Admixture with cultivated sunflower likely facilitated establishment and spread of wild sunflower (H. annuus) in Argentina

Abstract

ABSTRACTA better understanding of the genetic and ecological factors underlying successful invasions is critical to mitigate the negative impacts of invasive species. Here, we study the invasion history ofHelianthus annuuspopulations from Argentina, with particular emphasis on the role of post-introduction admixture with cultivated sunflower (alsoH. annuus) and climate adaptation driven by large haploblocks. We conducted genotyping-by-sequencing of samples of wild populations as well as Argentinian cultivars and compared them with wild (including related annualHelianthusspecies) and cultivated samples from the native range. We also characterized samples for 11 known haploblocks associated with environmental variation in native populations to test whether haploblocks contributed to invasion success. Population genomics analyses supported two independent geographic sources for Argentinian populations, the central United States and Texas, but no significant contribution of related annualHelianthusspecies. We found pervasive admixture with cultivated sunflower, likely as result of post-introduction hybridization. Genomic scans between invasive populations and their native sources identified multiple genomic regions with evidence of selection in the invaded range. These regions significantly overlapped between the two native-invasive comparisons and showed disproportionally high crop ancestry, suggesting that crop alleles contributed to invasion success. We did not find evidence of climate adaptation mediated by haploblocks, yet outliers of genome scans were enriched in haploblock regions and, for at least two haploblocks, the cultivar haplotype was favored in the invaded range. Our results show that admixture with cultivated sunflower played a major role in the establishment and spread ofH. annuuspopulations in Argentina.