Detecting Introgression in Helianthus Populations in Wisconsin

Abstract

Introgression is the incorporation of genetic material from one species into another and can contribute to evolution. The goal of this research was to detect if introgression occurred in population of three sunflower species in Wisconsin, Helianthus giganteus, H. grosseserratus, and H. maximiliani. Previous studies have detected introgression in other sunflower species and there are both historical records of morphological intermediates and evidence for hybridization from crossing experiments for these species. I used the bioinformatics pipeline ipyrad on raw RADseq data from 357 samples to clean, align, and detect SNPs across the dataset. I then used TreeMix to create a maximum likelihood phylogenetic tree for the set of populations to look for evidence for introgression. I found no detectable introgression among the sunflower populations in this study. Instead, it appears that two samples of unknown populations are not of hybrid origin, and instead likely belong to Helianthus giganteus.