Phylogeography, Systematics and Conservation Status of Boid Snakes from Madagascar (Sanzinia and Acrantophis)

Abstract. To assess the phylogeography and genetic variation of Malagasy boas of the genera Acrantophis (A. madagascariensis, A. dumerilii) and Sanzinia (S. madagascariensis), we analysed sequences of the 16S rRNA gene in 12 Sanzinia and seven Acrantophis specimens. We found a surprisingly high differentiation between eastern and western/north-western populations of Sanzinia. This
divergence was almost twice as high as between the two Acrantophis species. In spite of the absence of diagnostic morphological differences between eastern and western Sanzinia, the species status of these two ancient phylogeographic clades is probable, but can not be fully ascertained. We therefore describe the western Sanzinia populations as a new subspecies, based on a holotype specimen from Ankarafantsika forest, and diagnosed by its colour pattern (brown vs. mostly greenish in the nominate subspecies) and genetic differentiation. Unlike two widespread frog species that have a phylogeographically complementary east-west distribution, in Sanzinia the western subspecies reaches the Sambirano region (including Nosy Be) and probably Montagne des Français in northern Madagascar, while the rainforests of southern Madagascar (around Tolagnaro) are populated by the eastern subspecies. The Madagascar boas are widely distributed, relatively abundant and their occurrence is not restricted to pristine natural habitats. The current extent of local exploitation of these boas for food and leather apparently does not really threaten the species. However, the occurrence of the new subspecies seems to be more closely associated with the endangered dry forests of western Madagascar, and its status should therefore be carefully monitored.