Petra De Block

Palynological characters and their phylogenetic signal in Rubiaceae

In the 1990s Rubiaceae became a hot spot for systematists, mainly due to the comprehensive treatment of the family by Robbrecht in 1988. Next to the exploration of macromolecular characters to infer the phylogeny, the palynology of Rubiaceae finally received the attention it deserves. This article aims to present a state-of-the-art analysis of the systematic palynology of the family. The range of varíation in pollen morphology is wide, and some of the pollen features are not known from other angiosperm taxa; e.g., a looplike or spiral pattern for the position of apertures in pantoaperturate grains. We compiled an online database at the generic level for the major pollen characters and orbicule presence in Rubiaceae. An overview of the variation is presented here and illustrated per character: dispersal unit, pollen size and shape, aperture number, position and type, sexine ornamentation, nexine pattern, and stratification of the sporoderm. The presence/absence and morphological variation of orbicules at the generic level is provided as well. The systematic usefulness of pollen morphology in Rubiaceae is discussed at the (sub)family, tribal, generic, and infraspecific levels, using up-to-date evolutionary hypotheses for the different lineages in the family. The problems and opportunities of coding pollen characters for cladistic analyses are also treated.

Phylogeny of tricalysia (rubiaceae) and its relationships with allied genera based on plastid dna data: resurrection of the genus empogona

Abstract Recent studies on the circumscription of the tribe Coffeeae (Rubiaceae) revealed a weakly supported clade containing Tricalysia A. Rich. and the allied genera Argocoffeopsis Lebrun, Calycosiphonia Pierre ex Robbr., Belonophora Hook. f., Diplospora DC., Discospermum Dalzell, Nostolachma T. Durand, and Xantonnea Pierre ex Pit. The phylogenetic relationships of Tricalysia and these allied taxa are investigated further using sequence data from four plastid regions (trnL-F intron and intergenic spacer, rpL16 intron, accD-psa1 intergenic spacer, and PetD). Our results demonstrate that Tricalysia sensu Robbrecht is not monophyletic. The genus name Tricalysia should be restricted to taxa from subgenus Tricalysia; subgenus Empogona (Hook. f.) Robbr. is sister to the genus Diplospora and is recognized at the generic level. The 34 necessary new combinations for Empogona Hook. f. are provided: E. acidophylla (Robbr.) J. Tosh & Robbr., E. aequatoria (Robbr.) J. Tosh & Robbr., E. africana (Sim) J. Tosh & Robbr., E. aulacosperma (Robbr.) J. Tosh & Robbr., E. bequaertii (De Wild.) J. Tosh & Robbr., E. bracteata (Hiern) J. Tosh & Robbr., E. breteleri (Robbr.) J. Tosh & Robbr., E. buxifolia (Hiern) J. Tosh & Robbr. subsp. buxifolia, E. buxifolia subsp. australis (Robbr.) J. Tosh & Robbr., E. cacondensis (Hiern) J. Tosh & Robbr., E. concolor (N. Hallé) J. Tosh & Robbr., E. coriacea (Sond.) J. Tosh & Robbr., E. crepiniana (De Wild. & T. Durand) J. Tosh & Robbr., E. deightonii (Brenan) J. Tosh & Robbr., E. discolor (Brenan) J. Tosh & Robbr., E. filiformistipulata (De Wild.) Bremek. subsp. filiformistipulata, E. filiformistipulata subsp. epipsila (Robbr.) J. Tosh & Robbr., E. glabra (K. Schum.) J. Tosh & Robbr., E. gossweileri (S. Moore) J. Tosh & Robbr., E. kirkii Hook. f. subsp. junodii (Schinz) J. Tosh & Robbr., E. lanceolata (Sond.) J. Tosh & Robbr., E. macrophylla (K. Schum.) J. Tosh & Robbr., E. maputenis (Bridson & A. E. van Wyk) J. Tosh & Robbr., E. ngalaensis (Robbr.) J. Tosh & Robbr., E. nogueirae (Robbr.) J. Tosh & Robbr., E. ovalifolia (Hiern) J. Tosh & Robbr. var. ovalifolia, E. ovalifolia var. glabrata (Oliv.) J. Tosh & Robbr., E. ovalifolia var. taylorii (S. Moore) J. Tosh & Robbr., E. reflexa (Hutch.) J. Tosh & Robbr. var. reflexa, E. reflexa var. ivorensis (Robbr.) J. Tosh & Robbr., E. ruandensis (Bremek.) J. Tosh & Robbr., E. somaliensis (Robbr.) J. Tosh & Robbr., E. talbotii (Wernham) J. Tosh & Robbr., and E. welwitschii (K. Schum.) J. Tosh & Robbr.

