AGNARSSON, I.; MAY-COLLADO, L.J. 2008. The phylogeny of Cetartiodactyla: the importance of dense taxon sampling, missing data, and the remarkable promise of cytochrome b to provide realiable species-level phylogenies. Molecular Phylogenetics and Evolution 48:964-985.
Abstract. We perform Bayesian phylogenetic analyses on cytochrome b sequences from 264 of the 290 extant cetartiodactyl mammals (whales plus even-toed ungulates) and two recently extinct species, the "Mouse Goad" and the "Irish Elk". Previous primary analyses have included only a small portion of the species diversity within Cetartiodactyla, while a complete supertree analysis lacks resolution and branch lenghts limiting its utility for comparative studies. The benefits of using a single-gene approach include rapid phylogenetic estimates for a large number of species. However, single-gene phylogenies often differ dramatically from studies involving multiple datasets suggesting that they often are unrealiable. However, based on recovery of banchmark clades - clades supported in prior studies based on multiple independent datasets - and recovery of undisputed traditional taxonomic groups, Cytb performs extraordinarily well in resolving cetartiodactyl phylogeny when taxon sampling is dense. Missing data, however, (taxa with partial sequences) can compromise phylogenetic accuracy, suggesting a tradeoff between the benefits of adding taxa and introducing question marks. In the full data, a fez species with a short sequences appear misplaced, however, sequence lenght alone seems a poor predictor of this phenomenon as other taxa with equally short sequences were not conspicuously misplaced. Although we recommend awaiting a better supported phylogenetic hypotheses provided here represent the currently best available tool for comparative species-level studies within this group. Cytb has been sequenced for a large percentage of mammals and appears to be a reliable phylogenetic marker as long as taxon sampling is dense. Therefore, an opportunity exists now to reconstruct detailed phylogenies of most of the major mammalian clades to rapidly provide much needed tools for species-level comparative studies.