Melophorus diversus Heterick, Castalanelli & Shattuck

Heterick, Brian E., Castalanelli, Mark & Shattuck, Steve O., 2017, Revision of the ant genus Melophorus (Hymenoptera, Formicidae), ZooKeys 700, pp. 1-420 : 295-298

Melophorus diversus Heterick, Castalanelli & Shattuck sp. n.

Types.

Holotype minor worker (bottom ant) from SW of Sandringham, Queensland, 7-13 August 1980, P.J. M. Greenslade, SRM Traps, (18), 30) [ANIC32-900186] (ANIC). Paratypes: minor worker on same pin and with same details as holotype (ANIC); media and 2 minor workers from Sandringham Station 25[sic-should be ‘24’ -BEH]. 03S, 139.03E, 55 km NW of Bedourie, Queensland, 16 January 1980, S. R. Morton, p4 (BMNH); major worker and two media workers from Sturt National Park, New South Wales, 23 November 1979, P.J. M. Greenslade, (7) (MCZ); major worker from Sturt National Park, New South Wales, 22 November 1979, P.J. M. Greenslade, (4) [ANIC32-900062] (MCZ); media and 2 minor workers from Sandringham Station 24.03S, 139.03E, 55 km NW of Bedourie, Queensland, 16 January 1979, S. R. Morton, 12 [duplicate labels], ex C. (QM); 2 minor workers and a media worker from Kunoth Paddock, near Alice Springs, Northern Territory, 26 October 1974, P.J. M. Greenslade, (9), 3a) (SAM).

Other material examined.

New South Wales: 40 km NNW Louth, Lake Mere (Greenslade, P.J. M. ), Callubri Station (Greaves, T.), Conservation Park, Fowlers Gap (Greenslade, P.J. M. [ANIC32-900061]), CSIRO Lake Mere Field Station, near Louth (Bryannah, M. ), Fowlers Gap Station, 110 km N Broken Hill (Morton, S.), Fowlers Gap Station, 110 km N Broken Hill (Morton, S.), Fowlers Gap Station, 110 km N Broken Hill (Morton, S.), Olive Downs Station, 55 km NW Tibooburra (Morton, S.R.), Olive Downs Station, 55 km NW Tibooburra (Morton, S.R.), Olive Downs Station, 55 km NW Tibooburra (Morton, S.R.), Sturt National Park (Greenslade, P.J. M. ), Sturt National Park (Greenslade, P.J. M. ). Queensland: Sandringham (Greenslade, P.J. M. ), Sandringham (Morton, S.), Sandringham (Morton, S.), Sandringham Station, 55 km NW Bedourie (Morton, S.R.), Thilla, 1:25000 Barrolka (Forrest, J.). South Australia: 2.8 km NNW Four Hills Trig. Peake Stn (Stony Desert Survey UB02 [M98/M99]), Innamincka, 3.8 km NNW Patchawarra (Stony Desert Surv. PC002 [M112]).

Diagnosis.

Melophorus diversus can be placed in the M. biroi species-group on the basis of characters of the clypeus, propodeum, mandible and palps. The species is also placed in the M. wheeleri species-complex because it agrees with the follow ing apomorphies possessed by the complex: the minor worker often has more than five teeth, the largest major worker has a short, massive, elbowed mandible directed posteriad; in profile, the maxillary palps are short in the major and generally short in minor workers (in the minor worker, usually only attaining the neck sclerite at their maximum extent when the head is moderately inclined) and, in full-face view, the anterior margin of the clypeus in the large major worker is usually planar or weakly concave (variable in other subcastes but planar or narrowly protuberant anterior clypeal margins predominate). Melophorus diversus shares only with M. wheeleri the following combination of apomorphies: the anterior sector of the clypeus of minor worker is strongly folded back towards the mandible, and the clypeal psammophore is placed on a distinct ledge that may be carinate, the minor worker mandible has 5-9 teeth and denticles, the head, mesosoma and gaster of all workers have short, inconspicuous appressed setae that are usually separated by more than their own length (if more elongate, as in some small minor workers, then the ant is glossy and weakly sculptured) and the media and major workers are quite large Melophorus (HW of the large major worker ≥ 2.60 mm). Most workers of Melophorus diversus can be distinguished from M. wheeleri workers in having the head of the minor worker smooth with just vestigial sculpture (the head often glossy), erect non-marginal setae always present on first gastral tergite with one or two small erect setae also present on the pronotum of some individuals, the eye of the minor worker large (0.30 × length of side of head capsule) and the major worker usually with many fine, erect setae on the mesosoma (though these may be more sparse and bristly in a few individuals). (In Melophorus wheeleri the head of minor worker always has some sculpture and is matt to moderately shining in appearance, erect setae are almost always lacking on the pronotum and the first gastral tergite, and the eye of the minor worker is usually less than 0.30 × length of side of head capsule. The major worker is similar to the major worker of M. diversus but either has a glabrous mesosoma or possesses short, bristly setae on the mesosoma and is commonly matt in appearance [WA, NT] but may be glossy [eastern states]). However, the distinctions between these two species are not always observed and a few individuals, possibly hybrids, may be unable to be placed in either taxon with confidence.

