Congruence of molecules and morphology using a narrow allometric approach

There are many cases of incongruence between phylogenetic hypotheses produced from morphological data and those produced from molecular data. In such instances, many researchers prefer to accept the results of molecular phylogenies. For example, in a recent analysis of primate phylogenies based on craniodental characters, Collard and Wood [Collard M, Wood BA (2000) Proc Natl Acad Sci USA 97:5003-5006] argued that, because craniodental data do not yield relationships concordant with molecular studies, the results of studies that employ such characters must be considered suspect. As most of our knowledge of mammalian evolution and phylogenetic history comes from craniodental fossils, these results have dramatic implications. However, the aforementioned analysis did not take into account the potentially confounding effects of allometry on quantitative craniodental characters. In this article, we employ a previously undescribed narrow allometric coding method that accounts for such confounding influences in phylogenetic analyses of craniodental morphology. By using essentially the same raw data set as Collard and Wood [Collard M, Wood BA (2000) Proc Natl Acad Sci USA 97:5003-5006], 65 quantitative craniodental characters were adjusted in a parsimony analysis for the primate tribe Papionini, a group of monkeys argued to display extensive homoplasy. The resulting phylogenetic tree was congruent with the phylogenetic tree based on molecular data for these species, thereby meeting the "criterion of congruence." These results suggest that morphological data, when treated properly, can be considered as reliable as molecular data in phylogenetic reconstruction. Rather than accepting phylogenetic hypotheses from one data source over another, cases of incongruence should be examined with greater scrutiny.