Our research is broadly focused on the causes and consequences of biodiversity loss. As a corollary we hope to gain a better understanding of what it will take to slow extinction and mitigate its effects. We use experiments (field and lab), theory, and databases to tackle the following research projects:

1. Extinction in Fragmented Landscapes
2. The Functional Importance of Dispersal
3. Source-Sink Dynamics in Changing Environments
4. The Structure and Function of Metacommunities
5. Ecosystem Impacts of Climate Change
6. Anthropogenic Impacts on Adaptive Radiation
7. Economic Inequality and Biodiversity Loss

The unprecedented rates of population and species extinction we are experiencing are primarily due to habitat destruction and land-use change. An important result of this is the creation of fragmented landscapes, made up of a mosaic of disjoint habitat patches. Typically, extinction is the dominant population process in fragmented landscapes, even long after the initial loss of habitat.

We are using large carpets of moss, and their associated species-diverse community of microorganisms, as a natural model ecosystem (13) to study extinction in fragmented landscapes.

Our results have shown that fragmentation can cause delayed extinctions, and that particular species (e.g. predators) have a greater risk of extinction than others. Also, fragmentation-induced extinction can have significant impacts on community functioning (e.g. secondary productivity) (10).

We have also shown that habitat corridors can slow extinction and maintain community function (3, 5); this evidence suggests that corridors may represent a viable conservation strategy. In collaboration with Diane Srivastava a we are examining the inter-relation between local and regional diversity. In particular, how the direct manipulation of regional diversity may affect, via dispersal, local community structure and function (13).

An experimental moss landscape ©Andrew Gonzalez

Habitat fragmentation may also impact the dispersal of plants and animals. Little is known about how habitat fragmentation impacts animal mediated seed dispersal. For her Ph.D. Georgina O’Farrill is exploring this question in the tropical forests of the Yucatan peninsula, S.E. Mexico. In particular, she is studying how fragmentation may be disrupting the tapir mediated dispersal of the dominant tree species Manilkara zapota (chicle or gum tree), and the subsequent ecosystem impacts this disruption may have. This research is made possible by a close collaboration with Dr. Sophie Calmé of ECOSUR, in Chetumal, Mexico.

In fragmented habitats individuals may find themselves in poor quality habitat that may be of low conservation value. Surprisingly theory suggests that we shouldn’t give up on these populations, and that movement may permit populations to persist in such landscapes even though fluctuations in the biotic (e.g. competition, predation) and abiotic (e.g. changes in habitat quality) environment may suggest rapid extinction.

Recent experimental results, using the protozoan, Paramecium tetraurelia (8) (see figures below), have confirmed the theoretical predictions that persistence in sink habitats is possible in a variable environment as long at the rate of population decline is not too rapid, and environmental variation permits brief periods of positive growth. This result suggests strategies for saving species that appear to be on the brink of extinction in fragmented landscapes.

Population dynamics (daily densities) of Paramecium tetraurelia in stable and unstable sink habitats (continuous line, temperature). We see periods of strong population growth and high densities in the unstable sink, even though on average growth rate is negative. The ‘outbreak’ dynamics we see in the time series is an interesting ecological application of stochastic resonance.

Dave Matthews recently extended this experimental work and has demonstrated that sink-sink metapopulations can persist in changing environments. And in another experiment Adam Michel has also shown that adaptive evolution is possible in sink habitats within a relatively short time frame. These are exciting new directions in our research with obvious implications for conservation biology.

Metacommunity ecology emphasizes that local communities are connected to each other in the landscape and that this has important consequences for community structure and function (14). Theoretical work, in collaboration with Michel Loreau, Nicolas Mouquet and Frederic Guichard, is addressing the structural and functional properties of metacommunities, and in particular their stability.

This work inspired the spatial insurance hypothesis (11), the idea that spatial diversity and dispersal interact synergistically to increase the productivity and stabilize the dynamics of metacommunities. We are currently conducting experiments to test this theory. If verified this result would provide further reason to conserve both diversity and landscape connectivity.

Climate change is predicted to have a great impact on boreal ecosystems. The feathermoss, Pleurozium schreberi, is a very abundant species that, because of a symbiotic interaction with cyanobacteria, fixes atmospheric nitrogen. Biological fixation of nitrogen is an important pathway in the nitrogen cycle of the boreal biome. New research is examining the effects of climate change (temperature, precipitation) on the nitrogen fixing activity of P. schreberi. Ultimately, we want to know how climate change may disturb the nitrogen cycle and as a result affect forest ecology in the boreal biome. We are currently conducting studies in the field, at the McGill sub-Artic field station at Schefferville, and in the laboratory in the McGill Phytotron facility to explore this question.

©Doe Joint Genome Institute (University of California) Pseudomonas fluorescens Genome Project

We know almost nothing about how speciation by adaptive radiation is altered by anthropogenic disturbances. To address this issue experimentally we are using the bacterium Pseudomonas fluorescens, a useful biological model for adaptive radiation. This species undergoes adaptive radiation in vitro. Early experimental and theoretical results indicate that the process of adaptive radiation is strongly influenced by both the frequency and autocorrelation of environmental disturbance (20). Current work is using the robot facility in the LE3 to study metacommunity evolution, and consequently the combined effects of environmental change and habitat fragmentation on diversification. Theoretical work on this topic is being in done in collaboration with Stephane Legendre and Regis Ferriere in Paris, and Andrew Hendry at McGill. .

Economic Inequality and Biodiversity Loss Humans, both individually and collectively, are powerful drivers of environmental change. In collaboration with Greg Mikkelson and Garry Peterson we are studying how socioeconomic factors (for example economic inequality) affect biodiversity loss. In our current project, Tim Holland has begun to tackle the problem of how the distribution of income and wealth within and between societies may act directly and indirectly to cause biodiversity loss in North America.