The postbreeding period in migratory bird species is an important, but often neglected,area of knowledge. From May-October of 1993-95, I studied the breeding andpostbreeding ecology of 61 adults and postfledging movement of 43 juveniles in aradio-tagged population of Wood Thrushes (Hylocichla mustelina) on the U. S. MarineCorps Base, Quantico, Virginia (38 30' N, 77 25' W). Fledglings became independent 0 0from their parents at 28-36 days post hatching and dispersed 307-5300 m from their natalsites to join flocks of conspecifics. About half (46%) of the young birds stayed in onedispersal site until migrating, but the rest visited other sites. In 40 instances, 15fledglings moved up to 6 km out of the dispersal site and, after 1-5 days, returned to thelocality occupied before initiating the movement. After dispersal, fledglings' positions(n = 556) occurred in (1) second growth and sapling stage sites at the edge of forested areas [52%], (2) gypsy moth (Lymantria dispar) damaged deciduous forest [21.8%], (3)Virginia pine (Pinus virginianus) forest that had a heavy understory of young deciduous trees and an open canopy [15.6%], and (4) mature mixed forest [10.6%]. Most fledglings(73%) left the Marine Base in September at the mean age of 81 days. After finishing breeding, adult Wood Thrushes underwent molt that extended from late July to early October. Flight-feather molt lasted on average 38 days and may have impaired flight efficiency in some individuals. Of 30 observed adults, 15 molted in the same area where they nested, and 15 moved 545 to 7290 m from their nesting sites. Molting sites were located in areas with a larger number of pines, less canopy cover, fewer trees with dbh>38 cm, and a denser understory strata than nesting sites (P < 0.1). My data suggest that a conservation strategy that focuses on identifying and protecting nesting habitat in the temperate region, although important, is incomplete at best if the events and needs during the post reproductive and post fledging periods are not considered. / Ph. D.

The field of marine population connectivity is receiving growing attention from ecologists worldwide. The degree to which metapopulations are connected via larval dispersal has vital ramifications for demographic and evolutionary dynamics and largely determines the way we manage threatened coastal ecosystems. Here we addressed different questions relating to connectivity by integrating direct and indirect genetic approaches over different spatial and ecological scales in a coral reef fish in the Red Sea. We developed 35 novel microsatellite loci for our study organism the two-band anemonefish Amphiprion bicinctus (Rüppel 1830), which served as the basis of the following approaches. First, we collected nearly one thousand samples of A. bicinctus from 19 locations across 1500 km along the Saudi Arabian coast to infer population genetic structure. Genetic variability along the northern and central coast was weak, but showed a significant break at approximately 20°N. Implementing a model of isolation by environment with chlorophyll-a concentrations and geographic distance as predictors we were able to explain over 90% of the genetic variability in the data (R2 = 0.92). For the second approach we sampled 311 (c. 99%) putative parents and 172 juveniles at an isolated reef, Quita al Girsh (QG), to estimate self-recruitment using genetic parentage analysis. Additionally we collected 176 juveniles at surrounding locations to estimate larval dispersal from QG and ran a biophysical dispersal model of the system with real5 time climatological forcing. In concordance with model predictions, we found a complete lack (c. 0.5%) of self-recruitment over two sampling periods within our study system, thus presenting the first empirical evidence for a largely open reef fish population. Lastly, to conceptualize different hypotheses regarding the underlying processes and mechanisms of self-recruitment versus long-distance dispersal in marine organisms with pelagic larval stages, I introduce and discuss the concept of “origin effects”, providing the theoretical background to some of the questions that have arisen during this research. Overall, this thesis has generated significant new insights into the patterns of coral reef fish connectivity, specifically for the Red Sea, where such information has previously been scarce.

Urbanization is increasing at a dramatic rate as the human population increases. While it is well-known that urbanization tends to decrease species diversity (i.e., biotic homogenization), it is not known how urbanization affects the frequency and efficiency of species interactions. Seed dispersal is a plant-animal interaction that depends on disperser feeding rate, disperser diversity, probability of seed dispersal and germination. How these factors are affected by urbanization however is unknown. In this study, we evaluate how urbanization alters these factors. Urban sites had 2x higher feeding rate and 3x higher number of disperser species. The probability of seed dispersal however was the same between natural and urban sites. Moreover, the probability of germination after dispersal was 20% lower in urban sites, leading to overall negative effects of urbanization on T. radicans seed dispersal. In this study we demonstrated that urbanization can affect species diversity, as well as their ecological functions.

