Hypoponera

Bolton, B. & Fisher, B. L., 2011, Taxonomy of Afrotropical and West Palaearctic ants of the ponerine genus Hypoponera Santschi (Hymenoptera: Formicidae)., Zootaxa 2843, pp. 1-118 : 7-12

Genus Hypoponera

Hypoponera Santschi

Hypoponera Santschi, 1938: 79 [as subgenus of Ponera ]. Type-species: Ponera abeillei Andre , 1881: 61 and xlviii, by original designation. [Raised to genus: Taylor, 1967: 9.]

Diagnosis of worker

Members of subfamily Ponerinae , tribe Ponerini (sensu Bolton, 2003) that principally inhabit rotten wood, leaf litter and topsoil.

1 Mandible triangular and stout, short to moderate in length (MI 27 – 35), without a basal groove and without a basal pit; with a basal angle between masticatory and basal margins. When mandibles are fully closed there is no space between the masticatory margins, nor between basal margins of mandibles and the clypeus.

2 Masticatory margin of mandible with 7 to about 18 teeth and denticles in total.

3 Palp formula 1,1 or 1,2, the maxillary palp usually minute.

4 Clypeus simple, without extended lobes or teeth on either the median or the lateral portions and usually unarmed anteromedially. Median portion of clypeus inserted as a small narrow triangle between the extreme anterior ends of the frontal lobes.

5 Frontal lobes small, almost confluent medially, separated only by a median longitudinal impression; the frontal lobes not raised or specialised in any way and their anterior margins well behind the anterior clypeal margin. Frontal carinae and antennal scrobes absent.

6 Eyes absent or present; when present always small (generally of 1 to about 20 ommatidia), lateral and located well in front of the midlength of the head.

7 Antenna with 12 segments, the apical 4 – 6 antennomeres gradually incrassate; only extremely rarely with a sharply differentiated club.

8 Dorsum of mesosoma with or without a metanotal groove.

9 Mesopleuron without a distinct transverse sulcus that conspicuously divides it into anepisternum and katepisternum.

10 Epimeral sclerite usually absent.

11 Metapleural gland orifice small and simple, opening posteriorly.

12 Metasternal process small and simple.

13 Propodeal spiracle small, circular to slightly elliptical, located far down on the side, usually close to the bulla of the metapleural gland.

14 Propodeum unarmed; propodeal lobes vestigial to absent.

15 Mesotibiae, metatibiae, mesobasitarsi and metabasitarsi all without spines and without enlarged prominent setae to enhance traction on their dorsal (outer) surfaces.

16 Mesotibia and metatibia each with only a single spur; metatibial spur always pectinate.

17 Pretarsal claws small and simple, without preapical teeth.

18 Petiole tergite nodiform to squamiform, always unarmed.

19 Subpetiolar process usually simple, a rounded to angulate ventral lobe; never with paired prominent teeth at the posteroventral corner of the lobe; subpetiolar process usually without an anterior fenestra or thin-spot but a fenestra present in some abeillei group members.

20 Articulation of petiole to helcium simple.

21 Helcium arises low down on anterior face of first gastral tergite (Abd. III) and is always simple; anterior surface of first gastral tergite forms a tall vertical surface above the helcium.

22 Prora usually present (absent in only one Afrotropical species): an arched tranverse crest that extends across the first gastral sternite below the helcium; usually the prora extends up the anterior face of the first sternite on each side, so that the entire prora is broadly U-shaped in anterior view.

23 Cinctus of second gastral tergite (Abd. IV) present, usually conspicuous.

24 Stridulitrum absent or present on pretergite of abdominal segment IV. In addition, fine sculpture is predominantly present, uncommonly entirely absent. The sculpture is expressed as

various forms of punctation, that varies in density and intensity on different parts of the body and sometimes differs between species. Coarse, dense sculpture, such as rugae, costulae, or strong striation, appears never to be developed.

Comments on worker characters

The list of characters above forms a good inclusive diagnosis of the genus, but there is so much convergent evolution and parallelism among smaller species of various Ponerini genera, especially those that spend their lives in the leaf litter, topsoil and rotten wood, that no character can currently be singled out as unquestionably autapomorphic for Hypoponera . The numbers used below refer to the character numbers listed above.

