Extraordinarily rapid speciation in a marine fish

Paolo Momigliano, Henri Matias Jokinen, Antoine Fraimout, Ann-Britt Florin, Alf Norkko, Juha Merilä

Research output: Contribution to journalArticleScientificpeer-review

83 Citations (Scopus)

Abstract

Divergent selection may initiate ecological speciation extremely rapidly. How often and at what pace ecological speciation proceeds to yield strong reproductive isolation is more uncertain. Here, we document a case of extraordinarily rapid speciation associated with ecological selection in the postglacial Baltic Sea. European flounders (Platichthys flesus) in the Baltic exhibit two contrasting reproductive behaviors: pelagic and demersal spawning. Demersal spawning enables flounders to thrive in the low salinity of the Northern Baltic, where eggs cannot achieve neutral buoyancy. We show that demersal and pelagic flounders are a species pair arising from a recent event of speciation. Despite having a parapatric distribution with extensive overlap, the two species are reciprocally monophyletic and show strongly bimodal genotypic clustering and no evidence of contemporary migration, suggesting strong reproductive isolation. Divergence across the genome is weak but shows strong signatures of selection, a pattern suggestive of a recent ecological speciation event. We propose that spawning behavior in Baltic flounders is the trait under ecologically based selection causing reproductive isolation, directly implicating a process of ecological speciation. We evaluated different possible evolutionary scenarios under the approximate Bayesian computation framework and estimate that the speciation process started in allopatry similar to 2,400 generations ago, following the colonization of the Baltic by the demersal lineage. This is faster than most known cases of ecological speciation and represents the most rapid event of speciation ever reported for any marine vertebrate.

Original languageEnglish
Pages (from-to)6074–6079
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume114
Issue number23
DOIs
Publication statusPublished - 6 Jun 2017
Externally publishedYes
MoE publication typeA1 Journal article-refereed

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