Dixa appalachiensis, Moulton, John K., 2016

Moulton, John K., 2016, The Dixa inextricata Dyar & Shannon (Diptera: Dixidae) species group, with two new cryptic species from the eastern Nearctic Region, Zootaxa 4121 (4), pp. 458-472 : 460-463

Dixa appalachiensis sp. nov.

( Figs 1–2 , 5–8, 9, 12–14, 21, 25–28)

Type material. HOLOTYPE ♂, labeled: “ USA: NC / Haywood County / Woodfin Cascades @ Blue Ridge Parkway NP / N35°27′05.53″ W83°05′39.04″, 1256 m / 16.vii.2006 / J.K. Moulton ”; “HOLOTYPE/ Dixa / appalachiensis / J.K. Moulton [red label]” ( CNC). PARATYPES: Same data as holotype, 8♂ and 2♀ each to CNC and USNM .

Additional material examined. USA. KENTUCKY: BELL COUNTY, Cumberland Gap NHP, Tunnel Crk , 28.xi.2005, JKM— 6♂, 2♀. NORTH CAROLINA: BUNCOMBE COUNTY, Shope Frk, UV light trap, 25.v.2007, J. Robinson— 12♂, 3♀. Ox Crk, UV light trap, 25–26.v.2007, J. Robinson— 71♂, 12♀. HAYWOOD COUNTY, Great Smoky Mtns NP, small stream atop Hemphill Bald, 15.vi.2007, JKM— 4♂, 2♀. GSMNP-Cataloochee Section, Rough Frk, 862 m, N35°36′58.47″ W83°07′11.71″, 26.vii.2005, JKM— 4♂. Blue Ridge Parkway NP, Woodfin Cascades, 1256 m, N35°27′05.53″ W83°05′39.04″, 16.vii.2006, JKM— 82♂, 5♀. Pisgah National Forest, W Frk Pigeon R @ NC215, UV light trap, 12.vi.2008, J. Robinson— 1♂. MACON COUNTY, Upper Reynolds Branch, Coweeta Hydrological Laboratory/ LTER, Malaise trap, 980 m, N35°02.00′ W83°27.00′, 5–11.iv.2008, G.W. Courtney (3♂, ISU). GRAHAM COUNTY, Robbinsville, 9.vi.1976, G.E. Bohart (1♂, CSU). MACON COUNTY, Coweeta Hydrological Stn, Upper Shope Frk, 928 m, N35°03′37.00″ W83°27′35.10″, 28.iii.2012, JKM— 10♂, 3♀, 1L#. TRANSYLVANIA COUNTY, Bee Branch @ NC215, UV light trap, 12.vi.2008, J. Robinson— 2♂. Trib S Mills R @ jct. US 276 & FSR 1203, UV light trap, 12.vi.2008, J. Robinson— 2♂. 12 mi. NW of Brevard, UV light trap, 7.vi.1971, Anonymous— 2♂. WATAUGA COUNTY, Blue Ridge Parkway NP, Goshen Crk @ BRP MP286, UV light trap, N36°11′07″ W81°36′21″, 9–10.vi.2007, C. Parker & J. Robinson (8♂, 2♀, USGS). SOUTH CAROLINA: OCONEE COUNTY, Issaqueenah Falls @ US 28, 7.iii. 1987, D. Pinson— 2L. TENNESSEE: CLAIBORNE COUNTY, Cumberland Gap NP, Gap Crk, 405 m, N36°36′02.19″ W83°40′05.50″, UV light trap, 19–20.vii.2006, C. Parker & J. Robinson (93♂, 5♀, USGS). COCKE COUNTY, Great Smoky Mtns NP, Cosby Crk, N35°46′31.06″ W83°12′45.03″, 16.vi.2006, JKM— 1♂, 6♀. SEVIER COUNTY, Trib. Webb Crk., Pittman Center, 408 m, UV light trap, N35°45′18.84″ W83°23′20.98″, 27.v.2005. JKM— 9♂. VIRGINIA: BEDFORD COUNTY, Blue Ridge Parkway NP, Falling Rock Crk @ MP67.1, UV light trap, 17–18.vii.2007, C. Parker & J. Robinson (6♂, 3♀, USGS). PAGE COUNTY, Shenandoah NP, Lewis Falls, A.L. Melander (1♂, TX A & M).

