Endemism is one of the most important concepts in biogeography and is often used to guide biodiversity conservation, yet our understanding of the determinants of endemism in many biodiverse tropical regions is limited. This is true for western Central Africa, a region with one of the highest levels of plant diversity in tropical Africa, where endemism is poorly documented. This study examines the Gabonese Area of Endemism (GAE) and explores the main characteristics and determinants of its vascular plant endemism with regard to taxonomy, growth form, habitat, distribution, and range size. We compiled a comprehensive, verified specimen database of vascular plant taxa restricted to the GAE, comprising 19,876 occurrences of 1145 species and infraspecific taxa, and we characterized the habitat and habit for each taxon. We then calculated the proportion of taxa in the regional flora that are endemic to the GAE. A Wilcoxon rank-sum test was used to investigate range size among endemic taxa exhibiting different growth forms, and Fisher exact tests were used to explore the association between their habit and habitat, and to test the distribution of these attributes among higher-level taxa and growth forms compared to patterns in the regional flora as a whole. We found that endemic taxa represent ca. 13% of the GAE flora, and that the rate of endemism varies considerably among taxonomic groups and growth forms. Endemism is highest among shrubs (22%) and lowest in herbs (8%), especially monocotyledons (e.g., 5% among Poales). Most endemic taxa grow preferentially in forest habitats, the dominant vegetation type of the region. Endemic trees, which structure forest ecosystems, have significantly larger ranges than endemic herbs, climbers, and shrubs. About 17% of the flora of Gabon is endemic or subendemic to the country. Our results show that the dispersal capacity of taxa and the biogeographical history of the region appear to be critical factors in explaining differences in the rate of endemism among growth forms and taxonomic groups. Our findings also highlight the benefits of carefully building a comprehensive and verified database for studying rare and range-restricted plants, and they underscore the necessity to strengthen botanical exploration throughout western Central Africa in order to develop improved and better-informed conservation strategies.

Chromosome numbers are reported for 53 individuals of 10 species of Solidago L. sect. Maritimae (Torr. & A. Gray) Semple & Beck from eastern Canada and the eastern United States: S. austrina Small, S. chrysopsis Small, S. gracillima Torr. & A. Gray, S. mexicana L., S. pulchra Small, S. sempervirens L., S. simulans Fernald, S. stricta Aiton, S. uliginosa Nutt., and S. virgata Michx. Identifications of nearly all vouchers for 262 previously published counts for the section were confirmed or revised following the treatments of the section by Semple et al. No counts have been reported for the Mexican species S. maya Semple and S. paniculata DC. and for S. uliginosa var. terra-novae (Torr. & A. Gray) Fernald from Newfoundland. Polyploids are documented in six of the 13 species: S. austrina, S. mexicana, S. pulchra, S. stricta, S. uliginosa, and S. virgata. In addition, we provide the first chromosome count for S. chrysopsis (2n = 18) from Florida. All 315 count reports from 231 locations were used to map the cytogeography of all species in the section.

The systematics of the Barbacenia Vand. Atlantic Forest Inselberg group (Barbacenia AFI), and the description of two new AFI species, B. amphirupia Mello-Silva & Andr. Cabral and B. maritima Mello-Silva & Andr. Cabral, are here presented. Lectotypes are designated for B. fannieae (N. L. Menezes) Mello-Silva, B. mantiqueirae Goethart & Henrard, B. purpurea Hook. var. minor Seub., B. squamata Herb., and Vellozia coerulescens Hort. Belg. ex Gumbl., and a neotype is designated for B. foliosa Goethart & Henrard. Barbacenia burlemarxii L. B. Sm. & Ayensu was placed into synonymy of B. pabstiana L. B. Sm. & Ayensu, B. caricina Goethart & Henrard of B. brevifolia Taub., B. gaveensis Goethart & Henrard, B. foliosa, B. purpurea var. minor, and B. seubertiana Goethart & Henrard under B. squamata, B. ionantha L. B. Sm. and B. monticola L. B. Sm. & Ayensu under B. irwiniana L. B. Sm., and V. coerulescens under B. purpurea. An identification key and morphological and anatomical descriptions for the species are presented, as well as comments on the affinities among the species, geographical distribution, and conservation status.

A taxonomic revision of the Central American genus Mesoamerantha I. Ramírez & K. Romero is here presented. Each species entry includes full nomenclature, a morphological description, distributional and phenological data, a discussion of affinities, illustrations, and a conservation assessment following IUCN guidelines. In addition, epitypes are proposed for M. dichroantha (Donn. Sm.) I. Ramírez & K. Romero, a species endemic to Guatemala, and for M. malvernii (Gilmartin) I. Ramírez & K. Romero, a species restricted to Honduras and Nicaragua, the holotypes of which represent a single sex and are not sufficient for unambiguous identification. An artificial key is also included in order to identify live as well as herbarium specimens of all taxa.

