Systematic and Biogeographic Relationships of the Japanese White-Toothed Shrew (Crocidura dsinezumi)

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Abstract
To assess the Zoogeographie and phylogenetic relationships of C. dsinezumi, its systematic position has been investigated through electrophoretic comparisons. These comparisons comprise typical Indomalayan and Palaearctic species, including C mssula, the supposed sister taxon of the Japanese white-toothed shrew. The range of measured genetic distances that separate dsinezumi from the other shrews (Nei's D = 0.232–0.406) is typical for interspecific comparisons among Crocidura taxa. Our results reinforce morphologic considerations that suggest C. dsinezumi be treated as a valid species. Phylogenetic relationships deduced from a cladistic treatment of allozyme data refute the possibility that the western Palaearctic C mssula is the sister taxon of C. dsinezumi. Zoogeographie interpretation of the genetic results indicates that the Southeast Asian representatives constitute a clade distinct from one that includes the Palaearctic species. However, C dsinezumi is difficult to assign to either clade due to many intermediate or plesiomorphic electrophoretic characters. Unlike the major karyologic and biochemical separation that divides Afrotropical and Palaearctic species, the subdivision between Palaearctic and Indomalayan Crocidura is not correlated with any trend in karyotypic evolution. It also is shown that the Eurasiatic species of Crocidura possessing 2n = 40 chromosomes (including C. dsinezumi) do not represent a particular clade, but probably share a plesiomorphic character. Further analysis of other Indian or Asiatic species is needed to test whether the Palaearctic versus Indomalayan separation is due to real Zoogeographie barriers or whether it is the result of limited samples.

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