Phylogenetic relationships in the order Cucurbitales and a new classification of the gourd family (Cucurbitaceae)

Abstract

We analysed phylogenetic relationships in the order Cucurbitales using 14 DNA regions from the three plant genomes: the mitochondrial nad1 b/c intron and matR gene, the nuclear ribosomal 18S, ITS1‐5.8S‐ITS2, and 28S genes, and the plastid rbcL, matK, ndhF, atpB, trnL, trnL‐trnF, rpl20‐rps12, trnS‐trnG and trnH‐psbA genes, spacers, and introns. The dataset includes 664 ingroup species, representating all but two genera and over 25% of the ca. 2600 species in the order. Maximum likelihood analyses yielded mostly congruent topologies for the datasets from the three genomes. Relationships among the eight families of Cucurbitales were: (Apodanthaceae, Anisophylleaceae, (Cucurbitaceae, ((Coriariaceae, Corynocarpaceae), (Tetramelaceae, (Datiscaceae, Begoniaceae))))). Based on these molecular data and morphological data from the literature, we recircumscribe tribes and genera within Cucurbitaceae and present a more natural classification for this family. Our new system comprises 95 genera in 15 tribes, five of them new: Actinostemmateae, Indofevilleeae, Thladiantheae, Momordiceae, and Siraitieae. Formal naming requires 44 new combinations and two new names in Cucurbitaceae.