Cardiocondyla species groups

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The original species groups proposed by Seifert (2003) have been updated and expanded by Seifert (2022).

Cardiocondyla argentea group

Dorsal mesosomal profile evenly convex with absent or only suggested metanotal depression (MGr/CS 0–0.52%) and in dorsal view without pronotal corners. Propodeal spines well-developed (SP/CS 0.208–0.400). Postpetiolar sternite conspicuously bilobate or bicuspidate. Furthermore characterized by short head with rather low postocular index (CL/CW 1.051–1.133, PoOc/CL 0.408–0.436) and a wide frons (FRS/CS 0.242–0.337).

The clearest differences to the C. thoracica and C. wheeleri group are the conspicuously bilobate or bicuspidate postpetiolar sternite, the evenly convex dorsal mesosomal profile and the absence of any pronotal corners.

Six species in the East Orientalic and Australasian zone, no tramp species known.

Cardiocondyla batesii group

Eye very large (EYE/CS 0.263 ± 0.08), postocular distance very small (PoOc/CL 0.368 ± 0.016), head rather long (CL/CW 1.176 ± 0.023), metanotal depression always present (MGr/CS 3.51 ± 0.82%), propodeal spines short (SP/CS 0.100 ± 0.013), pubescence on first gaster tergite rather short (PLG/CS 5.50 ± 0.43%), postpetiolar sternite completely flat, without any protrusions.

Nine species from the southern zone of West Palaearctic, tramp species unknown, one undescribed species (Cardiocondyla sp. code VERD).

Cardiocondyla elegans group

Eye large (EYE/CS 0.250 ± 0.006), postocular distance small (PoOc/CL 0.395 ± 0.009), head rather short (CL/CW 1.156 ± 0.017), metanotal depression always present (MGr/CS 4.50 ± 0.76%), propodeal spines short (SP/CS 0.116 ± 0.013), pubescence on first gaster tergite very long (PLG/CS 7.84 ± 0.51%), postpetiolar sternite without any protrusions.

Three described and one undescribed species (Cardiocondyla sp. code DAOI) from the southern zone of the West Palaearctic.

Cardiocondyla emeryi group

Head elongated with rather high postocular index (CL/CW 1.227–1.246, PoOc/CL 0.454–0.472) and a very narrow frons (FRS/CS 0.200–0.227). Metanotal depression well developed (MGr/CS 2.33–3.22%), Propodeal spines relatively short (SP/CS 0.128–0.207). Postpetiole rather high (PpH/CS 0.292–0.335) and with a bulging sternite that does not show any lobes, cusps or dents. Pubescence on first gaster tergite rather long and dense (PLG/CS 6.7–7.6%, sqPDG 3.8–4.3).

At least two species with probably Afrotropical origin, one of these with worldwide tramp species properties.

Cardiocondyla longinoda group

Monotypical group. Assessment based on evaluation of images CASENT09011751 of the holotype in www.antweb.org. The most eye-catching character is petiole shape in lateral view which is not seen in any Afrotropical Cardiocondyla species. Overall, this slender ant shows similarity to members of the Cardiocondyla nuda and C. shuckardi group but it differs from these by a much narrower frons and lower petiole and a more approached spine base. The ratio FRS*PeH/SL is 3.40% in the holotype of C. longinoda but 5.34 ± 0.48 [3.99, 6.88]% in 759 individuals of the C. nuda and C. shuckardi group. The slenderness of C. longinoda is also expressed by the 2nd component of a PCA considering the characters CS, SL, FRS, SPBA and PeH which is −3.80 in the holotype of C. longinoda but 0.005 ± 0.991 [−2.36, 3.59] in 759 individuals of the C. nuda and C. shuckardi group.

Only a single Afrotropical species known.

Cardiocondyla minutior group

Head elongated with rather high postocular index (CL/CW 1.182–1.263, PoOc/CL 0.463–0.490) and a narrow frons (FRS/CS 0.221–0.246). Metanotal depression weak or absent (MGr/CS 0–1.25%), propodeal spines short (SP/CS 0.089–0.133). Postpetiole with a flat sternite and low (PpH/CS 0.230–0.274). Pubescence on first gaster tergite rather long and dense (PLG/CS 6.6–8.3%, sqPDG 2.8–4.0).

