Kenneth J. Wurdack

Oceanic islands are natural laboratories for investigating the processes that generate, maintain, and redistribute biodiversity through time. An ideal flowering plant system to investigate these processes is Grewia L. (Malvaceae, Grewioideae), comprising ca. 283 species, of which nearly 30% are endemic to Madagascar, where they display considerable morphological diversity. Using Angiosperms353 target-capture sequencing for 171 accessions (119 Grewia spp.), we reconstructed the first densely sampled phylogeny of Grewia and performed divergence-time estimation, diversification analyses, and ancestral-range reconstruction. Our results support a Malagasy origin of the crown group around 27 million years ago, followed by extensive in situ diversification of Grewia . Repeated dispersal events from Madagascar to continental Africa subsequently contributed to the establishment of new African lineages, whereas colonization of the western Indian Ocean islands was more recent and resulted in anagenetic dispersals. Africa acted as the principal source of dispersal toward Arabia and into tropical Asia, suggesting the presence of a Miocene Afro-Arabian migration corridor under warm and humid conditions. Subsequent eastward dispersal from Asia to Australia is consistent with the stepping stone pathway provided by the Sunda and Sahul regions during the Miocene. This complex dispersal history was likely aided by fleshy fruits adapted for endozoochory. Our new evolutionary framework provides a robust basis for future taxonomic revision of this morphologically and ecologically diverse genus, and for identifying which characters have contributed to its exceptional diversification. Highlights: This is the first phylogenomic analysis of Grewia , one of the largest genera in Malvaceae. We reconstruct dispersal events for Grewia across the Paleotropics. Miocene corridors and fleshy fruits aided dispersal out of Africa and eastward. Grewia originated in Madagascar at 27 Ma and colonised Africa at least 5 times. Madagascar is the center of Grewia diversity with more than 80 endemic species.

Cheilosoideae is the smallest and earliest-diverging of the four subfamilies of Euphorbiaceae, with seven species grouped in two morphologically similar pa

Floras and botanical collections are essential tools for understanding plant diversity, promoting its conservation, and supporting a wide range of scientific applications. Uruguay, located in the biodiverse grassland region of southern South America, has had only an incomplete Flora, the most comprehensive of which was published more than a century ago. We review the country's flora and the history of its study, and introduce the new Flora Uruguaya Online (FUO; https://florauruguaya.org ), which when completed will provide a comprehensive record of all vascular plant species, including information on their distribution, morphological, ecological, and phenological characteristics. This online Flora presently contains information on 182 families, 1053 genera, and 3112 species, 85.4% of which are native to Uruguay and 2.2% endemic. Although Uruguay accounts for only 25% of the surface area of the Río de la Plata Grasslands, it contains over 60% of their species and more than 50% of their endemic taxa, reflecting its core geographical position. Uruguay's flora faces increasing pressure from land‐use change, habitat fragmentation, and invasive species. FUO provides critical support for addressing these challenges, offering systematic botanical data for basic and applied research, conservation, sustainable uses, and land management, including practical applications such as the identification of toxic plants affecting livestock production. We highlight key features of FUO with its research‐enabling tools for the exploration of Uruguay's botanical richness by scientists, as well as by policymakers, educators, conservationists, and citizens. These features include its accessibility, interactivity, multiple filters (e.g., geographic regions, ecological characteristics, conservation status, or specific species attributes), rich graphics, and multiple sources of data inputs tied to herbarium specimens.

Morphological and molecular phylogenetic evidence indicate that Eleutherostylis Burret (Malvaceae, Grewioideae), a monotypic genus described from New Guinea, is best considered a synonym of Grewia L., a species-rich genus widespread across the Paleotropics and found in Africa, Arabia, Asia, Australia and the western Pacific. A new combination, based on E. renistipulata Burret, G. renistipulata (Burret) Dorr, comb. nov., is proposed. Original material of the basionym could not be located and a neotype is designated. A lectotype is designated for G. morotaiensis Kosterm., a synonym of G. renistipulata.

Bahiana is expanded from 1 to 2 species with the description of B. occidentalis K. Wurdack, sp. nov. as a new endemic of the seasonally dry tropical forests (SDTFs) of Peru. The disjunct distribution of Bahiana with populations of B. occidentalis on opposite sides of the Andes in northwestern Peru (Tumbes, San Martín) and B. pyriformis in eastern Brazil (Bahia) adds to the phytogeographic links among the widely scattered New World SDTFs. Although B. occidentalis remains imperfectly known due to the lack of flowering collections, molecular phylogenetic results from four loci (plastid matK, rbcL, and trnL-F; and nuclear ITS) unite the two species as does gross vegetative morphology, notably their spinose stipules, and androecial structure. Spinescence in Euphorbiaceae was surveyed and found on vegetative organs in 25 genera, which mostly have modified sharp branch tips. Among New World taxa, spines that originate from stipule modifications only occur in Bahiana and Acidocroton, while the intrastipular spines of Philyra are of uncertain homologies.

