Advances in integrative taxonomy and evolution of african murid rodents: How morphological trees hide the molecular forest

Species definitions include various concepts, among which are themorphological and palaeontological definitions (Eldredge and Cracraft, 1980). The latter are used for those species that can be described only on the basis of diagnostic morpho-anatomical characters or synapomorphies and have been commonly employed in addition to the biological (Mayr, 1963) and the phylogenetic species concepts (Wiley, 1978). The development of new systematic tools provides supplementary diagnostic characters such as karyotypes, chromosome banding patterns, DNA molecular sequences or morphometric discriminant functions for the description of new species. It has been reported that karyotyped data can provide good evidence of reproductive isolation at the specific level, without any signs of morphological discrimination even by more sophisticated morphometrical methods (Hausser and Jammot, 1974; Dobigny et al., 2002a). In other cases, only refined analyses of size and shape by conventional or geometric morphometrics allow specific separation into species complexes or between sibling species (Fadda and Corti, 2001; Lalis et al., 2009a). Finally, because only morpho-anatomical characters on fragmented specimens (generally dental characters) are available for palaeospecies definitions, it is useful to have well-defined biological species accompanied by morphological characters that allow comparison of present and past diversity (Stoetzel et al., 2013). The diversity of African rodents is relatively high, especially in the tropical regions of the continent. At present there are 98 genera (80 endemic) and 408 species (375 endemic) (Happold, 2013). This high level of endemism made the establishment of a stabilized classification relatively difficult until recent palaeontological discoveries and more sophisticated molecular analyses were developed. Among the most recent molecular analyses that have clarified rodent classification are Blanga-Kanfi et al. (2009) and Fabre et al. (2012), in which rodents are divided into three main clades: Ctenohystrica, squirrel-related, and mouse-related. All these clades are represented in Africa today and in the past. Analyses of fossil discoveries place their early occurrences in Africa as early as the Palaeocene for Ctenohystrica, Oligocene for the squirrel-related clade and Miocene for the mouse-related clade (Winkler et al., 2010).