Myrcia DC. sect. Calyptranthes (Sw.) A. R. Lourenço & E. Lucas is a section of the Neotropical genus Myrcia with ca. 260 known species. This paper provides a taxonomic revision of 89 species occurring across South and Central America, including the Amazon, Andes, Guiana Shield, and Mesoamerica, and extending into the Caribbean archipelago, but not including those previously treated from the Atlantic Forest of Brazil. The treatment includes an identification key, informal taxonomic groupings and notes, geographic distribution information, and extinction risk assessments. Figures illustrating key morphological characters of the genus are provided including common leaf, flower bud, and inflorescence arrangements. Ten new synonyms, eight new lectotypes, and four new combinations are proposed, and a key to treated species is supplied.

The monogeneric Daphniphyllaceae contain 36 taxa in the genus Daphniphyllum Blume that are endemic to Southeast Asia. Daphniphyllum is a morphologically homogeneous group of evergreen shrubs to trees divided into three sections: Daphniphyllum, Lunata T. C. Huang, and Staminodia Hurusawa. While the medicinal value of the Daphniphyllaceae has been explored in many studies, the understanding of their evolutionary history and infrageneric classification is still limited. To test the infrageneric classification and to examine evolutionary and classification hypotheses proposed by previous taxonomic studies, we reconstructed multilocus phylogenies by sampling 55.6% (= 20/36) of taxa in the genus based on both chloroplast (psbA-trnH spacer and trnL intron) and nuclear ITS (ITS1, 5.8S rDNA, and ITS2) regions. Our data do not support the monophyly of the three sections. Our results indicate that some hybridization events might have occurred in the evolutionary history of the genus. Moreover, our results support the classification hypotheses of D. glaucescens Blume in a strict sense but not in a broad sense. In addition, we elevate D. ×lanyuense (T. C. Huang) M. S. Tang, S. H. Liu & Yuen P. Yang, stat. nov., from varietal rank to species based on our results. Two putative natural hybrids, D. ×lanyuense and D. teijsmannii Zoll. ex Teijsm. & Binn., and their putative parental taxa are also revealed in our study. In sum, our results shed new insights into the sectional scope and understanding of evolutionary relationships among taxa in Daphniphyllum.

Chromosome numbers are reported for 35 individuals of one of three species of Solidago L. sect. Multiradiatae (Semple) Semple & J. B. Beck from Canada and the United States: S. multiradiata Aiton. Identifications of nearly all vouchers for 101 previously published counts for S. leiocarpa DC., S. multiradiata, and S. spithamaea M. A. Curtis ex A. Gray were confirmed or revised following the delimitation of the section by Semple and Beck (2021). Diploids 2n = 18 occur over much of the range of S. multiradiata with tetraploids occurring in some areas of the range but unknown from others. The two narrowly distributed high Appalachian Mountains species are both polyploid: S. leiocarpa is tetraploid 2n = 36 in New Hampshire, and S. spithamaea is hexaploid 2n = 54 in North Carolina.

El género Alternanthera Forssk. (Amaranthaceae) se encuentra principal y ampliamente distribuido en regiones tropicales y subtropicales de América. Se caracteriza por presentar hierbas o sufrútices de hojas opuestas, flores perfectas protegidas por una bráctea y dos bractéolas, con estigma capitado y apéndices en el tubo estaminal (o pseudoestaminodios) dispuestos en forma alterna con los filamentos estaminales con anteras funcionalmente uniloculares. En este trabajo se presenta la revisión taxonómica de las 31 especies del género que habitan en el Cono Sur y Bolivia. Se establece la nueva sinonimia de A. piptantha Pedersen con A. altacruzensis Suess. Se designan especies tipo para los nombres genéricos Brandesia Mart., Bucholzia Mart., Mogiphanes Mart., Steiremis Raf. y Telanthera R. Br. Asimismo, se designan lectotipos para Achyranthes porrigens Jacq., Alternanthera mexicana (Schltdl.) Hieron. var. gracilis Suess., A. nodiflora R. Br. var. linearifolia Moq., A. tenella Moq., Gomphrena elongata Willd. ex Roem. & Schult., T. meyeriana Regel & Körn, T. rufa (Mart.) Moq. var. glabrata Seub. y un lectotipo de segundo paso para A. denticulata R. Br. Se presentan claves para la identificación de las especies, subespecies y variedades, así como descripciones morfológicas, distribución geográfica, hábitat, nombres vulgares, usos, ilustraciones, notas nomenclaturales y especímenes estudiados para todas ellas.

