Abstract
The Chapada Diamantina (CD) is located in Bahia State, between 11-14 degrees S and 41-43 degrees W, being part of the Serra do Espinhaço. The occurrence of different habitats and transition areas permits an interesting mammal fauna composition, with species from different biomes living in sympatry. Species of Didelphimorphia and Rodentia are important members of mammal communities in almost all different habitats, and morphological and cytogenetic characters are important for a correct identification of most of these species. In this work 258 specimens of small mammals from the orders Didelphimorphia (six genera and six species) and Rodentia (two families, five Sigmodontinae tribes, nine genera and 11 species) were collected during the whole field work (44 nights with traps). Chromosome preparations were obtained from 145 specimens from the species: Marmosops incanus, Gracilinanus microtarsus, Monodelphis domestica, Akodon aff. cursor, Necromys lasiurus, Cerradomys sp., Oligoryzomys fornesi, O. nigripes, O. rupestris, Calomys expulsus, Rhipidomys macrurus, Wiedomys pyrrhorhinus and Thrichomys inermis. Didelphis albiventris, Micoureus demerarae, Thylamys karymii and Nectomys sp. were identified by morphological characters. Most analyzed specimens do not show karyotype variation. However, numerical chromosomic variation was found in two individuals of Akodon aff. cursor (2n = 15) and in one individual of Cerradomys sp. (2n = 51). Structural variation in karyotype was observed in seven individuals of Cerradomys sp., showing one additional pair of metacentric chromosomes.
Highlights
Small mammals represent 80% of all mammal richness from Brazil (Fonseca et al, 1996)
Morphological and cytogenetic characters are important for proper identification of most species, and the analysis of karyotypes is essential for cryptic species (Bonvicino and Geise, 1995; Geise, 1995 and Geise et al, 1998)
Karyotype was prepared in the field, tissue samples were collected and fixed in 96% ethanol, ectoparasites were collected, and skins, skulls and partial skeletons were prepared for future deposit in the Museu Nacional (MN) and Museu de Zoologia da USP (MZUSP) mammal collections
Summary
Small mammals (volant and non-volant) represent 80% of all mammal richness from Brazil (Fonseca et al, 1996). This diversity characterizes a transition area among three biomes - Atlantic Forest, Caatinga and Cerrado (Brazão and Araújo, 1981; Parrini et al, 1999), being considerated as Dry Forest from the Northeast, according to Dinnerstein et al (1995) Such heterogeneity is influenced by a mass of humid air from the ocean that is blocked by the mountain relief, making the east Chapada wet and the west Chapada dry. The occurrence of these transition areas and habitat diversity permits an interesting mammal fauna composition, with species from different biomes living in sympatry. We report on the karyotype composition of some non-volant small mammals species (marsupials and rodents) trapped in several specific localities of the Chapada Diamantina
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