Eight species with distributional center in the Orientalic and Australasian region of which two are worldwide tramp species.

Cardiocondyla monardi group

(Subgenus Loncyda Santschi, 1931)

Monotypical group. Head, mesosoma, waist and gaster on whole exposed surface with a rich silvery glinting pubescence having flattened hairs. Dorsal profile of mesosoma from anterior part of pronotum to caudal part of propodeum continuously convex, the latter without any suggestions of spines or dents. Petiole extremely slender, with a very long peduncle and a long and narrow node with a feebly convex dorsal profile. Postpetiole narrow and low, distinctly longer than wide, in dorsal view its anterior half conically narrowing frontad.

Only a single Afrotropical species known.

Cardiocondyla nivalis group

Very small (CS 357–402 µm). With exception of the dark brown to jet black gaster, whole body whitish or whitish-yellowish. Metanotal groove notable (MGr/CS 1.6–2.6%) and overall dorsal mesosomal profile more straight. Frons wider than in the former three species groups (FRS/CS 0.290–0.314). Head and scape rather short (CL/CW 1.095–1.149, SL/CS 0.787–0.857).

Two species of Australasian-Polynesian origin.

Cardiocondyla nuda group

Promesonotal and anterior propodeal profiles usually not forming evenly convex curvatures—as result, metanotal depression, if present at all, not as wide and with steeper anterior and posterior slopes. Propodeal spines short, appearing in lateral view as smaller angles of 60–95°. Postpetiole in dorsal aspect frequently with angulate-convex sides—the outlines of postpetiole thus resembling a hexagon. Eyes small (EYE/CS 0.231 ± 0.05), postocular index rather large (PoOc/CL 0.454 ± 0.013) and postpetiole rather narrow (PpW/CS 0.487 ± 0.030). Basic type of sculpture on paramedian vertex and mesosoma microreticulate, though varying in strength.

There are similarities to the C. shuckardi group questioning if a separation in different groups by subtle differences in mesosoma profile and postpetiole shape are reasonable. Yet, the morphometric separation of the C. shuckardi and C. nuda group is clear. Individual workers of seven available species in the C. shuckardi group and of all eight species of the C. nuda group were correctly classified by a linear discriminant function in 98.8% of the cases. With all linear measures in mm and sqPDG as square root of the µm value, the discriminant 195.98∗MGr + 0.29∗sqPDG − 9.636∗CW − 24.69∗FRS + 48.59∗SPBA − 71.61∗SP + 58.30∗PeW − 77.64∗PpW + 56.53∗PpH + 2.367 was −1.343 ± 0.973 [−4.100, 1.430] in 540 workers of the C. nuda group and 3.342 ± 1.065 [0.465, 6.606] in 217 workers of C. shuckardi group.

Eight species from the tropical to south temperate zones of the Old World, with one species introduced to the Americas.

Cardiocondyla shuckardi group

Dorsal profile of promesonotum and of propodeum frontal of spine base feebly but continuously convex—as result, the always developed and rather deep metanotal depression is formed by very shallow anterior and posterior slopes (MGr/CS 1.6–6.3%). Propodeal spines always short (SP/CS 0.029–0.088), reduced do blunt dents or obtusely angled corners. Petiole node in dorsal view always globular. Postpetiole rather narrow (PpW/CS 0.399–0.490), its sides in dorsal view rounded, outlines of postpetiole thus never not forming a hexagon.

About nine species occurring in Africa, the Arab Peninsula and Iran of which one species was introduced to the Caribbean and Hawaii.

Cardiocondyla sima group

(Subgenus Prosopidris Wheeler, 1935)

Antennae with 11 segments instead of 12 in all other species of the genus. Collective length of the three apical antennal segments 57–63% of whole funiculus length, in other species shorter. Anterior part of postpetiole in dorsal view conic. Petiole with a very long peduncle and well-developed node. Scape very long in terms of the genus (SL/CS 0.937–0.981).