1 MI above applies to Afrotropical species. A few extralimital species were also measured and fell into the same range, but the MI range recorded above does not reflect the world fauna. In all Afrotropical and West Palaearctic species the mandibles are smooth with scattered punctures; no species with mandibles striate or otherwise sculptured has been recorded.

2 Dentition in Afrotropical species is very uniform across all the species, contrary to Bernard (1953), who was of the opinion that dentition was very diverse between species. There is variation in dentition within species, within nest series and sometimes between left and right mandibles on the same specimen. In general, larger species have proportionately larger teeth and denticles than smaller species. Also, larger species and those with relatively longer mandibles (MI ca 35) usually have more teeth and denticles than smaller species and those with shorter mandibles (MI ca 27). These variations are found in a gradient across the genus, change with overall size, and usually do not isolate individual species. Total dental count (teeth plus denticles) recorded in Afrotropical species is 8 – 13 and is generally arranged as follows: three teeth apically, apical the largest and the second smaller than the third; then 0 – 2 denticles followed by a larger fourth tooth that is usually about the same size as the third; basal of this the margin is variously denticulate to the basal angle, most usually with 1 or 2 of the denticles somewhat larger than their neighbours. On occasion the basalmost section of the masticatory margin is more or less edentate, though this may be due to wear.

3 Without dissection the maxillary palp is often extremely difficult to see, even in specimens with the mouthparts fully everted. It may be absent in some species but is never of more than one segment.

6 In some species eyes are universally present but are always small and usually insignificant. Sometimes just a single ommatidium occurs but often there are 2 – 7 present, which may be partially fused. In others, the eye is reduced to a depigmented ommatidium or merely appears as a spot on the cuticle, which may be difficult to discriminate from the surrounding punctate sculpture. In several species eyes are univerally absent. However, there are a number of species where variation is apparent, with some workers eyeless but others with a faint eye spot and still others with a fairly distinct ommatidium. In some species where eyes are present they differ in size between individuals and in extralimital species up to about 20 ommatidia may occur.

7 Most Afrotropical species have funicular segments 7 – 11 gradually incrassate, some have 6 – 11 gradually incrassate. Only a single species, angustata , has a marked 4-segmented club.

8 In the majority of Hypoponera species there is either a strongly developed metanotal groove that forms a sharply incised narrow impression right across the dorsal mesosoma, or there is no trace of a groove at all. However, many intermediate species exist in which a vestige of the metanotal groove remains. This may take the form of an almost effaced weak concavity, a slight change of slope between mesonotum and propodeum, or merely a discoloured line that appears to represent the last vestige of the groove or perhaps a slight invagination of the cuticle. Taken together, the entire sequence is one of morphoclinal reduction and eventual elimination of the metanotal groove. In the group as a whole the presence or absence of a metanotal groove has variously been used in an attempt to isolate genera or subgenera (e.g. Santschi (1938), Bernard (1953)). The effort was misplaced, as it is now obvious that the metanotal groove comes and goes between various species groups of both Ponera and Hypoponera(Taylor (1967) and current study), as well as in other ponerine taxa, such as those currently assigned to Pachycondyla .

9 In the vast majority of species the mesopleuron forms a single sclerite. In a few there may be a faint remnant of a transverse impression, but there is never a strong sulcus.

10 Presence or absence of an epimeral sclerite has recently been used as a diagnostic feature of ponerine males (Yoshimura & Fisher, 2007; Bolton & Fisher, 2008c), but has not figured in the diagnoses of ponerine workers. When present in Ponerini workers it takes the form of a discrete small sclerite, usually subcircular, that covers the orifice of the metathoracic spiracle and is located on the side of the mesosoma, at the apex of the metapleuron just behind the posterodorsal margin of the mesopleuron, or behind the posterodorsal anepisternum in those taxa where the mesopleuron is subdivided. The sclerite is universally absent in both Hypoponera and Ponera , except for H. zwaluwenburgi (Wheeler) where it appears to be present (Imai, et al. 2003: 197).

18 In profile the petiole tergite is often a roughly rectangular, fairly narrow, tall node that has a distinct dorsal surface. In a few the node is lower and longer but in some major groups it is considerably narrowed and strongly tapered dorsally, producing a thickly squamiform appearance.

