Three species of Taiwanese murid rodents, Rattus losea, Niviventer cuituratus, and N. coxingi, are karyotyped. Their diploid chromosome number (2N) and fundamental number (FN) are as follows: R. losea, 2N = 42 and FN = 60; N. cuituratus 2N = 46 and FN = 52; and N. coxingi 2N = 46 and FN = 54. R. losea has the same karyotypic complements as its cqnspecific population from Thailand except for the X chromosome. All the species of Niviventer share the same 2N = 46, but vary in their FNs which range from 50 to 64. The karyotypic complements of N. culturatus and N. coxingi indicate that they are not sister taxa, supporting the hypothesis that their presence in Taiwan was derived from multiple incursions from the Asian continent.
Karyotype, Rattus, Niviventer, Speciation, Biogeography
