PARENT SESSION
Oral Session # 75: Biodiversity II.
Presiding: K Kirkman
Thursday, August 7. 1:30 PM to 5:00 PM, SITCC Meeting Room 100.
Patterns of taxonomic diversity among freshwater lakes: Sensitivity to scale, productivity gradients, and regional geographic influences.
Pither, Jason*,1, Cook, Michelle1, Aarssen, Lonnie1, 1 Department of Biology, Kingston, Ontario, Canada
ABSTRACT- Examining regional patterns of diversity within a spatially explicit framework adds insight to several current lines of inquiry in ecology and biogeography: local versus regional influences on site diversity; ecological versus evolutionary influences on site diversity; and the relationship between productivity and diversity. We explored patterns of taxonomic diversity using a dataset of 239 north-eastern U.S. freshwater lakes, sampled as part of the Environmental Monitoring and Assessment Program. The dataset is ideal for this research, owing in particular to its broad coverage and sampling design. Using matrices of environmental conditions (e.g. productivity, pH), species' tolerances (niches), spatial co-ordinates, and an index of the lakes' environmental uniqueness, we are examining the spatial details of diversity of diatom taxa in the contexts of the above lines of inquiry. Preliminary results have revealed that, consistent with recent published work, dissimilarity in species composition among lakes increases along the productivity gradient, and correspondingly, the proportion of the species pool represented by lakes decreases with increasing productivity. This pattern holds after accounting for geographical proximity. Water pH, however, explains regional patterns of alpha and beta diversity better than productivity for diatoms. A scale-sensitivity analysis of the patterns revealed that most trends in richness become apparent only at the coarsest scales, while others rear their head at within-ecoregion scales. As expected, patterns are also sensitive to the taxon: zooplankton and fish exhibit different scale-sensitivities. We developed an analytical approach to test for scale-sensitivities that uses generalized linear mixed models and randomization procedures, and suggest this as an appropriate framework for future analyses of geographical patterns of diversity.
Key words: diversity, productivity, scale, lake