CHROMOSOMAL EVOLUTION IN 3 SPECIES OF MURID RODENTS OF TAIWAN

Three species of Taiwanese murid rodents, Rattus losea, Niviventer cul turatus, and N. coxingi, are karyotyped. Their diploid chromosome numb er (2N) and fundamental number (FN) are as follows: R, losea, 2N = 42 and FN = 60; N. culturatus 2N = 46 and FN = 52; and N. coxingi 2N = 46 and FN = 54. R. losea has the same karyotypic complements as its cons pecific population from Thailand except for the X chromosome. All the species of Niviventer share the same 2N = 46, but vary in their FNs wh ich range from 50 to 64. The karyotypic complements of N. culturatus a nd N. coxingi indicate that they are not sister taxa, supporting the h ypothesis that their presence in Taiwan was derived from multiple incu rsions from the Asian continent.