Plectroctena

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 : 161-162

Plectroctena Genus Gr oup

The Plectroctena genus group is apparently the result of a gradual radiation into hypogeic niches in the African tropics, with the frequent evolution of prey specialization. Among the group’s members, only a few Centromyrmex species occur outside of Africa (in the Neotropics and Southeast Asia).

Discussion. The monophyly of the Plectroctena genus group is strongly supported by molecular data ( Schmidt, 2013), with the exceptions of Dolioponera and Feroponera , for which molecular data are lacking and for which placement in the Plectroctena group are tentative. An apparent synapomorphy of the group (excluding Feroponera ; see below) is the lateral opening of the metapleural gland orifice, which among ponerines is otherwise only found in Harpegnathos and Platythyrea . It should be stressed that due to uncertainty in relationships among ponerine genus groups, a laterally opening metapleural gland orifice may be plesiomorphic within Ponerini .

Centromyrmex forms the sister group of a clade consisting of Psalidomyrmex + ( Plectroctena + Loboponera ). These relationships are unequivocally supported by molecular data ( Schmidt, 2013) and are also supported by morphological evidence. Among these four genera, Psalidomyrmex , Plectroctena and Loboponera are supported as a clade by the derived shape of the anteroventral articulatory surface of the petiole ( Bolton & Brown, 2002). Plectroctena and Loboponera are united by the presence of longitudinal grooves on their meso- and metafemora and by the division of the mesopleuron, with the anepisternum appearing fused to the mesonotum and metapleuron.

Boloponera is almost certainly very closely related to Plectroctena and Loboponera , as it also has longitudinal grooves on its metafemora (but not mesofemora) and has the same division and fusion of the mesopleuron. In his original description of Boloponera, Fisher (2006) hypothesized that it was outside the clade of Psalidomyrmex + Loboponera + Plectroctena (the Plectroctena genus group sensu Bolton & Brown, 2002), due to its apparent lack of a similarly modified petiole articulatory surface. From consideration of the totality of morphological evidence, however, we reach a different conclusion. As noted above, Boloponera shares with Loboponera and Plectroctena the presence of a longitudinal groove on the metafemora as well as characters of the mesopleuron. In addition, Boloponera has several potential synapomorphies with Plectroctena (as Fisher noted): linear mandibles, anteriorly projecting frontal lobes, and propodeal lamellae. Boloponera lacks the semicircular clypeal excavations and dorsal mandibular groove of Plectroctena , however. Finally, in our evaluation the structure of the anteroventral petiolar articulatory surface in Boloponera is not different enough from that in Psalidomyrmex , Plectroctena and Loboponera to warrant its exclusion from that clade. If anything, the shape of the median depression in the petiolar articulatory surface of Boloponera is more similar to that of Plectroctena than is the shape in Loboponera . At best, this character is ambiguous about relationships among these genera.

In conclusion, the morphological evidence strongly suggests a close relationship between Boloponera , Plectroctena and Loboponera . The exact nature of the relationships among them is uncertain and depends on the assumptions made about the ancestral character states. The absence of a longitudinal groove in the mesofemora of Boloponera supports the monophyly of Loboponera + Plectroctena , but the linear mandibles and projecting frontal lobes of Boloponera suggest a sister relationship between it and Plectroctena . Boloponera could also be sister to Loboponera or even nested within Plectroctena .

The inclusion of Dolioponera and Feroponera in the Plectroctena genus group is less certain. In overall gestalt Dolioponera bears some resemblance to Psalidomyrmex , Plectroctena , Loboponera , Boloponera , and it shares with the latter three genera an apparent fusion of the mesopleuron to the mesonotum (though the mesopleuron in Dolioponera is undivided). The shape of the petiolar articulatory surface in Dolioponera is dissimilar to that in these four genera, but Dolioponera has a laterally opening metapleural gland orifice that is similar to that in members of the Plectroctena genus group (B. Bolton, pers. comm.). Given these observations, we consider the most likely phylogenetic placement of Dolioponera to be as sister to the Psalidomyrmex + Plectroctena + Loboponera + Boloponera clade. Its geographic range (central Africa) is also consistent with this view.

The phylogenetic placement of Feroponera is highly uncertain, though Bolton & Fisher (2008c) hypothesized that it may form a clade with Centromyrmex , given the shared lack of eyes, presence of tibial traction setae, and relatively high helcium. All of these characters occur elsewhere within Ponerini , however, so we do not consider them strong evidence of monophyly for these genera. Arguing against such a clade are the posteriorly opening metapleural gland orifice in Feroponera , which differs from the apparent synapomorphic condition for the Plectroctena genus group. In the absence of stronger evidence about its phylogenetic relationships, however, we are tentatively including Feroponera within the Plectroctena group.