Format: ORAL

Hanno Schaefer1, Gentaro Shigita1, Edgardo M. Ortiz1

1 Technical University of Munich, Freising, Germany

Cucurbitales currently includes eight plant families with diversity centers in the Tropics: Anisophylleaceae, Apodanthaceae, Begoniaceae, Coriariaceae, Corynocarpaceae, Cucurbitaceae, Datiscaceae, and Tetramelaceae. These families comprise 109 genera with more than 3,100 species. Morphologically, the taxa of Cucurbitales are rather diverse ranging from the holoparasitic Apodanthaceae, to annual and perennial herbs in Datiscaceae and Begoniaceae, to trees and shrubs in Anisophylleaceae, Corynocarpaceae, Coriariaceae, and Tetramelaceae and finally to woody or herbaceous climbers and creepers in Cucurbitaceae. Based on target-capture and whole genome sequencing data of 125 Cucurbitales samples representing all 102 genera currently accepted in the order, we inferred coalescent species trees and networks. We infer monophyletic and well supported families and tribes. The holoparasitic Apodanthaceae are placed outside Cucurbitales. For the remaining seven Cucurbitales families, the relationships vary. The best supported alternative shows a grade Coriariaceae + Corynocarpaceae, followed by Anisophylleaceae and then the remaining clades, but there is also considerable gene tree and site support for a clade Anisophylleaceae, Corynocarpaceae + Coriariaceae, rest. The woody Tetramelaceae is resolved as sister to the herbaceous families Begoniaceae and Datiscaceae but again there is also considerable gene support for the two alternative combinations within the triplet. Within Cucurbitaceae, there is gene support for different relationships between the tribes but the best supported topology is a clade Actinostemmateae + Gomphogyneae grouping as sister to the remaining tribes. A network analysis revealed ancient reticulation within and between Benincaseae, Coniandreae, and Cucurbiteae, suggesting that Benincaseae are the result of ancestral hybridization between Coniandreae and Cucurbiteae. A similar pattern of reticulation is found between Schizopeponeae and Sicyoeae. Finally, there is evidence for recent reticulation within Coniandreae and within Thladiantheae, indicating frequent hybridization events in the evolutionary history of Cucurbitaceae. We present a revised taxonomic classification of Cucurbitales and discuss the implications for character evolution in the group.