The Population and Evolutionary Genetics of the Ancient Murrelet (synthliboramphus Antiquus): a Summary

Genetic data can help answer questions about the basis of the contemporary population structure and evolutionary history of a species. Ancient Murrelets (Synthliboramphus antiquus) are north-Pacific seabirds that breed in a 9,000 km subarctic range from China to British Columbia. In this study, DNA sequence variation data from the cytochrome b gene and the mitochondrial control region are used to both estimate the extent of genetic differentiation, or structure, among current populations of the Ancient Murrelet, and to infer the evolutionary events responsible for this structure. Neither genotype frequencies nor sequence variation revealed any large-scale population structuring, suggesting that contemporary Ancient Murrelets form a single, panmictic population. Estimated rates of gene flow between colonies and regions are high enough to counter genetic drift. Genetic distances between haplotypes are small. Mismatch distribution and phylogenetic analysis are not consistent with an expanding population. Thus the null hypothesis that Ancient Murrelets are in genetic equilibrium with respect to mutation, migration and genetic drift cannot be rejected. INTRODUCTION ANCIENT Murrelets (Synthliboramphus antiquus) are small, migratory seabirds that breed in a 9,000 km arc around the northern rim of the Pacific Ocean (Fig. 1), becoming increasingly abundant from China to British Columbia (Gaston 1992). British Columbia supports about half of the world’s breeding population of Ancient Murrelets, while the majority of the remaining 50% nest in Alaska. Over the past several decades, dramatic population declines have been reported worldwide for Ancient Murrelets, and the species has been designated as “Vulnerable” by the Committee on the Status of Endangered Wildlife in Canada (Gaston 1994). Much of this population decline has been attributed to the introduction of mammalian predators, including rats (Rattus rattus and R. norvegicus) and raccoons (Procyon lotor). Little is known about the movements of Ancient Murrelets among different colonies, and there is no information about their global population genetic structure. Aspects of this population structure include gene flow (the loss or gain of genetic information