Pollen morphology of the Pavetteae (Rubiaceae, Ixoroideae) and its taxonomic significance

Pollen grains of the tribe Pavetteae (Rubiaceae, subfamily Ixoroideae) are examined using LM and SEM. Grains are 3‐ or 4‐colporate and (semi‐) tectate (in one Versteegia species atectate). Sexine patterns vary between perforate, microreticulate, reticulate, rugulate and striato‐reticulate. Supratectal elements are sometimes present. The variation in pollen morphology in the Pavetteae allows to recognize seven pollen types, the distribution of which is useful to evaluate generic delimitations and relationships within the tribe. Pollen characters corroborate the close relationships between the genera Coleactina, Dictyandra and Leptactina and between Homollea, Homolliella and Paracephaelis. All the genera of the tribe proved to be stenopalynous (the species examined possess the same pollen type), except Pavetta, Rutidea, Versteegia and Tarenna which are eurypalynous. In the huge genus Pavetta the existing infrageneric classification is supported pollen morphologically. Pollen morphology further indicates tha...

Dispersing towards Madagascar: Biogeography and evolution of the Madagascan endemics of the Spermacoceae tribe (Rubiaceae).

Despite the close proximity of the African mainland, dispersal of plant lineages towards Madagascar remains intriguing. The composition of the Madagascan flora is rather mixed and shows besides African representatives, also floral elements of India, Southeast Asia, Australia, and the Neotropics. Due to its proportionally large number of Madagascan endemics, the taxonomically troublesome Spermacoceae tribe is an interesting group to investigate the origin and evolution of the herbaceous Rubiaceae endemic to Madagascar. The phylogenetic position of these endemics were inferred using four plastid gene markers. Age estimates were obtained by expanding the Spermacoceae dataset with representatives of all Rubiaceae tribes. This allowed incorporation of multiple fossil-based calibration points from the Rubiaceae fossil record. Despite the high morphological diversity of the endemic herbaceous Spermacoceae on Madagascar, only two colonization events gave rise to their current diversity. The first clade contains Lathraeocarpa, Phylohydrax and Gomphocalyx, whereas the second Madagascan clade includes the endemic genera Astiella, Phialiphora, Thamnoldenlandia and Amphistemon. The tribe Spermacoceae is estimated to have a Late Eocene origin, and diversified during Oligocene and Miocene. The two Madagascan clades of the tribe originated in the Oligocene and radiated in the Miocene. The origin of the Madagascan Spermacoceae cannot be explained by Gondwanan vicariance but only by means of Cenozoic long distance dispersal events. Interestingly, not only colonization from Africa occurred but also long distance dispersal from the Neotropics shaped the current diversity of the Spermacoceae tribe on Madagascar.

