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Ackerfield, Jennifer [1], Siniscalchi, Carol [2], Mandel, Jennifer [3].

Hyb-Seq resolves relationships among Cirsium, a recently radiated group of Compositae in North America.

Cirsium (i.e., “thistles”) is one of the most taxonomically challenging groups of Compositae (Asteracea)e) in North America. Cirsium is also hypothesized to have recently radiated within North America during the Pleistocene (2-5 MYR). Thus, previous analyses using traditional Sanger sequencing were only partly able to resolve relationships within the group. However, the advent of modern phylogenomic methods has enabled evolutionary biologists to answer questions related to these recently diversified lineages. Through the use of high-throughput sequencing (HTS) techniques, we are now able to analyze millions of basepairs of DNA characters versus the relatively few (generally 4000-10,000) available using traditional Sanger sequencing technology. For this study, next-generation sequencing was used to test whether currently hypothesized species variety complexes within Cirsium constitute monophyletic lineages. Hybridization-sequencing (Hyb-Seq) is a combination of target enrichment and genome skimming and uses ‘baits’ (probes) to enrich specific target loci from DNA. This method allows for data collection of low-copy nuclear genes and high-copy genomic targets for evolution and phylogenetic studies. This presentation will focus on the Hyb-Seq results as they pertain to the polymorphic C. eatonii (mountaintop thistle) varietal complex. Currently, C. eatonii is treated as a single species with seven varieties. It is hypothesized to have originated from a common lowland progenitor and isolated on mountain tops in the Rocky Mountain and Intermountain Region, where varieties diversified to the present extent. However, the results from next-generation sequencing demonstrate that C. eatonii does not constitute a monophyletic lineage. I will highlight the use of not only genetic data, but also morphological, ecological, and geographical evidence to sort out the resulting taxonomic mess. Some good old detective work was even applied to make sense of confounding lines of evidence. The extensive taxonomic difficulty within Cirsium is hypothesized to be the result of several factors: 1) previously undescribed taxa, 2) inadequate representation of taxa from herbarium specimens, 3) phenotypic convergence, and 4) hybridization and/or incomplete lineage sorting. The previous results using traditional Sanger sequencing will also be compared with the next-generation sequencing results. Hyb-Seq is shown to be useful in resolving relationships among recently radiated species in Compositae.

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1 - Denver Botanic Gardens, Research and Conservation, 909 York St., Denver, CO, 80206, United States
2 - 500 Louisville St, Apt 2, Starkville, MS, 39759, United States
3 - University Of Memphis, Biological Sciences, 3744 Walker Ave, 339 Ellington Hall, Memphis, TN, 38152, United States


Presentation Type: Oral Paper
Session: PHYLOII, Phylogenomics II
Location: Virtual/Virtual
Date: Tuesday, July 20th, 2021
Time: 3:00 PM(EDT)
Number: PHYLOII001
Abstract ID:276
Candidate for Awards:None

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