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A treatment of the Rubiaceae of Angola is presented based on herbarium collections kept at BM, BR, COI, K, LISC, LISU, LUA, LUAI, P, and PRE. The basionyms, relevant synonyms, and types from Angola are cited. For each taxon, one collection is cited for each province. An exsiccata list with over 3300 collections examined and identified during this work is provided. There are 108 genera, 422 species, and 40 infraspecific taxa of Rubiaceae in Angola. Fourteen genera and 126 species and infraspecific taxa are restricted to Cabinda. The rate of endemism of the family is c. 19%, with 86 taxa endemic to Angola (16 of which are restricted to Cabinda). Two genera are endemic. A new subspecies and a new variety are described. There are 21 unnamed entities requiring further research. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 156, 537–638.

A treatment of the Rubiaceae of Cabinda (Angola) is presented based on various herbarium collections. There are 67 genera and 169 species of Rubiaceae represented in the flora of Cabinda. Eight entities are unnamed and could represent new taxa. Identification keys are provided for species and infraspecific taxa. A new combination is made in Rothmannia and two are made in Psychotria. A new name is provided in Psychotria. Eighteen taxa are endemic to Cabinda, two of which are also endemic to Angola. The conservation status of the endemic taxa is unknown due to the lack of collections over the last 40 years. © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society, 2007, 154, 455–495.

A synoptic treatment of the Rubiaceae of Sao Tome e Principe (Gulf of Guinea) is presented based on herbarium collections kept at BM, COI, K and LISC. There are 36 genera and 64 species of Rubiaceae represented in the flora of Sao Tome e Principe. Identification keys are provided for genera, species and infraspecific taxa. A new combination is made in Chassalia. Twenty-nine taxa are endemic to these islands, two of which are also endemic to Annobon. The conservation status of the endemic taxa is assessed and IUCN categories of threat are proposed for ten taxa. Nineteen taxa of Rubiaceae are considered under threat in Sao Tome e Principe and ten are considered nearly threatened. © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society, 2005, 149, 85–114.

A revision of the species of Psychotria from S.Tome e Principe is presented, including a key to the species, full descriptions, distribution, conservation status, notes and specimens examined. Twelve species occur on the islands of S.Tome and Principe; seven are endemic, six to S.Tome and one to Principe. One new species (P. exellii sp. nov.) is described from S.Tome. The conservation status of five endemic species is evaluated using IUCN guidelines/criteria and categories of threat are proposed. Two IUCN Red List endemics (P. guerkeana and P. grumilea) are re-evaluated and a different category of threat is proposed for P. grumilea. Three of the seven endemic species are considered Critically Endangered, one Endangered and three are Vulnerable, using the criteria for extinction threat set by the IUCN. © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society, 2004, 147, 469–481.

A contribution to the knowledge of Tylosema (Schweinf.) Torre & Hillc. is presented. The main objectives of this revision were: (1) to elucidate the taxonomic position of the specimens collected in south Angola, (2) to provide a review of species boundaries in the genus, especially between T. fassoglense (Schweinf.) Torre & Hillc. and T. esculentum (Burch.) A.Schreib. and (3) to evaluate the contribution of pollen morphology for delimitation of the species in this genus. Numerical analyses were performed based on morphometric data taken from herbarium specimens. Principal component analysis and cluster analysis divided specimens of Tylosema into four major groups, corresponding to three recognized species and a new taxon. A new micromorphometric character (swollen base of hairs) was found that further contributes to the distinction of T. humifusum (Pic.Serm. & Roti Mich.) Brenan from other species. A new species, T. angolense P. Silveira & S. Castro sp. nov., is described and illustrated. A taxonomic key and distribution map of studied taxa is also provided. The analyses of pollen morphology allowed for the distinction of the taxonomic groups. © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society, 2005, 147, 99–115.

A revision of the genus Calvoa Hook. f. (Melastomataceae) is presented. Principal Component Analyses (PCA) and Cluster Analyses (UPGMA) were performed to elucidate three cases of difficult species delimitation and infraspecific variation, with the following results. (1) The separation between C. crassinoda Hook. f. and C. grandifolia Cogn. was clear in the results obtained with both methods. (2) The group of the West-Central African species Calvoa angolensis A. Fern. & R. Fern C. calliantha Jacq.-Fel C. monticola A. Chev C. pulcherrima Gilg ex Engl C. sapinii De Wild C. seretii De Wild C. sinuata Hook. f. and C. subquinquenervia De Wild. proved difficult to resolve with either analysis, but the Cluster Analysis produced results which are more consistent with the identification of the specimens. (3) Neither of the two analyses supported the recognition of infraspecific categories in Calvoa orientalis Taub. Eighteen species are recognized in the genus. The new species Calvoa jacques-felixii E. Figueiredo is described and the new combination Calvoa seretii subsp. wildemaniana (Exell) E. Figueiredo is made. Four lectotypes are designated. The conservation status of some taxa is discussed. Six species are considered rare and possibly under threat.

Taxonomic resources are essential for the effective management of invasive plants because biosecurity strategies, legislation dealing with invasive species, quarantine, weed surveillance and monitoring all depend on accurate and rapid identification of non-native taxa, and incorrect identifications can impede ecological studies. On the other hand, biological invasions have provided important tests of basic theories about species concepts. Modern taxonomy therefore needs to integrate both classical and new concepts and approaches to improve the accuracy of species identification and further refine taxonomic classification at the level of populations and genotypes in the field and laboratory., This paper explores how a lack of taxonomic expertise, and by implication a dearth of taxonomic products such as identification tools, has hindered progress in understanding and managing biological invasions. It also explores how the taxonomic endeavour could benefit from studies of invasive species. We review the literature on the current situation in taxonomy with a focus on the challenges of identifying alien plant species and explore how this has affected the study of biological invasions. Biosecurity strategies, legislation dealing with invasive species, quarantine, weed surveillance and monitoring all depend on accurate and rapid identification of non-native taxa. However, such identification can be challenging because the taxonomic skill base in most countries is diffuse and lacks critical mass. Taxonomic resources are essential for the effective management of invasive plants and incorrect identifications can impede ecological studies. On the other hand, biological invasions have provided important tests of basic theories about species concepts. Better integration of classical alpha taxonomy and modern genetic taxonomic approaches will improve the accuracy of species identification and further refine taxonomic classification at the level of populations and genotypes in the field and laboratory. Modern taxonomy therefore needs to integrate both classical and new concepts and approaches. In particular, differing points of view between the proponents of morphological and molecular approaches should be negotiated because a narrow taxonomic perspective is harmful; the rigour of taxonomic decision-making clearly increases if insights from a variety of different complementary disciplines are combined and confronted. Taxonomy plays a critical role in the study of plant invasions and in turn benefits from the insights gained from these studies.