Abstract
Understanding the mechanisms of rapid adaptive radiation has been a central problem of evolutionary ecology. Recently, there is a growing recognition that hybridization between different evolutionary lineages can facilitate adaptive radiation by creating novel phenotypes. Yet, theoretical plausibility of this hypothesis remains unclear because, for example, hybridization can negate pre-existing species richness. Here, we theoretically investigate whether and under what conditions hybridization promotes ecological speciation and adaptive radiation using an individual-based model to simulate genome evolution following hybridization between two allopatrically evolved lineages. The model demonstrated that transgressive segregation through hybridization can facilitate adaptive radiation, most powerfully when novel vacant ecological niches are highly dissimilar, phenotypic effect size of mutations is small and there is moderate genetic differentiation between parental lineages. These results provide a theoretical basis for the effect of hybridization facilitating adaptive radiation.
Highlights
Understanding the mechanisms causing adaptive radiation is a fundamental challenge in evolutionary biology
We address the following four questions to theoretically examine the hybrid adaptive radiation hypothesis: (1) whether transgressive segregation through hybridization promotes adaptive radiation, (2) how genetic differentiation between parental lineages affects the likelihood of hybrid adaptive radiation, (3) what roles assortative mating plays in hybrid adaptive radiation and (4) whether hybridization can act as an essential cause of adaptive radiation
To investigate detailed mechanisms of how hybridization promotes ecological speciation and adaptive radiation, we developed and analysed an individual-based evolutionary simulation model in which two parental lineages independently evolve in separation and secondarily contact to hybridise
Summary
Understanding the mechanisms causing adaptive radiation is a fundamental challenge in evolutionary biology. There is a growing recognition that hybridization between different evolutionary lineages can cause rapid diversification of ecological phenotypes and facilitate adaptive radiation (Seehausen 2004; Mallet 2009) (hereafter, hybrid adaptive radiation hypothesis). Hybrids’ mosaic genomes aggregating genes from different parental lineages can create novel phenotypes Such novel phenotypes, mostly maladaptive, may occasionally facilitate adaptive invasion of hybrid organisms into novel ecological niches (Barton 2001; Mallet 2007). Hybridization and backcrossing can cause exchange of phenotypes among lineages by mediating gene introgression (Seehausen 2004; Jiggins et al 2008), which has possibly facilitated the adaptive radiation of Heliconius butterflies (The Heliconius Genome Consortium 2012) and Darwin’s finches (Lamichhaney et al 2015)
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