Examples of graduate student research
Daniel McGarvey
Doctoral student with Dr. Milt Ward
If natural resource managers
are to realize the ultimate objective of conservation biology, which is to
protect biological diversity, they must begin to switch their focus from the
autecological needs of specific, commercially important species, to the preservation
of entire assemblages and communities. Doing so will, however, require a better
understanding of community equilibrium. Equilibrium communities are those
in which sympatric species coexist by interspecific partitioning of finite
niche resources, such as food and habitat. Alternatively, non-equilibrium
communities tend to be structured by historical events, such as migration
and geological activity, as well as ecological factors. Community equilibrium
is central to conservation biology, because it regulates the degree to which
biota are likely to respond to various management strategies. Increasing spawning
habitat and reducing predation are, for example, less likely to benefit species
within non-equilibrium communities than ones in equilibrium communities. I
proposed to conduct an inter-regional study of North American stream fishes,
in which I will characterize the equilibrium status of complete assemblages
(i.e., all fishes within a given region). This research, which is a joint
project with multiple management agencies and universities, will integrate
and assess extensive fish data from Pacific Northwest, Southwest, and Southeast
streams and rivers. Preliminary evidence suggests that the Northwest and Southwest
assemblages are non-equilibrium communities, while the Southeast assemblages
have achieved equilibrium; using three critical tests of equilibrium, I will
substantiate or refute these anecdotal results. Such a holistic, macroecological
approach will advance the conservation of not one, but all species of North
American freshwater fishes. It will also serve as a model for future inter-agency
and interdisciplinary collaboration.
Jen Mosher Doctoral student with Dr. Bob Findlay
The river continuum hypothesis predicts low-order streams are net heterotrophic with most of heterotrophic activity embodied in microorganisms. The heterotrophic bacteria populations within these streams transform organic and inorganic nutrients into usable biomass for higher organisms. While extensive studies have addressed the role of dissolved organic matter in shaping benthic microbial community structure, little is known regarding the effects of geological formations on these communities.
My research, a combination of observational and experimental analyses, addresses an important question in aquatic microbial ecology: How are geological differences in stream channel bedrock reflected in the sedimentary microbial communities in forested low-order streams? To answer this question, I must first establish a pattern in microbial community structure and then discern proximal causes, whether direct or indirect, behind the pattern. Three processes: water chemistry, ecosystem connectivity and top-down effects; will be studied to rank order their affect on microbial communities in relation to streambed parental bedrock. In linking these processes together, I will be able to rank order the influence of external forces on microbial community structure in low-order forested streams.
The experimental design compares six streams, three of which originate in sandstone and three that originate in limestone regions of the William B. Bankhead National Forest in northern Alabama, USA. I am utilizing a suite of biochemical and molecular techniques: terminal-restriction fragment length polymorphism (T-RFLP) for bacterial composition and phospholipid fatty acid analysis (PLFA) for the total microbial community. The combination of these techniques and testing correlations with several chemical, physical and biological parameters throughout seasonal changes will identify driving forces and influential factors that shape benthic microbial community structure.