The genus Alternanthera Forssk. (Amaranthaceae) is widely distributed throughout tropical and subtropical areas of the Americas. It includes herbs or suffrutices with opposite leaves, perfect flowers protected by a bract and two bracteoles, with capitate stigma and appendages in the staminal tube (or pseudostaminodes) arranged alternately with the stamen filaments, which bear functionally unilocular anthers. Here, a taxonomic revision of the 31 species of Alternanthera that inhabit the Southern Cone and Bolivia is presented. The name A. piptantha Pedersen is synonymized with A. altacruzensis Suess. Type species are designated for genera Brandesia Mart., Bucholzia Mart., Mogiphanes Mart., Steiremis Raf., and Telanthera R. Br. In addition, lectotypes are designated for Achyranthes porrigens Jacq., Alternanthera mexicana (Schltdl.) Hieron. var. gracilis Suess., A. nodiflora R. Br. var. linearifolia Moq., A. tenella Moq., Gomphrena elongata Willd. ex Roem. & Schult., T. meyeriana Regel & Körn, T. rufa (Mart.) Moq. var. glabrata Seub., and a second-step lectotype for A. denticulata R. Br. Identification keys are included for the differentiation of species, subspecies, and varieties, as well as their morphological descriptions, geographic distribution, habitat, vernacular names, uses, illustrations, nomenclatural notes, and information about the studied specimens.

A taxonomic revision of the species currently circumscribed in Tarenaya Raf. (Cleomaceae) is presented here. Tarenaya comprises 38 species distributed from Mexico to Argentina (except for Chile) and the West Indies, and with one species disjunct in Central Africa. We present a new combination, 14 lectotypifications, and two neotypifications, and describe a new species endemic to Espírito Santo, Brazil. We provide a detailed description of the genus, an identification key to the species, and, for each species, we provide descriptions, geographic distribution data, and preferred habitats, diagnostic features, morphological comments, extinction risk assessment, photographs, illustrations, and distribution maps.

The genus Pseudognaphalium Kirp., segregated from Gnaphalium L., is one of the largest genera of the tribe Gnaphalieae (Asteraceae) with about 60 species, most of them found in South, Central, and North America, but some species also occurring in Africa, Asia, Europe, and New Zealand. We present a taxonomic revision of Pseudognaphalium for North America accepting 36 species, mainly distributed in the Nearctic Region and the Mexican Transition Zone, and about one third of the species occurring in the Neotropical Region. The following taxa are newly synonymized: G. oaxacanum Greenm. with P. semiamplexicaule (DC.) Anderb., G. schraderi DC. with P. attenuatum (DC.) Anderb. var. sylvicola (McVaugh) Hinojosa & Villaseñor, P. altamiranum (Greenm.) Anderb. with P. roseum (Kunth) Anderb., and P. beneolens (Davidson) Anderb. with P. thermale (E. E. Nelson) G. L. Nesom. Lectotypes are newly designated for G. oblanceolatum Greenm., G. panniforme S. F. Blake, G. ramosissimum Nutt., G. roseum Kunth var. angustifolium Benth., G. roseum var. hololeucum Benth., and G. roseum var. sordescens Benth. Morphological descriptions are provided as well as taxonomic data on nomenclatural types, including synonymies, illustrations, distribution maps, distribution and habitat, additional material examined, distinguishing characters and taxonomic affinities for each taxon, biogeographical and ecological comments, and a key for their identification.

Evolutionary shifts in breeding system are thought to have played key roles in the diversification of many lineages of plants, including the evening primrose family (Onagraceae), which includes the genus Oenothera L. Diversification in Oenothera has been accompanied by frequent breeding system shifts, but it is not clear whether these differences are due to shared evolutionary history or reflect repeated independent adaptations to varying ecological conditions. In this study, we focus on “Subclade B,” one of two primary clades within Oenothera, and combine phylogenetic reconstructions and breeding system data to evaluate evidence for multiple transitions to self-compatibility. This study includes 46 of the 58 named taxa (species and subspecies) of Oenothera Subclade B. Some taxa were sequenced in earlier analyses, available from GenBank, one was resampled here to add new sequences, and 28 taxa are newly sequenced here. We base our phylogeny on sequencing of portions of four chloroplast markers (rps16, ndhF, trnL-F, and rbcL) and two nuclear genes (ITS and ETS). We used pollination tests to verify or determine the breeding system of these taxa.

Our phylogeny supports the current classification of Oenothera with minor changes and provides greater insight and clarity to the relationships of these species. Our results provide support for the monophyly of most of the sections in Oenothera Subclade B, as well as greater resolution for topology within sections Gaura (L.) W. L. Wagner & Hoch, Hartmannia (Spach) Walpers, Kneiffia (Spach) Walpers, and Megapterium (Spach) Walpers. Relationships among these monophyletic lineages, and the placement of sections Paradoxus W. L. Wagner and Peniophyllum (Pennell) Munz, and of the allopolypoid O. hispida (Benth.) W. L. Wagner, Hoch & Zarucchi, are not uniformly well-supported and need further clarification, but these phylogenetic uncertainties had minimal impact on the inference of transitions in self-compatibility in Subclade B.

