Complex evolutionary processes maintain an ancient chromosomal inversion.
Patrik Nosil, Victor Soria-Carrasco, Romain Villoutreix, Marisol De-la-Mora, Clarissa F de Carvalho, Thomas Parchman, Jeffrey L Feder, Zachariah Gompert
Author Information
Patrik Nosil: CEFE, Univ Montpellier, CNRS, EPHE, IRD, Univ Paul Valéry Montpellier 3, Montpellier 34090, France.
Victor Soria-Carrasco: John Innes Centre, Norwich, NR4 7UH, UK.
Romain Villoutreix: CEFE, Univ Montpellier, CNRS, EPHE, IRD, Univ Paul Valéry Montpellier 3, Montpellier 34090, France. ORCID
Marisol De-la-Mora: CEFE, Univ Montpellier, CNRS, EPHE, IRD, Univ Paul Valéry Montpellier 3, Montpellier 34090, France. ORCID
Clarissa F de Carvalho: CEFE, Univ Montpellier, CNRS, EPHE, IRD, Univ Paul Valéry Montpellier 3, Montpellier 34090, France. ORCID
Thomas Parchman: Department of Biology, University of Nevada, Reno, NV 89557.
Jeffrey L Feder: Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556. ORCID
Zachariah Gompert: Department of Biology, Utah State University, Logan, UT 84322. ORCID
Genome re-arrangements such as chromosomal inversions are often involved in adaptation. As such, they experience natural selection, which can erode genetic variation. Thus, whether and how inversions can remain polymorphic for extended periods of time remains debated. Here we combine genomics, experiments, and evolutionary modeling to elucidate the processes maintaining an inversion polymorphism associated with the use of a challenging host plant (Redwood trees) in stick insects. We show that the inversion is maintained by a combination of processes, finding roles for life-history trade-offs, heterozygote advantage, local adaptation to different hosts, and gene flow. We use models to show how such multi-layered regimes of balancing selection and gene flow provide resilience to help buffer populations against the loss of genetic variation, maintaining the potential for future evolution. We further show that the inversion polymorphism has persisted for millions of years and is not a result of recent introgression. We thus find that rather than being a nuisance, the complex interplay of evolutionary processes provides a mechanism for the long-term maintenance of genetic variation.
