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Abstract Detail

Hybrids and Hybridization

Andreev, Victor [1], Olson-Manning, Carrie [2], Puzey, Joshua [3], Fishbein, Mark [1].

Hybridization between Asclepias speciosa Torr. and A. syriaca L. on the Great Plains: small gene flow casting a long shadow.

Asclepias speciosa and A. syriaca (Apocynaceae) are two morphologically similar prairie milkweeds. Asclepias speciosa is the most common in the western part of North America, while A. syriaca is the most common in the east. These species diverged in the late Cenozoic and are thought to be experiencing secondary contact that led to extensive hybridization on the Great Plains. The resulting hybrid zone spans for over 1000 km, from central Kansas to the Dakotas and Minnesota, which makes it the most widespread hybrid zone in North American milkweeds. This hybrid zone is an excellent natural setup for studying the magnitude and significance of introgression in plant systems, which is still not very well understood. Genome-wide single-nucleotide DNA polymorphisms (SNPs) were used to evaluate the level of variation within and between A. speciosa and A. syriaca, quantify the amount of variation transferred between these species, and estimate geographic spread of introgressed alleles into the species ranges. Plastome data were used to ascertain the prevalent direction of hybridization. Phenotypic classification of plants sampled in the hybrid zone based on vegetative and floral morphology is consistent with assignment of individuals by Bayesian clustering in STRUCTURE using nuclear SNPs. At the same time, clustering of the same individuals with one of the groups in a haplotype network based on plastome data indicate several chloroplast capture events. The STRUCTURE analysis also revealed that a few A. speciosa individuals show admixture from A. syriaca as far from the hybrid zone as Utah and Idaho, and for A. syriaca admixture was found as far away as New York. Despite the impressive geographic extent, the total amount of introgression outside of the hybrid zone is relatively modest and rarely exceeds 10% admixture in either species outside the hybrid zone. Nevertheless, introgression has led to an increase in genetic diversity (He) in A. speciosa by 3.3 % and in A. syriaca by 9.3 %.

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1 - Oklahoma State University, Dept Of Plant Biology, Ecology & Evolution, 301 Physical Science, Stillwater, OK, 74078, United States
2 - Augustana University, Biology Department, 2001 S Summit Ave, Sioux Falls, SD, 57197, USA
3 - College Of William And Mary, Biology Dept., 540 Landrum Dr., Williamsburg, VA, 23185, United States

gene flow

Presentation Type: Oral Paper
Session: HH1, Hybrids and Hybridization I
Location: /
Date: Wednesday, July 21st, 2021
Time: 10:15 AM(EDT)
Number: HH1002
Abstract ID:675
Candidate for Awards:Margaret Menzel Award

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