Monodelphis

Vilela, Júlio Fernando, Oliveira, João Alves De & Russo, Claudia Augusta De Moraes, 2015, The diversification of the genus Monodelphis and the chronology of Didelphidae (Didelphimorphia), Zoological Journal of the Linnean Society 174 (2), pp. 414-427 : 422-423

OF MONODELPHIS

Our biogeographic analyses focused on the diversification of Monodelphis ( Figs 3, S 2, and S3); however, the ancestral range for the Monodelphis lineage was only possible if other related genera were incorporat- ed into this analysis. For instance, Tlacuatzin , an endemic didelphid from Mexico, is the immediate sister group to Monodelphis . This fact might indicate a broader geographic range for the ancestral range of the Tlacuatzin – Monodelphis clade that would include the northern part of Central America. Nevertheless, our formal biogeographic analysis included more genera, and indicates that the Tlacuatzin ancestor colonized the Mexican region by dispersal, as previously proposed by Jansa et al. (2013). In this scenario, the ancestral of Monodelphis , Marmosa , and Tlacuatzin inhabited the northern part of South America. Although the diversity of Marmosa was not well represented here, it is not surprising that northern South America is considered the ancestral range for the Marmosini tribe.

For Monodelphis , however, northern South American lineages were the sister group to the remaining diversity in each of the three major clades. Curiously, all these cladogenetic events occurred by the end of the Oligocene, separating an NS (green) from an AF (brown) lineage ( Fig. 3). Thus, the Atlantic Forest may not be discarded as the first origin of Monodelphis diversification ( Fig. 3). The coincident divergence times and geographical patterns of the splits between the three Monodelphis clades indicate that a common geological event might be connected with these events. This is also supported by our biogeographical analysis indicating vicariant events for these nodes ( Figs S2 and S 3).

This geological event may have been the rise of the Andes. For example, Cenozoic faunal changes were deeply influenced by a progressive three-step rise of the Andes from south to north and from east to west ( Lamb & Davis, 2003; Antonelli et al., 2009); however, the rise of the northern section of the Andes ( Peru and above) would have occurred too late to account for these Monodelphis speciation events, as it has been dated to around the Pliocene ( Chaves, Weir & Smith, 2011).

On the other hand, geological data have indicated a distinct warming trend towards the Oligocene– Miocene boundary ( Lamb & Davis, 2003). This would certainly suggest a rise in sea level, and may be related to these first splits in our Monodelphis cluster. If this proves to be correct, the diversification of major Monodelphis lineages began immediately after the decline of the North American Mammalian fauna ( Figueirido et al., 2011), showing sensitivity to the extreme temperature fluctuations at the Oligocene– Miocene boundary.