Abstract
Previous studies have shown that assortative mating acts as a driver of speciation by countering hybridization between two populations of the same species (pre-zygotic isolation) or through mate choice among the hybrids (hybrid speciation). In both speciation types, assortative mating promotes speciation over a transient hybridization stage. We studied mate choice in a hybrid vertebrate complex, the allopolyploid fish Squalius alburnoides. This complex is composed by several genomotypes connected by an intricate reproductive dynamics. We developed a model that predicts the hybrid complex can persist when females exhibit particular mate choice patterns. Our model is able to reproduce the diversity of population dynamic outcomes found in nature, namely the dominance of the triploids and the dominance of the tetraploids, depending on female mate choice patterns and frequency of the parental species. Experimental mate choice trials showed that females exhibit the preferences predicted by the model. Thus, despite the known role of assortative mating in driving speciation, our findings suggest that certain mate choice patterns can instead hinder speciation and support the persistence of hybrids over time without speciation or extinction.
Highlights
Many studies have shown that assortative mating acts as a driver of speciation [1,2,3], especially through the reinforcement of pre-zygotic isolation [4,5,6,7,8]
Most scenarios that favored tetraploidization led populations to be exclusively composed by the self-sustainable PPAA genomotype, whereas the ones favoring the dominance of the PAA genomotype allowed the maintenance of the PA one (Fig 4), derived from the PAA females’ variable preference degree towards type II males (PP genome, P sperm)
The irrelevant role of the initial S. alburnoides genomotype composition over the final equilibrium reached in each simulation reveals that even a low frequency of the PPAA genomotype in a triploid-dominated population may tetraploidize it and even a low frequency of the PAA genomotype in a tetraploid-dominated population may triploidize it
Summary
Many studies have shown that assortative mating acts as a driver of speciation [1,2,3], especially through the reinforcement of pre-zygotic isolation [4,5,6,7,8]. The relationship between assortative mating and hybrid speciation is still not well understood. Hybrid speciation occurs when two species reproduce to form hybrid organisms which over time evolve into a new species, with or without genome multiplication (allopolyploid and homoploid hybrid speciation, respectively) [9, 10]. By recreating the original hybridization events through experimental crosses between the parental species, some empirical studies suggested a key role for mate choice in driving homoploid hybrid speciation [11,12,13]. The role of mate choice in PLOS ONE | DOI:10.1371/journal.pone.0132760. The role of mate choice in PLOS ONE | DOI:10.1371/journal.pone.0132760 July 16, 2015
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