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Karyological geographic variation of Oligoryzomys nigripes Olfers, 1818 (Rodentia, Cricetidae) from Brazil

2007; Brazilian Society of Genetics; Volume: 30; Issue: 1 Linguagem: Inglês

10.1590/s1415-47572007000100010

1678-4685

Roberta Paresque, Maria José de Jesus Silva, Yatiyo Yonenaga-Yassuda, Valéria Fagundes,

Genetic diversity and population structure

The karyotypes of 85 specimens of Oligoryzomys nigripes (Rodentia, Sigmodontinae) collected in the Cerrado and Atlantic Forest of seven states of Brazil were analyzed. Eighty four specimens presented a karyotype with 2n = 62 and one individual had 2n = 61 due to a monosomy of the X chromosome. High levels of intra- and inter-population karyotypic variability, due to sex chromosomes heteromorphisms and pericentric inversions in four autosomes (pairs 2, 3, 4 and 8), led to a variation of the autosomal arm numbers (fundamental number, FN) from 78 to 82. Synaptonemal complex analyses revealed normal meiosis in males heterozygous for pericentric inversions. We found 39 different cytotypes, 27 of which are herein described for the first time. A literature survey revealed 46 described karyotypes for O. nigripes. We tested the hypothesis that chromosomal variants frequencies are dependent on geographical distribution and we propose a model for the karyotypical evolution of Oligoryzomys nigripes with 2n = 62/FN = 78-82.