19 Most species of Afrotropical Hypoponera have a sensory seta that projects laterally or posterolaterally from the lateral surface of the subpetiolar process, close to its anterior margin. In many species where the subpetiolar process is relatively strongly developed, including importuna , lepida , molesta , natalensis and producta , the basal pit of this seta is large, distinct and quite obviously concave. The pit is even more strongly developed in boerorum and spei , where it often appears as a thin spot or fenestra that is reminiscent of the condition universal in Ponera . Coupled with this, in spei the subpetiolar process often has a distinct sharp posteroventral angle, so that in profile the Ponera-like condition becomes even more apparent. This is probably a convergence phenomenon because, unlike Ponera , the Hypoponera species with this fenestra do not have a posteriorly bifurcated ventral surface to the petiole sternite and the posteroventral apex of the subpetiolar process is never produced into a pair of sharp teeth that represent the apices of the bifurcation, such as is universal in genuine Ponera .

Two recently described species of Ponera , P. nangongshana Xu (2001) from China and P. yuhuang Terayama (2009) from Taiwan, are both characterised as lacking posteroventral teeth on the subpetiolar process, but possessing a fenestra anteriorly. In view of the morphoclinal development of a fenestra in Afrotropical Hypoponera and the otherwise universal presence of posteroventral subpetiolar teeth in Ponera , the generic combination of these two Oriental species should be re-assessed.

20 The sternite of the petiole and the articulation of petiole to helcium does not show any of the derived morphology that was described by Bolton & Fisher (2008a, 2008b) for Asphinctopone , Phrynoponera , or some other Ponerini groups mentioned in those papers.

22 The prora in some extralimital species may be represented by a short transverse bar that is slightly concave in frontal view, a reduction from the condition seen in Afrotropical species. In a single Afrotropical species ( aprora ) the prora has been lost.

Diagnosis of worker-queen intercaste (= ergatoid gyne)

Characters as worker but always with much larger eyes than conspecific worker (intercastes with 7 – 30 ommatidia in Afrotropical species in which workers have 0 – 7 ommatidia), but without ocelli; often with a shorter petiole node in profile and a somewhat enlarged gaster; sometimes with a gyne-like transverse sulcus on mesopleuron. One intercaste of punctatissima was dissected: a spermatheca was present and the ovaries were enlarged, though much smaller than in the gyne (see also Yamauchi, et al. (1996)).

Intercastes have been confirmed in the following species that occur in the Afrotropical region. H. abeillei group: austra , importuna , lepida , producta . H. punctatissima group: eduardi , ragusai , punctatissima . Possible intercastes are also suspected in ignavia and occidentalis (see discussions of those species). It seems reasonable to assume that intercastes occur in many more species but are not currently represented in collections. It is equally obvious that some species, such as the extremely common dulcis , do not produce them. In some previous publications, intercastes have been termed major workers or ergatoid females (e.g. Forel (1894), Le Masne (1956), Brown (1958)). Observations on the reproductive biology of intercastes can be found in Le Masne (1956), Yamauchi, et al. (1996) and Yamauchi, et al. (2001).

Diagnosis of queen (gyne)

Characters as listed for workers except for worker characters 6, 8, 9; with the following differences.

1 Eyes always present and large, usually obviously with> 50 ommatidia. Eyes are located in front of midlength of head and all species examined have small setae that project between the ommatidia.

2 Ocelli present.

3 Mesopleuron with a well developed transverse suture that divides it into anepisternum and katepisternum.

4 Mesosoma with a full complement of flight sclerites (alate when virgin).

5 Jugal lobe absent from hindwing.

6 Venation almost complete (only cross-vein 1r-rs absent); with 8 or 9 closed cells including the pterostigma (8 cells in those species with Cu2 incomplete or absent); Rs.f5 meets R1.f3 on the anterior margin (i.e. marginal cell always closed); cross-veins 2r-rs, 2rs-m, 1m-cu and cu-a all present; cu-a arises from M+Cu (i.e. proximal of point where M+Cu divides into M and Cu; 2rs-m distal of 2r-rs; a free abscissa of M (M.f2) present between Rs+M and 1m-cu; an angle or bend sometimes present in Rs.f2&3; a fenestra present in cu-a and fenestrae sometimes visible in Rs.f2&3 and 2rs-m, but not in minute species.

