Abstract Detail

Population Genetics/Genomics

Zhang, Jianqiang [1], Rieseberg, Loren [2].

Intraspecific geographic divergence within Helianthus niveus (Asteraceae) and the status of two new morphotypes from Mexico.

Wild germplasm are valuable sources of beneficial alleles for crop improvement; therefore, collecting and characterizing the genetic diversity of crop wild relatives can contribute importantly to sustainable crop production and food security. Wild sunflower Helianthus niveus is partially cross-compatible with the cultivated sunflower (H. annuus) and is known for its high seed oil content and resistance to biotic and abiotic stresses, especially drought. Here we assess patterns of genetic variation and divergence among three previously described subspecies (subsp. niveus, subsp. canescens, and subsp. tephrodes), as well as two new morphotypes of H. niveus recently discovered in extreme drought and dune habitats in Baja California, Mexico. We measured 50 plants (10 for each intra-specific taxon) growing in a common garden for 27 morphological traits, and conducted Principle Components Analysis (PCA) to assess patterns of phenotypic variation. Genome size of each accession was determined using flow cytometry. Pollen viability of first generation hybrids between taxa was tested to infer the strength of intrinsic postzygotic reproductive barriers. Finally, genotyping by sequencing (GBS) data were used to investigate the genetic structure and phylogenetic relationships among the previously described subspecies and new morphotypes. Intraspecific genetic and phenotypic divergence of H. niveus populations closely tracks their geographical distribution. Subspecies niveus is phenotypically, genetically and reproductively distinct from the other two subspecies, and has a larger genome size; therefore, it probably should be regarded as a full species. ABBA-BABA tests revealed substantial introgression between subsp. canescens and its sympatric congener H. petiolaris, which might contribute to their morphological similarities. The two new morphotypes collected in Mexico represent local ecotypes of subsp. niveus that occur in extreme drought and dune environments. Mantel tests showed a strong positive correlation between genetic and geographic distances. We conclude that geographic isolation is primarily responsible for intra-specific genomic divergence within H. niveus, while patterns of phenotypic variation appear to have been shaped by ecological selection and interspecific introgression.

1 - University of British Columbia, Department of Botany, Vancouver, BC, V6T 1Z4, Canada
2 - University Of British Columbia, Department Of Botany, 6270 University Blvd, Vancouver, BC, V6T 1Z4, Canada

Keywords:
Helianthus niveus
species divergence
phylogeny
population genetics.

Presentation Type: Oral Paper
Session: POPGEN2, Population Genetics/Genomics II
Location: Tucson H/Starr Pass
Date: Wednesday, July 31st, 2019
Time: 3:45 PM
Number: POPGEN2009
Abstract ID:472
Candidate for Awards:None