Ancient hybridization and phylogenetic discordance: Exploring evolutionary complexity in Asteraceae

Premise: Conflicting phylogenetic signals are common in plant phylogenomics and often reflect evolutionary histories shaped by processes like hybridization, incomplete lineage sorting, and whole-genome duplication (WGD). We aimed to identify and assess these complex processes in the hyper-diverse family Asteraceae to offer insight into the underlying causes of phylogenetic discordance. Methods: We used new and existing Hyb-Seq and transcriptome data to explore phylogenetic discordance by testing for nuclear/plastid incongruences, WGD, and reticulation. We present a tutorial detailing the execution of complex bioinformatic analyses to increase transparency, facilitate reproducibility, and support advancements in the field of plant evolution (https://github.com/erika-r-moore/Ellestad_etal_2025_APPS_Hybridizations). Results: We uncovered extensive discordance among nuclear gene trees and deep reticulation events, particularly among South American lineages. Signals of WGD were found across the family but were often difficult to interpret, likely due to variation in data completeness, the complexity of the events, and their ancient origins. Discussion: Our study and tutorial, along with a growing body of phylogenomic research, emphasize the role of reticulation and WGD in the evolution of large, diverse clades, while also underscoring the challenges. We anticipate continued advancements in theoretical approaches that will further enhance empirical studies in reticulate evolution.