Document: NIC-3-46-2

The evolution of dispersal in populations and communities: A direct test.

FRIEDENBERG, N.A.*

Dartmouth College, Hanover, New Hampshire, USA ¹

Abstract:
There is now broad acceptance of the landscape mosaic view of nature in which communities exist as patches connected by dispersal. Much attention has been focused on the effect of increased disturbance regimes or habitat fragmentation on the size and longevity of metapopulations and the results of these studies can be scaled up to metacommunities, as well. Field studies demonstrate that environmental instability is positively correlated with the prevalence of vagile organisms within both populations and communities. However, the difficulty of quantifying or manipulating dispersal and habitat quality in the field prevents a direct test of the hypothesis that habitat instability selects for individuals with high dispersal propensity. I use two mutant strains of the soil nematode Caenorhabditis elegans in controlled microcosm experiments to directly test for the causal link between random habitat fluctuations and dispersal propensity. C. elegans is a self-fertilizing hermaphrodite and does not hybridize during short-term experiments. Each strain is therefore the analogue of a species and each microcosm a community. One strain has higher fecundity, while the other strain has a higher propensity to disperse between patches of food on agar plates. I show that the strain with higher fecundity increases in frequency in stable habitats, whereas the strain with higher dispersal propensity increases in frequency in treatments with random patch extinction. The results of these experiments indicate that there is a causal link between habitat stability and the prevalence of vagile species. These results can also be applied to models of evolution within populations.

Keywords: dispersal, evolution, metacommunity, habitat stability

This abstract is being presented at: 8:30 AM in session:
Oral Session #56: Metapopulation Analysis.