Ants (Hymenoptera: Formicidae) of the madeiran archipelago

The subtropical Atlantic archipelago of Madeira is part of the Macaronesian biogeographic subregion. Absence of important mainland competitors and predators on Macaronesian islands has allowed the survival of many relicts of the subtropical biota that once inhabited the Mediterranean area. In the 19th century, however, two highly destructive exotic ant species, the big-headed ant (Pheidole megacephala) and the Argentine ant (Linepithema humile), invaded Madeira. Many authors have assumed that these invaders exterminated most or all native ants of Madeira, despite no research actually documenting such impact. In the present study, we compiled records and evaluated the native versus exotic status of all ant species collected in Madeira. We examined specimens of 27 ant species from Madeira: Cardiocondyla emeryi, Cardiocondyla mauritanica, Hypoponera eduardi, Hypoponera punctatissima, Hypoponera sp. 1, Lasius grandis, Linepithema humile, Messor structor, Monomorium carbonarium, Monomorium pharaonis, Monomorium subopacum,Myrmecinagraminicola,Paratrechinajaegerskioeldi,Paratrechina longicornis, Pheidole megacephala, Pheidole pallidula, Plagiolepis schmitzii, Pyramica membranifera, Solenopsis sp. 1, Solenopsis sp. 2, Strumigenys silvestrii, Tapinoma madeirense (new status), Technomyrmex pallipes, Temnothorax unifasciatus, Temnothorax wollastoni, Tetramorium bicarinatum, and Tetramorium caldarium. One previously reported species, Camponotus sylvaticus, we could not verify with specimens, but accept it was correctly identified, at least to genus. We determined that one ant taxon reported from Madeira is a junior synonym of another taxon present: Plagiolepis schmitzii madeirensis (= P. schmitzii, new synonymy). In addition, published records of eight ant taxa reported from Madeira appear to be misidentifications of other species present. Based on their known distribution and ecology, ten ant species (including the seven most common species) appear to be native to Madeira. Only one native ant species, T. wollastoni, has not been collected recently (1995 or later) in Madeira. Although exotic ants may have exterminated T. wollastoni, it seems likely that this species still survives.