Chapter 7 - The Phylogeny of Ratite Birds: Resolving Conflicts between Molecular and Morphological Data Sets

Abstract

The chapter attempts to investigate paleognath interrelationships and further augments both morphological and molecular data sets. It describes several new postcranial characters and adds new characters to the osteological database, based on an examination of cranial morphology. Within the framework of paleognath monophyly, the debate has shifted to controversies over the interrelationships among the ratites. At the heart of this debate are apparent conflicts over, first, what morphological characters appear to tell us about those interrelationships, and second, the seemingly disparate relationships implied by several different molecular data sets, on the one hand, and morphology, on the other. Because DNA hybridization distances suggest that the relative rates in the nuclear genome are essentially parallel to those in the mitochondrial genome, there is at least some reason to predict that any long-branch artifacts of clustering arising within one data set might also be present in the other. Thus, the fact that there is congruence in results from DNA hybridization studies and those based on mitochondrial gene sequences does not necessarily constitute a sufficient reason for believing that molecular data is producing a robust estimate of relationships.