Speciation and Diversification of Mammals on Islands

2014 REU Intern Chris Kyriazis


Junior Biology major at The University of Chicago

REU Mentors: Dr. John Bates (Curator, Birds, S&E) and Dr. Lawrence Heaney (Curator, Mammals, S&E)

Symposium Presentation Title: Speciation and Diversification of Mammals on Islands

Symposium Presentation Abstract: Islands have long fascinated biologists on account of the peculiar sets of organisms often found evolving in isolation from the mainland. The Philippines, an archipelago of over 7,000 islands, has increasingly become recognized as an ideal natural laboratory for studying the processes underlying the formation of new species, on account of a complex geological history that has produced some of the highest documented concentrations of endemic species, particularly in well-studied vertebrate groups including mammals and birds. Perhaps one of the most impressive radiations is that of the murid rodents, with at least 55 endemic species confined to the Philippine archipelago, a number that continues to rise as sampling of genetic data becomes more widespread. Particularly notable about the dynamics of speciation within murid rodents in the Philippines are the high rates of in situ diversification, in which new species arise on the same island, each species often confined to a single isolated mountain range. In this study, we examine the degree of divergence within an endemic lineage on the island of Luzon, Bullimus luzonicus, commonly known as the large Luzon forest rat. This species is distributed over most of the island and across a wide range of elevations, calling into question the degree to which local populations may have been able to diverge historically. We sequenced 149 tissue samples from 16 localities on the island of Luzon for the mitochondrial gene cytochrome b in order to investigate the fine-scale patterns of divergence within the island. Resulting phylogenies show significant divergence between groups from different geographic regions of the island, with at least three well supported groups that likely constitute new undescribed species, calling for further sampling of nuclear DNA to corroborate mitochondrial evidence. The results of this study add to a growing body of literature documenting the surprising volume of underappreciated mammalian diversity worldwide as well as the astounding levels of unique biodiversity found within the Philippines.

Original Project Title: Speciation and Diversification of Mammals on Islands

Original Project Description:Oceanic islands have been recognized as centers of unique biodiversity since before the time of Charles Darwin, and studies on islands have been key to developing our understanding of evolutionary and biogeographic processes.  The mammals of the Philippines are becoming a classic example of diversification, with over 90% of the species on some islands being the product of local speciation, based on extensive recent field and museum studies.  This project aims to investigate genetic divergence within the previously unstudied Bullimus luzonicus, a widespread endemic small mammal on Luzon, the largest of the Philippine islands, in the context of the dynamic geological history of the island. 

Research methods and techniques: REU participants will be introduced to conceptual issues in the evolutionary dynamics of island biogeography.  The participants will produce data in the museum’s molecular genetics lab, and will learn primary techniques for analyzing these data to produce estimates of evolutionary relationships.  The results will be compared to patterns shown by other small mammals, in an effort to detect general biogeographic patterns among species with differing ecologies and histories.