How Does Body Size Increase Post-Mass Extinction?

Body-size and time have a unique relationship. Cope’s Rule explains this relationship by stating as time progress so does body-size. As an organism’s lineage ages, the general body-size becomes larger. This increase can have many benefits, but also drawbacks. Things like intelligence, development time, and fecundity are affected by body size. A study just released by Nature though might show that this rule does not always apply. A new effect is being observed that shows body-sizes may actually decrease post-mass extinction. This effect is known as the Lilliput effect.
With 1120 fish body lengths, Lauren Sallan and Andrew Galimberti conducted a study on vertebrates that lived before and after the end-Devonian mass extinction. Vertebrates during the Devonian time period exhibited an increase in body size over time as predicted. Following the end-Devonian mass extinction, a new time period known as the Mississippian was established. Vertebrates within the Mississippian showed an overall reduction in body size as time progressed. The Lilliput effect had taken place post-extinction, but why? …show more content…
Sallan and Galimberti thus began to look at differences between these two factors pre- and post-extinction. Surprisingly, the Mississippian was more “abiotically stable.” This in turn showed no correlation with many abiotic models, but showed a negative correlation with one oxygen model and a positive correlation with one temperature model. Following these findings, the models above were fit with stasis, active trend, and random walk models. Once fitted, it became apparent that biotic factors played the crucial role in selection for body