Molecular phylogenetics of Oryzomyini: does a multigene approach help resolve a systematic conundrum?

The rodent tribe Oryzomyini is the most widely distributed new world rodent tribe. Since the description of the Oryzomyine group, this assemblage has received much attention; however intergeneric relationships are controversial and it is poorly understood at the specific level. The lack of clarity regarding taxonomic relationships of this tribe led to difficulties in producing a classification of the tribe. The polyphyletic arrangement of the genus Oryzomys has led to poor sampling in subsequent genetic studies as well as reduced the understanding of the biological diversity contained within this tribe. The most recent work on the tribe split the nominative genus into 10 additional genera (Weksler et al. 2006).

Because many of the taxa currently recognized as genera were placed into the genus Oryzomys, species level relationships were poorly understood. Considering the amount of diversity included in the genus at the time, it is understandable that the variation between what currently are considered species would seem to indicate nothing more than subspecific delineation. Molecular phylogenies have assisted in addressing some of the issues regarding relationships, and the combination of molecular and morphological studies have further resolved relationships. However, a single gene can lead to the recovery of a “gene tree” which represents the evolutionary history of that gene rather than the history of the phylogenetic group being studied. A solution to the potential problem of gene trees is to use multiple genes and combine the data generated using those genes into a multigene approach. By combining multiple genes, with varying rates of evolution, it may be possible to obtain better resolution throughout the tree.