Crematogaster dentata Dalla Torre, 1893

Blaimer, Bonnie B. & Fisher, Brian L., 2013, Taxonomy of the Crematogaster degeeri-species-assemblage in the Malagasy region (Hymenoptera: Formicidae), European Journal of Taxonomy 51, pp. 1-64 : 27-32

Crematogaster dentata Dalla Torre, 1893 stat. nov.

Figs 10-11

Crematogaster sewellei var. dentata Dalla Torre, 1893: 86 .

Crematogaster sewelli var. improba Forel, 1907: 80 (footnote). Worker syntypes from MADAGASCAR: Morondava (collector unknown) [ MHNG, examined] . Lectotype worker by present designation: CASENT0101677, image on AntWeb, middle w of 3w specimens on one pin. syn. nov.

Crematogaster sewelli mauritiana Forel, 1907: 79 ; worker syntypes from MAURITIUS ( Voeltzkow ) [ MHNG, examined] . Lectotype worker by present designation: CASENT0101752, image on AntWeb. syn. nov.

Crematogaster inermis r. sewellii var. dentatus – Forel 1891: 196; unavailable name.

Crematogaster sewellei dentata – Forel 1907: 79. — Donisthorpe 1946: 30.

C. (Acrocoelia) sewellei var. dentata – Emery 1922: 148.

C. (Acrocoelia) sewelli var. improba – Emery 1922: 148.

C. (Acrocoelia) s ewelli mauritiana – Emery 1922: 148.

Diagnosis

Crematogaster dentata stat. nov. is a highly variable, widespread species and thus very difficult to diagnose based upon a single or even a few characters. Workers can be very small to medium size (HW 0.72 - 1.10, WL 0.74 - 1.11), but usually have very abundant pilosity on the promesonotum (> eight setae) and sculpture is mostly aciculate to reticulate throughout. This species is most likely to be confused with C. degeeri and C. ramamy sp. nov.. Crematogaster degeeri , however, has a promesonotum very distinctly set off from the propodeum and bears posterolateral denticles on the mesonotum, whereas typically in C. dentata stat. nov. the transition between mesonotum and propodeum is fluent and the metanotal groove shallow. Crematogaster ramamy sp. nov. always shows costulate sculpture on the pronotum, whereas in C. dentata the sculpture on the pronotum is reduced-aciculate or reticulate. Genetic divergence in the barcode region of this species with respect to other taxa within the C. degeeri -assemblage ranges from 12.7 - 21.3 % in our analysis ( Table 3 ).

Type material examined

( MHNG): MADAGASCAR (M. Grandidier), 1 worker, holotype by monotypy [ CASENT0101683 ; imaged on AntWeb ].

Other material examined

( BBBC, CASC, MHNG, NHMB, PSWC, ZMHB): refer to Supplementary Material 1.

Worker

Measurements

(n = 31) HW 0.72 - 1.10; HL 0.70 - 1.03; EL 0.13 - 0.24; SL 0.52 - 0.78; WL 0.74 - 1.11; SPL 0.01 - 0.10; PTH 0.12 - 0.24; PTL 0.23 - 0.35; PTW 0.24 - 0.41; PPL 0.11 - 0.21; PPW 0.21 - 0.38; LHT 0.55 - 0.84; CI 1.01 - 1.11; OI 0.17 - 0.26; SI 0.69 - 0.82; SPI 0.01 - 0.10; PTHI 0.52 - 0.77; PTWI 0.95 - 1.31; PPI 1.51 - 2.02; LBI 1.26 - 1.46.

Description

( Fig. 10A - F ) Very small to medium-sized (HW 0.72 - 1.10, WL 0.74 - 1.11).

Masticatory margin of mandibles with four teeth; head shape quadrate, mostly as long as wide (CI 1.01 - 1.11); posterior margin of head in full-face view laterally rounded or subangular; occipital carinae usually distinct; antennal scapes variable, but often not reaching head margin; midline of eyes situated at midline of head in full-face view; eye size fairly variable (OI 0.17 - 0.26), usually only slightly protruding.

