Aim: Madagascar is renowned for its exceptional species diversity and endemism. The island's mountainous regions are thought to have played a role in lineage and species diversification, but this has yet to be explored across taxonomic groups and a temporal context has not yet been identified. We tested whether montane regions have promoted population divergence in Madagascar's vertebrate fauna and, if so, whether these divergence events were contemporaneous. Location: Moist evergreen forests of Madagascar. Taxa: Small mammals and reptiles. Methods: We analysed mitochondrial DNA data from 20 small-mammal and five reptile species widely distributed across Madagascar's moist evergreen forests. We used phylogenetic and population genetic analyses to identify major phylogeographic patterns, then used linear regression to determine if the strength of phylogeographic structure is related to taxon, body size or elevation. Finally, we tested whether or not divergence across highlands occurred synchronously in multiple species, and used simulations to assess the power of these analyses to accurately estimate divergence times. Results: We observed a shared phylogeographic pattern across multiple species that suggests Madagascar's northern, central and southern highlands have served as important regions of diversification on Madagascar. This pattern was recovered across taxa with varying body sizes and elevational distributions. We also identified four pulses of divergence between the northern and central highlands since the late Miocene, although simulations suggest that our empirical data cannot recover the number or timing of divergence events with high certainty. Finally, we observed several instances of deep intraspecific genetic splits, suggesting that several of the species we evaluated may represent cryptic species complexes. Main Conclusions: We identified a highland-driven phylogeographic pattern plus several cases of cryptic endemism and recent speciation, which have important evolutionary and conservation implications. This work presents a new phylogeographic hypothesis for recent diversification on Madagascar, reaffirms the urgent need for continued collection of voucher specimens and illuminates areas of particular importance for safeguarding genetic diversity in one of the world's foremost and threatened biodiversity hotspots.
Bibliographical noteFunding Information:
This research was supported by grants DEB-1120904 (L.E.O.) and DEB-1119918 (S.A.J.) and a Graduate Research Fellowship (K.M.E.) from the National Science Foundation; the University of Alaska Museum; a Bass Senior Fellowship awarded by the Field Museum of Natural History (L.E.O.); a Graduate Student Research Award from the Society of Systematic Biologists (K.M.E.); a Grant-in-Aid of Research from the American Society of Mammalogists (K.M.E.) and a Dissertation Completion Fellowship from the University of Alaska Fairbanks Graduate School (K.M.E.). We are grateful for the specimen and tissue loans, as well as general support throughout the course of this project, from the following individuals and institutions: Christopher J. Raxworthy, Nancy B. Simmons, Ross D. MacPhee and Neil P. Duncan (American Museum of Natural History); Bruce D. Patterson, Lawrence R. Heaney, Adam W. Ferguson and the late William T. Stanley (Field Museum of Natural History); Daniel Rakotondravony and Voahangy Soarimalala (Mention Zoologie et Biodiversit? Animale, Universit? d'Antananarivo); Linda Gordon, Darrin P. Lunde and Michael D. Carleton (U.S. National Museum of Natural History, Smithsonian Institution); James L. Patton and Christopher J. Conroy (Museum of Vertebrate Zoology, University of California, Berkeley); and Priscilla K. Tucker, Stephen H. Hinshaw, Cody W. Thompson and Philip Myers (University of Michigan Museum of Zoology). We also thank the following individuals for their support and assistance during various stages of this project: Savannah Anchinges, Robert P. Anderson, Krystal Fales, Kyndall B. P. Hildebrandt, Sushma Reddy, Derek S. Sikes, Naoki Takebayashi, Anne D. Yoder and our friend and colleague William T. Stanley. Constructive reviews by Michael N Dawson, Judith C. Masters, Miguel Vences and an anonymous reviewer greatly improved the quality of this manuscript.
- Comparative phylogeography
- gene flow