Leptogenys species groups

Lattke 2011. Revision of the New World species of the genus Leptogenys Roger (Insecta: Hymenoptera: Formicidae: Ponerinae). Arthropod Systematics & Phylogeny 69:127-264.

These groupings are based on similarities in worker morphology.

antillana species group

 * Leptogenys antillana
 * Leptogenys reggae

Worker diagnosis - Head subrectangular in full-face view; eye weakly convex, situated laterad at cephalic mid-length, eye longer than maximum scape width, circumocular sulcus well developed; scape surpasses posterior cephalic margin by not more than one-fourth its length, funicular segments with marked constrictions, third antennal segment longer than other basal funicular segments; suture between antennal sclerite and tentorial pit well impressed. Median clypeal lobe broadly triangular, with (L. antillana) or without (L. reggae) lamella, with or without apical setae; lateral lobe narrow; basal mandibular sulcus well impressed, basal and external mandibular margins subparallel. Mesosoma with promesonotum forming single broad convexity in lateral view; propleuron smooth and shining; mesonotum transverse; metanotal groove well impressed, smooth; metanotal-propodeal sulcus absent to weakly impressed propodeum unarmed; node longer than wide in dorsal view; cross-section of node at mid-length with convex sides; constriction between abdominal segments III and IV moderately to well developed; posterodorsal swelling of metacoxa well developed; pro- and metatibial apex without setae, mesotibial apex with single seta; body mostly smooth and shining, without appressed pubescence, scattered standing to decumbent hairs present on body.

Comments - The two known species from this group are island endemics, one found in Jamaica, and another in Hispaniola. The queens are still unknown in this group. The lack of propodeal lobes or teeth shown by L. antillana and L. reggae is rare within the pusilla clade, in which the phylogenetic analysis places this group.

Possible apomorphies - The lateral position of the eye on the head at cephalic mid-length is not seen in other species. The few species with eyes at cephalic midlength have the eyes dorsolaterally placed on the head.

arcuata species group

 * Leptogenys arcuata
 * Leptogenys donisthorpei
 * Leptogenys montuosa
 * Leptogenys santacruzi

Worker diagnosis - Compound eyes dorsolaterally situated on head, diameter greater than one-fourth lateral cephalic margin; clypeal apex with setae, median clypeal lobe small, shorter than maximum scape width, with lamella; mandibles arched, narrow, and parallel-sided; suture between antennal sclerite and tentorial pit well impressed; labrum with scattered pointed tubercles on anterior face; well-developed hypostomal lobes usually present (except L. arcuata); PF: 4,4. Antenna with each funicular segment gradually expanding apicad, third antennal segment not noticeably elongate; mesonotum subquadrate to wider than long, never narrow and transverse; propleuron mosly transversely striate (smooth in L. arcuata), metanotal groove well impressed, scrobiculate; metapleural-propodeal suture present, propodeum unarmed; node with posterior margin vertical in lateral view, without an apical crest or point, posterior face of node flat, smooth and shining, posterior and lateral margins separated by sharp angle (except L. santacruzi); meso-, metapleuron, and most of lateral face of petiole rugulose; anterior face of abdominal segment III flat, subpetiolar process with sloping posterior margin in lateral view; constriction between abdominal segments III and IV weak; body without pubescence; head, mesosoma, petiole and gaster with scattered standing pilosity, no appressed pubescence. Metacoxal dorsum without swelling at base; apex of protibia lacking setae; apex of mesotibia with 1 external seta; apex of metatibia without setae.

Comments - These ants are found from southern Mexico into northern South America, including an island endemic on Santa Cruz, Galapagos Islands. One species, L. arcuata, may actually represent a complex with representatives in the Amazon watershed and the Lesser Antilles. No queens are yet known for this species group, even in species that have been relatively well sampled, such as L. arcuata or L. donisthorpei, leading to the inference that egg laying workers fulfill this reproductive role in the group.

Possible apomorphies - The reduced clypeal lobe, presence of clypeal setae, slender, arched mandibles, and large hypostomal lobes are synapomorphic with the unistimulosa group, the apparent sister group to the arcuata group. The arcuata group claims as apomorphic the flattened posterior face of the node that is separated from the rest of the node by a sharp edge, lacking the curvature usually associated with this margin. The disc of the anterior face of abdominal segment III is also flattened. There is a lack of pubescence on the head and mesosoma dorsum which could be considered apomorphic as the loss of pubescence is common for the pusilla clade, but not for taxa outside of it. The unistimulosa group retains pubescence on the cephalic dorsum, and occasionally presents sparse pubescence on the mesosoma.