Diagnosis. Males of this species can be distinguished from those of all other Nearctic dixids by the following assemblage of characters: Morphological. (from Dixella spp.) katepisternum haired; flagellomere II slightly fusiform; gonocoxite with well-developed basal lobe. (from other Dixa spp.) scutum brown; wings lacking infuscation at junction of Rs, R2+3, R4+5, and crossvein r-m; epiproct reduced; gonostylus triangular. (from D. calciphila sp. nov. and D. inextricata ) basal gonocoxal lobe oval-round, directed dorsally, its width ca. 1/ 3X length of gonocoxite, not extended beyond proximal 2/3 of gonocoxite; gonostylus with ventral margin slightly convex; cercus blunt, directed posteriorly, its length 1/ 2X lateral width of proctiger. Proctiger square or nearly so in lateral view. Molecular. Among the most notable differences that serve to distinguish this species from the other two within the 66 nucleotides (22 codons) of BZF provided ( Fig. 38 ) is an amino acid substitution at codon position 15 (leucine vs. methionine).

Description. Male ( Fig. 1 ). Wing length (n =11) 3.0–3.3 (avg=3.1) mm. Head and its structures brown. Antenna (Fig. 5) ca. 2/ 3X length of wing, clothed with whorls of short setae. Scape small, collar-like. Pedicel globose, 4X width of flagellomere I. Flagellum with 14 articles. Flagellomere I 1.6X length of flagellomere II. Flagellomeres II & III most noticeably subcylindrical, with remaining flagellomeres gradually shortening and increasingly cylindrical. Apical flagellomere shortest with pair of divergent apical setae. Maxillary palpus 4- segmented; segments 1–4 as follows: 1:3:5:6. Thorax with scutum (Figs 7, 8) brown, lacking discernible stripes, with 4 rows of dark brown setae per side with a few additional setae interspersed, particularly anteriorly; midline raised, with adjacent lateral areas concave. Scutellum brown, with 10–13 posteriorly directed transverse setae along posterior margin. Pronotal lobe brown, with 2 short and 1–2 long apical setae. Anepisternum and anepimeron brown, concolorous with head and scutum, bare. Katepisternum (Fig. 8) brown, with 2–3 setae medially. Katepimeron light brown, bare. Metaepisternum and metaepimeron light brown, bare. Laterotergite brown, bare. Legs brown, ca. 5 mm in length (4.8–5.3). Pro- and mesothoracic legs symmetrical, with following segment length ratios [coxa, trochanter, femur, tibia, t1, t2, t3, t4, t5 (including claw)]: 2.2, 12, 14.4, 14.4, 10, 4, 2, 1, 1.2. Metathoracic legs differing in that t1 ca. 25–30% longer, i.e., ratio of 12.0–13.0, rather than 10. Coxae light brown, with setae anterolaterally, those of metacoxa positioned more laterally. Foretibia not expanded apically. Fore- and mesotarsal claws pectinate, with 4–5 prominent subapical tines, sometimes with additional, much smaller tines interspersed, especially basally. Metathoracic claw with 1 mesal and 1 basal much reduced secondary tines, sometimes with third one between them. Pro- and mesotibia not expanded