Euponera Forel

Schmidt, C. A. & Shattuck, S. O., 2014, The Higher Classification of the Ant Subfamily Ponerinae (Hymenoptera: Formicidae), with a Review of Ponerine Ecology and Behavior, Zootaxa 3817 (1), pp. 1-242 : 83-86

Euponera Forel

Figs 11 , 12

Euponera Forel, 1891: 126 (as subgenus of Ponera ). Type-species: Ponera (Euponera) sikorae Forel, 1891: 127 ; by monotypy. Gen. rev.

Euponera is a moderately large genus (26 described species) of medium-sized ants occurring in the Afrotropics, Madagascar and eastern Asia. Its habits are poorly known.

Diagnosis. Euponera species fall into two groups, the first, related to E. sikorae , can be diagnosed by the presence of a shiny integument, basal mandibular pits, cordate frontal lobes, divided mesopleuron, deep metanotal groove, and strong gastral constriction. This combination of characters does not occur in any other ponerine genus. The second set of species, which includes E. sjostedti , can be separated from others by the presence of basal mandibular pits, obsolete metanotal groove, elongate or slit-shaped propodeal spiracle, simple subpetiolar process without an anterior fenestra and a prora on anterior margin of first gastral sternite. A shiny integument occurs in some other ponerines, but is absent in most large species. Basal mandibular pits occur in most species of Brachyponera and Cryptopone . Cordate frontal lobes occur in most members of the Plectroctena group as well as in Bothroponera (s.s.). A divided mesopleuron and deep metanotal groove occur in combination only in some Brachyponera , Hagensia (in which the mesopleuron is only partially divided), and in Mesoponera subiridescens . Euponera superficially most closely resembles Bothroponera (s.s.) and Pseudoponera , but differs in the presence of basal mandibular pits. Some Euponera species are also similar to Cryptopone , but these differ in having eyes and lacking mesotibial traction setae. They are also similar to Mesoponera but are generally smaller in body size with smaller eyes, larger frontal lobes, a wider head and have shorter mandibles.

Synoptic description. Worker. Large (TL 6–10.5 mm) ants with the standard characters of Ponerini . Mandibles triangular, with numerous teeth and a basal pit. Anterior clypeal margin convex or medially emarginate. Frontal lobes moderatel large to large, cordate and closely approximated for most of their length (less close in the E. wroughtonii group). Eyes small (3-4 facets in diameter) to moderate in size, located just anterior of head midline (in E. sikorae ) or anteriorly on sides of head (in most species). Mesopleuron sometimes divided by a transverse groove. Metanotal groove varying from little more than a suture to deeply impressed. Metapleural gland orifice opening laterally in the P. wroughtonii group. Propodeal spiracle slit-shaped. Metatibial spur formula (1s, 1p). Petiole with a cuboidal node in most species but scale-like in a few. Girdling constriction between pre- and postsclerites of A4 apparent. Head and body varying from shiny and sparsely punctate, with sparse pilosity and pubescence to finely punctate and with abundant pilosity and scattered to dense pubescence. Color variable, ferrugineous to black.

Queen. Winged but otherwise similar to workers (Rakotonirina & Fisher, 2013).

Male. Not described.

Larva. Not described.

Geographic distribution. Euponera occurs in Sub-Saharan Africa and Madagascar and India eastward to Korea and Japan and south through the Philippines to Indonesia.

Ecology and behavior. Collections of Euponera sikorae have come from rainforest habitats, but nothing else is known about its ecology or behavior. Terayama (1999) reported that E. sakishimensis nests in soil and that workers forage on the ground, and K. Masuko observed very small colony sizes (4– 11 workers) in E. pilosior (pers. comm. in Peeters, 1993). Villet (1994) studied the colony demographics and reproductive strategy of E. fossigera . This species is a generalist predator, forms small colonies (up to 50 workers), and nests in soil, leaf litter, or rotting wood. Reproduction is performed by a single ergatoid.

