Leptanilloides

Ward, Philip S. & Brady, Seán G., 2009, Rediscovery of the ant genus Amyrmex Kusnezov (Hymenoptera: Formicidae) and its transfer from Dolichoderinae to Leptanilloidinae, Zootaxa 2063, pp. 46-54 : 52-53

Leptanilloides

Variable body size, HW ~0.40–0.64, LHT 0.40–0.72

Scape disproportionately longer: SI 0.37–0.41; scape more than twice the length of second antennal segment (SL/LA2 ~2.2)

Legs disproportionately longer, LHT/HL ~1.5

Paramere large, ~1.5× petiole length

Veins M and Cu diverging distal to crossvein cu-a by a distance greater than the length of the crossvein

Submarginal cell less elongate: no more than three times longer than wide, shorter than the basal cell, and terminating at level of stigma

Free M vein after Rs+M (may be weak)

However, in the UCDC collection there are several other male specimens that weaken these distinctions. First, there are seven additional leptanilloidine males—apparently representing two species—collected at Fazenda Rancho Grande, Rondônia, Brazil from the same series as Amyrmex BR01 and Amyrmex BR02 (12–22 November 1991, leg. E. M. Fisher) (CASENT0106187 to CASENT0106193). These are small (HW 0.22–0.38) and similar to Amyrmex except that (1) the forewing submarginal cell is less elongate, shorter in length than the basal cell, and does not exceed the stigma; (2) the mandibles are elongate-linear and bowed (i.e., falcate); and (3) the parameres are broad and paddle-shaped, subequal in length to the petiole. Thus, from a single collection from this one rainforest site in Rondônia there are males representing at least four species of Leptanilloidinae , two of them conforming to the strict Amyrmex diagnosis (above) and two other Amyrmex - like males. Second, a single male from Barro Colorado Island, Panama (12.viii.1978, leg. R. B. & L. S. Kimsey) (CASENT0106194) matches the Amyrmex description except that it is larger (HW 0.48, LHT 0.43) with disproportionately longer, falcate mandibles (ML/HW 0.52, ML/EL 1.33), and a short submarginal cell, not exceeding the stigma and approximately equal in length to the basal cell.

It is important to note that our concept of the male caste of Leptanilloides is based on only two species, L. mckennae Longino ( Ward 2007) and L. nubecula Donoso, Vieira & Wild (Donoso et al. 2006) , both with relatively large workers (HW 0.54–0.64). The L. mckennae males are also large (HW 0.59–0.64). The measurements given for the male of L. nubecula suggest a rather small male (HW 0.32, HL 0.32; see Donoso et al. 2006) but these may be in error. Based on the scale bar in the illustration of the male ( Donoso et al. 2006, figure 25) HW should be about 0.37 and HL 0.29, and both of these values are unusually low in relation to the size of the workers (HW 0.54–0.56) and gyne (HW 0.74). In any event these two species do not adequately represent the spectrum of diversity within the genus. No males have been associated with workers of the smaller species of Leptanilloides such as L. biconstricta Mann and L. sculpturata Brandão, Diniz, Agosti & Delabie. The leptanilloidine males from Rondônia and Panama with short submarginal cells and falcate mandibles might belong here.

A further complication is that neither males nor DNA sequence data are available for the other workerbased leptanilloidine genus Asphinctanilloides Brandão, Diniz, Agosti & Delabie (1999) , which was recovered as sister to Leptanilloides in morphological phylogenetic analyses ( Brandão et al. 1999; Brady & Ward 2005). The three known species of Asphinctanilloides are associated with lowland Amazon and Atlantic coastal rainforest, which contrasts with the predominantly Andean and Central American distribution of Leptanilloides . Thus it seems quite possible that Amyrmex , known currently from the Amazon basin of Brazil and from northern Argentina, represents a senior synonym of Asphinctanilloides . For this reason we refrain from describing any of the Amyrmex -like males as new species since names may already be available for them (i.e., Asphinctanilloides anae Brandão, Diniz, Agosti & Delabie , A. amazona Brandão, Diniz, Agosti & Delabie and A. manauara Brandão, Diniz, Agosti & Delabie ). Confirming this will require more extensive study. Since it may prove difficult to find worker-associated males of leptanilloidines in the field, DNA sequencing offers a reliable way of associating these disparate castes, if the material is sufficiently well preserved.

In the original description of Asphinctanilloides the workers were said to be distinguished from those of Leptanilloides by several features including (1) presence of a metanotal groove, (2) reduced postpetiole, smaller than the petiole as seen in profile, and (3) abdominal segments 5 and 6 lacking differentiated presclerites and hence without constrictions between abdominal segments 4 and 5, and 5 and 6 ( Brandão et al. 1999). With the subsequent discovery of Leptanilloides species whose workers have a metanotal groove and a short postpetiole the first two characters have lost their diagnostic value ( Longino 2003; Donoso et al. 2006). Brandão et al. (1999) also documented differences in the sting apparatus between Leptanilloides and Asphinctanilloides , however, and these have not been evaluated in the newly described species of Leptanilloides .

We examined two workers of Asphinctanilloides amazona ( BRAZIL Amazonas: 28km N Manaus, 1.xii.1998, Berlese soil sample, leg. M. Verhaagh; CASENT0006016, CASENT0006815) (CASC) and found that in both workers abdominal segment 5 has a differentiated presclerite, and is separated from abdominal segment 4 by a weak constriction. No such constriction occurs between abdominal segments 5 and 6. Further assessment of the morphological differences between the two genera is warranted. (Attempts to extract DNA from Asphinctanilloides workers belonging to this series were unsuccessful, apparently due to their initial collection into low concentration ethanol.)

Nevertheless, if a reduced worker postpetiole and an undifferentiated presclerite on abdominal segment 6 are derived features within Leptanilloidinae then it might still be possible to define Asphinctanilloides (or Amyrmex , if the two prove to be synonyms) in such a way that it is monophyletic, but this could also render Leptanilloides paraphyletic. These considerations, together with the discovery of a variable assortment of leptanilloidine males from scattered Neotropical localities, make the delimitation of genera in this group an ongoing challenge.