apically. Metafemur expanded apically, with transverse row of ca. 12–14 uniformly sized setae on bulge. Tarsomeres 3 and 4, most noticeably of meso- and metathoracic legs, with variably thickened, sometimes hooked, proximal seta on ventral surface. Wing (Fig. 6) smoky grayish brown, lacking infuscation at junction of Rs, R2+3, R4+5, and crossvein r-m. Wing veins brown, setose. Rs arising near terminus of Sc. R2+3 arising proximal to crossvein r-m. Crossvein m-m weakened medially. False vein (FV) prominent, clearly distinct from and running parallel to CuA for most of its length. Halter brown, stem mostly brown, lighter on basal 1/5. Abdomen mostly dark brown, with sparse blue-green iridescence visible under some lighting conditions. Basal fringe brown; segments 2–6 with dark brown terga and grayish brown pleura. Segments 7–9 dark brown. Terminalia ( Figs 9 , 12–14 , 21 ): Tergite 9 (9T; epandrium) subtrapezoidal, with anterior margin convex. Sternite 9 (9S; hypandrium) subrectangular. Epiproct reduced, weakly sclerotized ( Fig. 21 ). Cercus blunt, weakly sclerotized, directed posteriorly, one-half length of lateral width of proctiger ( Fig. 21 ). Proctiger square in lateral view, with distal portion very weakly sclerotized ( Fig. 12 ). Subepandrial sclerite (SES) bilobed, somewhat kidney-shaped in lateral view ( Figs 9 , 12 ), with proximal lobe adjoining posterodorsal margin of 9T and distal lobe articulating with ventral portion of proctiger by narrow strap-like connection. SES bearing medial projection articulated with aedeagal/parameral complex. Distal lobes of SES appearing as adjoined triangular processes beneath proctiger in dorsal view ( Fig. 21 ). Gonocoxite subcylindrical, tapered apically, ca. 2X as long as broad, with prominent basal and apical lobes ( Figs 9 , 12 ). Basal gonocoxal lobe directed dorsally, with prominent setae medially and spinules apically, its oval-rounded apex extended slightly beyond anterior coxal margin in lateral view, greatest width ca. 1/ 3X length of gonocoxite, not extended beyond basal 2/3 of gonocoxite, with horizontal margin not distended dorsally resulting in proximal bulge when viewed laterally ( Fig. 9 , 12 ). Apical gonocoxal lobe digitiform, ca. 1/ 3X length of gonostylus in lateral view, with prominent setae along posteroventral margin ( Figs 9 , 12 ). Anterior margin of basal gonocoxal lobe intimately associated with gonocoxal apodeme and origin of parameres and ventral wall of aedeagus. Gonostylus triangular, ca. 1.3–1.5X longer than greatest depth, clothed with posterodorsally directed moderately developed setae, those on inner surface longer, slightly thickened; ventral margin slightly convex; posterior margin strongly and irregularly serrated; in ventral view apices expanded laterally ( Fig. 13 ). Aedeagus membranous, wrinkled ( Fig. 14 ) positioned between complex strap-like parameres, claspettes, and penis valves. Ventral plate deeply divided medially into roughly diamondshaped halves. Ejaculatory duct short.

