PARENT SESSION
Oral Session 18: Ecological Theory I: Modeling.
Presiding: R Zabel
Monday, August 2, 8:00 AM to 11:30 AM, Meeting Room F 152.

The environmental sampling effect confounds interpretations of the niche: Implications for basic and applied ecology.

Pither, Jason^{*,1, 2}, Aarssen, Lonnie¹, ¹ Department of Biology, Kingston, ON, Canada² Department of Ecology and Evolutionary Biology, Tucson, AZ, U.S.

ABSTRACT- A broad range of basic and applied ecology research assumes that most species exhibit repeatable environmental niches, and that niche properties (e.g. optimum, tolerance) can be quantified reliably using survey methods. However, evidence sufficient to justify these assumptions exists only for a minority of species. It therefore seems prudent to step back and consider an alternative approach that more accurately reflects the balance of experimental evidence. Using a flagship survey dataset that includes estimates of total phosphorus (TP) and pH for 239 freshwater lakes, and the relative abundances of 252 sediment diatom taxa, we evaluate the following null hypothesis: the estimated value for a given species niche property on a given gradient is no different from expected given the random occupancy of an equal number of surveyed sites. We first demonstrate that the random model is appropriate for the majority (74%) of the species. We then show that, whether or not abundance-weighted niche measures are used, we fail to reject the null hypothesis for the majority of diatom taxa on both gradients. That is, few diatom species exhibit significantly narrow tolerances along either the TP or pH gradients. Sensitivity analyses clearly illustrate how what we call the environmental sampling effect has likely confounded standard estimates of species niche properties, and also the many niche-based analyses that frequently accompany them. The implications of our findings for both basic and applied ecology will be considered.

Key words: survey, tolerance, niche, paleolimnology