Title: Carrying capacity in a heterogeneous environment with habitat connectivity
Speaker: Bo Zhang (UC Davis)
Abstract: A large body of theory predicts that populations dispersing in heterogeneous environments reach higher total size than if non-diffusing, and, paradoxically, higher size than in a corresponding homogeneous environment. However, this theory and its assumptions have not been rigorously tested. Here I first extended previous theory to include exploitable resources, proving qualitatively novel results, which we tested experimentally using spatially dispersing laboratory populations of yeast. Consistent with previous theory, I predicted and experimentally observed that spatial dispersal increased total equilibrium population abundance in heterogeneous environments. Refuting previous theory, however, this work discovered that homogeneously distributed resources support higher total carrying capacity than heterogeneously distributed resources, even with species dispersal. Secondly, I further investigated how the spatial distribution of stressors interacts with dispersal to influence population dynamics by combining laboratory experiments with novel mathematical theory. Consistent with the mathematical predictions, I observe that a uniform spatial distribution of stressor minimizes the total equilibrium size of experimental metapopulations.
Ongoing work is to extend my previous work to multiple interacting species and use mathematical theory and laboratory work to predict how dispersal alters species coexistence and metacommunity dynamics in heterogeneous environments. I conducted rigorous experiments in microcosm system with genotypes of C. elegans that have different dispersal rates, foraging in an environment that is heterogeneous in the distribution of bacterial prey to test my theoretical results. Consistent with the theory, the experimental results clearly showed coexistence due to top-down effects of the resource by the consumer.