Myrmecia haskinsorum, Taylor, Robert W., 2015

Taylor, Robert W., 2015, Ants with Attitude: Australian Jack-jumpers of the Myrmecia pilosula species complex, with descriptions of four new species (Hymenoptera: Formicidae: Myrmeciinae), Zootaxa 3911 (4), pp. 493-520 : 498-501

Myrmecia haskinsorum sp.n.

( Figs 1–3)

Myrmecia haskinsorum is a species essentially of high elevations, known from the Snowy Mountains, Victorian Alps and upland Tasmania, with some Tasmanian records from lower elevations. In most localities of record nests are regularly covered or brushed by winter snow (as also in sympatric populations of M. pilosula (Eastern Race) on mainland Australia and M. pilosula (Western Race) on Tasmania). This species was discussed as M. haskinsorum by Imai, Taylor et al. (1994).

Type locality. NEW SOUTH WALES: Dead Horse Gap (-36 31, 148 15), Snowy Mountains National Park, near Thredbo.

Type deposition. Holotype and paratypes in ANIC, paratypes or type-compared vouchers in AMSA, MVMA, QMBA, SAMA, WAMA, TMHA) and in BMNH, CASC, MCZC, MHNG.

Material examined, distribution. NEW SOUTH WALES: Alpine Creek [-35 55, 148 33], 4/xi/1935, G.F. Hill (QMBA, ANIC—some labeled “ Promyrmecia pilosula ” by John Clark); near Corang River Bridge (-35 12, 150 03) HI87–152, HI99–14; Dead Horse Gap [-36 31, 148 15], HI87–233, 234, HI91–046, 0 47, HI99–017; 27/i/2006, SB&SM, 7 samples (AAVAS); Eucumbene [-36 0 8, 148 36], 22/ii/1959, EFR; Jamberoo [-34 39, 150 46], 7 km W 600 m, 26/xi/77, PSW acc 2900, 2907 (PSW collection); Pipers Creek [-33 3, 149 55], 10/xi/1960, EFR; near Smiggins Holes [-33 59, 148 48], 1650 m, 27/i/75, PSW acc 607 (PSW collection). AUSTRALIAN CAPITAL TERRITORY: Mt Ginini, [-35 32, 148 46], HI99–016. VICTORIA: Benambra [-36 57, 147 42], 700 m, 25/i/2006 SB&SM (AAVAS); Ben Cairn [-37 43, 145 37], 14/v/1937, TG; Mt Buffalo, near The Chalet ski lodge [-36 43, 146 49], HI87–224, 225, TASMANIA: near Bothwell [-42 23, 147 00], HI87–197–199; Epping Forest [-41 46, 147 21], BBL; Great Lake [-41 53, 146 44], 28/x/1949, TG; Miena [-41 59, 146 43], HI91–027, 0 41, HI 99–022; Murderers Hill [-41 58, 146 40], HI87–200; Tunbridge [-42 0 8, 147 25], BBL. All ANIC unless indicated.

Worker diagnosis. General features as illustrated and in key couplet 1 above. The most easily recognized species of the Myrmecia pilosula complex. Distinguished by the almost total lack of pilosity interrupting the dorsal body profile, by the lack of reddish-orange apical color-marking on the dark brown anterior femora, and the absence of brightly differentiated reddish-orange tibiae and tarsi on the more or less uniformly dark brown, apically lightly infuscated, middle and hind legs. The body often has a distinctive and sometimes very noticeable diffuse bluish cast in live specimens, recalling the bloom of grape skin. This feature seems unique to haskinsorum in Myrmecia and is lost in dry or spirit-preserved specimens. It has been observed in the Snowy Mountains, Mt Buffalo and central Tasmania, and appears less prominent at lower elevations of record. Labrum yellowish in the center with bilateral dark brown markings. Terminal two or three antennomeres usually darkly infuscated. Mesonotum (longitudinally striate-rugose) and petiolar dorsum (more or less transversely rugose) distinctly and quite strongly sculptured, with little evidence of allometric reduction in smaller specimens. Pubescence silvery, without yellowish reflections; very fine, short and sparse except on the clypeus, coxae, femora, postpetiole and gaster. A very few short hairs may be visible in profile view of the head and pronotum, and a few minute bristles on the mesonotum, less often on the petiole.

