Research Interests
I am broadly interested in the consequences of biodiversity, and the processes that structure it. I want to know what determines which species persist in communities, and the role of biodiversity at an ecosystem level. More importantly, I am interested in the role of environmental change in ecological systems: we know the environment is not constant, yet environmental change can be at times disruptive, yet also play a role in providing structure to ecological communities.
Photo of a field site from my Master's project (click image to enlarge).
My Master's project at Simon Fraser University focused on comparing community structure in the presence of anthropogenic disturbance, across large spatial scales. Many of the questions that came out of that research has led me to take an interest in species persistence in multi-species systems, patterns of extinction, and functional consequences of changes in biodiversity.
PhD Field Experiment set-up, with hexagonal open-top greenhouses containing
moss fragmentation treatments (click image to enlarge).
In my PhD project, I plan to use a combination of computer simulations and field experiments to link dispersal in space with changing environmental heterogeneity. Previous work has demonstrated the importance of spatial structure in determining scales and patterns of biodiversity. Disturbance, fluctuating resource inputs, and other types of environmental change have also been studied in both simulations and real ecosystems. I hope to be able to describe general principles of the interaction of these two processes on community structure, particularly in regards to conditions that can be stabilizing (leading to insurance effects) in the face of environments that may not change in a regular, predictable manner.
Study Systems
I prefer to let interesting questions lead my research, and use systems that are appropriate or convenient to the question at hand. This sometimes takes more time, while I familiarize myself with the details of a new system, but keeps me focused on the questions that interest me, rather than the comfort of familiar territory.
Intertidal: Pacific northwest
For my Master's project, I took advantage of relatively large-scale areas of clam aquaculture in British Columbia, Canada to look for consistent effects of predator exclusion and clam seeding on intertidal community structure.
Photo of a site of clam farming. Protective netting used to exclude large
surface predators is visible, with algae growing on it.
Predator exclusion has been used many times in marine intertidal systems as a way to release individual populations from release and allow competitive exclusion to lead to a reduction in local species richness and diversity, particularly in rocky intertidal communities. Because space is not as limiting in soft-bottom intertidal systems, competition (for space) has long been thought to be much less important in soft-bottom, compared to rocky intertidal communities.
A relatively small (10 x 10m) piece of protective netting commonly used
on clam farms in coastal British Columbia, Canada. This was part of a pilot
experiment I used to test patterns observed in a large-scale field study
of paired farm & reference sites.
The non-native, but commercially important Venerupis philippinarum
(Japanese littleneck clam) on the left, compared to the native Protothaca
staminea (Littleneck clam).
The results of our large-scale field study revealed no consistent differences in community structure between paired references sites and farms where both large surface predators were excluded and commercial species were added to the habitat (Whiteley & Bendell-Young 2007). However, our results also suggested differences in large-scale regional differences between the two groups of sites: sites being farmed were more similar to each other across large distances in terms of species composition and relative abundance, compared to reference sites, which displayed significant regional variation.
Uppogebia pugettensis, a burrowing mud shrimp, seen within stainless
steel quadrats (50x50cm x30cm deep) used to isolate an area of soft-bottom
intertidal to sample during low tide. Contained sediment was sifted (6mm
mesh) and sorted manually to find and identify macroinvertebrates.
These results are consistent with established theory that predation plays a minor role in structuring soft-bottom communities, in part because competition appears to be unaffected by the presence or absence of large surface predators. Nevertheless, infaunal (subsurface) predators may still be important, and were not excluded by most predator-exclusion methods (including those used in our study). In addition, our results showed very little effect of predator-exclusion even to overall abundance and biomass of intertidal clams. This suggests that either competition is more limiting than surface predation, or local abundance is determined by other factors.
Nereis brandti, a large, infaunal (subsurface) worm, possibly
a predator for some invertebrates (many Nereis spp are herbivorous,
however).
This led me to think more about the role of dispersal in affecting local community structure, a process that is poorly understood in marine and intertidal systems. Although many invertebrates can disperse as larvae, these are not completely passive and exhibit behaviours that can affect how they are affected and carried by water currents. There is also evidence implying that some small invertebrate adults can disperse even large distances by spinning mucus nets to move with water currents, or that adult clams can move not only vertically in the sediment, but also horizontally, even along the surface. These many uncertainties make it difficult to fully understand the mechanisms that determine community structure of intertidal invertebrates.
Moss microecosystems
close-up views of living patches of Pleurozium schreberi.
A close-up of a mix of Pleurozium, Hylocomium, and Ptilium
moss species. Lens-cap visible for scale.
I've just started working with this system for my PhD research. This is a speciose ecosystem in which the moss provides structure and ultimately detritus that feeds bacteria, fungus, and other microorganisms at the base of a complex food-web including mites and microarthropods. It has been used as a successful model system to study questions relating to habitat fragmentation and patterns of biodiversity (species-area relationships, metacommunity patterns of diversity, etc.)
Comparison of individual shoots of Pleurozium, Hylocomium,
and Ptilium moss species.
Although dispersal is still difficult to measure directly in this system, it can be effectively controlled at least on a qualitative level by using habitat corridors of varying size. Dispersal distances and paths have also been characterized for at least some mite species.
These images were taken through a microscope at 10x power. The first shows several colonies of cyanobacteria showing up as bright red,
most likely Stigonema sp. The cyanobacteria is highlighted in this image by using UV-fluorescence and a green filter ('Texas Red'). The second is the Exact same view in bright field (regular light microscope).
Models & simulations
This obviously allows for the most control of processes and can be a huge help in understanding the mechanisms underlying processes observed in natural systems. This is also a new area for me, but I am enjoying being able to apply computer skills and learning more about math applied to ecological research. I really do believe that experiments and theory are both needed to fully understand ecology and ecosystems.
I am beginning my foray into theoretical ecology by designing a spatially explicit metacommunity model of the spatial insurance hypothesis (Loreau et al. 2003). By adding space and distance as a component, dispersal can be more finely controlled, and I also hope to add more interesting spatial and/or temporal patterns of environmental change. Specifically, a directional gradient (with fluctuations) of environmental change in both space and time is a more accurate representation of the kinds of climate change the planet is facing. This is a new application of emerging ecological theory at the interface of metacommunity and diversity-stability theories.
One of the more detailed questions that has caught my attention so far is how to model the effect of the environment on species demographics? This choice can be highly influential to model behaviour, yet is often glossed over when discussing controversial results.
Other
I've also worked as a field assistant for many summers in central-eastern Canada, in a variety of terrestrial habitats from southern to northern Ontario, including Carolinian forest, the mixed forests of Algonquin Provincial Park, and boreal habitats of northern Ontario. I also worked in the streams around suburban Toronto for a summer mapping and improving fish habitat.