The phylogeography of Indoplanorbis exustus (Gastropoda: Planorbidae) in Asia
1 State Key Laboratory of Biotherapy, West China Hospital, West China Medical School, Sichuan University, Chengdu 610041, China
2 Department of Parasitology, Faculty of Veterinary Science, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh
3 Department of Microbiology and Immunology, College of Medicine, Sultan Qaboos University, Oman
4 Infectious Diseases Research Centre, IMR, Jalan Pahang, 50588 Kuala Lumpur, Malaysia
5 Department of Veterinary Pathobiology, Faculty of Veterinary Medicine and Animal Science, University of Peradeniya, Peradeniya 20400, Sri Lanka
6 Department of Animal Diseases and Veterinary Public Health, Faculty of Veterinary Medicine, Bogor Agricultural University (IPB), Jl. Agathis-Kampus IPB Darmaga, Bogor 16680, Indonesia
7 Veterinary Inspection Board, Vitas, Tondo, Metro Manila, Philippines
8 Department of Biology, Faculty of Science, Mahidol University, Bangkok, Thailand
9 Department of Medical Science, Faculty of Science, Burapha University, Bangsaen, Chonburi, Thailand
10 Department of Zoology, The Natural History Museum, London, UK
Parasites & Vectors 2010, 3:57 doi:10.1186/1756-3305-3-57Published: 5 July 2010
The freshwater snail Indoplanorbis exustus is found across India, Southeast Asia, central Asia (Afghanistan), Arabia and Africa. Indoplanorbis is of economic importance in that it is responsible for the transmission of several species of the genus Schistosoma which infect cattle and cause reduced livestock productivity. The snail is also of medical importance as a source of cercarial dermatitis among rural workers, particularly in India. In spite of its long history and wide geographical range, it is thought that Indoplanorbis includes only a single species. The aims of the present study were to date the radiation of Indoplanorbis across Asia so that the factors involved in its dispersal in the region could be tested, to reveal potential historical biogeographical events shaping the phylogeny of the snail, and to look for signs that I. exustus might be polyphyletic.
The results indicated a radiation beginning in the late Miocene with a divergence of an ancestral bulinine lineage into Assam and peninsular India clades. A Southeast Asian clade diverged from the peninsular India clade late-Pliocene; this clade then radiated at a much more rapid pace to colonize all of the sampled range of Indoplanorbis in the mid-Pleistocene.
The phylogenetic depth of divergences between the Indian clades and Southeast Asian clades, together with habitat and parasitological differences suggest that I. exustus may comprise more than one species. The timescale estimated for the radiation suggests that the dispersal to Arabia and to Southeast Asia was facilitated by palaeogeographical events and climate change, and did not require human involvement. Further samples from Afghanistan, Africa and western India are required to refine the phylogeographical hypothesis and to include the African Recent dispersal.