title: Systematics of the Madagascar Anelosimus spiders: remarkable local richness and endemism, and dual colonization from the Americas.
abstract: Despite the alarming rates of deforestation and forest fragmentation, Madagascar still harbors extraordinary biodiversity. However, in many arthropod groups, such as spiders, this biodiversity remains mostly unexplored and undescribed. The first subsocial Madagascan species of the theridiid spider genus Anelosimus were described in 2005 when six new species were found to coexist in the Périnet forest fragment within Andasibe-Mantadia NP. However, this discovery was based only on a few specimens and the extent of this Madagascan radiation has remained unknown. We here report on a thorough survey of >350 colonies from Périnet, and three pilot surveys into additional Madagascar forests (Ambohitantely, Ranamofana, and Montagne d'Ambre). The morphological, molecular and natural history data from these surveys facilitated a revised taxonomy and phylogenetic hypothesis of Madagascan Anelosimus. This subsocial clade currently comprises six previously known (Anelosimusandasibe Agnarsson & Kuntner, 2005, Anelosimusmay Agnarsson, 2005, Anelosimusnazariani Agnarsson & Kuntner, 2005, Anelosimussallee Agnarsson & Kuntner, 2005, Anelosimussalut Agnarsson & Kuntner, 2005, Anelosimusvondrona Agnarsson & Kuntner, 2005) and 10 new species: Anelosimusata sp. n., Anelosimusbuffoni sp. n., Anelosimusdarwini sp. n., Anelosimushookeri sp. n., Anelosimushuxleyi sp. n., Anelosimuslamarcki sp. n., Anelosimusmoramora sp. n., Anelosimustita sp. n., Anelosimustorfi sp. n., Anelosimuswallacei sp. n.. With the exception of Anelosimusmay and Anelosimusvondrona, all other species appear to be single forest endemics. While additional sampling is necessary, these data imply a much higher local richness and endemism in Madagascan forests than in any other comparable area globally. The phylogenetic results establish a sister clade relationship between the subsocial Anelosimus in Madagascar and the American 'eximius group', and between the solitary Anelosimusdecaryi on Madagascar and a solitary American clade. These findings imply duplicate colonizations from America, an otherwise rare biogeographical pattern, calling for more detailed investigation of Anelosimus biogeography.
authors.affiliation: Department of Biology, University of Vermont, Burlington, VT, USA ; Department of Entomology, National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
authors.forename: Ingi
authors.initials: I
authors.lastname: Agnarsson
authors.affiliation: Department of Biology, University of Vermont, Burlington, VT, USA.
authors.forename: Brian B
authors.initials: BB
authors.lastname: Jencik
authors.affiliation: Department of Biology, University of Vermont, Burlington, VT, USA.
authors.forename: Giselle M
authors.initials: GM
authors.lastname: Veve
authors.affiliation: Department of Entomology, University of Madagascar, Antananarivo, Madagascar.
authors.forename: Sahondra
authors.initials: S
authors.lastname: Hanitriniaina
authors.affiliation: Department of Biology, University of Puerto Rico, Rio Piedras, Puerto Rico, USA.
authors.forename: Diego
authors.initials: D
authors.lastname: Agostini
authors.affiliation: Department of Biological Sciences, National University of Singapore, Singapore.
authors.forename: Seok Ping
authors.initials: SP
authors.lastname: Goh
authors.affiliation: Department of Biological Sciences, National University of Singapore, Singapore.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Pruitt
authors.affiliation: Department of Entomology, National Museum of Natural History, Smithsonian Institution, Washington, DC, USA ; Institute of Biology, Scientific Research Centre, Slovenian Academy of Sciences and Arts, Ljubljana, Slovenia ; Centre for Behavioural Ecology and Evolution (CBEE), College of Life Sciences, Hubei University, Wuhan, Hubei, China.
authors.forename: Matjaž
authors.initials: M
authors.lastname: Kuntner
keywords: Cobweb spiders; Theridiidae; biogeography; colonization; congener coexistance; radiation; subsocial