Predation on an Upper Trophic Marine Predator, the Steller Sea Lion: Evaluating High Juvenile Mortality in a Density Dependent Conceptual Framework

The endangered western stock of the Steller sea lion (__Eumetopias jubatus__) – the largest of the eared seals – has declined by 80% from population levels encountered four decades ago. Current overall trends from the Gulf of Alaska to the Aleutian Islands appear neutral with strong regional heterogeneities. A published inferential model has been used to hypothesize a continuous decline in natality and depressed juvenile survival during the height of the decline in the mid-late 1980's, followed by the recent recovery of juvenile survival to pre-decline rates. However, these hypotheses have not been tested by direct means, and causes underlying past and present population trajectories remain unresolved and controversial. We determined post-weaning juvenile survival and causes of mortality using data received post-mortem via satellite from telemetry transmitters implanted into 36 juvenile Steller sea lions from 2005 through 2011. Data show high post-weaning mortality by predation in the eastern Gulf of Alaska region. To evaluate the impact of such high levels of predation, we developed a conceptual framework to integrate density dependent with density independent effects on vital rates and population trajectories. Our data and model do not support the hypothesized recent recovery of juvenile survival rates and reduced natality. Instead, our data demonstrate continued low juvenile survival in the Prince William Sound and Kenai Fjords region of the Gulf of Alaska. Our results on contemporary predation rates combined with the density dependent conceptual framework suggest predation on juvenile sea lions as the largest impediment to recovery of the species in the eastern Gulf of Alaska region. The framework also highlights the necessity for demographic models based on age-structured census data to incorporate the differential impact of predation on multiple vital rates. Phylogeography of California examines the evolution of a variety of taxa—ancient and recent, native and migratory—to elucidate evolutionary events both major and minor that shaped the distribution, radiation, and speciation of the biota of California. The book also interprets evolutionary history in a geological context and reviews new and emerging phylogeographic patterns. Focusing on a region that is defined by physical and political boundaries, Kristina A. Schierenbeck provides a phylogeographic survey of California’s diverse flora and fauna according to their major organismal groups. Life history and ecological characteristics, which play prominent roles in the various outcomes for respective clades, are also considered throughout the work. Supporting scholars and researchers who study evolutionary diversification, the book analyzes research that helps assess one of the major challenges in phylogeographic studies: understanding changes in population structures shaped by geological and geographical processes. California is one of only twenty-five acknowledged biological hotspots worldwide, and the phylogeographic history of the state can be extrapolated to study other regions in western North America. Further consideration is given to implications for conservation, recommendations concerning the biogeographic provinces that roughly define the state of California, and predictions related to climate change. Content: Acknowledgments -- Part I. Geologic and Organismal History. 1. Introduction 2. Historical processes that shaped California 3. The Cenozoic era : Paleogene and Neogene periods (65-2.6 Ma) 4. Quaternary geologic and climatic changes -- Part II. Phylogeographic Patterns in Various Taxa. 5. Conifers 6. Flowering plants 7. Insects 8. Fishes 9. Amphibians 10. Reptiles 11. Birds 12. Mammals 13. Marine mammals -- Part III. Summary. 14. Consistent phylogeographic patterns across taxa and major evolutionary events 15. Conservation implications and recommendations. 'Phylogeography of California' examines the evolution of ancient, recent, native, and migratory taxa to elucidate the major and minor evolutionary events that shaped the distribution, radiation, and speciation of the biota of California. This work examines and interprets the evolutionary history of the biota in California in a geological context, and it also examines any subsequent patterns in regional diversity that have emerged across combined phylogenies Examines the evolution of a variety of taxa ancient and recent, native and migratory to elucidate evolutionary events both major and minor that shaped the distribution, radiation, and speciation of the biota of California. This book also interprets evolutionary history in a geological context and reviews new and emerging phylogeographic patterns.