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DNA sequence support for a close phylogenetic relationship between some storks and New World vultures
J C Avise1, W S Nelson, C G Sibley
1Department of Genetics, University of Georgia, Athens 30602.
Summary
New World vultures are not closely related to storks, despite similarities. Their shared traits likely result from convergent evolution in carrion-feeding, not common ancestry, according to mitochondrial DNA analysis.
Area of Science:
- Avian Phylogenetics
- Molecular Evolution
- Comparative Genomics
Background:
- The evolutionary relationship between New World vultures, Old World vultures, and storks has been debated.
- Morphological and behavioral similarities between New World vultures and storks have suggested a close phylogenetic link.
Purpose of the Study:
- To investigate the phylogenetic placement of New World vultures using mitochondrial cytochrome b gene sequences.
- To resolve the controversial hypothesis suggesting a closer relationship between New World vultures and storks than with Old World vultures.
Main Methods:
- Phylogenetic analyses were conducted on 1-kb sequences from the mitochondrial cytochrome b gene.
- 18 avian species, including New World vultures, Old World vultures, and storks, were included in the analysis.
Main Results:
- Phylogenetic analyses indicate that similarities between New World and Old World vultures are likely due to convergent evolution for carrion-feeding, not close descent.
- Direct sequence evidence supports a phylogenetic alliance between some New World vultures and storks, consistent with previous DNA hybridization and morphology studies.
- Cytochrome b gene analyses showed limited resolution for other phylogenetic branches, likely due to closely clustered evolutionary nodes.
Conclusions:
- New World vultures are not closely related to storks; their similarities are attributed to convergent adaptations.
- Mistaken assumptions of homology based on organismal adaptations can lead to flawed biological classifications.
- The study highlights the utility of molecular data in resolving evolutionary relationships, while also noting limitations in phylogenetic resolution.