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UBC Theses and Dissertations

Independent gradients of producer, consumer and microbial diversity in lake plankton Longmuir, Allyson A.


Facilitation between trophic levels during food web assembly can drive positive correlations in diversity between producers, consumers and decomposers. However, the contribution of trophic interactions relative to local environmental factors in promoting species diversity are poorly understood with many studies of food web assembly only considering two trophic levels. Here we examine correlations in diversity among zooplankton, phytoplankton and bacteria in the pelagic zone of 31 lakes in British Columbia. We sampled species diversity of zooplankton and phytoplankton through morphological identification while bacterial genetic diversity was estimated by denatured gradient gel electrophoresis (DGGE) of 16s rDNA polymorphisms. We looked for correlations in diversity that were independent of the abiotic environment by statistically controlling for 18 limnological variables. No strong correlation was found between the diversity of zooplankton, phytdplankton and bacteria. In addition, the physical factors that were associated with species composition in one trophic level were independent of those that were important for another. Our results provide no support for the importance of direct feedbacks between producers, consumers and decomposers in maintaining diversity. Zooplankton, phytoplankton and bacterial communities are structured independently from one another and respond to different environmental variables.

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