Monodelphis, MONOPHYLY

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

MONODELPHIS MONOPHYLY

The immediate recognition of a Monodelphis specimen among other didelphids is a conspicuous short tail. The monophyly of the genus is supported by several morphological synapomorphies, such as the lack of a facemask, pedal digit III distinctly longer than adjacent digits II and IV; a single grooved rhinarium; maxilloturbinals small and unbranched, maxillary and alisphenoid in contact on orbital floor, and P3 distinctly taller than P2 ( Flores, 2009; Voss & Jansa, 2009).

The description of Glironia venusta (Caluromyinae) karyotype ( Fantin & da Silva, 2011) has broken the diploid number (2 n = 18) as exclusive to Monodelphis . This number remains exclusive to this genus, however, when compared with other Didelphinae that present 2 n = 14 or 2 n = 22 karyotypes ( Reig et al., 1977; Langguth & Lima, 1988; Palma & Yates, 1996; Carvalho et al., 2002, Di-Nizo et al., 2014). Previous molecular investigations ( Patton et al., 1996; Flores, 2009; Jansa et al., 2013; Pavan et al., 2014) and analyses of total evidence ( Voss & Jansa, 2009) have also endorsed the monophyletic status of Monodelphis . Exceptions include the analysis of Solari (2010) and in one of the approaches carried out by Pavan et al. (2014).

Our sample included sequences from 21 species and 160 specimens belonging to the genus Monodelphis , which clustered in our topology with only average statistical support (68 LB; Fig. 2). Nevertheless, when additional M. domestica sequences are included (i.e. more than 17), these sequences cluster with a high bootstrap value; however, in this case, the genus Caluromys is included within the diversity of Monodelphis , breaking the monophyletic status of the genus. On the other hand, if the sequence from Caluromys derbianus is eliminated from the data set the monophyletic status of Monodelphis is again confirmed.

These tests were performed only for the cyt b marker because sequences for C. derbianus and Monodelphis spp. remain unavailable for most nuclear genes, although major complexes of the genus are represented. In fact, these results are counterintuitive because both Caluromys spp. and M. domestica are clades with maximum statistical support. This issue might be related to an artifact, but this remains to be verified in a future analysis including more markers sequenced for Caluromys and Monodelphis . Long-branch attraction may have also been the origin of the problems faced by Solari (2010) and in one of the approaches performed by Pavan et al. (2014), more specifically when applying maximum parsimony, a method that is more prone to this type of error ( O’Connor et al., 2010).