Abstract Detail


Moore, Erika [1], Mandel, Jennifer [2].

Reconstructing evolutionary relationships in the genus Packera (Asteraceae: Senecioneae).

Senecioneae, the largest tribe in the Asteraceae family, comprises about 150 genera and 3,500 species. Within Senecioneae, the North American genus Packera (subtribe Senecioninae) has at least 64 described species and varieties, though the number is up to 88 or higher depending on the source. Packera was previously included in the genus Senecio as the informal group known as “aureoid senecios” by Asa Gray. They were then distinguished as the new genus Packera in 1976 by Á. Löve & D. Löve based on different base chromosome numbers (x=22,23), various morphological differences, and molecular phylogenetic data. Species boundaries in Packera are imprecise and taxonomy within Packera remains complex due to the species’ ability to easily hybridize, and because polyploidy is common throughout the genus, with roughly 40% of taxa being polyploids. The goal of this study is to reconstruct evolutionary relationships in Packera by generating a robust nuclear and plastid phylogeny. By doing so, we will investigate: 1) is Packera, as currently circumscribed, monophyletic and 2) do plastid and nuclear phylogenies share the same topologies? To address these questions, we employed targeted sequence enrichment methods combined with next generation sequencing (NGS) on a nearly complete sampling of the genus. Thus far, 85 out of the 88 taxa of Packera, as well as 24 outgroup species (total = 109 taxa), have been sequenced to reconstruct nuclear and plastid phylogenetic relationships. Both nuclear and plastid phylogenies indicate that the genus Packera is not monophyletic with some Packera species clustering in a Senecio outgroup clade. Additionally, both the nuclear and plastid phylogenies are incongruent when comparing species’ topologies, indicating that the nuclear and plastid genes have unique evolutionary histories. Finally, the nuclear phylogeny is not highly supported with ~50% of nodes having high support (≥ 0.97LPP). Given the widespread hybridization and introgression reported in this genus, we hypothesize that the low support and some unexpected species’ placements may be explained by historical reticulation and genome duplication events, though further work is needed. Even so, our study represents the largest and most completely sampled Packera phylogenies to date. Additionally, our findings exemplify the need to study the effects of hybridization, introgression, and polyploidy on species diversification in a complex group.

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1 - University Of Memphis, Biological Sciences, 3700 Walker Ave, 322 Ellington Hall, Memphis, TN, 38152, United States
2 - University Of Memphis, Biological Sciences, 3700 Walker Ave, 339 Ellington Hall, Memphis, TN, 38152, United States

nuclear genes

Presentation Type: Oral Paper
Number: PHYLO I009
Abstract ID:138
Candidate for Awards:None

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