Evolutionary stochastic dynamics of speciation and a simple genotype-phenotype map for protein binding DNA

Speciation is of fundamental importance to understanding the huge diversity of life on Earth. In contrast to current phenomenological models, we develop a biophysically motivated approach to study speciation involving the co-evolution of protein binding DNA for two geographically isolated populations. Our results predict that, despite neutral diffusion of hybrids in trait space, smaller populations have a higher rate of speciation, due to sequence entropy poising populations more closely to incompatible regions of phenotype space. A key lesson of this work is that non-trivial contributions of sequence entropy give rise to a strong population size dependence on speciation rates.