With increasing encroachment on natural communities by anthropogenic activity, it is important to understand the functions of natural ecosystems in an effort to conserve natural areas. A first-hand study of the population dynamics of South Florida Slash Pine (P. elliottii Engelm. var. densa) following a fire event provided insight to its recovery and dispersal following a fire. A natural fire (lightning-induced) occurred in the spring of 2000 at the T. Mabry Carlton, Jr. Reserve, Sarasota County, providing an opportunity to study aspects of slash pine in relation to fire. One objective of my research was to look at dispersal/recruitment conditions and slash pine dynamics in relation to fire. I looked at the varying degrees of tree mortality due to fire at different stands of slash pines. I also looked at the stands in terms of stand composition and spatial arrangement of surviving adults. Finally, I studied how variable seedling establishment and survival was between stands. Few inferences could be drawn between fire and these individual analyses; however, all analyses revealed that at the scale of this study, pine flatwoods are patchy. I also looked at the dispersal of slash pines following a fire event. I modeled my research after Ribbens et al. (1994) and Clark et al. (1998), who took a phenomenological approach to dispersal modeling. This approach involved using distances between adults and seeds/seedlings and fecundity of adults to create dispersal models based on maximum likelihood estimates (MLE). I found that, while I could predict a model within acceptable parameters for most of the stands, more data was needed to predict models that better fit the data. This finding, along with the fact that I recovered no seed data for analysis, suggests factors are contributing to dispersal and recruitment (e.g. cone-crop) that need to be accounted for in the future.

Spatial processes have a profound influence on the structure and function of community assemblages. The dispersal of organisms from their place of origin to the location in which they live out their reproductive life is particularly important for plant communities, which generally cannot adjust their location post-germination. Connection between communities at a landscape scale can also influence species persistence, local and regional diversity, and functional turnover at the metacommunity scale. Animals have been shown to disproportionately deposit propagules in particular microsites in many plant species, facilitating the arrival of plants to appropriate niche-space. Birds are particularly notable seed dispersers, given their ability to fly long distances and their behavioral inclination toward using specific microsites within their habitat for foraging and nest building. Despite the known influence of animal behavior on plant dispersal outcomes, little work has been done to investigate the role of animals in dispersing bryophyte (moss, hornwort, liverwort) propagules. In order to examine how birds may affect bryophyte dispersal, I conducted two studies focused on understanding how bird species identity and behavior influence the bryophyte propagules they carry. In addition, I conducted a study to understand how metacommunity structure across a landscape can be influenced by focal spatial scale. In the first study I examined how bird species and foraging behavior impact the topical load of bryophyte spores found on bird surfaces. In order to determine this, I captured passerine birds in mist nets and swabbed them for spores. I found that spores were more abundant on passerine tails than legs, and that overall spore load was higher on larger birds. Thrushes in particular carried more spores than other groups overall. Bark and foliage foraging birds had more spores on their tails than ground foraging birds. From these samples I was able to germinate 242 individual bryophytes, demonstrating that carried spores were readily viable. In the second study, I examined species-specific relationships between bryophytes and the birds carrying them. Swabs from captured birds were grown in the lab and bryophyte species were determined genetically. I used a bipartite network approach to determine the level of specialization of associations within the overall network, as well as how specialized the avian associations of individual bryophyte species were. I then used the phylogenetic distance of bryophytes found on individual bird species in order to assess how specialized the assemblages on a given bird species were compared with a null, random model. I found that bryophyte associations with birds were nonrandom, and that the extent to which those associations were specialized differed by bird foraging behavior. In addition, I found that the diversity of propagules on bird surfaces was significantly nonrandom, with the exception of those bryophytes found on Spotted Towhees. In the final study, I examined the metacommunity structure of bryophytes at both patch and landscape scales across a relict landscape of Valdivian forest in North-Central Chile. This landscape consists of distinct natural patches of forest maintained by coastal fog deposition, surrounding by a dry matrix inhospitable to patch-resident bryophytes. I used quadrats to sample bryophyte species abundance at the base and at breast height of ten trees in each patch, in 20 patches across the landscape. I found that when considering the whole park as one metacommunity, the bryophyte community exhibited a Gleasonian structure, in which individual species turnover was idiosyncratic. Considering assemblages from both heights separately, a Clemenstian pattern was observed, suggesting that within each height compartment, turnover of species tended to happen together. Treating each patch as a metacommunity of individual community trees resulted in a wide variety of metacommunity structures across the park that did not reflect either longitude or latitude. Low canopy cover and small DBH resulted in structures reflecting random species loss. Underlying Shannon diversity did not explain differences in the observed structures. This dissertation provides the first evidence that passerine birds carry bryophyte propagules, and that their individual species use of habitat and foraging behaviors are likely to influence the number and diversity of the bryophytes they are dispersing. This has implications for understanding disjunct species and genetic distributions observed in bryophytes that to date have lacked an explanatory mechanism for long distance directed dispersal. In addition, understanding how avian behavior may disperse propagules at a local to regional scale may provide better insight into the trajectory of bryophyte recruitment on impacted landscapes. I also found that assignation of metacommunity structure is sensitive to spatial scale in bryophytes. Together, these findings increase our understanding of the role that spatial processes play in forming bryophyte communities.

