Monophyly of the Convolvulaceae and circumscription of their major lineages based on DNA sequences of multiple chloroplast loci

Abstract

Convolvulaceae, a large family of worldwide distribution, exhibit a rich diversity of morphological characteristics and ecological habitats. Previous efforts to systematize this diversity without a cladistic phylogenetic framework have disagreed on the circumscription of the family as well as tribal composition and relationship. In order to circumscribe the family and assess the relationships among its major lineages, a broad data set was constructed containing representatives of all ten recognized tribes of Convolvulaceae plus representatives of putatively related families within Asteridae. This is done by using four chloroplast regions: rbcL, atpB, psbE-J operon, and trnL-trnF intron/spacer. The results indicate that Convolvulaceae are monophyletic and sister to Solanaceae. Two of the three groups that have been proposed previously as separate families, Cuscuta and Dichondreae, are nested within the Convolvulaceae in this analysis, and the third, Humbertia, is the sister to all other members of the family. The exact position of Cuscuta could not be ascertained, but some alternatives were rejected with confidence. The study identified several distinct monophyletic groups, some of which correspond to earlier taxonomic treatments. Close relationships of tribes Hildebrandtieae with Cresseae and Ipomoeeae with Argyreieae (forming Echinoconieae) were confirmed. The polyphyly of Merremieae, Convolvuleae, Poraneae, and Erycibeae is first identified in this study.