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Divergence date estimation and a comprehensive molecular tree of extant cetaceans
Michael R McGowen1, Michelle Spaulding, John Gatesy
1Department of Biology, University of California Riverside, Riverside, CA 92521, USA. mmcgo002@student.ucr.edu
Molecular Phylogenetics and Evolution
|August 25, 2009
Summary
This study resolves cetacean (whale and dolphin) evolutionary history by combining extensive molecular data. The new phylogeny clarifies relationships among toothed and baleen whales, revealing rapid radiations in oceanic dolphins.
Area of Science:
- * Evolutionary biology and molecular phylogenetics.
- * Cetacean (whale and dolphin) biology and evolution.
Background:
- * Cetaceans exhibit significant aquatic adaptations, but their evolutionary relationships are not fully understood.
- * Previous molecular data have been fragmented, hindering comprehensive phylogenetic analysis.
- * Resolving cetacean phylogeny is crucial for understanding mammalian adaptation to marine environments.
Purpose of the Study:
- * To construct a robust and comprehensive phylogenetic hypothesis for cetaceans using a large, integrated molecular dataset.
- * To resolve deep divergences and relationships within major cetacean clades, including toothed whales (odontocetes) and baleen whales (mysticetes).
- * To estimate divergence times for key cetacean lineages and identify periods of rapid diversification.
Main Methods:
- * Integration of 37 new nuclear gene sequences (RAG1, PRM1) with existing molecular data (45 nuclear loci, transposons, mitochondrial genomes).
- * Construction of a large phylogenetic supermatrix (42,335 characters) for 87 cetacean species.
- * Model-based phylogenetic analyses (Bayesian, Maximum Likelihood, Parsimony) and relaxed-clock divergence dating.
Main Results:
- * A well-supported phylogenetic tree resolving relationships within Odontoceti and Mysticeti, including the speciose Delphinidae family.
- * Confirmation of odontocete monophyly and stabilization of basal odontocete relationships.
- * Divergence estimates indicate rapid basal odontocete branching near the Eocene-Oligocene boundary, ancient river dolphin lineages, and recent radiations in mysticetes and Delphinidae.
Conclusions:
- * The comprehensive phylogenetic framework provides a reliable evolutionary history for 87 cetacean species.
- * The study clarifies evolutionary patterns, including rapid diversification events in key cetacean groups.
- * This time-calibrated phylogeny serves as a valuable tool for comparative evolutionary studies across Cetacea.
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