A series of experiments was conducted to: 1) investigate how feeding cattle with different amounts of different-sized seeds affects seed passage rate through the digestive tract, and the germinability of passed seeds; 2) examine how the location of seeds in dungpats of different thicknesses influences seedling emergence , development, and survival in cattle dungpats; and 3) characterize seedling emergence in naturally and artificially deposited cattle dungpats . Three perennial , cool-season grasses, bluebunch wheatgrass [Psuedoroegneria spicata (Pursh) A. Love], Sandberg bluegrass (Poa secunda Presl.), and 'Hycrest' crested wheatgrass [Agropyron desertorum (Fisch. ex Link) X A. cristatum (L.) Gaert.], were used as representative revegetation species for the Intermountain West region. When cattle were fed 60,000, 30,000, 15,000, and 7,500 seeds of bluebunch wheatgrass and Sandberg bluegrass, the recovery of passed seeds for both species declined as seed feeding levels decreased from 60,000 to 7,500 seeds per animal and as time after seed ingestion increased from 1 to 4 days. Sandberg bluegrass seeds had greater germinability than bluebunch wheatgrass seeds at all seed feeding levels and collection dates. In complementary greenhouse studies, artificially prepared cattle dungpats (20 cm diameter) with different thicknesses (1, 2, and 4 cm) were placed on a sandy loam soil (initially at field capacity) in large plastic containers. Pre-germinated seeds of blue bunch wheatgrass, Sandberg bluegrass, and/or Hycrest crested wheatgrass were planted separately in the center and periphery of dungpats at heights (from bottom of dungpats) of 0.5 cm for 1-cm-thick dungpats, 0.5 and 1.5 cm for 2-cm-thick dungpats , and 0.5, 2.0, and 3.5 cm for 4-cm -thick dungpats. Half of the dungpat treatments received no supplemental water while the other half received additional water simulating a wet spring . After 60 days, seedling emergence, development , and survival for all species were greatest at the 0.5 cm planting height , regardless of dungpat thickness , and greatest in 1 cm-thick dungpats , regardless of planting height. Seedling emergence , development , and survival were greatest for Hycrest crested wheatgrass, followed by bluebunch wheatgrass and Sandberg bluegrass. In a field study, cattle dung containing passed seeds of blue bunch wheatgrass, Hycrest crested wheatgrass, and Sandberg bluegrass was formed into artificial dungpats (2 kg in mass) with thicknesses of 1, 2, and 4 cm, and respective diameters of 40, 28, and 20 cm, and deposited on bare soil. Cattle also deposited natural dungpats varying in mass, thickness, and diameter. Seedling emergence for all species decreased as artificial dungpat thickness increased from 1 to 4 cm, and was lowest in natural dungpats. Seedling emergence for all dungpat types was greatest for Hycrest crested wheatgrass, followed by Sandberg bluegrass and bluebunch wheatgrass. These studies indicate that: 1) cattle should be fed about 60,000 seeds ( of these grass species) per animal to pass sufficient germinable seed to establish at least one seedling in a dungpat; and 2) seedling emergence, development, and survival in cattle dungpats are greatly influenced by plant species (seeds) ingested, thickness of dungpats, seed location in dungpats, and moisture content of the soil underlying dungpats.

No study has been done in the western United States concerning dispersal of dwarf mistletoe by mammals. At the outset of the study it was determined that the red squirrel, the yellow pine chipmunk (Eutamias amoenus), the northern flying squirrel, and the bushy-tailed wood rat (Neotaoma cinerea), were all potential vectors of seeds. The red squirrel was chosen as the main object of study because it is diurnal and is closely associated with ponderosa pine (Pinus ponderosa), a heavily infected species. The study was undertaken to determine whether small mammals play a significant role in transporting mistletoe seeds to uninfected areas. Understanding their role can be helpful both in further understanding of the biology of dwarf mistletoe and in evaluating current control practices.

Evolution of genotypes during range expansion is driven in part by colonization dynamics. I investigated genetic patterns of colonization and dispersal during initial expansion of an invasive bunchgrass, Brachypodium sylvaticum, into Oregon. Using microsatellite markers, I sampled plants at two different scales: at regular intervals along three parallel roads spanning about 30km, and in populations identified throughout Oregon. I also collected field-generated progeny from a subset of populations and used molecular identification of outcrossing events to estimate selfing rates in both central and peripheral populations. Dispersal patterns were similar at both scales, with non-contiguous dispersal responsible for colonization of new populations. High levels of differentiation were observed at all scales, though newly-colonized populations were more differentiated than older populations. Corvallis populations were responsible for colonization of a majority of populations throughout Oregon, while individuals from Eugene were only occasionally found in new populations. Admixture occurs between Corvallis and Eugene populations, decreasing differentiation, and potentially creating novel phenotypes and increasing evolutionary potential of populations. Selfing rates were high, but two populations in the areas of original introduction had lower rates of selfing, suggesting that selfing rates may decrease as population density and diversity increases with age. The influences of founder effects and bottlenecks on phenotypic evolution during range expansion require further investigation, as inbreeding, lag times, and selection may influence evolutionary trajectories of populations.

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