Dimensions. (Holotype, smallest available specimen (Mt Buffalo), largest available specimen (Mt Buffalo) (mm): TL = 11.6, 11.4, 12.0; HW = 2.36, 2.34, 2.46; HL = 2.15, 2.13, 2.22; CI = 109, 110, 111; EL = 0.92, 0.87, 0.92; OI = 39, 37, 41; SL = 1.94, 1.90, 1.93; SI = 82, 81, 78; PW = 1.48, 1.45, 1.48; WL = 3.64, 3.60, 3.78; PetW = 0.86, 0.85, 0.88; PpetW = 1.36, 1.33, 1.41.

Elevational range. The AAVAS Dead Horse Gap sites were recorded by GPS at 1,553 to 1,608m, the highest confirmed for the M. pilosula complex, 620m short of Mt Kosciusko summit. Wheeler (1933) probably referred partly to M. haskinsorum when reporting “ M. pilosula ” from Mt Kosciusko (see below). Elevations for other key localities are: Corang River Bridge, ca 580m (GPS reading), the lowest mainland record for haskinsorum ); Mt Buffalo, ca 1,300 m; and in Tasmania: Tunbridge, ca 200m (The lowest-elevation confirmed Tasmanian record) and Murderers Hill, ca 1,100 m (the highest-elevation Tasmanian record). Targeted search at the summit area of Mt William (= Mt Duwil – 1,167m), the highest peak in the Grampian Ranges, VIC, by four collectors including the author, failed to find M. haskinsorum , which perhaps does not range that far west.

Variation. The mainland and Tasmanian populations were presumably geographically isolated after dispersal of ancestral stock across intervening low elevation areas during a past cool climate episode prior to the separation of Tasmania (ca 14,000ybp) (since haskinsorum is present there). Diagnostic morphological characters are not significantly variable among available specimens. The Snowy Mountains and Mt Ginini populations are those most likely to have vestigial dorsal mesosomal pilosity. The body color is generally a little more blackish in haskinsorum than other pilosula -group species, and the brown sections of the legs darker in hue. Specimens from lower elevations tend to have the leg color lighter brown, as in Figs 1–3.

Etymology. Named for Caryl P. Haskins and his wife Edna Haskins in recognition of their important pioneering studies on the biology of Myrmecia and other Australian ants.

Karyology. Chromosome numbers vary between 2n=12 and 2n=24, the lower counts resulting mainly from centric fission, centric fusion and AM inversion (Imai, Taylor et al., 1994: 147, Fig 6). The karyotypes of colonies from Corang River Bridge and Mt. Buffalo, respectively with 2n=23/24 and 2n=20, were considered by Imai, Taylor et al. to be closely related to those from Tasmania with 2n=18. The Dead Horse Gap colonies have 2n=18/ 15/12, and are karyotypically most similar to a Tasmanian colony with 2n=17. Four fusions with different arm combinations were detected from colony HI87–234 (Dead Horse Gap).

Field associations. Sympatric with the Eastern Race of M. pilosula and M. croslandi near Corang River Bridge, with Eastern Race pilosula in the Snowy Mountains and on Mt Buffalo, and with the Western Race in Tasmania.

Discussion. Wheeler (1933: 56–57), who confused the two races of M. pilosula and M. haskinsorum , almost certainly referred to haskinsorum when describing “ pilosula ” workers and queens on Mount Kosciusco as “dull black, but when alive and in bright sunlight, with a distinct bluish tinge, probably due to a fugitive pigment”. Also, at least in part, when stating that on Kosciusko (“ M. pilosula ”) was “very abundant and the dominant species at elevations from 4000 to 6000 ft.” (c.a. 1220 to 1838 m).

Research prospects. Future potential research topics include (1) genetical and morphological comparison of the mainland and Tasmanian populations, which have a defined approximate time of geographical and phylogenetic separation; (2) investigation of the nature and role of the fugitive bluish flush in high alpine populations.