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Straub, Shannon [1], Wagner, Carl [2], Boutte, Julien [3], Fishbein, Mark [4].

Phylogenomics of a clade of temperate North American milkweeds based on extensive sampling of individuals within species.

American milkweeds (Asclepias, Apocynaceae) are a recent, rapid evolutionary radiation of ca. 130 species that are well known for their interactions with monarch butterfly larvae and other insect herbivores that are influenced by host plant chemistry. Low levels of DNA sequence variation in combination with high levels of incomplete lineage sorting (ILS), and some limited introgression, have made understanding the evolutionary relationships among these species difficult. In this study, we attempted to untangle these confounding factors through phylogenomic analysis of Hyb-Seq data (including ca. 3,300 single-copy nuclear genes and whole plastomes) from many individuals per species (n = 4 – 31) comprising a clade of 15 temperate ingroup species. These include some of the most abundant, ecologically important, and familiar North American species, including common milkweed (Asclepias syriaca), showy milkweed (Asclepias speciosa), butterfly weed (Asclepias tuberosa), and poke milkweed (A. exaltata). The clade also contains species of conservation concern, such as wooly milkweed (A. lanuginosa). The plastome phylogeny indicated that for 10 species, the plastomes from all sampled individuals formed reciprocally monophyletic groups. The phylogenetic patterns recovered for three other species (A. amplexicaulis, A. exaltata, and A. obovata) can be explained by ILS alone, while hybridization and ILS together explain the plastome relationships of A. lanceolata and A. rubra. Species relationships inferred from nuclear data show more complex patterns and strongly conflict with the plastome topology. However, the nuclear species tree aligns better with expectations of relationships based on morphology.

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1 - Hobart and William Smith Colleges, Department of Biology, 300 Pulteney Street, Geneva, NY, 14456, USA
2 - Brandeis University, Biology Department, 415 South Street, Waltham, MA, 02453, USA
3 - A2Bio2, 498 Chemin de Bouscaron, Molleges, 13940, France
4 - Oklahoma State University, Dept Of Plant Biology, Ecology & Evolution, 301 Physical Science, Stillwater, OK, 74078, United States

species tree
low-copy nuclear loci
incomplete lineage sorting

Presentation Type: Oral Paper
Session: PHYLOIV, Phylogenomics IV
Location: Virtual/Virtual
Date: Friday, July 23rd, 2021
Time: 1:30 PM(EDT)
Number: PHYLOIV005
Abstract ID:822
Candidate for Awards:None

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