Biogeography of Sulawesian shrews: testing for their origin with a parametric bootstrap on molecular data

In order to identify the zoogeographic origin of shrews (genus Crocidura) living on the oceanic island of Sulawesi, 15 taxa from Southeast Asia and 1 from Europe were examined for sequence variation in a segment (617 bp) of the mitochondrial cytochrome b gene. The null hypothesis of a monophyletic origin of all Sulawesian shrews was investigated by a phylogenetic reconstruction using maximum parsimony. According to a parametric bootstrap which simulated sequence evolution for these taxa, the null hypothesis could be rejected as highly unlikely (P < 0.01). Therefore, the molecular phylogeny strongly suggests that overwater colonization of Sulawesi by shrews succeeded on at least two occasions. The first, relatively ancient wave of colonizers radiated and gave rise to a surprizingly diverse assemblage of at least five species which now coexist in perfect sympatry on Sulawesi. The second wave, of more recent origin, gave rise to Crocidura nigripes, a species which retained close genetic affinities with other Malay shrews.