9806722 Doak Ecologists have increasingly recognized the role of disease in controlling natural populations and communities. Disease is of particular importance for the numerous species with small and/or restricted ranges than now host non-native, invasive pathogens - diseases for which introduction into new regions, as well as spread within a particular region, has resulted from increases in local and global transportation. The outcome of such host-pathogen interactions will often be highly dependent upon spatial heterogeneity of host, pathogen and landscape features. This research concerns a host-pathogen system that allows for quantification of disease spread and landscape pattern at three different spatial scales, and comparison of host-pathogen dynamics across landscapes with widely varying spatial pattern. In this study, the host species is the Port Orford cedar, a plant that is endemic to the region around the California-Oregon border. The pathogen is Phytophthora lateralis, a fatal, non-native root pathogen. This system is ideal for studying the importance of both spatial heterogeneity and scale in host-pathogen interactions. In this study, data will be collected using observation and manipulative methods to determine patterns of pathogen spread and changes in cedar demography at three different spatial scales. Field data will aid the development of spatially explicit models of host-parasite dynamics and interactions. The work has direct implications for the study and management of the many plant species currently threatened by invasive diseases, as well as general effects of habitat pattern and fragmentation for species interactions.
