Abstract Detail

Population Genetics/Genomics

Mitchell, Nora [1], Nguyen, Thu [2], Bylander, Michael Robert [2], McNabb, Lydia [2], Leonardson, Aleks [2].

Minimal evidence for contemporary introgression in closely related sunflowers of Wisconsin.

Hybridization and introgression are increasingly recognized as important evolutionary forces at both the macro and microevolutionary scales. Historical documentation of hybridization among close species has largely been dependent on observations of morphological intermediacy, yet the frequency of these admixture events, their genomic support, and their role in influencing contemporary population structure have not always been investigated. Here we further examine observations by R.W. Long and others into hybridization among sunflower species in the United States Midwest, focusing on the perennial sunflowers Helianthus giganteus L., H. grosseserratus M.Martens, and H. maximiliani Schrad. across the state of Wisconsin. We ask 1) Is there evidence of population differentiation in widespread sunflower species in Wisconsin? 2) Is there evidence for contemporary introgression in these species? 3) Are molecular and morphological differentiation related?
We sampled DNA and leaf traits from 20 populations across these three species of Helianthus, found in natural or restored populations across Wisconsin (and into Minnesota), as well as individuals grown from commercial seed sources in common gardens. We use genotyping-by-sequencing (GBS) and bioinformatics processing to obtain genomic information on 3087 single nucleotide polymorphisms (SNPs) across 334 individuals. We use AMOVA, fastStructure, ADMIXTURE, and PCA to assess overall population structure. We explicitly test for introgression or reticulation using ABBA-BABA tests, f4 tests, and SplitsTree analyses. Finally, we compare morphological and molecular differentiation using Mantel tests.
We overall find little evidence for widespread introgression among these three species of Helianthus in Wisconsin, although there is some evidence for hybridization between H. giganteus and H. maximiliani in one location. Species are genomically well-differentiated, while within-population diversity explains a greater proportion of total diversity than populations within speciesdo. Moreover, morphological and molecular differentiation are positively related both within and across species. Although cases of hybridization have been documented historically (and contemporarily), these instances may not have long-lasting impacts on population genetic patterns.

1 - University Of Wisconsin - Eau Claire, Department Of Biology, 651 University Drive, 330 Phillips Hall, Eau Claire, WI, 54701, United States
2 - University of Wisconsin - Eau Claire, 651 University Drive, 330 Phillips Hall, Eau Claire, WI, 54701, United States

Keywords:
population genomics
introgression
sunflower
hybridization.

Presentation Type: Oral Paper
Number: PGG3001
Abstract ID:61
Candidate for Awards:Margaret Menzel Award