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The Tangled Web Of Community Ecology: Making Sense Of Complex Data, Monica Lynn Beals

Doctoral Dissertations

Ecological communities are governed by complicated processes that give rise to observable patterns. Making sense of these patterns, much less inferring the underlying processes, has proved challenging for several reasons. Manipulative experiments in natural communities may not be feasible due to large numbers of variables, lack of adequate replication, or the risk of undesirable consequences (e.g., introducing an invasive species). The multivariate nature of ecological datasets presents analytical problems as well; many statistical techniques familiar to ecologists have difficulty handling large numbers of potentially collinear variables. I present results from three studies of spider communities in which I employ a …

Avian Community Ecology: Patterns Of Co-Occurrence, Nestedness, And Morphology, Michael David Collins

Doctoral Dissertations

A central tenet of the competition paradigm is that community structure is governed by deterministic rules. The competition paradigm pervades nearly all subdisciplines and extends to the broadest, deepest questions in ecology. To determine whether patterns of co-occurrence, nestedness, and morphology in avian communities are consistent with a competition hypothesis, I use null models to compare observed patterns to patterns expected in the absence of competition.

I use presence-absence matrices of birds in three archipelagoes to test whether species exhibit exclusive distributions. Congeneric birds co-occur significantly less frequently than predicted in two archipelagoes, consistent with a competition hypothesis. However, when …

Vertical Export Of Biogenic Matter In The Chukchi And Barents Seas, Catherine Lalande

Doctoral Dissertations

Drifting sediment traps were deployed in 2004 in the ChukchiSeato investigate the variability in the vertical flux of biogenic matter in the presence and absence of sea ice. Measurements of chlorophyll-a, particulate organic carbon (POC), particulate organic nitrogen, phytoplankton, zooplankton fecal pellets, and the stable carbon isotope composition of the sinking material were accomplished along two shelf-to-basin transects. POC fluxes obtained in ice-covered and ice-free conditions were of different composition but of similar magnitude, indicating that the export fluxes in the presence of ice cover contributed significantly to the annual export of biogenic matter in the Chukchi Sea. …

Explaining Species Diversity By Linking Local And Large Scale Processes, Marc William Cadotte

Doctoral Dissertations

Large-scale processes are known to be important for patterns of species richness, yet the ways in which local and larger scale processes interact is not clear. I first examined published experiments that manipulated dispersal among local communities using meta- analyses. I show that local communities often readily increase diversity, but that there may be declines at larger spatial scales. I then used metacommunities consisting of microbial aquatic communities to examine how processes at different scales affect local and metacommunity richness. Specifically, I manipulated the potential dispersal rate, whether dispersal was localized or global, and variation in initial community composition. I …

Applying Landscape-Scale Modeling To Everglades Restoration, Scott M. Duke-Sylvester

Doctoral Dissertations

In this dissertation I describe the implementation and application of three spatially-explicit, landscape-scale models designed to address specific aspects of Everglades restoration. The first is a model of vegetation succession for the Everglades. The second is a fire model for the Everglades. The third is a model of the spread and optimal spatial control of an invasive, non-native plant.

I developed the succession and fire models as part of the Across Trophic Level System Simulation (ATLSS). These models are used to assess the relative effects of alternative hydrology scenarios on the distribution of vegetation and fires. In addition to the …