crudelis species group

 * Leptogenys crudelis
 * Leptogenys iheringi
 * Leptogenys vogeli

Worker diagnosis - Head longer than wide; eye diameter not more than one-third the length of lateral cephalic margin, eye weakly convex, dorsolaterally placed on head, circumocular sulcus absent; median clypeal lobe with lateral lamella, clypeal apex without setae, lateral clypeal lobe poorly developed; mandible shuts tight against clypeus, basal mandibular sulcus well developed, mandible subtriangular; sulcus between tentorial pit and antennal sclerite shallow, scape surpasses posterior cephalic margin by at least one-fourth its length; third antennal segment longer than neighboring basal funicular segments. Mesonotum wider than long, not narrow; metanotal groove smooth, not scrobiculate; metapleural-propodeal suture absent; declivitous propodeal margin shorter than dorsal margin in mesosomal lateral view, propodeum with lobe or tooth; node subtriangular (L. iheringi, L. vogeli) to subquadrate (L. crudelis) in lateral view, petiolar node longer than wide in dorsal view; anterodorsal margin of third abdominal segment convex in lateral view, constriction between abdominal segments III and IV well developed; metacoxa with low posterodorsal swelling; protibial apex lacking seta, mesotibial apex with single seta, metatibial apex with (L. crudelis) or without (L. iheringi) apical seta; body mostly with smooth and shining sculpture; appressed pubescence lacking, scattered standing hairs present on dorsum of body

Comments - This group has three member species, all of similar size and general appearance, in southeastern Brazil. Ergatoid queens are known for L. crudelis, and L. iheringi.

Possible apomorphies - This group needs more scrutiny to extract decent support. The absence of a circumocular sulcus is uncommon amongst New World Leptogenys, yet ascertaining the extent of presence or absence of this sulcus is not without difficulties. A smooth and polished cuticle will hinder clear observation, especially in smaller sized species even if a strip of mylar is used to diffuse the light source. The sulcus between the tentorial pit and antennal sclerite is quite shallow, and this is usually well impressed in most species.

elongata species group

 * Leptogenys bifida
 * Leptogenys chamela
 * Leptogenys elongata
 * Leptogenys foraminosa
 * Leptogenys honduriana
 * Leptogenys manni
 * Leptogenys oaxaca
 * Leptogenys peninsularis
 * Leptogenys sianka
 * Leptogenys sonora
 * Leptogenys volcanica

Worker diagnosis - Head not subrectangular, lateral margins convex, posterolateral margins convergent. Mandible variable in shape, ranging from triangular to elongate and falcate, mandibular masticatory margin edentate, basal sulcus variably developed from shallow to deep; median clypeal lobe prominent, longer than ocular malar distance (except L. oaxaca, L. chamela); no setae on clypeal apex (except L. foraminosa); PF: 4,3. Eyes dorsolaterally situated on head; eye diameter usually between one-fourth and one-third the length of lateral cephalic margin in full face view, rarely more; scape surpasses posterior cephalic margin by over one-fourth its length, third antennal segment elongate compared with neighboring funicular segments; funicular segments sub cylindrical (except L. chamela, L. bifida); median clypeal lobe with lateral lamella; mesosoma with abundant sculpturing, not smooth and shining; propleuron transversely striate to rugulose; metanotal groove deeply impressed (variable in L. sianka), smooth or scrobiculate; mesonotum longer than wide to wider than long, never narrow and transverse; anteroventral carina weak to absent especially ventrad (distinct in L. volcanica, L. elongata); metapleural-propodeal suture weakly developed to absent; propodeum unarmed or with low lobes or teeth; propodeal spiracle mostly elongate to almost slit-shaped, sometimes oval, facing posterad (posterolaterally in L. bifida), followed posterad by sulcus; dorsal and declivitous propodeal margins form single convexity in lateral view; node subquadrate in lateral view; anterior margin of abdominal segment III mostly vertical and weakly convex; constriction between abdominal segments III & IV usually weak, moderate at best; dorsum of head, mesosoma, petiole, and at least gastral segments I – II with appressed pubescence and standing hairs; protibial apex lacking setae; apex of mesotibia usually with single seta (none in L. peninsularis, L. sonora); metatibial apex with 0 or 1 seta; metacoxa lacking basal swelling.

Comments - These are the New World Leptogenys with the northernmost distribution, including L. elongata found from northern Mexico to Texas and Louisiana (U.S.A.), and L. manni, found in Florida, U.S.A. Most species are found in Mexico and Central America with a few reaching northwestern Colombia. All are of moderate to large size. Besides species found in temperate climates, the group also has species endemic to arid localities such as L. sonora in the Sonoran Desert and L. peninsularis in the Baja Peninsula of Mexico, and in lowland and montane humid forests also. The extent of development of the propodeal armature can vary from distinct teeth to low lobes or entirely edentate (L. sonora, L. chamela, L. peninsularis, and L. manni). Within L. elongata, the lobes may vary in development. The propleuron is usually mostly smooth and shining in this genus with sculpturing limited to the periphery, but the elongata species bear rough sculpturing throughout this sclerite and on most of the head and mesosoma as well. This is also accompanied by the presence of pubescence on the head and mesosoma. The trend in many groups seems to be towards smooth and shining sculpturing, and loss of pubescence. Ergatoid queens are known for several species in this group.

Possible apomorphies - A good number of plesiomorphies provide uniting criteria for this collection of species, where the only possible apomorphy detected so far seems to be the weakening and effacement of the anteroventral mesopleural carina, especially ventrad. This carina is normally well-defined in this genus. Noise is produced by two exceptions to this within the group and by the lack of this carina in L. panops, an incertae sedis species with enough characters to place it closer to the arcuata-unistimulosa lineage, safely away from the elongata species.