Jasmine Foo

Memory in trait macroevolution

Discrete trait evolution along phylogenetic trees is typically modeled with Poisson processes.  By definition, these models assume that the history of a trait within a lineage does not influence its future evolutionary trajectory, conditioned on the present state.  However, this assumption may fail to take into account gradual adaptation to a state, and how this adaptation may impact the likelihood of switching to a different state.  For example, consider  the simple binary trait of living in cave versus surface habitat. The longer a species has been cave-dwelling, the more may accumulated loss of vision, pigmentation, and defense restrict future adaptation if the species encounters the surface environment.  Here we propose a model that allows for 'memory' in trait evolution, adopting a renewal process model of trait changes on trees.  We then show how the two-state renewal process can be used for inference, and we investigate the potential of phylogenetic comparative data to reveal different influences of trait duration, or ‘memory’ in trait evolution. We hope that such approaches may open new avenues for modeling trait evolution and for broad comparative tests of hypotheses that some traits become entrenched.  (joint work with Emma Goldberg)