7 Petiole node in profile is usually more slender, and often more tapered dorsally, than in the conspecific worker.

Generally slightly larger than conspecific worker; gaster sometimes distinctly larger.

Comments on gyne characters

The numbers used below refer to the character numbers listed above.

1 The presence of short setae that project between the ommatidia has been confirmed in the following species: angustata , aprora , austra , blanda , coeca , comis , dema , dulcis , eduardi , fatiga , hebes , ignavia , importuna , inaudax , lassa , lepida , meridia , molesta , obtunsa , occidentalis , odiosa , producta , punctatissima , ragusai , segnis , spei , sulcatinasis, tristis , and also in a number of extralimital species from the Holarctic, Oriental, Malesian and Neotropical regions (BMNH).

6 For a recent illustration of general ponerine venation see Yoshimura & Fisher (2007: 24, fig. 1).

Diagnosis of alate male

1 Mandible lobiform to unidentate (apical tooth only present), not meeting at full closure. Basal cavity of mandible extends to its front face and is visible in full-face view.

2 Eyes large and conspicuous, with minute setae projecting from between the ommatidia. Three distinct ocelli present.

3 Antenna with 13 segments, filiform.

4 Scape short, shorter than second funicular segment.

5 Second funicular segment longer than the first and also longer than the third.

6 Palp formula 1,1; 1,2; 1,3; 1,4; very rarely maxillary palp of 2 segments.

7 Mesonotum in profile not overhanging pronotum.

8 Mesoscutellum convex in profile.

9 Notauli absent; parapsidal grooves present but sometimes very faint.

10 Epimeral sclerite absent.

11 Mesotibia and metatibia each with a single spur; metatibial spur always pectinate.

12 Pretarsal claws simple.

13 Venation as alate gyne.

14 Jugal lobe absent from hindwing.

15 Petiole unspecialised ventrally; helcium very low on anterior face of first gastral segment.

16 Prora present, small.

17 Cinctus of second gastral tergite (Abd. IV) present.

18 Tergite of abdominal segment VIII (pygidium) without a median downcurved spine.

19 Pygostyles (= cerci) present.

Comments on alate male characters

Among Afrotropical species alate males that have been found associated with workers are known only for austra, coeca , dulcis , eduardi , obtunsa and ragusai . The characters and comments are supplemented with observations based on unidentified males and extralimital species.

1 The reduced state of the male mandible is characteristic of all alate male Ponerini (Bolton, 2003). The basal cavity character was first used by Yoshimua & Fisher (2007) for Malagasy species.

2 All alate males examined also have short setae that project between the ommatidia, as in the gynes, but so few are known that the universality of the character is unclear.

3 – 5 The configuration of the four basal antennal segments in Hypoponera alate males is extremely common in Ponerini . See for example Ogata (1987), Yoshimura & Fisher (2007), Bolton & Fisher (2008b).

6 The palp formulae are originally from Taylor (1967), with additions and confirmations by Bolton (2003). The discovery of a 2-segmented maxillary palp in one Malagasy species is by Yoshimura & Fisher (2007).

Diagnosis of ergatoid male

1 Body form extremely worker-like but male genitalia present.

2 Mandibles reduced (similar to alate males) or worker-like.

3 Antenna with 12 or 13 segments, worker-like or specialised but without the basal segment arrangement of alate males (male characters 4 and 5, above). Scape distinctly shorter than in conspecific worker.

4 Eyes present or absent.

Comments on ergatoid male characters

The production of ergatoid males appears to be restricted to species of the punctatissima group (see below). The characters above are based on eduardi , punctatissima and ragusai , but ergatoid males are also produced by extralimital members of the group, such as opacior (Forel) , opaciceps (Mayr) and nubatama Terayama & Hashimoto.

