New karyotype for (Rodentia, Echimyidae) from the Brazilian Amazon: A case for species complex?

Wagner, 1845 (Rodentia, Echimyidae, Eumysopinae) currently has four recognized species, three of which occur in Brazil: (probably a species complex), .  and . . is found in montane forests of northern Peru. , the focus of the present study, has a distribution that is restricted to the central and eastern Amazonia south of the Amazon River, extending from the left bank of the Tapajós River to the right bank of the Tocantins River, and south to the southeast portion of Pará State. The genus presents karyotypes with diploid number 2n = 60 and Fundamental Number (FN) = 116 for .  and . , and 2n = 42, FN = 54 for . . We studied the karyotype of a female specimen of .  collected from the Tapirapé-Aquiri National Forest, Marabá, Pará, Brazil, in the Xingu/Tocantins interfluvium. The obtained karyotype (2n = 60 and FN = 110) differs from that described in the literature for both .  and .  by exhibiting more biarmed chromosomes, probably due to pericentric inversions and/or centromeric repositioning, and exhibiting differences in the amount and distribution of constitutive heterochromatin (CH). These results suggest that, similar to what has already been proposed for . , .  may represent a species complex and/or cryptic species. The mechanisms of chromosomal diversification in and the biogeographic implications are discussed reinforcing the need for broad systematic review for .