Pan-biogeografia dos gêneros Didelphis, Philander, Metachirus, Chironectes e Lutreolina (Didelphimorphia: Didelphidae)

Abstract

The order Didelphimorphia, family Didelphidae of American marsupials includes 19 genera and 96 species and is divided into two subfamilies, Caluromyinae and Didelphinae. The subfamily Didelphinae contains (not exclusively) the tribes Didelphini and Metachirini. The tribe Didelphini comprises 15 species of four genera: Chironectes (1 species), Lutreolina (1), Didelphis (6) and Philander (7) and Metachirini tribe is monotypic, with only one species of the genus Metachirus. These five genera are widely distributed throughout the Americas, from southern Canada to central Argentina. The aim of this study was to identify and to explain the species s distribution patterns trough pan-biogeographic analysis. So, a survey was carried on using databases, visiting scientific collections and searching for published records to obtain data on localities were species were registered. Localities, for each separate species were marked on maps and the most close localities were connected with lines (individual tracks). The overlapping of individual tracks are the generalized tracks and the intersection of two or more generalized tracks are called nodes. Localities were also plotted on biomes maps. We found three generalized tracks and two nodes, one in the center of Bolivia in the biogeographic province of Pune and the other in Argentina, in Misiones. Four species do not participated in any generalized tracks, probably due to its restricted distribution (Philander delta, P. andersoni, P. olrogi and P. mcilhennyi). Chironectes minimus and Metachirus nudicaudatus had their tracks overlapped with two generalized tracks, which is in accordance with their known subspecies geographic distribution. In those species which are divided in subspecies, a separate analysis was carried on. Different patterns on the northern South America (Venezuela) were identified, all already pointed out by authors. Some species distribution limits were identified, such as the Tehuantepec Isthmus in Mexico for C. minimus and M. nudicaudatus and the neotropical region north limit to P. opossum and D. marsupialis. The south limit of P. opossum and P. frenatus is the Paraguay river, which seems to be a barrier. The mischaracterization of natural environments by human activities is changing the natural distribution patterns, as we can see by the occurrence of open areas species in forest biomes. Lutreolina crassicaudata presents a disjunct distribution, occupying two open vegetation areas, in northwest and center-southeast South America, probably generated by periods of contraction and expansion of savanna areas during the later Miocene to Holocene, leading to open vegetation enclaves surrounded by forests. The generalized tracks that we identified coincided with those found by other authors. Despite the pan-biogeography methodology can be used to propose protected areas, our nodes are in areas where conservation units already exist. There still is a great need for a better data of the distribution and taxonomy of these species, which would promote a better understanding of their biogeographic patterns