Shifting continents, not behaviours: independent colonization of solitary and subsocial Anelosimus spider lineages on Madagascar (Araneae, Theridiidae)

Agnarsson, I., Kuntner, M., Coddington, J. A. & Blackledge, T. A. (2010). Shifting continents, not behaviours: independent colonization of solitary, and subsocial Anelosimus spider lineages oil Madagascar (Araneae, Theridiidae). - Zoologica Scripta, 39, 75-87. Madagascar is a biodiversity hotspot, thought to be colonized mostly via Cenozoic dispersal from Africa, followed by endemic radiation of multiple lineages. Anelosimus spiders are diverse in Madagascar, and, like their congeners in the Americas, are most diverse in wet montane forests. Most Anelosimus species are social in that the), cooperate in web building and prey capture either during a part of their life cycles (subsocial), including hitherto studied Malagasy species, or permanently (quasisocial). One Central American coastal species, Anelosimus pacificus, has secondarily switched to solitary living, and available evidence suggests that its closest relatives from S. America and Europe are likely also solitary. Here, we show that the only known coastal Anelosimus species in Madagascar and Comoros - Anelosimus decaryi and Anelosimus amelie sp. n. - are also solitary. Using it phylogenetic approach, we test two competing hypotheses: (i) that Malagasy Anelosimus ire monophyletic and thus represent a second example of reversal to solitary living in a littoral habitat or (it) that solitary, and subsocial lineages independently colonized Madagascar. We find that solitary Malagasy Anelosimus are closely related to their solitary counterparts from Europe and the Americas, while subsocial Malagasy species nest sister to Anelosimus nelsoni from S. Africa. This finding suggests that (i) the two Anelosimus lineages colonized Madagascar independently and (it) a reversal to solitary behaviour has occurred only once in Anelosimus. Thus, solitary littoral Malagasy species did not descend from Malagasy mountains, but arrived from Much further afar. African and possibly American origin of the two lineages is implied by our findings. To restore natural classification of Anelosimus, Seycellocesa Kocak & Kemal is synonymized with it.