We use maximum likelihood, Bayesian inference and stochastic character mapping to estimate the minimum and maximum number of transitions necessary to explain the phylogenetic distribution of self-compatible lineages. Our results confirm at least 12 and possibly up to 15 independent transitions from self-incompatibility to self-compatibility in Oenothera Subclade B. This lability in breeding system, which is also seen broadly across Oenothera, lends strong support to the hypothesis that this trait plays a key role in the diversification of the genus.

A new genus, Andea van der Werff, is described. It consists of 25 gynodioecious species, all occurring in the Andes except for one species found in the mountains of Costa Rica. Morphological characteristics are discussed and a key to the species is presented.

The grass genus Styppeiochloa De Winter (Arundinoideae: Poaceae) as it occurs in Madagascar is reviewed, two new species are described, and two subspecific taxa are elevated to species status. These new species, as well as the additional collections made since the latest treatment of the genus for Madagascar in 1954, greatly expand the documented geographic and ecological range of Styppeiochloa as a whole and demonstrate that a substantial diversification of the genus has occurred in Madagascar.

Metapetrocosmea W. T. Wang and Deinostigma W. T. Wang & Z. Y. Li were originally monotypic with M. peltata (Merr. & Chun) W. T. Wang and D. poilanei (Pellegr.) W. T. Wang & Z. Y. Li, respectively. Recent molecular phylogenetic research expanded Deinostigma to include several species previously transferred from Chirita D. Don to Primulina Hance. However, the relationship between Metapetrocosmea and Deinostigma has not been well addressed. In the present study, the type species of Metapetrocosmea and Deinostigma were sampled together with related taxa, and the systematic relationships were reexamined using the nuclear ribosomal internal and external transcribed spacer regions (ITS and ETS) and four chloroplast regions (rpL32-trnL, rps16, trnH-psbA, trnL-F). Phylogenetic analyses demonstrate that M. peltata is embedded in the species of Deinostigma and sister to D. poilanei. All of these species form a highly supported branch, i.e., Metapetrocosmea–Deinostigma clade, which is sister to Oreocharis Benth. Morphological analyses show that species in the Metapetrocosmea–Deinostigma clade share a series of morphological traits, i.e., alternate leaves, arcuate filaments, densely lanate anthers with the hair surface covered with granular or vermiform appendages, bilobed stigma that vary from dorsal to ventral and almost equal in size to a dorsal-ventral oblique lamella with the dorsal one sterile, hooked hairs and T-shaped glandular hairs occurring on the whole plant, and riblike seed surfaces. Both molecular and morphological evidence strongly suggest that the Metapetrocosmea–Deinostigma clade is monophyletic and should be combined into a single genus, i.e., Metapetrocosmea W. T. Wang. Therefore, we present a taxonomic treatment for this group.

Copaifera L. is a tropical genus with its highest diversity in the New World, renowned for the “copaiba oil” extracted from the trunk of many of its species, which has wide applications in traditional medicine and the pharmachemical industry. Despite relatively recent revisions, the genus is still deemed complex and its species difficult to recognize due to often overlapping circumscriptions. A crucial step in species delimitation and correct application of names is the analysis of types. Advances in the digitization of biological collections and bibliographical material have facilitated the access to type collections, but the information available is still fragmented and, in many cases, equivocal. The aim of this work was to perform a typological assessment of the names of Copaifera based on material from the New World, providing a nomenclatural revision toward a better understanding of its species and a broad taxonomic revision of the genus.

A taxonomic study of Cyperus L. (Cyperaceae) in the Central-West region of Brazil is presented. We examined more than 1300 herbarium specimens. Many of the species were also studied in the field. Our results recognize 59 species of Cyperus in the Central-West of Brazil, including three species endemic to the country that are potentially threatened with extinction, i.e., C. hooperae G. C. Tucker, C. longiculmis Pereira-Silva, Hefler & R. Trevis., and C. tuckerianus Pereira-Silva, Hefler & R. Trevis. Cyperus oxylepis Nees ex Steud. is reported from Brazil for the first time. Cyperus incomtus Kunth var. miguelii Kük. is proposed as a synonym of C. pearcei C. B. Clarke. We designate lectotypes for 20 names, a neotype for C. oxylepis, and an epitype for C. surinamensis Rottb. and select second-step lectotypes for 10 names. We also provide detailed morphological descriptions, illustrations, distribution data, an identification key for all species, and assessments of the conservation status for most species.