Melophorus biroi Forel

Heterick, Brian E., Castalanelli, Mark & Shattuck, Steve O., 2017, Revision of the ant genus Melophorus (Hymenoptera, Formicidae), ZooKeys 700, pp. 1-420 : 147-153

Melophorus biroi Forel

Melophorus biroi Forel 1907: 29 (combination in M. (Erimelophorus) by Wheeler 1935: 71).

Type. Melophorus biroi Forel. Holotype (probable) major worker, Mt Victoria, Blue Mountains, New South Wales [HNHM] (examined: images of HNHM specimen provided by Zoltán Vas).

Melophorus marius Forel 1910: 66 (combination in M. (Erimelophorus) by Wheeler 1935: 71).

Type. Holotype major worker Tennants [sic] Creek, Northern Territory [MHNG] (examined: MHNG specimen No. 235). Syn. n.

Melophorus fieldi propinqua Viehmeyer 1925: 36.

Type. Syntype major worker, Liverpool, New South Wales [ZHMB] (examined: Automontage images © B.Schurian/ MfN-Berlin.de, of ZHMB specimen 5C8576). Syn. n.

Other material examined.

Australian Capital Territory: Black Mt., Site 5 (Barnett, N.J. [ANIC32-029813]), Black Mt., Site 5 (Barnett, N.J. [ANIC32-029821]), Mt Ainslie (Lowery, B.B.), Yarralumla (Lowery, B.B.). New South Wales: 40 km NNW Louth, Lake Mere (Greenslade, P.J. M. ), Armidale (Lowery, B.B.), Belanglo State Forest (Gush, T.), Bomaderry, Nowra (Lowery, B.B.), Cowan Creek (Lowery, B.B.), Fowlers Gap (Greenslade, P.J. M. ), Kapunda, N Nyngan (Greenslade, P.J. M. ), Lane Cove River, Burns Bay, Sydney (Lowery, B.B.), Mudgee (Lowery, B.B.), Myall Lakes (York, A.), Myall Lakes (Greenslade, P.J. M. ), Myall Lakes (York, A.), Myall Lakes National Park (York, 0A.), Newholme Road, near Armidale (Sakurai, Y.), Pymble (Lowery, B.B.), Richmond (Greenslade, P.J. M. ), St. Ives, Sydney (Lowery, B.B.). Northern Territory: 105 km N Yuendumu (Greenslade, P.J. M. ), 25 km N Alice Springs (Shattuck, S.O.), about 3 km W Alice Springs (Feehan, J.E.), Tanami (Greenslade, P.J. M. ), Tanami (Greenslade, P.J. M. ), Tanami Desert (Greenslade, P.J. M. ), vicinity of Ayers Rock (Allwood, A.). Queensland: ‘Gumbardo’ (Beutel, T.), ‘Merigol’ (Beutel, T.), 3.6 km NW homestead on Plum Pudding Track, Cravens Peak Station (Lemann, C. [ANIC32-036837]), 40 km E Cameron Corner (Greenslade, P.J. M. ), 75 km E Cunnamulla (Greenslade, P.J. M. ), Blair Athol Mine (Houston, W. [ANIC32-040331]), Proserpine, Thompson Creek (Raven & Burwell), Sandringham (Greenslade, P.J. M. ), Sandringham (Greenslade, P.J. M. ), St. George (Lowery, B.B.), Tindaree, Hannaford Rd South via Tara (House, A./Brown, S.), Wacol, Brisbane (Lowery, B.B.). South Australia: 10 km E Mt Ive Homestead (Greenslade, P.J. M. ), 15 km NE Mt Bryan (Greenslade, P.J. M. ), 50 km E Vokes Hill, Victoria Desert (Greenslade, P.J. M. ), 53 km E Vokes Hill, Victoria Desert (Greenslade, P.J. M. ), 5 km NW Ketchowla Homestead (Greenslade, P.J. M. ), 5 km W Mt. Rough, Coorong-Keith (Greenslade, P.J. M. ), 5 km WSW Pitlochry Homestead (Greenslade, P.J. M. ), 6 km NW Mt Pleasant (Greenslade, P.J. M. ), Belair (Greenslade, P.J. M. ), Belair (Greenslade, P.J. M. [ANIC32-900109]), Belair (Greenslade, P.J. M. ), Belair (Greenslade, P.J. M. ), Belair (Greenslade, P.J. M. ), Blyth (Lowery, B.B.), Brookfield Conservation Park (Shattuck, S.O.), Cambrai (Greenslade, P.J. M. ), Cambrai (Greenslade, P.J. M. ), Cambrai (Greenslade, P.J. M. ), Cambrai (Greenslade, P.J. M. ), Cambrai (Greenslade, P.J. M. ), Chowilla (Greenslade, P.J. M. ), Eyre Hwy, 9.7 km NE Cootra (Heterick, B.E. [M328]), Fairview Conservation Park, N Lucindale (Greenslade, P.J. M. ), Gawler Ranges (Greenslade, P.J. M. ), Glen Osmond (Greenslade, P.J. M. ), Hale (Greenslade, P.J. M. ), Katarapko Island (Loxton High [ANIC32-046389]), Koonamore (Greenslade, P.J. M. ), Koonamore (Greenslade, P.J. M. ), Koonamore, Milang Conservation Park (Greenslade, P.J. M. ), Moorowie Plain (Greenslade, P.J. M. ), Mt. Gunson (Case, T.J.), Mt. Remarkable, Flinders Ranges (Greenslade, P.J. M. ), Napperby, Flinders Ranges (Greenslade, P.J. M. ), North of Breakneck River, Kangaroo Island (Greenslade, P.J. M. ), North Sandy Creek, Kangaroo Island (Greenslade, P.J. M. ), Ocean Beach, Streaky Bay (Lowery, B.B.), Oraparinna, Flinders Ranges (Greenslade, P.J. M. ), Para Wirra (Greenslade, P.J. M. ), Rocky River, Kangaroo Island (Greenslade, P.J. M. ), Salt Creek, Coorong (Greenslade, P.J. M. ), Streaky Bay (Lowery, B.B.), vicinity of Nanam Well, Scorpion Springs Conservation Park (Museum Party), Victor Harbour (Greenslade, P.J. M. ), Wudinna townsite (Heterick, B.E. [M331/M333]). Tasmania: Barnes Bay, N. Bruny Island (Lowery, B.B.), George Town (Littler, F. M. ), Lefroy (Lowery, B.B.). Victoria: 15 km W Nyarrin (Greenslade, P.J. M. ), 15 km WNW Yaapeet (Andersen, A.N.), 15 km WNW Yaapeet (Andersen, A.N.), Cape Schank (Lowery, B.B.), Cape Schank (Lowery, B.B.), Glenaladale National Park (Andersen, A.N.), Heathcote, near Bendigo (Lowery, B.B.), Hopetoun (Andersen, A.N.), Hurstbridge (Lowery, B.B.), Murray Sunset Natl. Park, Millewa South Bore Track, 5.2 km WSW Shearers Quarters (Lambkin, C., Yeates, D., Starwick, N. & Recsei, J. [ANIC32-043283]), Rotamah Island, Gippsland Lakes (Andersen, A.N.), Studley Park, Kew (Lowery, B.B.), Watsonia (Lowery, B.B.), Watsonia (Lowery, B.B.), Watsonia (Lowery, B.B.). Western Australia: 1 km W Canna (Heterick, B.E. [M317/M319]), 1.5 km S Koolyanobbing (Heterick, B.E. [M15]), 11 km W Terhan Water Hole (Heatwole, H.), 4 km W Ellendale Rd (Heterick, B.E. [M239/M240/M241/M242]), 4 km W Ellendale Rd (Heterick, B.E. [M243/M244/M245]), 46 mi WNW Norseman (Taylor, R.W.), 8 km NW Bluff Knoll, Stirling Ranges National Park (Ward, P.S.), Argyle Diamonds via Kununurra (Postle, A.T. [JDM32-001931]), Christmas Tree Well (Heterick, B.E. [M20]), Coomallo Downs (Heterick, B.E. [M12/M49]), County Downs Hsd (south boundary) (Heterick, B.E. [M248]), Eneabba-Leeman Rd. (Dunn, R. [JDM32-001943]), Ethel Creek (Varris, P.A. [JDM32-001940]), Eyre Hwy, 20 km N Norseman (Heterick, B.E. [M338]), Harrismith (Heterick, B.E. [JDM32-001927]), Hines Hill (Heterick, B.E. [JDM32-001929]), Hyden Cemetery (Heterick, B.E. [JDM32-001930]), Int. Holland Tr./Norseman Rd. (Heterick, B.E. [JDM32-001926]), Jurien (collector unknown [JDM32-001972]), Kojonup (Majer, J.D. [JDM32-001935]), Little Sandy Desert (Guthrie, N. A. [M144]), Mt Gibson rest area (Heterick, B.E. [M299/M300/M301]), Mulga, NE Goldfields (Pringle, H.J.R. [ANIC32-029570]), Ongerup-Jerramungup Rd. (Heterick, B.E. [JDM32-001925]), Sandstone Rd turnoff (B..E Heterick [M296/M297/M298]), Sandstone Rd turnoff (Heterick, B.E. [M294]), Tammin (Clark, J.), The Granites’ Mt Magnet (Heterick, B.E. [M171]), Wannamal West (Heterick, B.E. [JDM32-001939]), Woolgangie (Heterick, B.E. [JDM32-001924]).