Pronotum laterally subangular; promesonotal suture indistinct, mesonotum more or less forming one plane with pronotum; mesonotum usually without a distinct posterior face; laterally mesonotum angular and often with posterolateral tubercules or denticles; mesonotum longitudinally depressed with respect to lateral borders, sloping gently into metanotal groove; metanotal groove more or less absent; propodeal spines highly variable, from reduced minute denticles to short and spiniform (SPI 0.01 - 0.10), if spiniform then often downcurved; propodeal spiracles large, situated directly at base of spines; dorsal face of propodeum variable, from almost as long as posterior face to nearly absent; posterior face of propodeum from gently to steeply sloping; petiole in dorsal view oval, or moderately to strongly flared, moderately to strongly concave, usually not dorsolaterally carinate and without posterolateral tubercules or denticles; subpetiolar process variable; postpetiole wider than long, distinctly bilobed with a broad median impression; subpostpetiolar process absent.

Head sculpture aciculate; promesonotum usually dorsally reticulate or aciculate, rarely pronotum carinulate; propleuron aciculate, mesopleuron areolate, metapleuron mostly reticulate; dorsal face of propodeum reticulate or aciculate, posterior face shiny; dorsal face of petiole reticulate to shiny; helcium reticulate; postpetiole dorsally aciculate; lateral and ventral face of petiole and postpetiole reticulate; face usually with four to eight erect, longer setae, and regular, shorter, appressed to suberect pubescence; erect pilosity on promesonotum variable, but usually very abundant> eight long setae; otherwise promesonotum dorsally with regular to sparse appressed to subdecumbent pubescence; petiole and postpetiole usually with a pair of longer erect setae posterolaterally, and shorter suberect, decumbent or appressed pubescence; abdominal tergites four to seven with moderately abundant, short, erect pilosity, and regular appressed to decumbent pubescence throughout. Color light brown to dark brown, black, orange-red with black abdominal segment four to seven (western and southern dry and spiny forest localities).

Queen

Measurements

(n = 5) HW 1.13 - 1.41; HL 1.17 - 1.46; EL 0.30 - 0.42; SL 0.67 - 0.88; MSNW 0.92 - 1.19; MSNL 1.00 - 1.30; WL 1.73 - 2.43; SPL 0.00; PTH 0.30 - 0.38; PTL 0.35 - 0.43; PTW 0.41 - 0.52; PPL 0.26 - 0.39; PPW 0.40 - 0.55; LHT 0.80 - 1.05; CI 0.95 - 1.03; OI 0.25 - 0.31; SI 0.57 - 0.67; MSNI 0.86 - 0.92; SPI 0.00; PTHI 0.76 - 0.90; PTWI 1.10 - 1.21; PPI 1.39 - 1.68; LBI 2.17 - 2.32.

Description

( Fig. 11A - C ) Small to medium size (HW 1.13 - 1.41, WL 1.73 - 2.43). With worker characters, except as follows.

Masticatory margin of mandibles with five teeth. Antennal scapes very short, often not reaching level of lateral ocelli; eyes fairly large (OI 0.25 - 0.31), situated distinctly below midline of head in full-face view; head shape usually rectangular, elongate, longer than wide (CI 0.95 - 1.03); posterior margin straight.

Mesoscutum in dorsal view longer than wide (MSNI 0.86 - 0.92); dorsal face of propodeum distinct but short; propodeal spines or tubercules absent; petiole moderately flared, postpetiole merely impressed behind; subpetiolar process variable.

Sculpture shiny to aciculate throughout; face usually with> six longer erect setae and abundant, shorter, erect to suberect pilosity; mesonotum with abundant short, and scattered longer, erect setae; petiole and postpetiole with dense short suberect pilosity, and postpetiole often with additional longer dorsoposterior setae; abdominal tergites and sternites four to seven with abundant appressed pilosity and sparse, short, erect pilosity. Color similar to respective workers; wings clear.

Male

Measurements

(n = 3) HW 0.56 - 0.64; HL 0.42 - 0.48; EL 0.21 - 0.23; SL 0.10 - 0.13; MSNW 0.65 - 0.74; MSNL 0.50 - 0.69; WL 1.09 - 1.40; SPL 0.00; PTH 0.16 - 0.17; PTL 0.20 - 0.24; PTW 0.22 - 0.27; PPL 0.12 - 0.14; PPW 0.24 - 0.27; LHT 0.54 - 0.62; CI 1.32 - 1.35; OI 0.47 - 0.53; SI 0.23 - 0.27; MSNI 1.08 - 1.45; SPI 0.00; PTHI 0.71 - 0.83; PTWI 0.97 - 1.24; PPI 1.74 - 2.16; LBI 2.01 - 2.25.

