Friday, August 7, 2009

PS 92-174: Genetic variation and environmental heterogeneity: Studies on a metapopulation of the bdelloid rotifer Habrotrocha rosa

D. Liane Cochran-Stafira and Tatiana C. Tatum. Saint Xavier University

Background/Question/Methods Environmental heterogeneity is ubiquitous in the natural world, and may well be one of the most important factors influencing species interactions and population dynamics.  This study is part of a larger project that looks at the influence of environmental heterogeneity on the dynamics of ecological communities and the close interplay between processes at both local and regional scales. We focus on the population genetic structure and dispersal abilities of Habrotrocha rosa, an asexual rotifer that lives in the water-filled, pitcher-shaped leaves of the carnivorous pitcher plant Sarracenia purpurea.  Each pitcher represents an ephemeral habitat patch within the bog landscape, and H. rosa exists as a metapopulation, persisting through the colonization of new pitchers.  We are attempting to correlate environmental variation within habitat patches with genotypic and phenotypic differences among clones.  We hypothesize that the metapopulation is composed of multiple genotypes whose presence/absence is determined by colonization rate, calendar date, leaf age, and types of bacteria present.  During July-September, 2008, and continuing in March 2009, rotifer clones were established from pitcher fluid isolates.  Pitcher fluid was inoculated into EcoPlates to establish physiological profiles of the bacterial assemblages.  Genetic analysis involves cellulose acetate gel electrophoresis and Cox1 and Cob gene sequencing. 
Results/Conclusions Bacterial assemblages differ distinctly among pitchers, but show some consistency in physiological profiles across the time.  Similarly, there is considerable similarity among H. rosa clones isolated from the same leaf at different times within the growing season.  Surprisingly, there appears to be a certain degree of homogeneity among clones isolated from leaves on different plants during this time.  Preliminary results suggest however, that clones which must endure a period of freezing during the winter months exhibit considerable phenotypic and genetic variation compared to those prevalent during the warmer months.Results/Conclusions Bacterial assemblages differ distinctly among pitchers, but show some consistency in physiological profiles across the time.  Similarly, there is considerable similarity among clones isolated from the same leaf at different times within the growing season.  Surprisingly, there appears to be a certain degree of homogeneity among clones isolated from leaves on different plants during this time.  Preliminary results suggest however, that clones which must endure a period of freezing during the winter months exhibit considerable phenotypic and genetic variation compared to those prevalent during the warmer months.