Extinction, extirpation, and exotics: effects on the correlation between traits and environment at the continental level

Ecometrics is the study of the relationship between organismal traits and environments. This study used Monte Carlo methods to assess the effects of extinction, extirpation, and exotic species on ecometric correlations at the continental scale. These potentially confounding processes arise from anthropogenic activities, taphonomic biases in fossil assemblages, and selective mass extinctions. Random, independent local extinctions introduced a predictable downward bias in ecometric correlations, which can be corrected by rarefaction if correlations are being estimated from fossil assemblages. Random global extinctions on species have a less predictable effect on ecometric correlations and introduce pronounced effects if more than 25% of the continental fauna is affected; however, global extinctions do not bias the estimation of R2 even though they increase its uncertainty. Selective extinction and introduction of exotic species had little impact on ecometric correlations, though caution is urged in generalizing this result.