We are investigating the influence of environmental heterogeneity on the dynamics of ecological communities.  Our model system is the detritus-based aquatic food web composed of microbes and invertebrates that develops in the vase-like leaves of the carnivorous pitcher plant Sarracenia purpurea.  Each pitcher represents an ephemeral habitat patch within the bog landscape, and the rotifer Habrotrocha rosa exists as a metapopulation, persisting through the colonization of new pitchers.  We hypothesize that the metapopulation is composed of multiple clones whose presence/prevalence is determined by environmental factors such as temperature and food quality/quantity which vary temporally.  During July-September, 2008, rotifer clones were established from pitcher fluid samples.  We are looking for differences in life history and stress tolerance among clones, as well as variations at the genetic and molecular level. Our results will provide insights into the role of genetic variation in the survival of species that live in fragmented habitats.

Results/Conclusions

Mean life span and egg production per day did not differ significantly for July and September clones.  Under natural conditions rotifers are exposed to environmental stresses such as freezing and desiccation.  We exposed the animals to gradually decreasing temperatures and froze them at -20^o C.  After thawing at  2-4^oC there were no survivors.  In contrast, 41% of the September animals survived freezing at -75^oC and rapid thawing at 37^oC.  No July animals survived.  Neither clone survived desiccation at 22^o C for seven days followed by rehydration.  This suggests that there may not be a significant time difference between July and September.