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Timing strains of the marine insect Clunio marinus diverged and persist with gene flow
Author(s) -
Kaiser Tobias S.,
von Haeseler Arndt,
TessmarRaible Kristin,
Heckel David G.
Publication year - 2021
Publication title -
molecular ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.619
H-Index - 225
eISSN - 1365-294X
pISSN - 0962-1083
DOI - 10.1111/mec.15791
Subject(s) - biology , sympatric speciation , sympatry , gene flow , ecology , reproductive isolation , ecological speciation , ecological niche , range (aeronautics) , niche , evolutionary biology , genetic divergence , genetic variation , gene , genetics , population , habitat , demography , materials science , sociology , genetic diversity , composite material
Genetic divergence of populations in the presence of gene flow is a central theme in speciation research. Theory predicts that divergence can happen with full range overlap – in sympatry – driven by ecological factors, but there are few empirical examples of how ecologically divergent selection can overcome gene flow and lead to reproductive isolation. In the marine midge Clunio marinus (Diptera: Chironomidae) reproduction is ecologically restricted to the time of the lowest tides, which is ensured through accurate control of development and adult emergence by circalunar and circadian clocks. As tidal regimes differ along the coastline, locally adapted timing strains of C. marinus are found in different sites across Europe. At the same time, ecologically suitable low tides occur at both full and new moon and twice a day, providing C. marinus with four nonoverlapping temporal niches at every geographic location. Along the coast of Brittany, which is characterized by a steep gradient in timing of the tides, we found an unusually large number of differentially adapted timing strains, and the first known instances of sympatric C. marinus strains occupying divergent temporal niches. Analysis of mitochondrial genotypes suggests that these timing strains originated from a single recent colonization event. Nuclear genotypes show strong gene flow, sympatric timing strains being the least differentiated. Even when sympatric strains exist in nonoverlapping temporal niches, timing adaptations do not result in genome‐wide genetic divergence, suggesting timing adaptations are maintained by permanent ecological selection. This constitutes a model case for incipient ecological divergence with gene flow.

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