Diversity-dependent cladogenesis occurs when a colonizing lineage exhibits increasing interspecific competition as it ecologically diversifies. Repeated colonization of a region by closely related taxa may cause similar effects as species within each lineage compete with one another. This may be particularly relevant for secondary colonists, which could experience limited diversification due to competition with earlier, incumbent colonists over evolutionary time. We tested the hypothesis that an incumbent lineage may diminish the diversification of secondary colonists in two speciose clades of Philippine “Old Endemic” murine rodents—Phloeomyini and Chrotomyini—on the relatively old oceanic island of Luzon. Although phylogenetic analyses confirm the independent, noncontemporaneous colonization of Luzon by the ancestors of these two clades, we found no support for arrested diversification in either. Rather, it appears that diversification of both clades resulted from constant-rate processes that were either uniform or favored the secondary colonists (Chrotomyini), depending on the method used. Our results suggest that ecological incumbency has not played an important role in determining lineage diversification among Luzon murines, despite sympatric occurrence by constituent species within each lineage, and a substantial head start for the primary colonists.
Bibliographical noteFunding Information:
We are grateful to A. Ferguson, J. Phelps, the late W. Stanley (FMNH), as well as D. Lunde (USNM) for their assistance in lending specimens for use in this study. We would like to thank C. Martin for laboratory assistance and P.-H. Fabre who provided Hapalomys delacouri and Abditomys latidens sequences. We also thank F. K. Barker and two anonymous reviewers who provided comments on drafts of the manuscript. The Florence Rothman Fellowship and Dayton Wilkie Fellowship awarded to DMR by the Bell Museum of Natural History provided funding necessary to perform DNA extraction and sequencing for this project. DMR was also supported by the Wallace and Mary Dayton Fellowship awarded by the Bell Museum of Natural History. Field research that produced most of the Philippines specimens utilized herein has been supported by the Barbara Brown Fund for Mammal Research of the Field Museum, and the Negaunee Foundation. Field research permits were provided by the Biodiversity Management Bureau of the Philippine Department of Environment and Natural Resources.
© 2018 The Author(s). Evolution © 2018 The Society for the Study of Evolution.
- adaptive radiation
- oceanic island