Genomic insights into the local adaptation of spontaneously occurring populations of olive trees (Olea europaea ssp. europaea var. sylvestris) in the Mediterranean Basin

Abstract

Living organisms are increasingly threatened by significant environmental changes, primarily driven by human-induced global alterations. Understanding and forecasting species adaptive responses to these environmental changes is therefore crucial for enhancing conservation efforts. In the Mediterranean Basin (MB), the average temperature is rising at a rate 20% faster than the global average, placing regional biodiversity at heightened risk. The study of local adaptation is thus particularly relevant. In the western MB, spontaneously occurring olive populations consist of both wild olives and admixed resulting of crop-to-wild gene flow. The wild is likely harbouring adaptive genetic variation shaped by local environmental pressures. In this study, we analysed target genomic sequencing data from spontaneously occurring populations (comprising both wild and admixed trees) as well as cultivated olive trees. We performed selective sweep and GEA analyses in wild olives to identify genomic regions associated with environmental variables. Our findings identified signatures of adaptation particularly associated with precipitation and temperature. Notably, admixed individuals retained many wild candidate SNPs in their genomes suggesting that they might retain a certain level of adaptation to their local environment. Those results are in line with recent studies suggesting hybrids could adapt more rapidly to novel environments than their parental populations. Key-words: Local adaptation, selective sweep detection, crop-to-wild gene flow, Olea europaea L., population genomics, genome-environment association