Admixture affects the rate and repeatability of experimental adaptation to a stressful environment in Callosobruchus maculatus

Admixture is common in nature, and can serve as a crucial source of adaptive potential through the generation of novel genotype combinations and phenotypes. Conversely, the presence of hybrid incompatibilities can decrease the fitness of hybrids. Due to the pervasiveness of admixture in nature and its potential role in facilitating adaptation, understanding how admixture affects the rate and repeatability of evolution is important for furthering our understanding of evolutionary dynamics. However, few studies have assessed how patterns of evolutionary parallelism in admixed lineages are affected by the presence of strong ecological pressure. In this experiment, we assessed patterns of evolution and parallelism across admixed and non-admixed cowpea seed beetles (Callosobruchus maculatus) during adaptation to a novel, stressful host: lentil. Specifically, we asked (1) whether admixture facilitates adaptation to lentil, (2) whether parallelism was higher in admixed or non-admixed lineages, and (3) to what degree parallelism in admixed lineages was associated with selection on globally adaptive alleles versus epistatic effects and hybrid incompatibilities. We found that admixture facilitated adaptation to lentil, and evolutionary rescue–defined as adaptation that prevents population extinction–occurred in all lineages. The degree of evolutionary parallelism was highest in two admixed lineages, but notable in all lineages. Adaptation to lentil appeared to be driven by selection on alleles that were globally adaptive. However, even during evolutionary rescue in a marginal environment, the purging of hybrid incompatibilities appeared to contribute substantially to evolutionary parallelism in admixed lineages. Supplementary Material File (cmac_main.pdf) - Download - 3.11 MB Information & Authors Information Version history Peer review timeline Published Molecular Ecology Version of Record4 Jun 2025Published Copyright This work is licensed under a Non Exclusive No Reuse License. Collection

Authors Metrics & Citations Metrics Article Usage 381views 250downloads Citations Download citation Amy Springer, Brian Kissmer, Zachariah Gompert. Admixture affects the rate and repeatability of experimental adaptation to a stressful environment in Callosobruchus maculatus. Authorea. 10 March 2025. DOI: https://doi.org/10.22541/au.174161896.68544875/v1 DOI: https://doi.org/10.22541/au.174161896.68544875/v1 If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download. For more information or tips please see 'Downloading to a citation manager' in the Help menu.