Karyotype Polymorphism Of Crocidura Tanakae In Chinese Mainland

The gray shrew Crocidura attenuata and Taiwanese gray shrew C.tanakae are both belong to genus Crocidura,and they can not be distinguished in external morphology,they are common in distribution area.We named"Morphological Crocidura attenuata"as Crocidura attenuata species complex.It is reported that both C.attenuata and C.tanakae are widely distributed in South China and Southeast Asia,and C.tanakae was regarded errorly as an endemic species of Taiwan Island for a long time.Due to the limitation of molecular identification,there may be having some mistakes in the cytological studies of both shrews in early years.Main aim of the study is to explore the phylogenetic relationship of C.attenuata species complex and truly clarify the karyotype characteristics of C.attenuata species complex distributed in mainland China.In the study,cytological means were performed on the samples of C,attenuata species complex collecting from Chinese mainland on the basis of molecular taxonomy.The results show that(1)Phylogeny of C.attenuata species complex was analysed with Cytb gene.The C.attenuata species complex distributed in mainland China including three valid species:C.attenuata,C.tanakae,and a new cryptic species C.sp.;the genetic distance between three species was 12.2%-13.1%.C.tanakae has the largest number of individuals and the widest geographical distribution area,relatively.(2)On the premise of correct species identification by molecular taxonomy means,C.tanakae has karyotype polymorphism phenomenon:the number of diploids 2n=24-40,6-20(m+sm)+1~10st+0-26t+X(sm)Y(t)/X(sm)X(sm),the fundamental chromosome arm FN=45~58;autosome are composed of 6-20 metacentric or submetacentric chromosomes,1~10 subtelocentric chromosomes,0~26 telocentric chromosomes.The same and unique karyotype characteristic of C.attenuata and C.sp is 2n=40,6(m+sm)+6st+26t+X(Sm)Y(t),FN=54,chromosome composition:3 pairs with metacentric or submetacentric chromosomes,3 pairs with subtelocentric chromosomes,13 pairs telocentric chromosomes,and X and Y chromosomes are submetacentric and telocentric chromosome,respectively.The result was contrary to Motokawa et al.(2001),which showed that C.attenuata has karyotype polymorphism.(3)In the study,the factors(geographical distribution and phylogenetic relationship)effected karyotype polymorphism of C.tanakae were studied.The karyotype polymorphism of C.tanakae is assumed to occur randomly and has no obvious regular relationship with its geographical distribution and phylogenetic relationship.Otherwise,it is inferred that this phenomenon only occurs in mainland China and there is no karyotype polymorphism report on the population in Taiwan.(4)Due to the same karyotype number 2n=40,FN=54 in three species,cytotaxonomy means cannot be used as an effective method for taxonomical study of C.attenuata species complex.However,due to the karyotype polymorphism of C.tanakae,and the karyotype 2n=40,FN=54 only recognised in just one individual of C.tanakae,cytotaxonomy can be used to distinguish C.tanakae from the other two species in some ways.