Journal Article

Morphological and Genetic Variation between Two Sympatric Forms of <i>Oxymycterus</i> (Rodentia: Sigmodontinae): An Evaluation of Hypotheses of Differentiation within the Genus

Pablo R. Gonçalves and João A. de Oliveira

in Journal of Mammalogy

Published on behalf of American Society of Mammalogists

Volume 85, issue 1, pages 148-161
Published in print February 2004 | ISSN: 0022-2372
Published online February 2004 | e-ISSN: 1545-1542 | DOI: http://dx.doi.org/10.1644/BER-012
Morphological and Genetic Variation between Two Sympatric Forms of Oxymycterus (Rodentia: Sigmodontinae): An Evaluation of Hypotheses of Differentiation within the Genus

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Species limits in the genus Oxymycterus have been controversial because of difficulties in detecting discrete morphological and cytogenetic variation. Several authors have considered many of the species described from Brazil to be conspecific with O. rufus, including O. dasytrichus described from Bahia. This tendency represents a null hypothesis for the species-level diversity within the genus. A recently proposed alternative hypothesis based on analyses of allopatric samples recognizes O. rufus and O. dasytrichus as valid species within rufus and dasytrichus species complexes, respectively. Two sympatric forms of Oxymycterus from Viçosa, Minas Gerais State, southeastern Brazil, are phenotypically similar to members of these 2 species-groups. Investigation on the status of these populations and their relationships to the rufus and dasytrichus complexes provided a test of the alternative hypothesis regarding diversity within the genus. Morphometric, morphological, and molecular (cytochrome-b DNA sequences) comparisons of samples representing the rufus, dasytrichus, and judex species-groups provided evidence that the 2 sympatric forms from Viçosa are distinct evolutionary units, one related to the dasytrichus species-group and the other to the rufus species-group. The structures of morphological and molecular variation within each species-group supported an isolation-by-distance model of phenotypic differentiation in the rufus group, and a smooth pattern of phenotypic differentiation along a north–south axis in the dasytrichus group. The relevance of these patterns for species delimitation within these groups and the validity of O. dasytrichus and O. rufus are discussed.

Keywords: cytochrome b; geographic distribution; geographic variation; morphology; morphometrics; Oxymycterus; species boundaries; sympatry

Journal Article.  9018 words.  Illustrated.

Subjects: Zoology and Animal Sciences ; Animal Behaviour and Behavioural Ecology ; Animal Ecology ; Animal Physiology ; Mammalogy

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