Intercontinental karyotype–environment parallelism supports a role for a chromosomal inversion in local adaptation in a seaweed fly

• Published in: Proceedings of the Royal Society. B, Biological sciences Vol. 285; no. 1881; p. 20180519
• Main Authors: Mérot, Claire, Berdan, Emma L., Babin, Charles, Normandeau, Eric, Wellenreuther, Maren, Bernatchez, Louis
• Format: Journal Article
• Language: English
• Published: England The Royal Society Publishing 27.06.2018; The Royal Society
• Edition: Royal Society (Great Britain)
• Subjects: 1976; Adaptation; Adaptation, Biological; adult size; alcohol-dehydrogenase locus; Algae; Animals; arlesworth b; balancing selection; Biodiversity; Biologi; Biological Sciences; Canada; chromosomal inversions; Chromosome Inversion; Chromosome rearrangements; Clines; coelopa-frigida; Diptera; Diptera - genetics; Diptera - physiology; drosophila-melanogaster; Ecological monitoring; Ecological studies; Ecology; Environment; Environmental conditions; Environmental factors; Environmental gradient; Environmental Sciences; Europe; Evolution; Evolutionary Biology; Female; Gene polymorphism; genetic-variation; Genetics; Genotyping; Inversion; Inversions; Karyotype; Karyotypes; Life history; Life Sciences & Biomedicine - Other Topics; local adaptation; Male; Microhabitats; Natural populations; p181; parrallelism; Phenotyping; Polymorphism; Population genetics; Population studies; Populations; Recombination; Seaweeds; sexual selection; Specialization; Species diversity; trade-offs; United States; v83; Canada; United States; Europe; North America; local adaptation; parrallelism; chromosomal inversions; balancing selection; environmental gradient; Diptera
• ISSN: 0962-8452; 1471-2954; 1471-2954
• DOI: 10.1098/rspb.2018.0519

Large chromosomal rearrangements are thought to facilitate adaptation to heterogeneous environments by limiting genomic recombination. Indeed, inversions have been implicated in adaptation along environmental clines and in ecotype specialization. Here, we combine classical ecological studies and population genetics to investigate an inversion polymorphism previously documented in Europe among natural populations of the seaweed fly Coelopa frigida along a latitudinal cline in North America. We test if the inversion is present in North America and polymorphic, assess which environmental conditions modulate the inversion karyotype frequencies, and document the relationship between inversion karyotype and adult size. We sampled nearly 2000 flies from 20 populations along several environmental gradients to quantify associations of inversion frequencies to heterogeneous environmental variables. Genotyping and phenotyping showed a widespread and conserved inversion polymorphism between Europe and America. Variation in inversion frequency was significantly associated with environmental factors, with parallel patterns between continents, indicating that the inversion may play a role in local adaptation. The three karyotypes of the inversion are differently favoured across micro-habitats and represent life-history strategies likely to be maintained by the collective action of several mechanisms of balancing selection. Our study adds to the mounting evidence that inversions are facilitators of adaptation and enhance within-species diversity.