Molecular phylogenetic analyses of Malvaceae subfamily Dombeyoideae based on a 6‐marker dataset sampling all 21 currently accepted genera (including extinctAstyria) yielded improved resolution and evidence for multiple generic circumscription problems. The taxonomy of the subfamily is adjusted with the synonymization of 10 genera (eight in current use) and the description of one new one, for a revised Dombeyoideae comprised of 14 genera and supported by morphological, anatomical, and/or palynological evidence.Eriolaenais expanded from a narrow Indo‐Asian group to include the Malagasy endemic generaHelmiopsisandHelmiopsiella, and a recently described species from continental Africa. A conspectus is presented of the new broadly circumscribedEriolaenawith 27 species (28 taxa, including 3 new Malagasy species and 16 new combinations) and defined by a unique winged‐seed morphology. A new monotypic Malagasy genus (Hafotra), resolved as sister toEriolaena, is described. A conspectus is presented of a broadly circumscribed Mascarene‐MalagasyRuizia(+AstyriaandTrochetia, with 13 new combinations). Two other genera are expanded and recircumscribed:Melhania(+TrochetiopsisandParamelhania, with one new name and two new combinations) andCorchoropsis(+Paradombeya, with two new combinations). Additionally, two genera are typified, and 21 names are lectotypified.

The systematics of Tryssophyton, herbs endemic to the Pakaraima Mountains of western Guyana, is reviewed and Tryssophyton quadrifolius K.Wurdack & Michelang., sp. nov. from the summit of Kamakusa Mountain is described as the second species in the genus. The new species is distinguished from its closest relative, Tryssophyton merumense, by striking vegetative differences, including number of leaves per stem and leaf architecture. A phylogenetic analysis of sequence data from three plastid loci and Melastomataceae-wide taxon sampling is presented. The two species of Tryssophyton are recovered as monophyletic and associated with mostly Old World tribe Sonerileae. Fruit, seed and leaf morphology are described for the first time, biogeography is discussed and both species are illustrated.

Plukenetia is a small pantropical genus of lianas and vines with variably sized edible oil-rich seeds that presents an ideal system to investigate neotropical and pantropical diversification patterns and seed size evolution. We assessed the biogeography and seed evolution of Plukenetia through phylogenetic analyses of a 5069 character molecular dataset comprising five nuclear and two plastid markers for 86 terminals in subtribe Plukenetiinae (representing 20 of ~ 23 Plukenetia species). Two nuclear genes, KEA1 and TEB, were used for phylogenetic reconstruction for the first time. Our goals were: (1) produce a robust, time-dependent evolutionary framework for Plukenetia using BEAST; (2) reconstruct its biogeographical history with ancestral range estimation in BioGeoBEARS; (3) define seed size categories; (4) identify patterns of seed size evolution using ancestral state estimation; and (5) conduct regression analyses with putative drivers of seed size using the threshold model. Plukenetia was resolved into two major groups, which we refer to as the pinnately- and palmately-veined clades. Our analyses suggest Plukenetia originated in the Amazon or Atlantic Forest of Brazil during the Oligocene (28.7 Mya) and migrated/dispersed between those regions and Central America/Mexico throughout the Miocene. Trans-oceanic dispersals explain the pantropical distribution of Plukenetia, including from the Amazon to Africa in the Early Miocene (17.4 Mya), followed by Africa to Madagascar and Africa to Southeast Asia in the Late Miocene (9.4 Mya) and Pliocene (4.5 Mya), respectively. We infer a single origin of large seeds in the ancestor of Plukenetia. Seed size fits a Brownian motion model of trait evolution and is moderately to strongly associated with plant size, fruit type/dispersal syndrome, and seedling ecology. Biome shifts were not drivers of seed size, although there was a weak association with a transition to fire prone semi-arid savannas. The major relationships among the species of Plukenetia are now well-resolved. Our biogeographical analyses support growing evidence that many pantropical distributions developed by periodic trans-oceanic dispersals throughout the Miocene and Pliocene. Selection on a combination of traits contributed to seed size variation, while movement between forest edge/light gap and canopy niches likely contributed to the seed size extremes in Plukenetia.

Raveniopsis microphyllus K.Wurdack, sp. nov., a new species known only from a single peak in the Pakaraima Mtns. of Guyana, is described and illustrated. This white-flowered shrub adds to the many narrow-endemic Guiana Shield species in the genus, and is unique in bearing small, trifoliate, sclerophyllous leaves. Leaf anatomy and surface micromorphology of the new species were examined to document its montane adaptations. The multiple trichome types of the leaves and flowers of new species were characterized, and the systematics value of the considerable foliar trichome variation in Raveniopsis is discussed.

Dendrothrix condorensis K.Wurdack, sp. nov. from the sub-Andean cordilleras of Ecuador and Peru is described and illustrated. The new species is geographically widely separated from its likely closest relative, D. yutajensis, which is endemic to the Guiana Shield region of southern Venezuela and adjacent Brazil, and notably differs in leaf morphology. Vegetative (i.e., epidermal micropapillae, trichomes) and reproductive (i.e., cymule glands, flowers, pollen) micromorphological features were examined with SEM. Rare tristaminate flowers were documented among the typical bistaminate ones. Seeds and diagnostic features among the four species of Dendrothrix are compared. Dendrothrix condorensis K.Wurdack, sp. nov. from the sub-Andean cordilleras of Ecuador and Peru is described and illustrated. The new species is geographically widely separated from its likely closest relative, D. yutajensis, which is endemic to the Guiana Shield region of southern Venezuela and adjacent Brazil, and notably differs in leaf morphology. Vegetative (i.e., epidermal micropapillae, trichomes) and reproductive (i.e., cymule glands, flowers, pollen) micromorphological features were examined with SEM. Rare tristaminate flowers were documented among the typical bistaminate ones. Seeds and diagnostic features among the four species of Dendrothrix are compared.