Molecular phylogenetics and generic assessment in the tribe Pavetteae (Rubiaceae)

This is the first phylogenetic study focused on the Pavetteae, one of the most species-rich and morphologically diverse tribes within the coffee family (Rubiaceae). Fifteen of the 17 currently recognized genera, represented by 85 taxa, were sequenced for rps16, trnT-F and ITS and analysed using Bayesian inference and maximum likelihood methods. The monophyly of the Pavetteae is confirmed. Four major lineages are identified, but their phylogenetic relationships are not fully resolved. The continental African genera Rutidea, Nichallea and Tennantia, the Madagascan genera Homollea and Robbrechtia, and the paleotropical genus Pavetta are monophyletic. Other genera are paraphyletic in their current circumscriptions and the following changes are made: Homolliella is placed in synonymy with Paracephaelis, and Coleactina and Dictyandra with Leptactina, resulting in four new combinations. The large paleotropical genus Tarenna is shown not to be monophyletic. In the future, the name Tarenna should not be used for continental African species. Most of these could be transferred to the hitherto monospe- cific genus Cladoceras, but other species might constitute altogether new genera. The relationship between the monophyletic Asian-Pacific and Madagascan Tarenna species remains unclear. The phylogeny of the Madagascan genera of the Pavetteae is largely unresolved and the largest Madagascar-centred genus Coptosperma was not recovered as monophyletic. The low resolution for the Madagascan taxa can be considered as an indication of rapid radiation. Further molecular and morphologi- cal studies are necessary to clarify the phylogeny of the Pavetteae, especially regarding the African Tarenna species and the Madagascan genera of the tribe.

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.

Craterispermum capitatum and C. gabonicum (Rubiaceae): two new species from the Lower Guinean and Congolian Domains

Abstract Craterispermum capitatum and C. gabonicum, two new species of Rubiaceae, are described from the Lower Guinea and Congolian Domains. Detailed descriptions and distribution maps are provided for each species, their conservation status is assessed and their taxonomic affinities are discussed. Craterispermum gabonicum is unique within the genus because of the strong dimorphism in brevistylous and longistylous flowers and inflorescences. We hypothesize that this species shows some form of dioecy. The distribution of C. capitatum shows a wide disjunction: the species is present in the Lower Guinean and Congolian Domains but absent from Gabon and South Cameroon. An identification key for the Craterispermum species present in the Lower Guinean and Congolian Domains is given.

Third International Rubiaceae Conference: Introduction1

The family Rubiaceae is the fourth largest family of flowering plants in terms of the number of species known, with worldwide distribution, but most of its diversity is concentrated in the highly threatened and rapidly disappearing moist ecosystems of tropical and subtropical regions. Rubiaceae are badly in need of study by systematists, ecologists, and conservationists at a basic level, and their important role in these tropical ecosystems together with the active threat to the existence of so many species adds urgency to this work. The pace and intensity of this research are significantly increased by conferences specifically targeting this family. The First International Rubiaceae Conference, held at the Missouri Botanical Garden in St. Louis in 1993, brought together students of Paleotropical and Neotropical groups for the first time; selected proceedings were published in 1995 in the Annals of the Missouri Botanical Garden (volume 82, issue 3, pp. 355–439). The Second International Rubiaceae Conference, held at the National Botanic Garden of Belgium in Meise in 1995, focused on Rubiaceae as part of the Gentianales (then a fairly new consensus classification for the family) and delimitation of subfamilies and problematic tribal and generic complexes; the full proceedings were published in 1996 in Opera Botanica Belgica (volume 7, pp. 1–432). For more than 10 years after that, no meeting was held until 2005, when a half-day symposium focused on Rubiaceae during the XVII International Botanical Congress in Vienna (no proceedings were published). This symposium clearly showed interest in and need for a longer meeting. The Third International Rubiaceae Conference was subsequently co-organized by the Katholieke Uni-

Plate 447. Didymosalpinx norae

Didymosalpinx norae (Swynn.) Keay (Rubiaceae) is a shrub native of eastern Africa, with a disjunct distribution. It occurs in the rain forests of the Indian Ocean coastal belt and in submontane forests of the Chimanimani range at the border of Mozambique and Zimbabwe. Living material at the National Botanic Garden in Belgium is used here to illustrate and describe it. Taxonomic history, distribution, habitat and cultivation requirements are also discussed. The affinity of the genus Didymosalpinx raises some questions. The material used here was also included in recent phylogenetic analyses shortly reviewed here; its belonging to the tribe Gardenieae is questionable.