The Impact of Parsimony Weighting Schemes on Inferred Relationships among Toucans and Neotropical Barbets (Aves: Piciformes)

摘要

The development of new schemes for weighting DNA sequence data for phylogenetic analysis continues to outpace the development of consensus on the most appropriate weights. The present study is an exploration of the similarities and differences between results from 22 character weighting schemes when applied to a study of barbet and toucan (traditional avian families Capitonidae and Ramphastidae) phylogenetic relationships. The dataset comprises cytochrome b secuences for representatives of all toucan and Neotropical barbet genera, as well as for several genera of Paleotropical barbets. The 22 weighting schemes produced conflicting patterns of relationship among taxa, often with conflicting patterns each receiving strong bootstrap support. Use of multiple weighting schemes helped to identify the source within the dataset (codon position, transitions, transversions) of the various putative phylogenetic signals. Importantly, some phylogenetic hypotheses were consistently supported despite the wide range of weights employed. The use of phylogenetic frameworks to summarize the results of these multiple analyses proved very informative. Relationships among barbets and toucans inferred from these data support the paraphyly of the traditional Capitonidae. Additionally, these data support paraphyly of Neotropical barbets, but rather than indicating a relationship between Semnornis and toucans, as previously suggested by morphological data, most analyses indicate a basal position of Semnornis within the Neotropical radiation. The cytochrome b data also allow inference of relationships among toucans. Supported hypotheses include Ramphastos as the sister to all other toucans, a close relationship of Baillonius and Pteroglossus with these two genera as the sister group to an (Andigena, Selenidera) clade, and the latter four genera as a sister group to Aulacorhynchus.