Monophyly and Phylogenetic Relationships of the Pelecaniformes: A Numerical Cladistic Analysis

Abstract

A phylogenetic analysis was undertaken to evaluate the monophyly of the Pelecaniformes and to determine interfamilial relationships within the order. A total of 52 characters was subjected to a numerical cladistic analysis. Pelecaniform monophyly was highly corroborated, with 12 postulated synapomorphies supporting that hypothesis. Within the pelecaniforms, the phaethontids are the sister-group of the remaining families, which are divided into two lineages, the fregatids on the one hand and the pelecanids, sulids, and phalacrocoracids (including anhingids) on the other. Within the latter clade, sulids and phalacrocoracids are each other's closest relatives. This pattern of interfamilial relationships was strongly corroborated by the data, and alternative hypotheses, especially those postu- lating a close relationship between phaethontids and fregatids, are much less parsimonious. The study also presents corroborating evidence that pelecaniforms and procellariiforms are sister-taxa, although this hypothesis requires further analysis. Evidence supporting a relationship between pelecaniforms and ciconiiforms is evaluated and considered insuffi- cient to warrant acceptance of that hypothesis at this time. The hypothesis that the Whale-headed Stork (Balaeniceps rex) has a relationship to one or more pelecaniform taxa was investigated and rejected. The characters said to indicate a close relationship are interpreted here to be convergences that arose as mechanical responses to similarities in feeding behavior. Received 10 January 1985, accepted 16 May 1985.