Minor worker description.

Head. Head square, or quadrate (i.e., heart-shaped); posterior margin of head planar to strongly convex; frons shining with superficial shagreenation or microreticulation only, or matt or with weak sheen, shagreenate; 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 full-face view, eyes set above midpoint of head capsule; in profile, eye set anteriad of midline of head capsule, or set around midline of head capsule; eyes elliptical or slightly reniform, or elongate. In full-face view, frontal carinae straight or weakly convex; frontal lobes straight in front of antennal insertion. Anteromedial clypeal margin straight; clypeal psammophore set at or just above anterior clypeal margin; palp formula 6,4. Five to nine mandibular teeth in minor worker; mandibles triangular, weakly incurved; third mandibular tooth distinctly shorter than apical tooth, but equivalent in length to remaining teeth. Mesosoma. Integument of pronotum, mesonotum and mesopleuron moderately shining and shagreenate throughout; anterior mesosoma in profile broadly convex; erect pronotal setae absent; in profile, metanotal groove shallow, broadly V or U-shaped; propodeum shining and shagreenate; 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 shorter (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, shagreenate ('LP record’ appearance); pilosity of first gastral tergite consisting of well-spaced, erect and semi-erect setae interspersed with regularly placed appressed setae, or consisting of well-spaced short, inconspicuous, appressed setae, erect setae (present in at least some workers) confined to margin of sclerite. General characters. Colour light to dark brown, legs may be paler distally.

Major worker description.

Head. Head quadrate (i.e., heart-shaped); posterior margin of head weakly concave; cuticle of frons shining and smooth except for piliferous pits; 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). Eyes 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. Frontal carinae concave in full-face view, or straight, divergent posteriad; frontal lobes curved inward in front of antennal insertion. Anterior clypeal margin broadly emarginate; clypeal psammophore set at or above midpoint of clypeus; palp formula 6,4. Mandibular teeth in major worker always 4; mandibles strongly incurved, apical sector weakly carinate or incompletely carinate; third mandibular tooth absent; masticatory margin of mandibles medially indented. Mesosoma. Integument of pronotum, mesonotum and mesopleuron moderately shining and shagreenate throughout; anterior mesosoma in profile broadly convex; erect pronotal setae short, (i.e., shorter than length of eye) and unmodified; in profile, metanotal groove shallow, broadly V- or U-shaped; propodeum shining and finely striolate and microreticulate; propodeum angulate, propodeal angle blunt; length ratio of propodeal dorsum to its declivity greater than 1:2; erect propodeal setae present and abundant (at least a dozen), or present and sparse to moderate (1-12); appressed propodeal setae short, separated by more than own length and inconspicuous; 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 tapered with median indentation; node shining and faintly shagreenate-microreticulate. Gaster. Gaster shining, shagreenate ('LP record’ appearance); pilosity of first gastral tergite consisting of well-spaced, erect and semi-erect setae interspersed with regularly spaced appressed setae. Colour. Colour of head brownish-crimson to cherry red; trunk russet, legs light brown to ochre, gaster chocolate.

Measurements.

Worker (n = 6): CI 99-124; EI 14-38; EL 0.21-0.42; HL 0.56-2.48; HW 0.55-3.08; ML 0.74-2.31; MTL 0.45-1.39; PpH 0.09-0.26; PpL 0.31-0.93; S 45-103I; SL 0.57-1.37.

Comments.

As characterized here, Melophorus diversus is integrated in a clinal pattern with eastern Australian populations of M. wheeleri , and some specimens are not amenable to being allocated to either taxon with any confidence. In all likelihood, however, two separate taxa can be recognized here, albeit there appears to be limited gene flow, either simple hybridization or perhaps introgression, between the two species. The taxonomic key acknowledges the difficulty in determining the status of the workers of a few populations where gene flow with the parent species may be occurring. Apart from M. wheeleri , the ant can be distinguished from others in its complex by its glossy, weakly sculptured cuticle, the folded-back clypeus and the sparse nature of the appressed setae on the body and gaster, which are generally separated from one another by more than their own length. Sequencing of old material from SAMA has been unsuccessful, probably due to the denaturing of the preservative and the degradation of the DNA over time.

Most collections have made in NSW, with a few samples taken from southern QLD and one from Kunoth Paddock, near Alice Springs, in the NT. Regrettably, collection details are entirely lacking for this species.

Etymology.

Latin diversus ( ‘different’); adjective in the nominative singular.