Evolutionary trends, major lineages, and new generic limits in the dioecious group of the tribe vanguerieae (rubiaceae): Insights into the evolution of functional dioecy
2009 (English)In: Annals of the Missouri Botanical Garden, ISSN 0026-6493, Vol. 96, no 1, 161-181 p.Article in journal (Refereed) Published
New generic circumscriptions of the Paleotropical tribe Vanguerieae in the subfamily Ixoroideae s.l. (Rubiaceae) have recently been established its a result of it series of phylogenetic studies conducted by Lantz and Bremer. The genus Canthium Lam. was shown in their study to be highly polyphyletic, and a largely dioecious group was for the first little identified within Vanguerieae. dioecious group sensu Lantz and Bremer comprises about 140 species classified in eight genera: Canthium (Canthium subg. Bullockia Bridson), Dinocanthium Bremek., Leroya Cavaco, Neoleroya Cavaco, Peponidium (Baill.) Arenes, Pseudopeponidium Homolles ex Arenes, Pyrostria Comm. ex Juss., and Scyphochlamys Balf. f. We sequenced 79 Vanguerieae taxa and performed phylogenetic analyses based on sequence data from two nuclear (EN and ITS) markers to: (1) pinpoint the phylogenetic positions of the Comorean and Indian Ocean Canthium and the Southeast Asian Canthium confertum Korth. group in Vanguerieae; (2) evaluate the phylogenetic utility of three taxonomic characters (bract type, locule number, and fruit shape) previously and currently used for delimiting genera in the dioecious group; and (3) assess the evolution of functional dioecy in Vanguerieae. The results support it further disintegration of Canthium s.l., as the Comorean and Malagasy Canthium species are shown for the first time to be closely related to Peponidium. Similarly, C. confertum appears to have a close affinity with Cyclophyllum Hook. f. The combined analyses show that [lie dioecious group call he subdivide(] into four morphologically distinct clades formally recognized as genera: Bullockia (Bridson) Razafim., Lantz & B. Bremer, here elevated from Canthium subgen. Bullockia Bridson, Lis well its Cyclophyllum, Peponidium (including all Comorean, Malagasy, and Seychellean Canthium species), and Pyrostria (including Dinocanthium, Leroya, Neoleroya., Pseudopeponidium, and Scyphochlamys). All described species of Canthium subgen. Bullockia are transferred to Bullockia: B. dryscriton (Bullock) Razafim., Lantz & B. Bremer, B.fadenii (Bridson) Razafim., Lantz & B. Bremer, B. impressinervia (Bridson) Razafim., Lantz & B. Bremer, B. mombazensis (Baill.) Razafim., Lantz & B. Bremer, B. pseudosetiflora (Bridson) Razafim., Lantz & B. Bremer, and B. setiflora (Hiern) Razafim., Lantz & B. Bremer. Furthermore, the results seem to point to a single origin of functional dioecy followed by subsequent reversals [lack to tire hermaphroditic conditions at least within the Cyclophyllum-Canthium confertum clade and Pyrostria s.l. The Malagasy Bullockia species seem to have an African ancestor, whereas the Comorean Peponidium and the African Pyrostria appear to have originated from Malagasy progenitors.
Place, publisher, year, edition, pages
2009. Vol. 96, no 1, 161-181 p.
Biogeography, Bullockia, Canthium, Cyclophyllum, ETS, functional dioecy, ITS, Peponidium, Pyrostria, Rubiaceae, Vanguerieae
IdentifiersURN: urn:nbn:se:uu:diva-148879DOI: 10.3417/2006191ISI: 000265462000011OAI: oai:DiVA.org:uu-148879DiVA: diva2:403466