ISLAND BIOGEOGRAPHY OF GALÁPAGOS LAVA LIZARDS (TROPIDURIDAE: MICROLOPHUS): SPECIES DIVERSITY AND COLONIZATION OF THE ARCHIPELAGO |
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Authors: | Edgar Benavides Rebecca Baum Heidi M Snell Howard L Snell Jack W Sites Jr |
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Institution: | Department of Biology, Brigham Young University, Provo, Utah 84602;M. L. Bean Life Science Museum, Brigham Young University, Provo, Utah 84602;Department of Chemistry, Brigham Young University, Provo, Utah 84602;Department of Biology and Museum of Southwestern Biology, University of New Mexico, Albuquerque, New Mexico 87131;Charles Darwin Research Station, Puerto Ayora, Isla Santa Cruz, Galápagos, Ecuador;E-mail: |
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Abstract: | The "lava lizards" ( Microlophus ) are distributed throughout the Galápagos Archipelago, and consist of radiations derived from two independent colonizations. The "Eastern Radiation" includes M. bivittatus and M. habeli endemic to San Cristobal and Marchena Islands. The "Western Radiation" includes five to seven historically recognized species distributed across almost the entire Archipelago. We combine dense geographic sampling and multilocus sequence data to estimate a phylogenetic hypothesis for the Western Radiation, to delimit species boundaries in this radiation, and to estimate a time frame for colonization events. Our phylogenetic hypothesis rejects two earlier topologies for the Western Radiation and paraphyly of M. albemarlensis , while providing strong support for single colonizations on each island. The colonization history implied by our phylogeny is consistent with general expectations of an east-to-west route predicted by the putative age of island groups, and prevailing ocean currents in the Archipelago. Additionally, combined evidence suggests that M. indefatigabilis from Santa Fe should be recognized as a full species. Finally, molecular divergence estimates suggest that the two colonization events likely occurred on the oldest existing islands, and the Western Radiation represents a recent radiation that, in most cases, has produced species that are considerably younger than the islands they inhabit. |
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Keywords: | Galápagos lizards mitochondrial DNA molecular timing of colonization nuclear DNA oceanic islands phylogeny |
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