The diversity of Vanilla Mill. in Andean South American countries remains significantly understudied, highlighting the urgent need for a robust taxonomic framework as a foundation for future biogeographic, monographic, phylogenetic, and ecological research. Drawing on extensive herbarium studies and fieldwork conducted by the authors over the past decade, we present a curated checklist of this economically important genus in South America, focused on the Andean countries of Bolivia, Colombia, Ecuador, and Peru. Our review records 31 Vanilla species across the four countries, with Colombia emerging as the most species rich, followed by Peru, Ecuador, and Bolivia. Among this diversity, we identified 25 species of potential interest as crop wild relatives of the globally cultivated V. planifolia Andrews. Moreover, we report several species not previously documented in our study area, including a new species from Ecuador, which we describe here as V. sekut Damián, Garzón & Bentley. As part of our extensive herbarium and literature revision, we also designate six lectotypes, one neotype, and four epitypes. This checklist provides a critical baseline for future monographic and evolutionary studies on Vanilla in South America, offering valuable insights into its biodiversity and potential for agricultural and ecological applications.

A taxonomic revision of the 20 species of the Marlierea clade (Myrcia DC. sect. Aulomyrcia (O. Berg) Griseb., Myrtaceae) is presented, including an identification key to the species, morphological descriptions, IUCN conservation risk assessments, and notes. While this lineage cannot be assigned a Linnean taxonomic rank until relationships in Myrcia are better resolved, it is here described for the first time. The species in the Marlierea clade are found in forests, sandy vegetation, and rocky outcrops along the Atlantic domain and the Espinhaço Mountains in Brazil. Myrcia botryoidea Gaem & Mazine, M. multipaniculata Gaem & Mazine, and M. regia Gaem & E. Lucas are described as species new to science. Nine new synonyms are proposed: Marlierea excoriata Mart. var. angustifolia O. Berg and Marlierea suaveolens Cambess. under Myrcia excoriata (Mart.) E. Lucas & C. E. Wilson; Marlierea estrellensis O. Berg, Marlierea glabra Cambess. var. gracilis O. Berg, and Marlierea grandifolia O. Berg var. minor O. Berg under Myrcia neoglabra E. Lucas & C. E. Wilson; Myrtus rufa Vell. under Myrcia neoobscura E. Lucas & C. E. Wilson; Eugeniopsis riedeliana O. Berg and Marlierea spathulata O. Berg under Myrcia neotomentosa E. Lucas & C. E. Wilson; and Calyptranthes langsdorffii O. Berg var. macrophylla Kiaersk. under Myrcia parviflora (O. Berg) Gaem & E. Lucas. Additionally, six lectotypes and one epitype are proposed. Eleven species are currently under risk of extinction, emphasizing the need for conservation initiatives targeted to the distribution areas of this group. The present work poses a major change in the systematics of the Marlierea clade, demonstrating that species of relatively well-explored tropical floras, such as the Atlantic Forest, remain understudied.

Species are considered basic units of study and management in several areas of biology, despite a persistent debate about whether different organisms, and in particular plants, form discrete units that correspond to species. This debate is particularly relevant when taxonomic divisions at the species level are used for practical purposes of broad interest. Such is the case of the taxonomic species of “frailejones” (Espeletiinae, Asteraceae), a monophyletic group of plants that is important for the functioning of high mountain ecosystems in northern South America and, at the same time, is quite vulnerable to global change. Previous studies suggest that frailejones from the Sumapaz region, in the Colombian Eastern Cordillera, form a syngameon: a group of species that are morphologically distinct despite exchanging genes through hybridization and introgression. This hypothesis has not been formally tested, but it predicts that morphological groups differ in their ecological niche. The aim of this study was to examine this prediction in terms of a facet of the ecological niche: recruitment and growth during early ontogeny. To achieve this aim, a common garden experiment was carried out in a nursery at 3400 m of elevation, in the Sumapaz region, where 100 seeds of each of 43 mother plants belonging to four morphological groups were sown. The recruitment and growth of the progeny from each mother plant were measured during four years. The morphological groups of mother plants did not form distinct groups of recruitment in the common garden. However, one morphological group showed a lower growth rate than the others. These results only partially supported the syngameon hypothesis, because concordance between morphological groups and groups according to growth was low, albeit statistically significant. Potential causes of demographic exchangeability among “frailejones” are discussed, along with implications of the results for their propagation in the context of ex situ conservation and restoration programs.

