Questions: 1. Are there differences among species in their preference for coniferous vs. deciduous forest? 2. Are tree and shrub species better colonizers of recent forest stands than herbaceous species? 3. Do colonization patterns of plant species groups depend on tree species composition? Location: Three deciduous and one coniferous recent forest areas in Brandenburg, NE Germany. Methods: In 34 and 21 transects in coniferous and deciduous stands, respectively, we studied the occurrence and percentage cover of vascular plants in a total of 150 plots in ancient stands, 315 in recent stands and 55 at the ecotone. Habitat preference, diaspore weight, generative dispersal potential and clonal extension were used to explain mechanisms of local migration. Regression analysis was conducted to test whether migration distance was related to species’ life-history traits. Results: 25 species were significantly associated with ancient stands and ten species were significantly more frequent in recent stands. Tree and shrub species were good colonizers of recent coniferous and deciduous stands. In the coniferous stands, all herbaceous species showed a strong dispersal limitation during colonization, whereas in the deciduous stands generalist species may have survived in the grasslands which were present prior to afforestation. Conclusions: The fast colonization of recent stands by trees and shrubs can be explained by their effective dispersal via wind and animals. This, and the comparably efficient migration of herbaceous forest specialists into recent coniferous stands, implies that the conversion of coniferous into deciduous stands adjacent to ancient deciduous forests is promising even without planting of trees.

Discerning the extent and patterns of genetic connectivity and understanding population demographic processes is essential for framing proper management and conservation measures for species of concern. Although genetic connectivity may be influenced by numerous biotic and abiotic factors, habitat utilization and dispersal potential are often key factors driving connectivity, especially in marine fishes. While dispersal potential is of key importance with respect to shaping connectivity, other extrinsic (e.g., oceanographic processes) and intrinsic (e.g., reproductive behavior) factors may also influence connectivity; however, the relative influence of such factors is immensely variable across species and life-stages. This dissertation explores genetic connectivity and demographic history in marine fishes with diverse dispersal potentials to determine which processes, in addition to the known dispersal potential of the species, may be shaping connectivity. Genetic connectivity and demographic history is assessed for four marine fishes: two shark species with juxtaposing dispersal potentials, the highly migratory tiger shark (Galeocerdo cuvier) and the reef associated Caribbean reef shark (Carcharhinus perezi), which possess high and low dispersal potentials, respectively, and two teleost species, the pelagic roundscale spearfish (Tetrapturus georgii) and the Nassau grouper (Epinephelus striatus), which possess high and low adult dispersal potentials, respectively. This work demonstrates that dispersal potential does, in fact, play a key role in delineating genetic structure for these species; however, other factors, such as contemporary oceanographic currents (e.g., upwelling and temperature), habitat availability (e.g., coral cover), and historical events, such as cyclical glacial cycles, also influence genetic connectivity across variable spatial scales, thereby creating complex patterns of genetic population structure, requiring composite management strategies to ensure the persistence of these species.

xv, 99 p. : ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. / The trochid gastropod Chlorostoma (Tegula) funebralis is found in rocky intertidal habitats along the west coast of North America from Baja California to Vancouver Island. Size-frequency distributions of populations were analyzed along a latitudinal gradient from northern Oregon to Baja California. Populations in California and southern Oregon were dominated by individuals in the juvenile size classes (0.1g-2g). Along the Oregon coast, populations dominated by juveniles were correlated with coastline topography, with protected areas having large numbers of juveniles and exposed areas dominated by larger size classes. The largest size classes (>9g) were rarely present in southern populations. The seasonality of reproduction was investigated in a southern California population and an Oregon population to determine whether continuous reproduction in southern populations increases recruitment success over the year and decreases inter-annual variation in reproductive success. Constant recruitment may cause populations to have a large number of juveniles, the observed pattern in southern populations. Although individuals capable of reproduction were found year-round in both populations, the southern population experienced multiple spawning events over the year, while the northern population experienced only one such event. Constant recruitment may be a strategy to compensate for shorter life spans and smaller sizes of individuals in southern California. To investigate whether variations in predation rates on large adult C. funebralis affect the size structure of populations, the main predators and predation rates for different populations in Oregon were identified. All observed predation events were by the intertidal seastar Pisaster ochraceus . Predation pressure by P. ochraceus varied significantly with site and between sampling dates but did not remove enough C. funebralis from the adult population to have a significant effect on population size structure. To determine the connectivity between populations and the maximum dispersal potential, the mitochondrial gene COI was sequenced from individuals from nine populations ranging from southern California to northern Oregon. Although haplotype diversity was high, no genetic structure was found between populations. Rather than an indication of high dispersal potential and a panmictic species, the lack of isolation by distance may be a result of range expansion following the last glacial maximum. / Committee in charge: Patrick Phillips, Chairperson, Biology; Alan Shanks, Advisor, Biology; Craig Young, Member, Biology; Richard Emlet, Member, Biology; Jon Erlandson, Member, Anthropology; Gregory Retallack, Outside Member, Geological Sciences