Female. ( Fig. 2 ). Similar to male except as follows: Wing length (n =8) 2.9–3.6 (avg=3.3) mm. Body coloration generally lighter. Antenna slightly more robust. Tarsal claws simple. Thoracic pleurae light brown. Abdominal terga light brown, with pinkish-purple sheen. Terminalia ( Figs 25–28 ): 9S thin, strap-like. Cercus in dorsal view ( Fig. 25 ) roughly triangular, with apices slightly divergent; in lateral view ( Fig. 25 ) cercus rounded. 10S lobes ( Fig. 26 ) thin, oblong, comma-shaped, with apices expanded gradually. Spermatheca ( Fig. 27 ) golden brown, round, smooth, with short sclerotized neck. Spermathecal duct with whorls of cuticular outgrowths yielding bottlebrush appearance. Bursa copulatrix with two groups of ca. 8–10 setae positioned laterally of central group of variably numbered thorn-like spicules, much like depicted for D. inextricata in Figure 29 .

Etymology. Named for the geographic region in which this species is distributed.

Distribution. Dixa appalachiensis sp. nov. is known to occur in the southern Appalachian Highlands from Shenandoah National Park (NP) south to Great Smoky Mountains NP of western North Carolina and eastern Tennessee ( Fig. 37 ).

Remarks. Dixa appalachiensis sp. nov. is most often found in and around second order, high gradient streams between 3–5 meters in width characterized by having falls and cascades among large boulders ( Figs 31, 32 ). To date it has not been found in the same streams as D. inextricata , with which it is sympatric. It is frequently found in association with D. modesta Johannsen sensu Peters , another species complex in this genus (JK Moulton, unpublished). Adults emerge by mid-March in Great Smoky Mountains NP. There is little doubt that it will eventually be taken in adjacent northeastern Georgia. The northern limit of the distribution is less certain and requires further field studies to elucidate.

FIGURES 5–8. Antennae, wing, head and thorax, Dixa appalachiensis sp. nov. 5, antennae (male). Scale bar = 1 mm; 6, left wing (male). Scale bar = 1 mm. 7, head and scutum, anterodorsal view. Scale bar = 0.1 mm; 8, thorax, lateral view. Blue circle denotes katepisternal setae. Scale bar = 0.1 mm. Abbreviations: A1 = first anal vein; C = costal vein; CuA = anterior branch of cubital vein; CuP = posterior branch of cubital vein; FV = false vein; h = humeral crossvein; M1 = first branch of media; M2 = second branch of media; M3+4 = third branch of media; m–cu = medial-cubital crossvein; m–m = medial crossvein; Rs = radial sector; R1 = anterior branch of radius; R2 = first branch of R2+3; R2+3 = second branch of radius; R3 = second branch of R2+3; R4+5 = fourth branch of radius; r–m = radial – medial crossvein; Sc —subcostal vein.

Figures

FIGURE 37. Known distributions of the three recognized members of the D. inextricata species group.

FIGURE 38. Selected portion of big zinc finger (BZF) gene useful for distinguishing the three recognized species of the D. inextricata species group.

FIGURES 1 – 4. Habitus images. 1 – 2, Dixa appalachiensis sp. nov. 1, male; 2, female. 3 – 4, D. calciphila sp. nov. 3, male; 4, female. Scale bar = 1 mm.

FIGURES 9 – 11. Male terminalia, lateral view, in non-rotated (dorsal-ventral) orientation. 9, Dixa appalachiensis sp. nov.; 10,

FIGURES 12 – 20. Male terminalia. 12, Dixa appalachiensis sp. nov., lateral view (rotated); 13, D. appalachiensis sp. nov., ventral view; 14, D. appalachiensis sp. nov., terminal view; 15, D. calciphila sp. nov., lateral view (rotated); 16, D. calciphila sp. nov., ventral view; 17, D. calciphila sp. nov., terminal view; 18, D. inextricata, lateral view (rotated); 19, D. inextricata, ventral view; 20, D. inextricata, terminal view. Scale bar = 50 µm.

FIGURES 21 – 24. Male terminalia, 10 th tergum, dorsal view. 21, Dixa appalachiensis sp. nov.; 22, D. inextricata; 23, D. calciphila sp. nov.; 24, D. lobata Garrett. Scale bar = 50 µm.

FIGURES 25 – 30. Female terminalia. 25 – 28, Dixa appalachiensis sp. nov., 25, dorsal view. Scale bar = 50 µm; 26, ventral view. Scale bar = 50 µm; 27, spermatheca; Scale bar = 0.5 µm. 28, lateral view. Scale bar = 50 µm; 29 – 30, D. inextricata, 29, bursal armature, Red River Gorge, KY specimen. Scale bar = 50 µm; 30, bursal armature, Brasstown Bald, GA specimen. Scale bar = 50 µm.

FIGURES 31 – 36. Examples of D. inextricata group habitats. 31 – 32, D. appalachiensis sp. nov., 31, type locality, Woodfin Cascades, Blue Ridge Parkway NP, Haywood County, NC; 32, Upper Shope Fork, Coweeta LTER, Macon County, NC. 33 – 34, D. calciphila sp. nov., 33, Little Angel Spring, Taylor County, KY; 34, 300 Springs, Hart County, KY. 35 – 36, D. inextricata, 35, Brasstown Bald seepage, Chattahoochee NF, Towns County, GA; 36, Watt Creek, Blanton Forest State Nature Preserve, Harlan County, KY (photo courtesy of J. Bender-KSNPC).