Hybridisation and diversification in the adaptive radiation of clownfishes

Glenn Litsios,Nicolas Salamin

doi:10.1186/preaccept-1517039684139971

Abstract

The importance of hybridisation during species diversification has long been debated among evolutionary biologists. It is increasingly recognised that hybridisation events occurred during the evolutionary history of numerous species, especially during the early stages of adaptive radiation. We study the effect of hybridisation on diversification in the clownfishes, a clade of coral reef fish that diversified through an adaptive radiation process. While two species of clownfish are likely to have been described from hybrid specimens, the occurrence and effect of hybridisation on the clade diversification is yet unknown. We generate sequences of three mitochondrial genes to complete an existing dataset of nuclear sequences and document cytonuclear discordance at a node, which shows a drastic increase of diversification rate. Then, using a tree-based jack-knife method, we identify clownfish species likely stemming from hybridisation events. Finally, we use molecular cloning and identify the putative parental species of four clownfish specimens that display the morphological characteristics of hybrids. Our results show that consistently with the syngameon hypothesis, hybridisation events are linked with a burst of diversification in the clownfishes. Moreover, several recently diverged clownfish lineages likely originated through hybridisation, which indicates that diversification, catalysed by hybridisation events, may still be happening.

Highlights

The importance of hybridisation during species diversification has long been debated among evolutionary biologists
Building on those evidences and others, Seehausen proposed that hybridisation may promote speciation and adaptive radiation by generating new genetic and phenotypic variation that can be the target of selection
We define from phylogenetic inference eight monophyletic groups of species to facilitate the interpretation of our results (Table 1)

Summary

Introduction

The importance of hybridisation during species diversification has long been debated among evolutionary biologists. We study the effect of hybridisation on diversification in the clownfishes, a clade of coral reef fish that diversified through an adaptive radiation process. Common examples of hybridisation inducing diversification can be found in the Galapagos finches [2], Hawaiian Lapaula crickets [3] and Rift Lakes cichlids [4,5]. Building on those evidences and others, Seehausen proposed that hybridisation may promote speciation and adaptive radiation by generating new genetic and phenotypic variation that can be the target of selection [6]. With more and more cases of hybrid speciation being documented [7], the main question is shifting towards understanding how evolutionary radiations are facilitated or even catalysed, rather than prevented, by hybridisation [8]

Methods

Results

Conclusion