October 2016

To assess the repeatability of an ecological study, Assistant Professor Matt Knope recently led a publication that both partially replicates and extends a previous study on the site fidelity (the likelihood of an animal to stay in one “home”) and homing ability of two abundant and ecologically important species of rocky intertidal sculpin fishes on the Oregon Coast. Knope and colleagues report in their new paper in the Journal of Fish Biology that by using a traditional mark and recapture technique in the field, that they find both species have high site fidelity and homing ability to individual tide pools, confirming the findings of previous work. However, unlike in the previous study, they find that body size was not a good predictor of homing ability, but that sex was. In addition, their study extends the maximum homing distance of both species, but finds that homing success was negatively related to displacement distance from the “home” tide pools. These findings suggest that adult sculpin populations are likely to be highly sub-structured geographically, possibly contributing to the exceptionally high species richness of the group.

September 2016

The effects of extinction events are not only caused by the intensity of the taxonomic losses (e.g., the number of species lost at a mass extinction event), but also by the selectivity of the extinction event (e.g., one group of animals being more susceptible to being lost at a mass extinction than another group). Assistant Professor Matt Knope recently co-authored a study in Biology Letters that proposes the use of logistic regression to quantify extinction selectivity, because the selectivity metric is independent of the extinction intensity and multiple predictor variables can be assessed simultaneously. The study uses this statistical technique to illustrate that the end-Permian mass extinction, the largest mass extinction in terms of taxonomic losses in the history of life (~252 million year ago), also had the largest influence on the physiological composition of the fauna. That is, marine animals that had little physiological buffering, or sophistication of their respiratory and circulatory systems (such as polychaete worms, sea cucumbers, and jellyfish), were statistically more likely to go extinct than animals with greater physiological buffering during the end-Permian mass extinction when ocean acidification and anoxia were thought to be widespread. This approach provides an avenue for quantifying the risk posed by the emerging biodiversity crisis that goes beyond simple projection of taxonomic losses.