At least two polymorphic Australasian species, no tramp species known.

Cardiocondyla stambuloffii group

True foveolae on vertex completely absent. Instead the bases of pubescence hairs are placed in the center of flat tubercles or flat pits of small diameter, giving a finely punctate surface appearance at lower magnifications, dFov 8.13 ± 0.78 [5.0, 10.0]. Frons very wide, FRS/CS 0.320 ± 0.015 [0.269, 0.353]. Propodeal spines reduced to blunt dents, SP/CS 0.070 ± 0.013 [0.027, 0.096]. Metanotal depression deep, MGr/CS 3.57 ± 0.83 [1.63, 6.16]%; all numeric data from 153 worker individuals of five species.

The members of the C. batesii, C. elegans and C. ulinanini groups as they are proposed below are morphologically similar. This grouping is confirmed by an LDA considering all morphometric characters with positive checks in wild-card runs for rare species with very few samples available.

SE Europe across Asia Minor eastwards to Tibet and Mongolia with four described and one undescribed species (Cardiocondyla sp. code ROLA).

Cardiocondyla sulcata group

Monotypical group. Metanotal groove very deep and with an extremely steep posterior slope that forms with the anterior slope a distinct angle of 90–100°. Petiole with a very long peduncle, in dorsal view more than twice as long than wide and with a small circular node, in profile the node is low with a convex dorsum. Postpetiolar sternite almost flat, only with suggested and very rounded anterolateral corners.

Only a single Orientalic species known from Malaysia.

Cardiocondyla thoracica group

Pronotal corners in dorsal and lateral view very prominent and sharp. Dorsal mesosomal profile not evenly convex and with an absent to well-developed metanotal depression (MGr/CS 0–7.6%). Postpetiolar sternite differently shaped but not distinctly bilobate or bicuspidate, without any prominent structures. Spine base narrower and spines shorter than in the C. wheeleri group (SPBA/CS 0.237–0.368, SP/CS 0.230–0.365).

Three Australasian species, all occurring east of the Wallace Line, no tramp species known.

Cardiocondyla ulianini group

Eye large (EYE/CS 0.248 ± 0.012), postocular distance larger (PoOc/CL 0.407 ± 0.031), head longer (CL/CW 1.160 ± 0.022), metanotal depression always present (MGr/CS 3.85 ± 0.84%), propodeal spines short (SP/CS 0.114 ± 0.015), pubescence on first gaster tergite rather long (PLG/CS 6.55 ± 1.06%), postpetiolar sternite without any protrusions.

Seven described and one undescribed species (Cardiocondyla sp. code CASP) from the southern zone of the West and Central Palaearctic.

Cardiocondyla wheeleri group

Pronotal corners in dorsal view developed but blunt. Dorsal mesosomal profile not evenly convex with a small metanotal depression (MGr/CS 1.4–3.0%). Postpetiolar sternite flat or shallowly convex and without any prominent structures. Spine base very broad and spines rather long (SPBA/CS 0.341–0.374, SP/CS 0.296–0.418).

Four Australasian species, all occurring east of the Wallace Line, no tramp species known,

Cardiocondyla wroughtonii group

Head rather short with comparably low postocular index (CL/CW 1.099–1.189, PoOc/CL 0.415–0.440) and a variably wide frons (FRS/CS 0.219–0.282). Scape short to very short (SL/CS 0.682–0.825). Metanotal depression well developed (MGr/CS 3.25–3.65%). Propodeal spines rather short (SP/CS 0.184–0.201). Postpetiole higher (PpH/CS 0.276–0.337) with a bilobate or bicuspidate sternite. Pubescence on first gaster tergite variable.

Five described and two undescribed species (Cardiocondyla sp. code HEIN, Cardiocondyla sp. code AFRI) with origin in the tropics of the Old World, two of these occur as worldwide tramp species.

References