Genomic evidence of introgression and adaptation in a model subtropical tree species, Eucalyptus grandis

The genetic consequences of adaptation to changing environments can be deciphered using landscape genomics, which may help predict species' responses to global climate change. Towards this, we used genome-wide SNP marker analysis to determine population structure and patterns of genetic differentiation in terms of neutral and adaptive genetic variation in the natural range of Eucalyptus grandis, a widely cultivated subtropical and temperate species, serving as genomic reference for the genus. We analysed introgression patterns at subchromosomal resolution using a modified ancestry mapping approach and identified provenances with extensive interspecific introgression, suggesting early hybrid speciation in response to increased aridity. Furthermore, we describe potentially adaptive genetic variation as explained by environment-associated SNP markers, which also led to the discovery of a large structural variant. Finally, we show that genes linked to these markers are enriched for biotic and abiotic stress responses.