Diagnosis.

Melophorus biroi can be placed in the M. biroi species-group on the basis of characters of the clypeus, propodeum, mandible and palps. The species is placed in the M. biroi species-complex on the basis of a further suite of characters (viz, metatibia of major worker with only one preapical spur [except rarely in the mjobergi clade]; clypeal psammophore placed anteriorly at or just above anterior margin of clypeus in the minor worker and often in the major worker; head dorsoventrally compressed to varying degrees in the minor worker of most species with the eyes placed high on the sides; compact legs, and small body size [[(excluding mjobergi clade) HW of smallest minor 0.36 mm, average HW of smallest minors 0.46 mm; HW of largest known major 1.29 mm, average HW of largest majors (where known) 1.05 mm]). Melophorus biroi is very similar to several other small or very small Melophorus . The minor worker can be distinguished from similar forms by its almost invariably glabrous mesosoma, the lack of erect setae, especially marginal setae, on the gaster, the weakly impressed metanotal groove, the truncate propodeum, the thin, widened petiolar node and the lack of heavy sculpture on the mesopleuron. Since the major worker of many M. biroi complex species is not known, the M. biroi major worker cannot be diagnosed with high definition, and is best identified from nest series in which minor workers are also included. However, this subcaste has a weakly convex pronotum and mesonotum and a weakly ot moderately impressed metanotal groove enabling it to be separated from the very similar M. castanopus (flattened pronotum and mesonotum) and M. dicyrtos (strongly convex pronotum and mesonotum and deeply impressed metanotal groove), and the posterior clypeal margin is arched. The anterior clypeal margin often has a small dimple (as in many members of the M. fieldi complex). Melophorus biroi shows a lot of morphological variation, and there is substantial molecular evidence that this is a species complex of at least several species. Further investigation into Melophorus biroi is needed.

Minor worker description.

