Phylogeny and evolution of secondary pollen presentation, corolla aestivation patterns, fruit types, and seed number in the Ixoroideae (Rubiaceae)

• Phylogenetic reconstructions using Bayesian and parsimony analyses of six chloroplast DNA region were performed in order to investigate character evolution and tribal relationships within the subfamily Ixoroideae (Rubiaceae). In the inferred phylogenetic hypotheses, the tribal relationships were mostly well supported, with the subfamily comprised of a crown group of two major sister clades termed the Coffeeae-alliance and Vanguerieae-alliance respectively, and a basal grade comprising Condamineeae, Henriquezieae, Posoquerieae, Retiniphyleae, Sipaneeae, and Steenisia. Five new tribes are here recognized (Airospermeae, Augusteae, Scyphiphoreae, Steenisieae and Trailliaedoxeae). Secondary pollen presentation, corolla aestivation patterns,fruit types, and number of ovules are all characters that have been considered of great importance in the classification of Rubiaceae. Ancestral state reconstructions of these characters using likelihood optimization indicate that secondary pollen presentation is synapomorphic for a clade comprising the Ixoroideae crown group and Retiniphyllum, whereas left-contorted corolla aestivation is synapomorphic for a clade comprising the crown group, Retiniphyllum, and Steenisia. Capsular fruits with numerous seeds are plesiomorphic in Ixoroideae, from which dry or fleshy indehiscent fruits have evolved numerous times independently. Reductions in seed number appears to have occurred within several lineages, none of which show a secondary increase in the number of seeds.

Subject headings

NATURVETENSKAP  -- Biologi -- Biologisk systematik (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Biological Systematics (hsv//eng)

Keyword

character evolution

cpDNA

pollen presentation

Rubiaceae

seed number

systematics

Systematics and phylogenetics

Systematik och fylogeni

växtsystematik

Plant Systematics

Publication and Content Type

vet (subject category)

ovr (subject category)