Systematics of new subsocial and solitary Australasian Anelosimus species (Araneae:Theridiidae)

Abstract

Species of the cobweb spider genus Anelosimus range from solitary to subsocial to social, and sociality has evolved repeatedly within the genus. Thus, this genus allows studies of the traits that play a role in social evolution. However, taxonomic knowledge of Anelosimus is geographically narrow and nearly all sociobiological studies have been done in the Americas. Only one behaviourally unknown species has been described from all of Australasia. Here, I describe seven new Anelosimus from Papua New Guinea (Anelosimus potmosbi, sp. nov., Anelosimus pomio, sp. nov., Anelosimus eidur, sp. nov. and Anelosimus luckyi, sp. nov.), Bali (Anelosimus bali, sp. nov.), Australia (Anelosimus pratchetti, sp. nov.) and an unknown locality (Anelosimus terraincognita, sp. nov.), ranging from solitary to subsocial. A phylogenetic analysis supports the inclusion of these species in Anelosimus, and suggests that solitary Papuan species represent a second reversal from subsocial behaviour. Both solitary species inhabit the beachfront, a habitat that appears not to be conducive to social behaviour in spiders. Subsocial species, as in other parts of the world, are found in montane tropical forests of Papua New Guinea, and at relatively high latitudes in Australia. Thus, a global ecological pattern of sociality in Anelosimus is emerging as taxonomic, phylogenetic and ethological knowledge extends beyond the Americas.