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Geographic morphometric and environmental differentiation of the water opossum, genus Chironectes Illiger, 1811 (Didelphimorphia: Didelphidae)

Cerqueira, Rui, Weber, Marcelo M.
Mammalia 2016 v.81 no.3 pp. 275-287
Didelphidae, body size, environmental factors, forests, morphometry, opossums, phenotypic variation, temperature, Bolivia, Central America, Colombia, Peru, Venezuela
We studied phenotypic variation in water opossum Chironectes minimus through morphological variation in size and shape of 16 cranial characters among six groups of populations of Chironectes defined by a transect analysis named according their main distributions: Central America, Venezuela/Colombia, Guianas, Belem, Bolivia/Peru, and Atlantic Forest. We also studied environmental variation among the groups and the influence of temperature seasonality and minimum temperature of coldest month on the body size of C. minimus. Morphometric differences in both size and shape were sharp between two major groups: Atlantic Forest and Central America+Venezuela/Colombia+Belem. The same pattern of differentiation was also observed in the environmental variables each group experiences. We also found a negative relationship between body size and temperature seasonality which showed that C. minimus follows a converse Bergmann’s rule cline. Our results on morphometric and environmental space suggest that specimens from the Atlantic Forest are different from specimens from Central America+Venezuela/Colombia+Belem both in size and shape and environmentally. We suggest that these major groups may comprehend different clades but a proper taxonomic assessment is needed to confirm our hypothesis.