Sciadocephala gentryi Pruski & R. Ortiz (Compositae: Eupatorieae: Adenostemmatinae) is a newly described serrate-leaved understory herb endemic to Pasco, Peru, that we compare to its congeners. The second of two Peruvian species is S. amazonica R. M. King & H. Rob., herein newly reported for Peru and vouchered by entire-leaved material found near Iquitos, Loreto. In Peru, each of these two species was first collected and identified to genus by Alwyn Gentry, and these are the only species of Sciadocephala Mattf. with pinnately veined leaf blades and pubescent nectaries. Previously, the two Peruvian collections of S. amazonica were determined in the literature as S. schultze-rhonhofiae Mattf., a trinervate-leaved Ecuador endemic herewith excluded from the flora of Peru. A key to the species of Sciadocephala, a distribution map of Sciadocephala, and preliminary conservation assessments of the two species in Peru are given. Sciadocephala gentryi has several floral characters that have been associated with wind pollination in Eupatorieae.

Hibiscus L. sect. Lilibiscus Hochr. comprises 31 species, the majority of which occur on volcanic islands in the Indian and Pacific Oceans. Four species are currently described in the Mascarene Archipelago: H. boryanus DC., H. fragilis DC., H. genevei Bojer, and H. liliiflorus Cav. Though they are a small group, the Mascarene species in section Lilibiscus have a complex taxonomic history. While type collections and species descriptions are sufficiently detailed to apply the existing names H. liliiflorus and H. genevei to species, the brief species descriptions and insubstantial type collections of H. boryanus and H. fragilis have complicated the application of these two names to the remaining two species. In addition, morphological variation within H. boryanus s.l. as it is currently delimited suggests that the name comprises three distinct species. Thus, the names H. boryanus and H. fragilis could each be applied to one of four species, leaving two species to be described. To determine the proper application of the names H. boryanus and H. fragilis, we conducted a thorough study of herbarium specimens and species descriptions combined with morphometric analyses of seven floral characters obtainable from the 220-year-old type specimens of H. boryanus and H. fragilis and 70 other flowering specimens. Although morphometric analyses were sufficient to determine that the name H. fragilis is best applied to the red-flowered species in Mauritius, additional lines of evidence inferred from the original description of H. boryanus were necessary to apply this name to the yellow-flowered species in Réunion. Consequently, we describe two new species formerly treated under H. boryanus s.l.: a magenta-flowered species endemic to Mauritius (H. dargentii Mashburn) and a red-and-yellow–flowered species endemic to Réunion (H. igneus Mashburn). We provide an identification key to differentiate the Mascarene Hibiscus sect. Lilibiscus species and new and updated species descriptions for all six species.

In memory of George E. Schatz (1953–2024)

Diospyros schatzii Lowry, A. G. Linan & H. N. Rakouth (Ebenaceae), a new species from northeastern Madagascar, is described in honor of George E. Schatz (1953–2024), a renowned expert on the Malagasy flora and a passionate student of the genus Diospyros L. The new species occurs in low- and mid-elevation humid forest at 0–700 m. A preliminary risk of extinction assessment using the IUCN Red List criteria reveals that D. schatzii is Near Threatened (NT).

