Holocene Phylochronology and Ecology of the Northern Fur Seal

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Historical and paleoecological data provide crucial contextual information on the behavior, ecology, and biogeography of species, particularly those that were decimated by pre-20th century harvesting. These data serve as a baseline against which to judge the significance of recent ecological shifts and to guide management decisions affecting species conservation. The objective in this research is to use genetic and isotopic tools to explore how environmental and anthropogenic factors interacted to generate ecological shifts of a top marine consumer, the northern fur seal (Callorhinus ursinus) on the northeastern Pacific coast over the past 5000 years. The most complete record of these changes is found in coastal archaeological sites, where the faunas of past terrestrial and marine ecosystems can be studied to investigate paleoecologic shifts. Furthermore, the recognition of major ecological shifts will be important for archaeologists attempting to decipher changes in human demography and resource utilization along the northeast Pacific margin throughout the Holocene. Isotopic and archaeological data show that the northern fur seal has changed its breeding and migratory behavior over the past 5000 years. Direct dating of northern fur seal bones show that the collapse of local breeding colonies was not synchronous across the Pacific margin. These data suggest that the central and northern California coastal populations experienced a prehistoric bottleneck at ~800bp. This research will directly test these results using ancient genetic data from a series of geographically distinct locations and from several time units through the Holocene. The results will be analyzed using recently developed serial coalescent models that reveal historic population connectivity and effective population size. Thus, we will be able to detect how, or if, local extinction of the southern population resulted in major effects elsewhere across the North American species range. This study will show how insights into the ecology of threatened species may be gleaned from archaeological data. This is important for species in relict populations, whose current ecology may be shaped by recent exploitation or environmental change. The species of study is presently undergoing severe population declines in the northeast Pacific Ocean, but the cause(s) for this decline are far from clear. This work will provide baseline data on the genetic diversity and population/stock structure of this species over deep and historic time, and indicate whether or not they experienced similar declines in the past in relation to anthropogenic and/or environmental perturbations. The investigators will work with conservation biologists and pinniped ecologists to make the data available to those directing management decisions. DNA sequences will be made publicly available on Genbank. The scientific impact on teaching and education is extensive. This project will contribute to the interdisciplinary education of postdoctoral scholars, graduate and undergraduate students at Stanford University. The broad appeal of ancient DNA and fossils continues to motivate the education of the general community and stimulate scientific thought in children (age 7-10) with public lab days and demonstrations.