Head. Head square, or approximately oval with straight sides; posterior margin of head planar to strongly convex; frons shining with superficial shagreenation or microreticulation only; frons consisting exclusively or almost exclusively of well-spaced, appressed setae only (small, erect setae, if present, usually confined to ocular triangle or posterior margin of head). Eye moderate (eye length 0.20-0.49 length of side of head capsule); in profile, eye set at about midpoint of head capsule; in profile, eye set around midline of head capsule; eyes elliptical or slightly reniform. In full-face view, frontal carinae straight or weakly convex; frontal lobes straight in front of antennal insertion. Anteromedial clypeal margin broadly and evenly convex; clypeal psammophore set at or just above anterior clypeal margin; palp formula 6,4. Five mandibular teeth in minor worker; mandibles triangular, weakly incurved; third mandibular tooth distinctly shorter than apical tooth and teeth numbers two and four; masticatory margin of mandibles approximately vertical or weakly oblique. Mesosoma. Integument of pronotum, mesonotum and mesopleuron with weak to moderate sheen and superficial microreticulation (more pronounced on mesopleuron); anterior mesosoma in profile broadly convex, or smoothly rounded anteriad, thereafter pronotum and whole of mesonotum flattened and on same plane as propodeum, or weakly elevated anteriad, thereafter gently sinuate, pronotum and mesonotum on same plane; erect pronotal setae absent; in profile, metanotal groove shallow, broadly V or U-shaped, or a weak or vestigial furrow; propodeum shining and microreticulate; propodeum angulate, propodeal angle blunt; length ratio of propodeal dorsum to its declivity between 1:1 and 1:2; erect propodeal setae always absent; appressed propodeal setulae short, separated by more than own length and inconspicuous; propodeal spiracle situated on or beside declivitous face of propodeum, and longer (length ≥ 0.50 × height of propodeum). Petiole. In profile, petiolar node squamiform; in full-face view, shape of petiolar node uniformly rounded; node shining and smooth with vestigial sculpture. Gaster. Gaster shining with superficial microreticulation; pilosity of first gastral tergite consisting of well-spaced short, inconspicuous, appressed setae only, erect setae always absent. General characters. Colour variable, often orange-and-brown or concolorous brown; if foreparts light-coloured, gaster always brown to black.

Major worker description.

Head. Head square; posterior margin of head weakly concave; cuticle of frons shining and smooth except for piliferous pits and a few striolae around antennal insertions and frontal carinae; pilosity of frons a mixture of a few well-spaced, erect setae interspersed with appressed setae only. Eye small (eye length less than 0.2 × length of head capsule); in full-face view, eyes set above midpoint of head capsule; in profile, eye set anteriad of midline of head capsule; eyes elliptical. In full-face view, frontal carinae concave; frontal lobes straight in front of antennal insertion. Anterior clypeal margin broadly and evenly convex; clypeal psammophore set at or just above anterior clypeal margin; palp formula 6,4. Five mandibular teeth in major worker; mandibles triangular, weakly incurved; third mandibular tooth distinctly shorter than apical tooth and teeth numbers two and 4; masticatory margin of mandibles approximately aligned vertically or weakly oblique. Mesosoma. Integument of pronotum, mesonotum and mesopleuron with weak to moderate sheen, shagreenate on pronotum and dorsum of mesonotum, otherwise microreticulate; anterior mesosoma in profile broadly convex, or pronotum smoothly rounded anteriad and flattened posteriad, mesonotum narrowly convex; erect pronotal setae short and unmodified, or weakly expanded distally; in profile, metanotal groove shallow, broadly V- or U-shaped; propodeum shining and finely striolate and microreticulate; propodeum smoothly rounded or with indistinct angle, or angulate, propodeal angle blunt; length ratio of propodeal dorsum to its declivity greater than 1:2; erect propodeal setae absent; appressed propodeal setae sparse or absent, if present then not regularly spaced; propodeal spiracle situated on or beside declivitous face of propodeum, and shorter (length less than 0.50 × height of propodeum). Petiole. In profile, petiolar node squamiform; in full-face view, shape of petiolar node uniformly rounded, or square with rounded angles; node shining and smooth with vestigial microreticulation anteriad. Gaster. Gaster shining, shagreenate ('LP record’ appearance); pilosity of first gastral tergite consisting of short, bristly, erect setae over well-spaced, short, appressed setae. General characters. Colour mostly orange with brown gaster, head may be brown with yellow pronotum and mesonotum and brown propodeum and metasoma, or head and gaster may be brown with tan mesosoma.

Measurements.

Worker (n = 8): CI 92-113; EI 22-37; EL 0.18-0.24; HL 0.53-0.97; HW 0.49-1.10; ML 0.69-1.24; MTL 0.36-0.66; PpH 0.09-0.12; PpL 0.29-0.51; SI 69-105; SL 0.51-0.76.

