Abstract
The taxonomy of the Tetramorium naganum, T. plesiarum, T. schaufussii, and T. severini species groups are revised for the Malagasy region. A total of 31 species are treated, of which 22 are newly described and nine redescribed. This increases the richness of the hyper-diverse genus Tetramorium in the Malagasy region to 106 species, which makes it the most species-rich genus in the region. Twenty-nine of the treated species are endemic to Madagascar, one is endemic to the Comoros, and one species is found predominantly in Madagascar but also on the island of Reunion. The T. naganum species group contains five species, which are mainly distributed in the rainforests and montane rainforests of eastern and northern Madagascar: T. alperti sp. n., T. dalek sp. n., T. enkidu sp. n., T. gilgamesh sp. n., and T. naganum Bolton, 1979. The T. plesiarum species group holds five species: T. bressleri sp. n., T. hobbit sp. n., T. gollum sp. n., T. mars sp. n., and T. plesiarum Bolton, 1979. All five are arid-adapted species occurring in the southwest and west of Madagascar. The second-most species-rich group in the region is the T. schaufussii species group with 20 species, most of which inhabit rainforests or montane rainforests of eastern and northern Madagascar. This group includes two species complexes each containing ten species: the T. cognatum complex with the species T. aspis sp. n., T. camelliae sp. n., T. cognatum Bolton, 1979, T. freya sp. n., T. gladius sp. n., T. karthala sp. n., T. myrmidon sp. n., T. proximum Bolton, 1979, T. rumo sp. n., and T. tenuinode sp. n.; and the T. schaufussii complex with the species T. merina sp. n., T. monticola sp. n., T. nassonowii Forel, 1892 stat. n., T. obiwan sp. n., T. pseudogladius sp. n., T. rala sp. n., T. schaufussii Forel, 1891, T. sikorae Forel, 1892 (= T. latior (Santschi, 1926)), T. scutum sp. n., T. xanthogaster Santschi, 1911. The last group treated in this study is the T. severini species group, which contains only the species T. severini (Emery, 1895). This very conspicuous species is widely distributed in the rainforests and montane rainforests of eastern and northern Madagascar. All four groups are fully revised with group diagnoses, illustrated species-level identification keys, and detailed descriptions for all species that include multifocused montage images and distribution maps.
Highlights
The hyper-diverse genus Tetramorium Mayr is widely distributed throughout all biogeographic regions, and with currently 520 described species (Bolton 2014) one of the most species-rich ant genera
Tetramorium alperti cannot be confused with T. dalek since the latter has no long standing hairs on the waist segments and the first gastral tergite, while these are present in T. alperti
We were able to reveal several consistent patterns of pilosity/pubescence in the T. naganum species group, and the pattern of T. alperti is unique to this group, it resembles the one seen in T. ryanphelanae Hita Garcia & Fisher from the T. bessonii species group, and a few species from the T. schaufussii species complex
Summary
The hyper-diverse genus Tetramorium Mayr is widely distributed throughout all biogeographic regions, and with currently 520 described species (Bolton 2014) one of the most species-rich ant genera. The T. bessonii, T. bonibony, T. dysalum, T. kelleri, T. marginatum, T. tortuosum, T. tsingy, and T. tosii species groups were revised shortly afterward (Hita Garcia and Fisher 2012a, 2012b). The latter two studies dealt with 58 species, of which 45 were described as new, and increased the species count for the Malagasy region to 84. This study increases the number of recently revised Malagasy Tetramorium species groups to 16 (Hita Garcia and Fisher 2011, 2012a, 2012b), leaving only two species groups untreated: the species-rich T. ranarum group and the less diverse but abundant T. simillimum group. MHNG Muséum d’Histoire Naturelle de la Ville de Genève, Geneva, Switzerland NHMB Naturhistorisches Museum, Basel, Switzerland
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