Abstract Detail

Hybrids and Hybridization

Andreev, Victor [1], Straub, Shannon [2], Fishbein, Mark [3].

Asymmetry in gene flow between Asclepias speciosa Torr. and A. syriaca L.

Asclepias speciosa (showy milkweed) and A. syriaca (common milkweed) are morphologically similar species among the American milkweeds, a group that underwent fast adaptive radiation during the late Cenozoic. These species are phylogenetically close and form a small clade with a third species (A. ovalifolia). Asclepias speciosa is the most common milkweed species of the western part of North America, while A. syriaca is the most common in the east. Currently, these species meet and hybridize on the Great Plains of the US. The extensive hybrid zone spans for over 1000 km, from central Kansas north to the Dakotas and Minnesota. It is known that hybridization can alter the genetic makeup of participating species, but the extent of this process in plants, and how far introgressed variation can permeate into species ranges, are still largely unknown. Preliminary study of the extent and amount of introgression in a range-wide sample of A. speciosa and A. syriaca that utilizes 5507 SNPs extracted from a HybSeq dataset of 3300 nuclear loci, showed that introgression in A. syriaca is mostly restricted to the hybrid zone. At the same time, introgression in A. speciosa is more widespread both genetically and geographically and extends at least as far as Montana and Utah. Most of the A. speciosa individuals demonstrate relatively high amount of introgression (up to 35 % of the analyzed alleles), while the amount of introgression in A. syriaca is noticeably lower. However, the resolution of the analysis may be restricted by the relatively low number of the analyzed samples. The observed pattern of shared variation can be also explained by incomplete linage sorting that one would expect in recently diverged species. Comparative analysis of differentiation and genetic variation in sympatric and allopatric populations of A. syriaca and A. speciosa demonstrated that the observed pattern is consistent with introgressive hybridization. This research sheds light on the role that hybridization plays in generating shared genetic diversity in milkweed species, and contributes to our understanding of the geographic extent of hybridization in plants, and its possible impact on adaptive introgression.

1 - Oklahoma State University, 301 Physical Sciences, 301 Physical Sciences, Stillwater, OK, 74078, United States
2 - Hobart And William Smith Colleges, Department Of Biology, 300 Pulteney St., Geneva, NY, 14456, United States
3 - Oklahoma State University, Dept Of Plant Biology, Ecology & Evolution, 301 Physical Science, Stillwater, OK, 74078, United States

Keywords:
hybridization
gene flow
milkweeds
Asclepias.

Presentation Type: Poster
Session: P, Hybrids and Hybridization Posters
Location: Virtual/Virtual
Date: Wednesday, July 29th, 2020
Time: 5:00 PM Time and date to be determined
Number: PHH003
Abstract ID:436
Candidate for Awards:None