Linking a Biological Mechanism to Evolvability

Abstract

Evolvability has become a concept used to explain the common observation of clade asymmetry. However, the concept of evolvability means different things to different workers. Recent work has formalized the concept and we apply the formalized concept to a developmental system (primordial germ cell determination mechanism) that has been proposed to explain clade size disparity. In a simplified view, there are two general primordial germ cell (pgc) determination mechanisms: determinative and induced. The determinative mechanism is associated with species rich clades and the induced mechanism with species poor clades. The formal equations of evolvability provide a theoretical framework under which we can assess the relative influence of pgc determination mechanisms on clade evolvability. We propose that the determinative mechanism has enhanced evolvability in most clades that possess the trait.