Crematogaster sabatra, Blaimer, Bonnie B., 2010

Blaimer, Bonnie B., 2010, Taxonomy and Natural History of the Crematogaster (Decacrema) - group (Hymenoptera: Formicidae) in Madagascar, Zootaxa 2714, pp. 1-39 : 28-29

Crematogaster sabatra NEW SPECIES

( Fig. 34 & 40 )

Holotype worker. MADAGASCAR: P.N. Befotaka–Midongy, -23.84080, 46.95750, 1250m, 17.–19.xi.2006, beating low vegetation, montane rainforest, B.L.Fisher et al. #15075 (CASENT0193162, specimen image on antweb) (deposited in CASC).

Paratypes. 4w, same locality as holotype, ex dead branch above ground (B.L.Fisher #15066, CASENT0193541, CASENT0193554, CASENT0193553 and CASENT0193552) (deposited in MCZC, SAMC, MHNG, UCDC).

Material examined. ( CASC) MADAGASCAR: Fianarantsoa: 29km SSW Ambositra, Ankazomivady [=P.C. Ankazomivady]: -20.77667, 47.16500, 1700m (B.L.Fisher); 40km S Ambalavao, Rés. Andringitra (=P.N. Andringitra): -22.21667, 46.96667, 1275m (B.L.Fisher); R.S. Kalambatritra: -23.46350, 46.46310, 1270m (B.L.Fisher et al.); P.N. Befotaka-Midongy: -23.84080, 46.95750, 1250m (B.L.Fisher et al.).

Worker measurements (n=10). HW 1.15–1.31; HL 1.03–1.15; EL 0.26–0.30; SL 0.86–0.98; WL 1.20– 1.34; SPL 0.27–0.42; PTH 0.22–0.25; PTL 0.29–0.38; PTW 0.32–0.37; PPL 0.20–0.23; PPW 0.28–0.31; LHT 0.96–1.10; CI 1.09–1.15; OI 0.23–0.28; SI 0.84–0.88; SPI 0.22–0.33; PTHI 0.60–0.84; PTWI 0.89–1.26; PPI 1.31–1.52; LBI 1.16–1.24.

Worker description. Large to very large species (HW 1.15–1.31,WL 1.20–1.34).

Masticatory margin of mandibles with 5 teeth; posterior margin of head straight, laterally forming subangular corners; antennal scapes surpassing posterior margin of head easily; midline of eyes situated well above midline of head in full face view.

Pronotum laterally angular; promesonotal suture usually incomplete, impressed only laterally; dorsum of promesonotum more or less flat in lateral view; antero-medial portion of mesonotum from slightly raised to prominently raised with respect to pronotum, but not tuberculate; dorsal face of mesonotum flat, lateral portion from broadly to sharply angular; mesonotum postero-laterally angular or tuberculate, and with a distinct posterior face; propodeal spines massive, medium to large size (SPI 0.22–0.33), at least longer than width between their bases, evenly tapering, in lateral profile fairly straight, in dorsal view moderately diverging (<30˚); petiole in dorsal view hexagonal, not lobed, lacking carinae or tubercule; dorsum of petiole flat; subpetiolar process variable, articulated as broadly rounded or angular antero-ventral tooth, or close to absent.

Head sculpture aciculate to reticulate; mesosoma with mesopleuron partly aciculate, partly reticulate, and metapleuron carinulate to costulate; dorsal face of propodeum costulate; posterior face largely smooth and shiny; otherwise mesosoma largely aciculate, or aciculate-reticulate; dorsal face of petiole mostly shiny; lateral and ventral face coarsely reticulate; postpetiole dorsally feebly, ventrally more strongly rugulose; helcium carinulate; face with 4-6 erect setae; promesonotum with 2 erect humeral setae and sometimes 2 erect setae laterally on mesonotum; petiole and postpetiole devoid of erect pilosity.

Colour mostly black, rarely brown.

Variation. Populations from P.N. Andringitra and P.C. Ankazomivady show a mostly reticulate sculpturing on the head and on parts of the promesonotum, in contrast to the aciculate sculpture of workers collected from the southern localities R.S. Kalambatritra and P.N. Befotaka–Midongy.

Comments. Crematogaster sabatra is very closely related to the C. hova -complex, from which it can be distinguished by size, the angular postero-lateral character of the mesonotum and the reduced sculpture. The species is further morphologically similar to C. mahery ; characters to separate these two species are given above (see description of C. mahery ). Both mitochondrial and nuclear DNA data support populations of C. sabatra from all localities as being conspecific. However, in phylogenetic analysis specimens from the sampled populations (P.N. Andringitra, P.C. Ankazomivady and P.N. Befotaka–Midongy) form a cluster within the C. hova -complex, rendering the latter a paraphyletic grouping. The speciation event between C. sabatra and the hova -complex thus may have been very recent and reciprocal monophyly is not yet reached, at least in the markers implemented in this study. Considering the sympatry of C. sabatra with the C. hova - complex across its entire distribution, strong reproductive isolating mechanisms must already be in place.

This, together with the morphological distinctness, is here regarded as sufficient evidence to describe C. sabatra as a species.

Distribution and biology. Crematogaster sabatra is known only from a few localities in Madagascar: the P.N. Andringitra, P.C. Ankazomivady, P.N. Befotaka–Midongy and R.S. Kalambatritra ( Fig. 58 ). All of these localities are mountainous regions in the Central Region and harbour mid-elevation to montane rainforest, very much reminiscent of the distributions of C. mahery and C. malala . Crematogaster sabatra has been collected only from elevations of 1250 m and above (up to 1700m). I surmise that this may be the result of competitive exclusion by the dominant C. hova -complex, which is very common at lower elevations in and around these regions, but far less abundant at higher elevations. Queens or males of this species have never been collected, and little information exists on its ecology. Fisher et al. have collected C. sabatra mostly while beating vegetation and during other ground sampling methods. On a few occasions colonies were found in dead branches or twigs and carton nests. It seems likely that it shares a very similar arboreal lifestyle as the rest of the Malagasy Decacrema .

Etymology. “ Sabatra ” is the Malagasy word for “sword”, naming the species after its workers’ long and sword-like propodeal spines. In this combination “ sabatra ” is used as a noun in apposition.

Figures

FIGURES 32 – 37. Malagasy Crematogaster (Decacrema) species; a: full-face view, b: lateral view, c: dorsal view. 32: C. nosibeensis; 33: C. sisa; 34: C. sabatra; 35: C. mahery; 36: C. malala; 37: C. grevei.

FIGURES 38 – 43. Malagasy Crematogaster (Decacrema) species; a: petiole & postpetiole in dorsal view, b: petiole & postpetiole in lateral view. 38: C. nosibeensis; 39: C. sisa, 40: C. sabatra; 41: C. mahery; 42: C. malala; 43: C. grevei.

FIGURES 58 – 61. Distributions of Malagasy Crematogaster (Decacrema). 58: C. sabatra; 59: C. sisa; 60: C. hovacomplex, entire distribution; 61: C. hova- complex morphotype 1.