missouri). E. D. trispina. F. D. subfunebris.

FIG. 9. Female terminalia (oviscapts, spermathecal capsules, and minutely scaled oviprovector membrane [internal]) of North American species of the D.funebris group (all to same scale).A. D. funebris (introduced). B. D.limpiensis. C. D. macrospina (spermatheca of limpiensis and macrospina is identical). D. D. subfunebris. E. D. trispina.