Bhavin Khatri
Crick Institute
Evolutionary stochastic dynamics of speciation for a coarse-grained model of protein binding DNA
[When and where]
Speciation is fundamental to understanding the huge diversity of life on Earth. Current theory does not address how the speciation rate varies with population size in the important weak mutation regime of evolution, despite some evidence that smaller populations develop reproductive isolation more quickly. Here, we address an underlying biophysical basis of speciation by using a simple model of transcription factor-DNA binding and examine how their co-evolution in two allopatric lines leads to incompatibilities. We tackle this using both theory and simulations of sequence evolution. To develop a tractable analytical theory, we derive a coarse-grained Smoluchowski Equation for the dynamics of binding energy evolution due to the co-evolution of protein and DNA sequences; the high dimensionality of sequence evolution is accounted for by defining a Boltzmann sequence entropy for the binding energy of transcription factors, such that the flux of populations go up gradients in Iwasa’s free fitness. We find these simple considerations lead to a new prediction for the monomorphic regime of evolution, born out by theory and simulations, that smaller populations should develop incompatibilities more quickly; this arises as the effect of sequence entropy is to poise the common ancestor of smaller populations more closely to incompatible regions of phenotype space, so less substitutions are needed on average for incompatibilities to arise. Overall, these predictions are consistent with observations of large species diversity in small habitats such as Cichlids in the East African Great Lakes, contrasted with the observed smaller rate of developing reproductive isolation in marine animals and birds, which have large ranges and population sizes.
Invited talk Mini-symposium 9 Biophysical approaches to genotype-phenotype maps in evolution and speciation
Updated May 12, 2015, by Minus