Novel phylogeny of whales revisited but not revised.

Molecular phylogenetic data, if analyzed correctly, have the demonstrated capacity to resolve evolutionary relationships (i.e., the topology of phylogenetic trees) with confidence and can additionally suggest ages of lineages if assumptions about the rate of accumulation of mutations are accepted. Based on detailed maximumparsimony, neighbor-joining, and maximum-likelihood analyses of 930 base pairs (bp) of mitochondrial DNA ( mtDNA ) from 16 cetacean species (of 13 genera) and four outgroups, we (Milinkovitch et al. 1993) published a novel phylogenetic hypothesis which is in conflict with the classic division (Barnes et al. 1985) of living cetaceans into toothed whales and baleen whales. Our major finding was the suggestion that the suborder Odontoceti (toothed whales) is paraphyletic and, more specifically, that the sperm whales are more closely related to baleen whales (suborder Mysticeti) than to any other group of toothed whales. Further support for the (sperm whale + baleen whale) relationship derives from cladistic analyses of myoglobin amino-acid sequences (McKenna 1987; Czelusniak et al. 1990; Milinkovitch et al. 1993). Importantly, the sister-group relationship between sperm whales and baleen whales was recently reaffirmed by an expanded phylogenetic analysis (Milinkovitch et al. 1994) of 1,352 bp of mtDNA from 2 1 cetacean species (including a river dolphin and representatives of three baleen whale families) and several artiodactyl outgroup species. Independently, based on the analysis of 657 bp of the 16s mitochondrial gene from three cetacean species, Arnason et al. ( 1993 ) presented a neighbor-joining tree where the sperm whale is more closely related to the fin whale than to the only dolphin species included in that analysis. Although that result supports our hypothesis (Milinkovitch et al. 1993) of toothed whale paraphyly, Arnason et al. ( 1993) and Arnason and Gullberg ( 1994) concluded that it must be artifactual. Based on a new data set of complete cytochrome b DNA sequences ( 1,140 bp) fro-m 14 cetacean species (of 7 genera) and 1 outgroup, Arnason and Gullberg