A phylogenomic analysis and revised infrageneric classification of Thesium (Santalaceae).
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TAXON_-_2026_-_Lombard_-_A_phylogenomic_analysis_and_revised_infrageneric_classification_of_Thesium__Santalaceae.pdf.crdownload
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74.01 MB
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Resource type
Journal article
Date published
June 25, 2026
Abstract
A phylogenomic analysis and revised infrageneric classification of Thesium (Santalaceae) is presented based on targeted enrichment using the Angiosperms353 probe set. This first targeted sequencing study includes 137 samples representing 106 species (approximately 32% of the genus). Our results provide substantially improved resolution compared to previous studies that utilised only a few gene regions, with an almost fully supported backbone topology. Thesium (including Austroamericium, Chrysothesium, Kunkeliella, and Thesidium) is confirmed as monophyletic and sister to a clade containing Lacomucinaea and Osyridicarpos. We recognise six monophyletic subgenera with full or strong support: T. subg. Hagnothesium, T. subg. Thesium, T. subg. Spinosa (newly described), T. subg. Discothesium (with revised circumscription), T. subg. Frisea, and T. subg. Psilothesium. We found T. subg. Discothesium as previously delineated to be paraphyletic and describe a new subgenus, T. subg. Spinosa, to ensure monophyly of all subgenera. We formally recognise 18 sections in Thesium, of which 8 are newly described and 2 are raised from lower ranks. Our phylogenetic clades show a strong biogeographic signal and despite sporadic morphological synapomorphies, most subgenera and sections can be distinguished by a combination of their distribution and morphology. We provide the first genetic evidence of potential hybridisation in Thesium paving the way for further exploration of this long-hypothesised compounding factor. This study provides a robust framework for future taxonomic, biogeographic, and evolutionary studies of this diverse and problematic genus.
Project(s)
Priority 1: Ecosystem Stewardship
Funder
| Funder name | Awards |
Botanical Education Trust, South Africa | |
Bentham-Moxon Trust, United Kingdom | |
Royal Botanic Gardens, Kew, United Kingdom | Emily Holmes Memorial Scholarship |
Journal title
TAXON
Volume
75
Issue
3
Article number
e70171
Publisher
Published by John Wiley & Sons Ltd on behalf of International Association for Plant Taxonomy.
Place of publication
UK
ISSN
0040-0262
eISSN
1996-8175
Date accepted
February 11, 2026
Official URL
Rights statement
In Copyright
Additional information
IF = 1.9 (2025)