Abstract—The diverse and spectacular Hibisceae tribe comprises over 750 species. No studies, however, have broadly sampled across the dozens of genera in the tribe, leading to uncertainty in the relationships among genera. The non-monophyly of the genusHibiscusis infamous and challenging, whereas the monophyly of most other genera in the tribe has yet to be assessed, including the large genusPavonia.Here we significantly increase taxon sampling in the most complete phylogenetic study of the tribe to date. We assess monophyly of most currently recognized genera in the tribe and include three and thirteen newly sampled sections ofHibiscusandPavonia,respectively. We also include five rarely sampled genera and 137 species previously unsampled. Our phylogenetic trees demonstrate thatHibiscus, as traditionally defined, encompasses at least 20 additional genera. The status ofPavoniaemerges as comparable in complexity toHibiscus. We offer clarity in the phylogenetic placement of several taxa of uncertain affinity (e.g.Helicteropsis,Hibiscadelphus, Jumelleanthus,andWercklea). We also identify two new clades and elevate them to the generic rank with the recognition of two new monospecific genera: 1)BlanchardiaM.M.Hanes & R.L.Barrett is a surprising Caribbean lineage that is sister to the entire tribe, and 2)AstrohibiscusMcLay & R.L.Barrett represents former members ofHibiscus caesiuss.l.CraveniaMcLay & R.L.Barrett is also described as a new genus for theHibiscus panduriformisclade, which is allied toAbelmoschus. Finally, we introduce a new classification for the tribe and clarify the boundaries ofHibiscusandPavonia.

Quantifying spatial species richness is useful to describe biodiversity patterns across broad geographic areas, especially in large, poorly known plant groups. We explore patterns and predictors of species richness across Africa in one such group; the paleotropical genus Grewia L. (Malvaceae). Grewia species richness was quantified by extracting herbarium records from GBIF and Tropicos and creating geographic grids at varying spatial scales. We assessed predictors of species richness using spatial regression models with 30 environmental variables. We explored species co-occurrence in Madagascar at finer resolutions using Schoener's index, and compared species’ range sizes and IUCN status among ecoregions. Lastly, we derived a trait matrix for a subset of species found in Madagascar to characterize morphological diversity across space. Grewia species occur in 50 countries in Africa, with the highest number of species in Madagascar (93, with 80 species endemic). Species richness is highest in Madagascar, with up to 23 Grewia species in a grid cell, followed by coastal Tanzania/Kenya (up to 13 species), and northern South Africa and central Angola (11 species each). Across Africa, higher species richness was predicted by variables related to aridity. In Madagascar, a greater range in environmental variables best predicted species richness, consistent with geographic grid cells of highest species richness occurring near biome/ecoregion transitions. In Madagascar we also observe increasing dissimilarity in species composition with increasing geographic distance. The spatial patterns and underlying environmental predictors that we uncover in Grewia represent an important step in our understanding of plant distribution and diversity patterns across Africa. Madagascar boasts nearly twice the Grewia species richness, compared to the second most species-rich country in Africa, which might be explained by complex topography and environmental conditions across small spatial scales.

Recent phylogenetic studies have demonstrated that Hibiscus L. as traditionally defined is grossly polyphyletic. In a major step towards making Hibiscus monophyletic, the genus Sabdariffa (DC.) Kostel. is here reinstated for Hibiscus section Furcaria DC. In total, 123 new combinations are provided (for 117 species and 6 subspecies). Numerous lectotypes are designated. Sabdariffa has a pantropical distribution, with high species diversity in tropical Africa, tropical America and northern Australia. False roselle (Sabdariffa acetosella (Welw. ex Hiern) M.M.Hanes & R.L.Barrett), kenaf (Sabdariffa cannabina (L.) M.M.Hanes & R.L.Barrett) and roselle (Sabdariffa gossypiifolia (Mill.) M.M.Hanes & R.L.Barrett) are all of global economic significance. Ma‘o hau hele (Sabdariffa brackenridgei (A.Gray) M.M.Hanes & R.L.Barrett) is the official state flower of Hawai’i. Full synonymy and type details are included, along with distributions and references to existing descriptions for all species. A series of regional keys to species is presented here with current names in Sabdariffa.

The spiny thicket of southwestern Madagascar represents an extreme and ancient landscape with extraordinary levels of biodiversity and endemism. Few hypotheses exist for explaining speciation in the region and few plant studies have explored hypotheses for species diversification. Here, we investigate three species in the endemic genus Megistostegium (Malvaceae) to evaluate phylogeographic structure and explore the roles of climate, soil, and paleoclimate oscillations on population divergence and speciation throughout the region. We combine phylogenetic and phylogeographic inference of RADseq data with ecological niche modeling across space and time. Population structure is concurrent with major rivers in the region and we identify a new, potentially important biogeographic break coincident with several landscape features. Our data further suggests that niches occupied by species and populations differ substantially across their distribution. Paleodistribution modeling provide evidence that past climatic change could be responsible for the current distribution, population structure, and maintenance of species in Megistostegium.

Hanes, M.M., B. Mashburn & M.W. Callmander (2022). Transfert des espèces endémiques malgaches du genre Kosteletzkya à Hibiscus et Perrierophytum (Malvaceae). Candollea 77: 161–171. En anglais, résumés anglais et français. Madagascar abrite huit espèces qui sont actuellement assignées au genre pantropical Kosteletzkya C. Presl. (Malvaceae). Des études phylogénétiques ont révélé que ces espèces ne sont pas monophylétiques et, au contraire, se répartissent en trois clades distinctes, de rang générique. L'espèce africaine répandue K. adoensis (Hochst. ex A. Rich.) Mast. est la seule espèce du genre Kosteletzkya reconnue à Madagascar, tandis que les sept espèces endémiques malgaches de Kosteletzkya sont transférées à Hibiscus L. et Perrierophytum Hochr. conformément à la morphologie, à la compréhension phylogénétique et à la délimitation générique. Nous proposons donc sept nouvelles combinaisons: Hibiscus retrobracteatus (Hochr.) M.M. Hanes & Callm., Perrierophytum macranthum (Hochr.) M.M. Hanes & Callm., P. madagascariense (Baker) M. Hanes & Callm., P. malvocoeruleum (Hochr.) M. Hanes & Callm., P. reflexiflorum (Hochr.) M.M. Hanes & Callm., P. thouarsianum (Baill.) M.M. Hanes & Callm. et P. velutinum (Garcke) M.M. Hanes & Callm. Quatre nouveaux synonymes sont également proposés et cinq lectotypes sont désignés. Les évaluations du risque d'extinction de ces sept espèces indiquent que deux taxons doivent être classés dans la catégorie «Préoccupation mineure», une «En danger» et quatre «En danger critique d'extinction».