New Method Reveals How Sampling Bias Has Been Skewing Biodiversity Research

We have identified a fundamental problem in biodiversity studies: when scientists find differences in species composition between sites, it's often unclear how much reflects real ecological processes versus simply having counted fewer individuals in some places. This matters because many ecological forces like predation or nutrient limitation affect both actual diversity patterns and the number of individuals available to sample.

Stier, Bolker, and Osenberg developed stochastic simulation models to explore how sampling affects beta diversity under different scenarios, then created a modified rarefaction technique to control for these sampling effects. Their simulations revealed that decreasing sample size could either increase or decrease observed beta diversity, depending on which metric we used and the properties of the community being studied. The direction and magnitude of these sampling effects were predictable when considering how sampling influences variance, but most studies don't account for this.

When We applied their rarefaction approach to separate sampling effects from environmental filtering, they found that it successfully isolated the ecological signal from the statistical noise. The effects of sampling bias in beta diversity were actually first demonstrated in the 1950s, but ecologists still lack effective techniques to adjust observed beta diversity for differences in abundance.

Our work is important because beta diversity is arguably as important as local diversity for conservation. Resource managers use beta diversity patterns to design reserve networks that maximize species complementarity across sites, and to track how species turnover changes through time under human impacts. If measurements are biased by sampling artifacts, conservation decisions may be based on flawed information. The new method provides a way to make biodiversity studies more reliable and comparable.

Citation

Stier, Adrian C.; Bolker, Benjamin M.; Osenberg, Craig W. (2016). Using rarefaction to isolate the effects of patch size and sampling effort on beta diversity. Ecosphere.

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This paper is Open Access.