The extended ‘common cause’: causal links between punctuated evolution and sedimentary processes

The common-cause hypothesis suggests that the factors that control the availability of the Earth’s sedimentary record may also affect probabilities of speciation and extinction and thus exert macroevolutionary controls on standing biodiversity.  Here I show through computational modeling that common causes may also link sedimentary biases and microevolutionary processes of trait evolution.  Using Gould’s classic “evolutionary microcosm” of Bermuda and its diverse endemic clade of land snails, Poecilozonites, I show that the glacial-interglacial sea level cycles that toggle local sedimentation between rapid eolian accumulation and slow pedogenesis could easily toggle trait evolution between rapid bursts of morphological change driven small effective population size, disruptions in gene flow, and “genetic surfing” expansion events punctuated with long periods of slow morphological evolution associated with geographic range coalescence, large effective population size, and panmixia.  The pattern produced by this interaction is expected to be similar to that produced by punctuated equilibria, even without accompanying speciation events.  The spatial dynamics of this system are expected to produce patterns of random trait evolution that are more likely multi-rate evolutionary models than like the standard single-rate Brownian motion models that are currently used as the null model in many phylogenetic comparative methods.  The Bermudian example of links between sedimentation and evolution is arguably extreme, but the principles of the extended common cause are likely to extend to many other paleontological systems.

Methods
The data in this archive were generated using computational modeling.