Prionopelta seychelles Overson & Fisher

Overson, Rick & Fisher, Brian L., 2015, Taxonomic revision of the genus Prionopelta (Hymenoptera, Formicidae) in the Malagasy region, ZooKeys 507, pp. 115-150 : 128

Taxon classification Plantae Hymenoptera Formicidae

Prionopelta seychelles Overson & Fisher sp. n. Figs 3C, 8

Type material.

Holotype, pinned worker, SEYCHELLES, Silhouette Island, ridge from Mont Corgat to Mont Cocos Marrons, 4.50126°S, 55.23985°E, 455 m, forest, sifted litter (leaf mold, rotten wood), collection code BLF23364, 24.ii.2010 (B.L. Fisher et al.) (CASC: CASENT0161311). Paratypes, eight pinned workers with same data as holotype (BMNH: CASENT0161314; CASC: CASENT0161310; CASENT0161312; CASENT0161313; CASENT0161315; CASENT0161316; CASENT0161317; CASENT0161319).

Diagnosis.

Prionopelta seychelles is the only known species from Seychelles. It can be distinguished from all other Malagasy Prionopelta through the following characters: twelve antennal segments; densely arranged cephalic foveae with virtually no space for additional foveae and no shining integument visible between; pronotum consisting of shallow foveae much larger in diameter than those on the head with punctures between; median cephalic band which is devoid of foveae not swelling above the surrounding integument, and often characterized as being wider anteriorly and narrower posteriorly.

Worker measurements

(N=15). HL 0.44-0.48 (0.46); HW 0.33-0.37 (0.35); SL 0.22-0.26 (0.24); WL 0.47-0.54 (0.5); PetL 0.13-0.17 (0.14); PetW 0.17-0.21 (0.18); T1W 0.29-0.31 (0.3); CI 73.63-80.41 (76.39); PI 106.92-144.44 (128.7); SI 64.56-73.43 (69.77).

Worker description.

Twelve antennal segments; posterior margin of the head weakly concave in full-face view; small cephalic foveae densely positioned so that no flat, shining integument is present between; median cephalic band which is devoid of foveae does not appear to swell above the surrounding integument, but rather appears as a smooth, shining surface which is widest anteriorly, narrowing posteriorly; apical tooth intermediate in length; pronotum with foveae which range from shallow to deep and are interspersed regularly with punctures; mesonotum and propodeum consisting of large, shallow foveae; metanotal groove strongly visible, and mesopropodeal suture visible to barely visible, but some depression always present; posterior propodeal edge viewed dorsally is straight or only very slightly concave; no protruding lamellae of the posterior propodeum.

Etymology.

This species is named after the Seychelles archipelago, to which it is endemic. The species epithet is a noun in apposition, and thus invariable.

Distribution and ecology.

This species is known only from Seychelles and is found between 15-660 meters of elevation on the islands of Mahé, Conception, Thérèse, Silhouette, Praslin, La Digue, Félicité Island, and the Little Sister island group. It does not appear to have strict habitat preferences as it has been collected in mixed forest, littoral forest, non-native forest, palm forest, and coastal scrub. Prionopelta seychelles has also been collected from a diversity of microhabitats including from leaf litter, inside rotten logs, under rocks, under moss on live trees, and under root mats.

Taxonomic notes.

Prionopelta seychelles is most likely to be confused with Prionopelta subtilis , as both have very small cephalic foveae that are densely arranged on the head. However, the two species are not sympatric, as Prionopelta seychelles is known only from Seychelles, and Prionopelta subtilis only from Madagascar. The median cephalic bands contrast markedly between these taxa, as that of Prionopelta seychelles is wide anteriorly, often tapering posteriorly, with an interrupted border caused by aberrantly placed foveae which break up the margins which define the smooth shining area (Fig. 8A). That of Prionopelta subtilis , on the other hand, is very thin throughout its length, with clearly defined borders which are swollen above the surrounding integument (Fig. 3A, B) On average, Prionopelta subtilis also has a wider head than Prionopelta seychelles : 0.39-0.45 (0.42) vs. 0.33-0.37 (0.35), respectively. Additionally, the cephalic foveae of Prionopelta subtilis are smaller and the cephalic sculpture overall appears more delicate than that of Prionopelta seychelles .

Non-type material.

SEYCHELLES: Conception Island, 4.6631°S, 55.3682°E, 65 m, mixed forest, 12.ii.2010 (B.L.Fisher et al.); Félicité Island, 4.3258°S, 55.8698°E, 120 m, forest, 1.ii.2010 (B.L.Fisher et al.); La Digue Island, 4.3561°S, 55.8433°E, 300 m, forest, 31.i.2010 (B.L.Fisher et al.); La Digue Island, Veuve Réserve, 4.357°S, 55.8279°E, 15 m, littoral forest, 2.ii.2010 (B.L.Fisher et al.); Mahé Island, Casse Dent, Morne Seychellois National Park, 4.6528°S, 55.4374°E, 465 m, mixed forest, 11.ii.2010 (B.L.Fisher et al.); Mahé Island, Morne Blanc, 4.6574°S, 55.4333°E, 660 m, mixed forest near glacis, 10.ii.2010 (B.L.Fisher et al.); Mare Aux Cochon, Mahé Island, 30.vii.2002 (J. Gerlach); Praslin Island, 4.3546°S, 55.748°E, 25 m, coastal scrub, 6.ii.2010 (B.L.Fisher et al.); Praslin Island, Praslin tower, 4.3409°S, 55.7451°E, 370 m, mixed forest, 3.ii.2010 (B.L.Fisher et al.); Praslin Island, Vallée de Mai, 4.331°S, 55.7389°E, 200 m, palm forest, 2.ii.2010 (B.L.Fisher et al.); Silhouette Island, above Jardin Marron on crest to Mont Plaisir and Pot à Eau, 4.4867°S, 55.2341°E, 520 m, forest, 20.i.2010 (B.L.Fisher et al.); Silhouette Island, Gratte Fesse, 4.4917°S, 55.2389°E, 450 m, forest, 6.iv.2009 (J. Gerlach); Silhouette Island, Jardin Marron, 4.4864°S, 55.2363°E, 395 m, non native forest, 27.i.2010 (B.L.Fisher et al.); Silhouette Island, Jardin Marron, 4.4864°S, 55.2364°E, 390 m, 24.iii.2009 (J. Gerlach); Silhouette Island, La Passe, 4.4847°S, 55.2508°E, 20 m, park/garden, 12.vii.2001 (J. Gerlach); Silhouette Island, on path to Anse Mondon, 4.4689°S, 55.2294°E, 255 m, forest, 23.i.2010 (B.L.Fisher et al.); Silhouette Island, on plateau toward Gratte Fesse, 4.4879°S, 55.2342°E, 490 m, forest, 22.i.2010 (B.L.Fisher et al.).