Phylogenetic and taxonomic considerations. Other than Pachycondyla itself, Euponera has been the focus of the greatest taxonomic lumping within the Ponerinae , having at various times housed Brachyponera , Mesoponera , Pseudoponera , Xiphopelta (here treated as a junior synonym of Mesoponera ) and Hagensia , all of which (except Xiphopelta) we consider to be distinct genera. Euponera was originally erected as a subgenus of Ponera by Forel (1891) to house the single species E. sikorae . Emery raised Euponera to full genus status (1900a) and described Brachyponera (1900a) and Mesoponera (1900b) as subgenera of Euponera . Emery’s treatment was generally accepted by most authors (but see Bingham, 1903) until Wilson (1958c) moved both Brachyponera and Mesoponera to full genus status. Forel (1901a) moved Pseudoponera to subgenus status under Euponera , where it generally remained until Wheeler (1922b) revived it as a distinct genus (but again see Bingham, 1903). Emery (1911) treated Trachymesopus (now Pseudoponera ) as a subgenus of Euponera , though Wilson (1958c) eventually raised it to full genus status. Arnold (1915) synonymized Hagensia under Euponera (subgenus Mesoponera ), while Forel (1917) raised Hagensia to subgenus status under Euponera . Arnold (1926) later raised Hagensia to generic status. Forel (1917) placed Xiphopelta (= Mesoponera ) under Euponera as a distinct subgenus, where it remained on and off until Brown (1973) synonymized it with Pachycondyla . Euponera was treated as a distinct genus until W. L. Brown (in Bolton, 1994) lumped it under Pachycondyla without phylogenetic justification.

Euponera became the type genus for Emery’s (1909, 1911) Euponerinae , which he considered a section of Ponerinae and which basically conformed to the present definition of Ponerini . Emery (1911) gave a diagnosis for Euponera that included Brachyponera , Mesoponera and Trachymesopus (= Pseudoponera ) as subgenera. He united these taxa based on characters of their mandibles (subtriangular and toothed, with a distinct angle between the masticatory and basal margins), eyes (located in the anterior third of the head), mesosoma (presence of a distinct metanotal groove), and the alate queens. All of these characters are likely plesiomorphic within the Ponerini , and do not indicate a close relationship among these genera.

We are reviving Euponera as a distinct genus based on both molecular and morphological evidence. Schmidt's (2013) molecular phylogeny of the Ponerinae and Ward's (pers. comm.) examination of selected African taxa places Euponera with strong support within the Odontomachus group, but its sister group is unresolved. It is not closely related to Pachycondyla or Pseudoponera as these are placed in separate genus groups ( Pachycondyla group and Ponera group, respectively). Morphologically, Euponera shares basal mandibular pits and a deep metanotal groove with Brachyponera , and while these taxa are otherwise morphologically quite different, Schmidt's and Ward's molecular data suggest a close relationship between them. Ward's molecular results suggest a close relationship between Euponera and Fisheropone , even though they share few morphological characters. Similarly, the distinctive Cryptopone hartwigi was also found to be closely related to Euponera (and Fisheropone ). The highly divergent morphologies among these three close relatives belie their true relationships, and have contributed to the fluidity of generic concepts within the subfamily.

Morphologically, some Euponera species are superficially closest to certain members of Bothroponera , particularly Bothroponera comorensis , while other species are separable from selected Pseudoponera species only by careful examination. However, molecular evidence suggests these similarities are due to convergence as they are not closely related.

Figures

FIGURE 11. Worker caste of Euponera sikorae: lateral and dorsal view of body and full-face view of head (CASENT0487847, April Nobile and www.antweb.org); world distribution of Euponera.

FIGURE 12. Worker caste of Euponera antsiraka: lateral and dorsal view of body and full-face view of head (CASENT0317590, Jean Claude Rakotonirina and www.antweb.org).