Comments.

Melophorus biroi is the most abundant and widespread of all the small Melophorus and is found in all mainland Australian states and in Tasmania. The glabrous mesosoma in the minor worker, lack of erect non-marginal setae on the first gastral tergite and the straight appearance of the mesosoma in profile differentiate this ant from others in its clade. The taxon exhibits a variety of colours and morphologies: most southwestern populations have tawny orange foreparts and a dark gaster, while populations in the northern part of the Swan Coastal plain are uniformly large and dark. Melophorus biroi specimens in northern Australian and in arid parts may be rather rugose and brownish in colour, often with darker heads and gasters, while M. biroi from the eastern NSW tend to be dark coloured, quite gracile, and with longer heads (although not as long or compressed as seen in M. longiceps ).

Material for sequencing came from only a portion of the phenotypes seen for this taxon, and this requires caution in interpreting the genetic output. Thus, there may be hidden species among the morphological variations that have not been sequenced. Regarding the sequenced material, there was found to be a rather odd dichotomy between three geographically closely associated collections made in the Kimberley and the remainder of the material for the genes COI, H3 and AA, but all successfully sequenced samples clustered together for genes LR and Wg. Given the widespread nature of the ant and its varied colouration and morphology, the dispersion evident in several of the genes used is unsurprising. However, samples M240 and M241 (which cluster with the quite unrelated M. xouthos for gene AA and COI, and, along with sample M248, at the base of all Melophorus for gene H3) produced an anomalous result, making the taxon polyphyletic when five- and three-gene trees were generated (since the M. biroi samples in the three-gene tree are not monophyletic, they have been assigned alpha suffixes to denote separate morphospecies status). The pinned voucher for sample M240 reveals a planar mesosoma with only a hint of a metanotal groove when seen in profile, and this may be suggestive of a distinct genotype. However, the profile of the sequenced sample M248 and its accompanying pinned voucher are unremarkable and typical of M. biroi . Unfortunately, M241 is a singleton and the M240 sequenced sample is represented only by the gaster. All of these workers were collected within a metre or so of each other and at the same time, and were assumed to be nestmates.

Melophorus marius Forel represents the lighter coloured version of this taxon ( M. biroi is dark), but the habitus is the same and the later name marius becomes provisionally a junior synonym in this monograph. Also relegated to the position of a junior synonym here is M. fieldi propinqua. The syntypes seen for this taxon, both major workers, are superficially similar to M. fieldi , but the low placement of the clypeal psammophore, the appearance of the tibiae and tibial spurs and the narrow propodeum reveal its correct identity. Unfortunately, Viehmeyer did not describe minor workers, which look very different to the minor workers of M. fieldi . Viehmeyer’s ants constitute a sample of the large-eyed form of M. biroi , seen in pockets throughout Australia.

At present, the species diagnosis is the best that can be managed, but there are undeniably questions regarding the monophyly of M. biroi , and the possibility that, on further investigation, M. biroi , M. fieldi propinqua and M. marius may prove to constitute more than one species. In fact, the wide genetic divergence makes this putative taxon polyphyletic on a three-gene tree (see Figure 3), and more material - especially from the Kimberley region and from the eastern states - is needed to untangle the currently confusing picture, in which phenetics and genetics are in conflict.

Although the collection data follows the same pattern as for other Melophorus in being scant in nature, the sheer volume of specimens collected has resulted in what is likely to be a comprehensive list of habitats: these include Eucalyptus woodland, inland dunes, 'dry sclerophyll’, 'coastal scrub’, sandstone scrub, mallee, mallee heath, burned mallee, grazed eucalyptus dieback area, box-pine scrub, twig litter, scattered shrubs and spinifex over red sand, relict Kwongan bushland, mulga bushland, remnant brigalow, closed forest, semi-arid red clay soil, white sand over leaves, and paddock. This species also occurs in suburban areas, particularly those with some remnant vegetation. The ant is a ground forager and almost certainly a generalist in its habits.