Multilocus species trees and species delimitation in a temporal context: application to the water shrews of the genus Neomys

Background Multilocus data are becoming increasingly important in determining the phylogeny of closely related species and delimiting species. In species complexes where unequivocal fossil calibrations are not available, rigorous dating of the coalescence-based species trees requires accurate mutation rates of the loci under study but, generally, these rates are unknown. Here, we obtained lineage-specific mutation rates of these loci from a higher-level phylogeny with a reliable fossil record and investigated how different choices of mutation rates and species tree models affected the split time estimates. We implemented this strategy with a genus of water shrews, Neomys, whose taxonomy has been contentious over the last century.