Salvator Ntore

Pollen and seeds reveal that Spermacoce thymoidea s.l. (African Rubiaceae, Spermacoceae) represents three endemic or disjunct species from the Zambezian high plateaus

Abstract Pollen and seed morphological data refute that Borreria hockii (R.D. Congo, Katanga) is synonymous to Spermacoce thymoidea (Southwest Angola, Huila). For the former, the necessary combination Spermacoce hockii is given; Spermacoce homblei, described from Katanga, is shown to be synonymous. The name Spermacoce thymoidea was also used for Zambian material from Mwinilunga that represents in fact a new species, Spermacoce stipularis, also collected from central Angola and Katanga. Spermacoce stipularis mainly differs from Spermacoce thymoidea in the presence of an elaiosome and in the type of pollen grain, and from Spermacoce hockii in the more slender and taller habit, the absence of heterophylly, and the smaller flowers. The value of the characters used in the taxonomy of the genus Spermacoce is briefly reviewed with special emphasis on the importance of seed and pollen data. The three species are restricted to high plateaus of the Zambezian regional center of endemism; they are geoxylic plants, a life form very common in the grass savannahs of these plateaus. Further comments on the ecology of the plateaus and their endemism are also provided. Communicating Editor: James F. Smith

Contributions to the Wood Anatomy of the Rubioideae (Rubiaceae)

Damnacanthus, Lasianthus, Saldinia, and Trichostachys are also included. Wood anatomical characters are compared with recent phylogenetic insights into the study group on the basis of molecular data. The observations demonstrate that the delimitation and separation of several taxa from the former Coussareeae/Morindeae/Prismatomerideae/Psychotrieae aggregate is supported by wood anatomical data. The Coussareeae can be distinguished from the other Rubioideae by their scanty parenchyma, septate libriform fibres, and the combination of uniseriate and very high multiseriate rays with sheath cells. Axial parenchyma bands and fibre-tracheids characterise Gynochtodes and some species of Morinda (Morindeae s.str.), but the latter genus is variable with respect to several features (e.g. vessel groupings and axial parenchyma distribution). Wood data support separation of Rennellia and Prismatomeris from Morindeae s.str.; vessels in both genera are exclusively solitary and axial parenchyma is always diffuse to diffuse-in-aggregates. Damnacanthus differs from the Morindeae alliance by the occurrence of septate fibres, absence of axial parenchyma, and the occasional presence of fibre wall thickenings. There are interesting similarities between members of the Lasianthus clade and the Pauridiantheae/Urophyleae group such as the sporadic occurrence of spiral thickenings in axial parenchyma cells.

Four new endemic genera of Rubiaceae (Pavetteae) from Madagascar represent multiple radiations into drylands

Abstract The taxonomic positions and phylogenetic relationships of six Pavetteae species endemic to Madagascar were tested with a phylogenetic study of the Afro-Madagascan representatives of the tribe Pavetteae based on sequence data from six markers rps16, trnT-F, petD, accD-psa1, PI and ITS. The six species were resolved into four well-supported and morphologically distinct clades which we here formally recognise at generic level. The new genera are the monospecific Exallosperma and Pseudocoptosperma, each with a single species, and Helictosperma and Tulearia, each with two species. Each genus is characterised by one or more autapomorphies or by a unique combination of plesiomorphic characters. Mostly, the distinguishing characters are found in fruit and seed; Exallosperma differs from all other Pavetteae genera by the fruit consisting of two stony pyrenes, each with a single laterally flattened seed with irregularly distributed ridges on the surface; Helictosperma is unique by its single spherical seed rolled-in on itself in the shape of a giant pill-millipede. Pseudocoptosperma is characterised by the combination of three ovules pendulous from a small placenta and triangular stipules with a strongly developed awn, whereas Tulearia is characterised by robust sericeous flowers, small leaves, uni- or pauciflorous inflorescences and fruits with two pyrenes, each with a single ruminate seed. The four new genera show marked adaptations to the dry habitats in which they grow. They represent multiple radiations into drylands and highlight the importance of the dry forest and scrub vegetation in western, southern and northern Madagascar for plant biodiversity. The description of the four new genera shows that the tribe Pavetteae exhibits the same pattern as many plant groups in Madagascar, which are characterised by a high proportion of endemic genera comprising a single or a few species. In the four new genera, five new species are described and one new combination is made: Exallosperma longiflora De Block; Helictosperma malacophylla (Drake) De Block, Helictosperma poissoniana De Block, Pseudocoptosperma menabense Capuron ex De Block; Tulearia capsaintemariensis De Block and Tulearia splendida De Block.