At first glance ergatoid males can easily be mistaken for workers, especially as the characteristic male genitalia are retractile and may be almost entirely concealed within the body. The ergatoid male of eduardi is monomorphic, with reduced mandibles, 13-segmented antennae and small eyes present. The ergatoid male of punctatissima is dimorphic. Both morphs have worker-like mandibles and head shape and 12-segmented antennae, but the larger morph is brown and has small eyes, while the smaller morph is yellow and lacks eyes. Ergatoid males of ragusai have not yet been found in the Afrotropical region, but specimens from the U.S.A. have a worker-like head and mandibles, as punctatissima , but possess 13-segmented antennae.

Separation of Hypoponera from convergent genera

1 Ponera

No native species of Ponera has ever been found in sub-Saharan Africa and it is probably now safe to say that the genus is not represented by endemic species in this region. However, some Ponera species have tramping ability and one small, as yet unidentified, species has been intercepted in East Africa (BMNH), which is the only confirmed record from the entire Afrotropical region. There are also three species found on islands in the Southwest Indian Ocean, all of which are assumed to be introduced. The West Palaearctic contains two indigenous species of Ponera , coarctata (Latreille) and testacea Emery ( Csösz, 2003; Csösz & Seifert, 2003). At first glance Ponera workers may be difficult to separate from Hypoponera , but Ponera workers (and queens) have a 2-segmented maxillary palp and a specialised subpetiolar process on which an anterior fenestra is present and the posteroventral angles of which project into a pair of sharp teeth (Taylor, 1967). Sometimes the petiolar sternite itself is bifurcated posteriorly. In Hypoponera the maxillary palp is 1-segmented at most, there is usually no fenestra (but see worker comment 19, above) and the posteroventral angle of the subpetiolar process, no matter how acute, never terminates in a pair of teeth. The males of Ponera always have the tergite of abdominal segment VIII produced into an elongate, downcurved median spine, whereas in male Hypoponera abdominal tergite VIII is a simple triangular sclerite.

2 Cryptopone

Only a single Afrotropical species seems correctly placed in Cryptopone , C. hartwigi Arnold (1948) from South Africa. Brown (1963: 6) regarded hartwigi as a member of Ponera , saying that true Cryptopone had not been taken in Africa south of the Sahara. This appears to have led Taylor (1967: 12) to transfer hartwigi to Hypoponera as it did not conform to his diagnosis of Ponera , but it is unlikely that either author had seen an actual specimen at that time. Genuine hartwigi workers have a basal mandibular pit, a characteristic of Cryptopone that is absent from all Hypoponera and Ponera . A second African species, originally described as Cryptopone angustata , properly belongs in Hypoponera and is discussed below. There is a single West Palaearctic species of Cryptopone , ochracea (Mayr), that has a distinct basal mandibular pit.

3 Pachycondyla

In the Afrotropical region there is a discrete group of at least three small, yellow Pachycondyla species that bear a superficial close resemblance to Hypoponera . This group currently contains Pachycondyla gulera Oezdikmen , 2010: 992 (a replacement name for Ponera ambigua Weber , 1942: 46, which was a junior secondary homonym of Pachycondyla ambigua Andre , 1890: 316), P. w e b e r i (Bernard, 1953: 194), and a third, apparently undescribed species from Cameroun and Gabon (CASC). P. gulera and the undescribed species will run to Hypoponera in standard keys to genera because they have lost the anterior mesotibial and metatibial spurs. The absence of these features gives them, convergently, the same spur formula as Hypoponera ; the anterior spurs on both tibiae are retained in weberi . Taken together the three species are quickly distinguished from Hypoponera by their elongate triangular mandibles (MI ca 45 – 50) and palp formula of 3,3.

In West and Central Africa there are also two apparently undescribed species of eyeless but darkly coloured Pachycondyla (BMNH, CASC) in which the subpetiolar process terminates posteroventrally in a Ponera-like pair of teeth. These species retain mesotibial and metatibial anterior spurs and have an epimeral sclerite, and by in situ count appear to have a palp formula higher than 2,2. At first glance they are reminiscent of the very common and widespread P. brunoi Forel (see Brown, 1963), but are considerably different in detail.

Afrotropical and West Palaearctic species groups of Hypoponera

The groups as presently constituted are designated and defined only to reflect what is seen in the Afrotropical and West Palaearctic faunae; some of them may prove to be inaccurate or artificial on a world-wide basis.