A Concern for Evidence and a Phylogenetic Hypothesis of Relationships among Epicrates (Boidae, Serpentes)

Abstract

Character congruence, the principle of using all the relevant data, and character independence are important concepts in phylogenetic inference, because they relate directly to the evidence on which hypotheses are based. Taxonomic congruence, which is agreement among patterns of taxonomic relationships, is less important, because its connection to the underlying character evidence is indirect and often imperfect. Also, taxonomic congruence is difficult to justify, because of the arbitrariness involved in choosing a consensus method and index with which to estimate agreement. High levels of character congruence were observed among 89 biochemical and morphological synapomorphies scored on 10 species of Epicrates. Such agreement is consistent with the phylogenetic interpretation attached to the resulting hypothesis, which is a consensus of two equally parsimonious cladograms: (cenchria (angulifer (striatus ((chrysogaster, exsul) (inornatus, subflavus) (gracilis (fordii, monensis)))))). Relatively little (11.4%) of the character incongruence was due to the disparity between the biochemical and morphological data sets. Each of the clades in the consensus cladogram was confirmed by two or more unique and unreversed novelties, and six of the eight clades were corroborated by biochemical and morphological evidence. Such combinations of characters add confidence to the phylogenetic hypothesis, assuming the qualitatively different kinds of data are more likely to count as independent than are observations drawn from the same character system. Most of the incongruence occurred in the skeletal subset of characters, and much of that independent evolution seemed to be the result of paedomorphosis.