Reproductive isolation of hybrid populations driven by genetic incompatibilities.

Molly Schumer,Gil G Rosenthal,Peter Andolfatto,Rongfeng Cui,Bret A Payseur

doi:10.1371/journal.pgen.1005041

Abstract

Despite its role in homogenizing populations, hybridization has also been proposed as a means to generate new species. The conceptual basis for this idea is that hybridization can result in novel phenotypes through recombination between the parental genomes, allowing a hybrid population to occupy ecological niches unavailable to parental species. Here we present an alternative model of the evolution of reproductive isolation in hybrid populations that occurs as a simple consequence of selection against genetic incompatibilities. Unlike previous models of hybrid speciation, our model does not incorporate inbreeding, or assume that hybrids have an ecological or reproductive fitness advantage relative to parental populations. We show that reproductive isolation between hybrids and parental species can evolve frequently and rapidly under this model, even in the presence of substantial ongoing immigration from parental species and strong selection against hybrids. An interesting prediction of our model is that replicate hybrid populations formed from the same pair of parental species can evolve reproductive isolation from each other. This non-adaptive process can therefore generate patterns of species diversity and relatedness that resemble an adaptive radiation. Intriguingly, several known hybrid species exhibit patterns of reproductive isolation consistent with the predictions of our model.

Highlights

The evolutionary significance of hybridization has been a hotly debated topic for decades [1]
It has been suggested that hybridization could generate new species because hybrids can display novel combinations of traits that induce reproductive isolation from their parental species
We describe a new model of hybrid reproductive isolation that results from selection against genetic incompatibilities in hybrids, which are predicted to be common

Summary

Introduction

The evolutionary significance of hybridization has been a hotly debated topic for decades [1]. Speciation that occurs as a result of hybridization without a ploidy change [2, 3], is generally thought to be an exceptionally rare outcome of hybridization, and there are only a handful of well-supported cases of this phenomenon [4]. Though it is not uncommon for species’ genomes to exhibit evidence of past hybridization, hybrids are often thought to be weakly isolated from parental species, though few studies have explicitly investigated this. This work has lead to the idea that novel hybrid phenotypes are key to hybrid speciation [13]

Methods

Results

Discussion

Conclusion