Description

( Fig. 10G - H ) Small (HW 0.56 - 0.64, WL 1.09 - 1.40).

Mandibles short and reduced, blunt and edentate; clypeus moderately protruding; eyes moderately sized (OI 0.47 - 0.53) and protruding, midline of eyes situated well below midline of head, almost extending to clypeal margin; antennae 12-segmented; head wider than long (CI 1.32 - 1.35); in full-face view ocellar triangle situated at posterior head margin, but not much elevated with respect to rest of face; occipital carinae distinct.

Mesoscutum in dorsal view as wide as long or wider than long (MSNI 1.08 - 1.45); scutellum in dorsal view broadly tapering from anterior to posterior end, dorsoposterior part rounded; metanotum protruding from below scutellum; dorsal face of propodeum almost as long as posterior face; propodeal

spines absent; petiole in dorsal view oval, laterally rounded, in lateral view greatly tapering anteriorly; subpetiolar process absent; postpetiole fairly flat, lacking median impression.

Head sculpture, including clypeus, shiny to rugulose; mesoscutum with very fine longitudinal carinulae; otherwise sculpture more or less shiny to aciculate; scattered short, erect pilosity and a few longer setae on face, mesoscutum, and scutellum; remaining pilosity as in queens. Color brown.

Distribution and biology

MADAGASCAR, MAURITIUS, MAYOTTE and JUAN DE NOVA. Crematogaster dentata stat. nov. is the most widespread species within the C. degeeri -assemblage in the Malagasy region ( Fig. 11 D-E). The species occurs in dry deciduous and littoral forests of western, southwestern and northern Madagascar, in the spiny forest of southern Madagascar and in coastal shrub and mangrove habitats. A few records exist from rainforest sites, but the species is clearly adapted to more mesic habitats. Crematogaster dentata stat. nov. is thus most common at low elevations, but its elevational distribution range seems to be quite broad, with a maximum record of 1410 m in transition forest in Ambohitantely Reserve. On Mayotte and Juan de Nova it has been found to occupy coastal shrub habitats, whereas on Mauritius it is known to occur in rainforest habitat. Given its broad distribution range, this species co-occurs with most other species in the C. degeeri -assemblage, with the exception of the species generally adapted to higher elevations ( C. alafara sp. nov., C. degeeri , C. malahelo sp. nov.). Crematogaster dentata stat. nov. is most often found nesting arboreally in dead twigs and branches, and also in live plant parts. In baiting surveys in western Madagascar this species was active and attracted to fish baits during both day and night.

Comments

Crematogaster dentata stat. nov. is morphologically the most variable species within the C. degeeri -assemblage. Workers show a wide range of gradual variation in size and mesosomal structure. The variation in mesosomal characters in particular can lead to confusion with other species, making C. dentata stat. nov. difficult to diagnose. A general trend seems to be that workers from populations of the southern and western spiny forests are on average larger than on the rest of the island. Dry and spiny forest populations are reddish to orange in color, whereas rainforest populations are brown.

The allopatric population of Crematogaster dentata stat. nov. on Mauritius shows 8.8 - 11.2 % divergence with respect to Madagascar. The decision of whether or not to give species status to this population is arbitrary, since it is unknown if reproductive isolation exists with the mainland. A species name would already be available (with C. sewellii mauritiana ). We decided against describing a separate species for Mauritius, since we were not able to find any distinct diagnostic morphological characters for this population.

Figures

Fig. 10. Crematogaster dentata Dalla Torre, 1893 stat. nov., workers and male. A-C. Worker (CASENT0456641). A. Full-face. B. Profile. C. Dorsal. D-F. Worker (CASENT0138289). D. Full-face E. Profile F. Dorsal. G-H. Male (CASENT0456644). G. Full-face. H. Profile.

Fig. 11. Crematogaster dentata Dalla Torre, 1893 stat. nov., queen and distribution. A-C. Queen (CASENT0484998). A. Full-face. B. Profile. C. Dorsal. D-E. Species distribution.