Systematics of the subgenus of mouse opossums Marmosa (Micoureus) (Didelphimorphia, Didelphidae) with noteworthy records from Paraguay

Abstract

The subgenus Marmosa (Micoureus) Lesson, 1842 includes six species of long-tailed, black masked mouse-opossums widely distributed in forested areas of the Neotropics from northern Argentina to Belize. Most of the nominal forms of Marmosa (Micoureus) have not been revised since 1933 and some currently accepted synonymies are in need of revision; similarly distributions of these forms remain for the most part unclear. Herein, we report Paraguayan new and noteworthy locality records for Marmosa (Micoureus), including the first records for the western Dry Chaco region. Specimens were identified to the species level on the basis of morphological and molecular data. In addition, we conducted a phylogenetic analysis that includes sequences of five of the six species currently recognized of Micoureus incorporating a total of 70 sequences of the subgenus. This constitute the most taxonomically and geographically dense phylogenetic analysis of Micoureus. Results show that the most basal dichotomy of the Micoureus clade does not delimit cis- and trans-Andean reciprocally monophyletic groups, rending the cis group paraphyletic to the single trans-species included, suggesting that the colonization of the western (trans) side of the Andes was a relatively late event in the biogeographic history of Micoureus. In addition, the phylogenetic analysis shows that additional taxonomic work is much needed to clarify the number of distinct biological units, either species or subspecies, within Micoureus.

Introduction

The subgenus Marmosa (Micoureus) Lesson, 1842 includes six species of long-tailed, black masked mouse-opossums: M. (M.) alstoni (J.A. Allen, 1990), M. (M.) constantiae (Thomas, 1904), M. (M.) demerarae (Thomas, 1905), M. (M.) paraguayana (Tate, 1931), M. (M.) phaea (Thomas, 1899), and M. (M.) regina (Thomas, 1898). Micoureus is widely distributed in forested areas of the Neotropics from northern Argentina to Belize (Gardner and Creighton, 2008, Voss and Jansa, 2009). Despite recent systematic assessments (Voss et al., 2009, Rossi, 2005, Rossi et al., 2010, Gutiérrez et al., 2010), most of the nominal forms of Marmosa (Micoureus) have not been revised since Tate (1933), and some currently accepted synonymies are in need of revision (Voss and Jansa 2009). As a logical consequence, distributional and ecological aspects of these species are poorly known, especially towards the southern part of the range of the genus (e.g., Flores et al. 2000). Similarly, no phylogenetic study has focused on the relationships among the species of Micoureus, hampering an understanding of the historical biogeography of the subgenus.

Two species of Marmosa (Micoureus) have been recorded in Paraguay, M. (M.) constantiae Thomas, 1904 and M. (M.) paraguayana Tate, 1931. The former is only known from Parque Nacional Cerro Corá, in eastern Paraguay (Voss et al. 2009), while the second has several records throughout the eastern forested regions of this country (Brown, 2004, Gardner, 2005, Gardner and Creighton, 2008, Krumbiegel, 1941). Herein, we report new and noteworthy locality records for Marmosa (Micoureus) in Paraguay, including the first records for the western Dry Chaco region. These records are identified to the species level (cf. Tate, 1931, Tate, 1933, Voss and Jansa, 2009, Dias et al., 2010, Gutiérrez et al., 2010) on the basis of morphological and molecular data (including the first sequence of a Paraguayan specimen of M. (M.) paraguayana) and by comparison with the original descriptions and photographs of the holotypes. Paraguayan sequences were analyzed in the context of a phylogenetic analysis that includes sequences of five of the six species currently recognized in the subgenus Micoureus. The analyzed matrix incorporates a total of 70 sequences of Micoureus. This constitute the most taxonomically and geographically dense phylogenetic analysis of Micoureus.