Evolutionary relationships in the Spermacoceae alliance (Rubiaceae) using information from six molecular loci: insights into systematic affinities of Neohymenopogon and Mouretia

Abstract

Several recent phylogenetic studies of Rubiaceae have dealt with enigmatic taxa whose systematic positions have been previously unknown or controversial. We address evolutionary relationships in the Spermacoceae alliance (Rubioideae) with special emphasis on the Asian genera Mouretia and Neohymenopogon, here sequenced for the first time. Both genera belong in the tribe Argostemmateae and have persistent calyx lobes on the fruit in common with Argostemma and Mycetia. Other previous uncertainties are resolved with strong support; Saprosma is sister to Paederieae s. str. and Carpacoce is sister to remaining Anthospermeae. Our results further reveal some phylogenetic problems. Danaideae is sister to remaining taxa in the Spermacoceae alliance with high posterior probability, which contradicts results in a recent study. The uncertainty concerning evolutionary relationships of Dunnia and Theligonum is reinforced, despite a denser taxon sampling in the Spermacoceae alliance compared with earlier studies. We also demonstrate yet another example of the controversial correlation between molecular substitution rate and plant life history.

Foonchewia guangdongensis gen. et sp. nov. (Rubioideae: Rubiaceae) and its systematic position inferred from chloroplast sequences and morphology

“…4). The results also elucidated that the tribes Spermacoceae and Knoxieae, which were classified as a subclade of the Spermacoceae alliance by Rydin et al (2009b), grouped into an isolated clade too. Danaideae separated from other clades with very strong support values, as revealed by Rydin et al (2009b).…”

“…Our extensive sampling from the all available taxa in the Spermacoceae alliance and preliminary phylogenetic analyses on the basis of single or combined loci indicated that the new genus was nested within the subclade that included the tribes Anthospermeae, Argostemmateae, Dunnieae, Paederieae, Putorieae, Rubieae, and Theligoneae (Rydin et al, 2009b). Further phylogenetic analysis based on four combined chloroplast sequences revealed that Foonchewia was sister to Dunnieae, which included the monotypic genus Dunnia Tutch., with high support value (88% bootstrap value and 100% Bayesian posterior probability, Fig.…”

“…Recent studies of the evolutionary relationships within Rubiaceae have resulted in the recognition of three subfamilies, Rubioideae, Ixoroideae, and Cinchonoideae (Bremer et al, 1995; Bremer, 1996; Bremer et al, 1999; Andersson & Rova, 1999; Rova et al, 2002). The Spermacoceae alliance within subfamily Rubioideae forms a well‐supported clade (Bremer & Manen, 2000) comprising nearly 3000 species (Rydin et al, 2009b), most of which have dry fruits. It was shown to include 10 tribes in two major subclades consisting of: (i) tribes Knoxieae and Spermacoceae; and (ii) tribes Anthospermeae, Argostemmateae, Dunnieae, Paederieae, Putorieae, Rubieae, and Theligoneae, as well as the tribe Danaideae with inconsistent systematic position (Rydin et al, 2009b).…”

“…The Spermacoceae alliance within subfamily Rubioideae forms a well‐supported clade (Bremer & Manen, 2000) comprising nearly 3000 species (Rydin et al, 2009b), most of which have dry fruits. It was shown to include 10 tribes in two major subclades consisting of: (i) tribes Knoxieae and Spermacoceae; and (ii) tribes Anthospermeae, Argostemmateae, Dunnieae, Paederieae, Putorieae, Rubieae, and Theligoneae, as well as the tribe Danaideae with inconsistent systematic position (Rydin et al, 2009b). The phylogenetic relationships between these tribes lack significant morphological support, possibly due to the great diversity of life forms, morphology, and ecology among the numerous constituent species (Rydin et al, 2009a).…”

A developmental model for the corolla in Rubiaceae. Cryptic character states in corollas of the Spermacoceae alliance

“…The c. 21 tribes of the Rubioideae fall into a basal grade and two major groups: the Psychotrieae alliance (sensu Razafimandimbison et al 2008, Rydin et al 2009a = supertribe Psychotriidinae sensu Robbrecht & Manen 2006; see also fig. 1) and the Spermacoceae alliance (sensu Rydin et al 2009b = supertribe Rubiidinae sensu Robbrecht & Manen 2006; see also fig. 1).…”