Alwyn Gentry had unique insights into the diversity of Neotropical rainforests. He observed plant diversity with incredible detail and used the data he and colleagues collected to answer questions on the distribution, ecology, and evolutionary origins of tropical rainforest diversity. Leaning on patterns of species distributions accumulated from intense fieldwork, Gentry discussed numerous ideas and proposed important hypotheses on the evolution of Neotropical rainforests. However, he never advanced these evolutionary ideas in a unified and consistent framework across all scales he treated. For instance, comparing intercontinental differences in rainforest taxa, he suggested Neotropical forests to be “uniquely and phenomenally enriched” compared to other rainforests. This he attributed, among other factors, to increased speciation especially in Andean-centered taxa, linked both directly and indirectly to the uplift of the northern Andes. Even at the smallest scales, he put forward specific hypotheses on the processes of speciation in the Neotropics, ranging from specialization to edaphic conditions in Amazonia to founder-effect–mediated speciation in the Andes. The ensemble of hypotheses and ideas proposed by Gentry on tropical and Neotropical plant evolution, his evolutionary legacy, remains relevant even today. Despite this, many of his contributions may not have received the attention they rightly deserve. Overall, those hypotheses put forward by Gentry that have been tested are well supported, in particular the ones concerning regional and intercontinental scale processes. However, many of his smaller-scale hypotheses have not been tested to our knowledge, or remain inconclusive, highlighting significant knowledge gaps in our understanding of tropical rainforest diversity and evolution. Furthermore, his work and thinking, 30 years on, emphasize significant biases in our current understanding, that being concentrated on large woody plants and specific taxa. Contrary to this, Gentry’s perspective is refreshingly encompassing, not being limited to specific taxa or growth forms. To consolidate and underline his important contributions to tropical plant evolution, we summarize and assemble Al Gentry’s evolutionary ideas and hypotheses here. Leveraging his comprehensive view of tropical rainforest diversity, his ideas provide succinct starting points for future research across disciplines on the ecology and evolution of tropical rainforests.

A taxonomic revision is presented of the Ecuadorian species of Sciodaphyllum P. Browne (Araliaceae) belonging to the Violaceum group, characterized by leaves that often dry with a distinctive purplish or brownish-purple cast, the presence of a long, clawlike, generally adaxially incurved stipular ligule, and flowers borne in umbellules. Analysis of herbarium material supplemented by field observations has revealed a total of 11 species, all but one of which are described as new. This brings the total number of published Sciodaphyllum occurring in Ecuador to 47. An identification key is provided; each species is mapped and illustrated by scans of the type collection, accompanied by color photos taken in the field of four of the new taxa. Preliminary extinction risk assessments conducted using the IUCN Red List criteria indicate that one species is Critically Endangered (CR), four are Endangered (EN), and three are Vulnerable (VU), while three are regarded as Least Concern (LC).

Ecotones are transition zones of plant species compositional turnover, with inherent fractal characteristics corresponding to the shape of boundaries between adjacent bioregions. We characterize present-day ecotones of vascular plants across mainland sub-Saharan Africa and investigate environmental factors associated with their shapes. Specifically, we explore, (1) whether a fractal dimension is appropriate for characterizing the spatial patterns of ecotones, and (2) how the fractal dimensions of present-day ecotones may vary along latitudes and reflect other environmental contrasts between adjacent bioregions. Distributions of 23,189 vascular plant species were partitioned into bioregions across mainland sub-Saharan Africa according to the nonmetric multidimensional scaling (MDS) of Jaccard dissimilarity at 20 km resolution. The optimal number of clusters was determined using K-medoids and Clustering Large Applications (CLARA) algorithms, with the clustering validity evaluated using the silhouette coefficient. The present-day ecotones were then extracted as boundaries between adjacent bioregions, and their spatial patterns measured by the box-counting fractal dimension. Using generalized additive models (GAMs), we explained the variation of the fractal dimensions of present-day ecotones by the absolute differences in mean annual precipitation, mean annual temperature, bulk density, soil clay content, soil sand content, soil organic carbon, soil pH, topographic roughness, fire frequency, human footprint, geographic extent, and latitude, separately, between two adjacent bioregions. The MDS performed reasonably well (stress = 0.057), while CLARA succeeded in partitioning seven geographically distinct clusters (0.49 silhouette coefficient), from which 11 ecotones were identified, with eight characterized as true fractals but having low fractal dimensions (range: from 1.018 to 1.154). The GAM identified the difference in mean annual precipitation as significant (P = 0.02) for explaining the variation of the fractal dimensions of present-day ecotones with the difference in soil organic carbon near-significant (P = 0.07). The fractal dimensions also showed a moderate correlation with the difference in human footprint between adjacent bioregions (Spearman’s rho = 0.619), albeit not significant (P = 0.11). Overall, by spatially characterizing the present-day ecotones between different bioregions, we showed that the fractal dimension is an appropriate method for shape quantification and characterization of ecotones. We further highlighted key environmental factors that could explain the formation of present-day ecotones and thus the compositional turnover of vascular plant species across sub-Saharan Africa.