Journal
EVOLUTION
Volume 68, Issue 11, Pages 3166-3183Publisher
OXFORD UNIV PRESS
DOI: 10.1111/evo.12502
Keywords
Adaptation; balancing selection; genetic polymorphism; invasive species; marginal overdominance; temporally varying environment
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Funding
- National Science Foundation [NSF DEB-0448827, DEB-0745828, DEB-1050565]
- NSF
- Directorate For Geosciences
- Division Of Ocean Sciences [1046372] Funding Source: National Science Foundation
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Maintenance of genetic variation at loci under selection has profound implications for adaptation under environmental change. In temporally and spatially varying habitats, non-neutral polymorphism could be maintained by heterozygote advantage across environments (marginal overdominance), which could be greatly increased by beneficial reversal of dominance across conditions. We tested for reversal of dominance and marginal overdominance in salinity tolerance in the saltwater-to-freshwater invading copepod Eurytemora affinis. We compared survival of F1 offspring generated by crossing saline and freshwater inbred lines (between-salinity F1 crosses) relative to within-salinity F1 crosses, across three salinities. We found evidence for both beneficial reversal of dominance and marginal overdominance in salinity tolerance. In support of reversal of dominance, survival of between-salinity F1 crosses was not different from that of freshwater F1 crosses under freshwater conditions and saltwater F1 crosses under saltwater conditions. In support of marginal overdominance, between-salinity F1 crosses exhibited significantly higher survival across salinities relative to both freshwater and saltwater F1 crosses. Our study provides a rare empirical example of complete beneficial reversal of dominance associated with environmental change. This mechanism might be crucial for maintaining genetic variation in salinity tolerance in E. affinis populations, allowing rapid adaptation to salinity changes during habitat invasions.
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