Speciation in the Derrida-Higgs model with finite genomes and spatial populations

TL;DR

This study revisits the Derrida-Higgs model of speciation, demonstrating that a large number of genes (~100,000) are needed for neutral sympatric speciation in finite genomes, contrasting with models requiring fewer genes.

Contribution

It provides a finite-genome simulation of the Derrida-Higgs model, quantifying the gene number necessary for speciation and comparing spatial effects with models involving fewer genes.

Findings

Approximately 10^5 genes are needed for speciation in typical parameters.

Fewer genes (~100) can also lead to speciation in spatial models.

Spatial segregation is stronger with fewer genes, less so with many genes.

Abstract

The speciation model proposed by Derrida and Higgs demonstrated that a sexually reproducing population can split into different species in the absence of natural selection or any type of geographic isolation, provided that mating is assortative and the number of genes involved in the process is infinite. Here we revisit this model and simulate it for finite genomes, focusing on the question of how many genes it actually takes to trigger neutral sympatric speciation. We find that, for typical parameters used in the original model, it takes of the order of $10^5$ genes. We compare the results with a similar spatially explicit model where about 100 genes suffice for speciation. We show that when the number of genes is small the species that emerge are strongly segregated in space. For larger number of genes, on the other hand, the spatial structure of the population is less important and the species distribution overlap considerably.