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    A thorny tale: The origin and diversification of Cirsium (Compositae)
    (Academic Press Inc Elsevier Science, 2025) Moreyra, Lucia D.; Susanna, Alfonso; Calleja, Juan Antonio; Ackerfield, Jennifer R.; Arabaci, Turan; Blanco-Gavalda, Carme; Brochmann, Christian
    Widely distributed plant genera offer insights into biogeographic processes and biodiversity. The CarduusCirsium group, with over 600 species in eight genera, is diverse across the Holarctic regions, especially in the Mediterranean Basin, Southwest Asia, Japan, and North America. Despite this diversity, evolutionary and biogeographic processes within the group, particularly for the genus Cirsium, remain underexplored. This study examines the biogeographic history and diversification of the group, focusing on Cirsium, using the largest molecular dataset for the group (299 plants from 251 taxa). Phylogenomic analyses based on 350 nuclear loci, derived from target capture sequencing, revealed highly resolved and consistent phylogenetic trees, with some incongruences likely due to hybridization and incomplete lineage sorting. Ancestral range estimations suggest that the Carduus-Cirsium group originated during the Late Miocene in the Western Palearctic, particularly in the Mediterranean, Eastern Europe, or Southwest Asia. A key dispersal event to tropical eastern Africa around 10.7 million years ago led to the genera Afrocarduus and Afrocirsium, which later diversified in the Afromontane region. The two subgenera of Cirsium-Lophiolepis and Cirsium-began diversifying around 7.2-7.3 million years ago in the Western Palearctic. During the Early Pliocene, diversification rates increased, with both subgenera dispersing to Southwest Asia, where extensive in situ diversification occurred. Rapid radiations in North America and Japan during the Pleistocene were triggered by jump-dispersals events from Asia, likely driven by geographic isolation and ecological specialization. This added further layers of complexity to the already challenging taxonomic classification of Cirsium.Keywords: Biogeography; Carduinae; Cirsium; Diversification; North Hemisphere; Target-enrichment; Taxonomy.
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    A prickly puzzle: Generic delimitations in theCarduus-Cirsiumgroup (Compositae: Cardueae: Carduinae)
    (Wiley, 2020) Ackerfield, Jennifer; Susanna, Alfonso; Funk, Vicki; Kelch, Dean; Park, Daniel S.; Thornhill, Andrew H.; Yildiz, Bayram
    Generic delimitations within the cosmopolitanCarduus-Cirsiumgroup (i.e., thistles) have a long history of taxonomic confusion and debate. We present the most comprehensive molecular phylogeny of the group to date to test generic limits, reconstruct the evolution of pappus type, and elucidate the role of chromosomal evolution. We offer two solutions for the recognition of monophyletic genera: (1) consolidate all taxa into one large genus (CarduusorCirsium), or (2) recognize each major clade as a genus (Carduus,Cirsium,Eriolepis,Notobasis,Picnomon,Silybum, andTyrimnus). Under the second proposal, the cryptic genusEriolepisis segregated fromCirsium, and the AfricanCarduusare included withinCirsium. The best diagnosable morphological character to delimit the genera is pollen type, which is not practical in field-based application. We caution that prior to implementing either solution, a thorough, comprehensive morphological analysis of all current members ofCirsiumsect.Epitrachys(= genusEriolepis) be completed. Future morphological studies may find additional achene or leaf surface characters that could be used for practical field identification of the segregate genera. The data show that the plumose pappus state is symplesiomorphic for the group, with one transition to barbellate pappus, likely followed by a reversal to its ancestral state as the group colonized Eurasia. The data are consistent with a North African origin in the region of the Mediterranean and a single colonization event to North America. An ancestral chromosome state ofn= 17 is hypothesized for the group, and a descending dysploidy series inCarduusis hypothesized to correspond with the aridification of the Mediterranean region. TheCarduus-Cirsiumgroup highlights the difficulty of delimiting morphologically similar, cryptic genera.