Mitracarpus longicalyx (Rubiaceae, Spermacoceae), a new species from northeastern Brazil

Mitracarpus longicalyx is here described and illustrated from sandy areas of the caatingas of northeastern Brazil. The new species is similar toM. hirtus andM. megapotamicus.     

Relationships, circumscription, and biogeography of Arcytophyllum (Rubiaceae) based on evidence from cpDNA

A cladistic analysis was performed using nucleotide sequence variation in therps16 intron and thetrmL-F region (plastid DNA).Arcytophyllum belongs in a subclade of the tribe Spermacoceae (s.l.) together with the American species presently classified in the generaHedyotis andHoustonia. This subclade is morphologically characterized by cymbiform seeds.Arcytophyllum is the sister group of all AmericanHedyotis andHoustonia and it is suggeste that these latter would be most conveniently treated as a single genus, the correct name of which would beHoustonia.Arcytophyllum should be circumscribed such that it excludesA. serpyllaceum, which is not a member of theArcytophyllum-Houstonia clade but more closely related toBouvardia. The phylogeny that was reconstructed suggests that the ancestral area of theArcytophyllum-Houstonia clade is the South American tectonic plate.     

Novelties in spermacoceae (Rubiaceae) from Bolivia and Paraguay

One new Bolivian species (Borreria pazensis) and three new varieties (Borreria densiflora var.minima, Richardia, scabra var.chacoensis andStaelia virgata var.killeenii) are described and illustrated. The genusDiodella, with three species (D. apiculata comb. nov., D. radula comb. nov., andD. teres), is reported for the first time.Borreria limae, B. wunschmannii, B. scabiosoides var.scabiosoides, andB. scabiosoides var.anderssonii are also reported as new to Bolivia.     

Evolution of flower morphology, pollen dimorphism, and nectar composition in Arcytophyllum, a distylous genus of Rubiaceae

A phylogenetic study of Arcytophyllum based on ITS was conducted and compared with an earlier study based on cpDNA. The position of the widespread A. thymifolium as sister to all other species was confirmed and several well-supported clades could be retrieved. The Central American A. lavarum is well embedded between exclusively or predominantly South American species. To understand the expression of heterostyly in the genus, we analyzed inter- and intraspecific variation in floral morphology, nectar, pollen–ovule (P/O) ratio and seed set of ten species in 11 populations. Stigma and anther levels differed significantly between the morphs in the species/populations investigated, except for A. filiforme, in which anther levels did not differ significantly between the two morphs. Different expressions of heterostyly in Arcytophyllum seem independent of phylogenetic relationships. Nectar sugar composition was similar between the morphs. Nectar of most species presented a larger proportion of hexoses than of sucrose; only the most derived species, A. macbridei and A. vernicosum, have higher sucrose proportions. There is a significant positive correlation between corolla tube length and the proportion of sucrose. Pollen dimorphism, with regard to both number (long-styled>short-styled) and size (short-styled>long-styled), was observed in all taxa investigated except A. filiforme. According to the P/O ratios, the breeding systems range from facultative autogamy to facultative xenogamy. The lowest P/O ratios were found in A. filiforme, and the highest in A. rivetii. Hymenoptera, Diptera and Coleoptera were observed as flower visitors. Seed production did not differ significantly between the morphs in eight of the 11 species/populations investigated. There is, however, a tendency in all species/populations (except in A. macbridei Peru) for the short-styled morph to have a higher percentage of seeds per ovule, indicating that the short-styled morphs display higher female reproductive success.     

Notes on Galianthe (Spermacoceae, Rubiaceae) in the Bolivian flora

Four new species ofGalianthe (G. boliviana, G. chiquitosana, G. sudyungesis, andG. kempffiana) for Bolivia are described and illustrated.Galianthe kempffiana is also known from Brazil.Galianthe laxa andG. bisepala are reported for the first time for Bolivia.     

The phylogenetic utility of chloroplast and nuclear DNA markers and the phylogeny of the Rubiaceae tribe Spermacoceae

The phylogenetic utility of chloroplast (atpB-rbcL, petD, rps16, trnL-F) and nuclear (ETS, ITS) DNA regions was investigated for the tribe Spermacoceae of the coffee family (Rubiaceae). ITS was, despite often raised cautions of its utility at higher taxonomic levels, shown to provide the highest number of parsimony informative characters, in partitioned Bayesian analyses it yielded the fewest trees in the 95% credible set, it resolved the highest proportion of well resolved clades, and was the most accurate region as measured by the partition metric and the proportion of correctly resolved clades (well supported clades retrieved from a combined analysis regarded as “true”). For Hedyotis, the nuclear 5S-NTS was shown to be potentially as useful as ITS, despite its shorter sequence length. The chloroplast region being the most phylogenetically informative was the petD group II intron.We also present a phylogeny of Spermacoceae based on a Bayesian analysis of the four chloroplast regions, ITS, and ETS combined. Spermacoceae are shown to be monophyletic. Clades supported by high posterior probabilities are discussed, especially in respect to the current generic classification. Notably, Oldenlandia is polyphyletic, the two subgenera of Kohautia are not sister taxa, and Hedyotis should be treated in a narrow sense to include only Asian species.