Global biodiversity loss threatens not only species survival but also the loss of unique evolutionary history, highlighting the need to understand how macroevolutionary processes shape the evolutionary diversity and its vulnerability to extinction. Radiations of arid-adapted plants provide a useful system to examine how diversification and dispersal generate present-day biodiversity patterns.Here, we reconstruct the evolutionary history of Agave across the Americas using a time-calibrated phylogenomic framework (207 taxa, 286 nuclear genes) and integrate these results with biogeographic inference and Evolutionarily Distinct and Globally Endangered (EDGE) metrics to identify conservation priorities.We find that Agave originated in Aridoamerica during the late Miocene (∼7 Ma), followed by dispersal into Mesoamerica, Central America, and the Caribbean. This history has generated a spatially uneven distribution of evolutionary distinctiveness, with arid ecosystems harboring a disproportionate share of evolutionarily unique and threatened lineages. We identify 70 EDGE taxa, with exceptional conservation priority (the most endangered species were: Agave montium-sancticaroli, A. aurea var. promontorii, and A. albopilosa in EDGE and EDGE2). We identify key regions in Mexico, USA, and Guatemala—such as the Tehuacán–Cuicatlán Valley, Oaxaca, the Chihuahuan Desert and Arizona—that combine high phylogenetic diversity with elevated concentrations of threatened evolutionary history.These patterns reflect the interaction between macroevolutionary dynamics, and ecological specialization, and are further intensified by anthropogenic pressures, as evidenced by the high proportion of Agave species listed under the IUCN Red List. Our results demonstrate that integrating evolutionary history with extinction risk can improve spatial conservation prioritization.

The Itremo Massif Protected Area was established and is managed by Kew Madagascar. Here, we publish a plant species checklist of the Itremo Massif Protected Area. It is one of the first expert-verified plant species checklists to be generated for a protected area in Madagascar and includes 749 plant species, 353 genera and 103 families. For each species, full synonymy, notes on vernacular names, global distribution, distribution in Madagascar, elevation, habitat and ecology, flowering period, conservation status and specimen lists are provided.

A new range-restricted species of Placodiscus Radlk. is described, mapped and illustrated. Placodiscus bijugus is a cauliflorous tree (4 –) 5 – 10 m tall, characterised by having leaves with two pairs of leaflets, 1 (– 2)-flowered cymules with minute bracts, a glabrous disk, pedicels 3 – 3.2 mm long and large (3 – 4 cm diam.), shortly stipitate, retuse fruits, orbicular in outline. It is similar to P. caudatus Pierre ex Pellegr., which has been reported from surveys in Cameroon. We discuss the typification and range of the latter species, which in fact appears to be absent from Cameroon. Placodiscus bijugus is provisionally assessed as Endangered [EN B1ab(iii)+2ab(iii)] using the IUCN Red List Categories and Criteria, since only three locations with threats are reported. The species has a small, slightly disjunct range between Mt Cameroon and Korup National Park in coastal South West Region Cameroon. We review other species with this disjunct range.

Malvales is a diverse order of flowering plants, economically and ecologically relevant, and it is known for its broad morphological variability. Recent phylogenomic studies have revealed a complex evolutionary history for the order, including localised phylogenetic discordances among nuclear loci. However, since the late 1990s, Malvales classification has largely been neglected. This study aims to address this gap by revisiting the classification of Malvales, with a focus on its largest family, Malvaceae. By integrating phylogenomic and morphological datasets, our primary goals are to provide an updated phylogeny for the order and to map key traits supporting a revised suprageneric classification, while accounting for gene and species tree conflicts. Our molecular dataset included 194 genera and 309 nuclear genes, obtained through target sequence capture using Angiosperms353 probes. This dataset covers approximately half of the known genera in the order, representing all families and subfamilies, as well as nearly all tribes, and all subtribes. A coalescent approach utilising nuclear gene trees was used to infer phylogenetic relationships. A morphological matrix with 50 characters relevant for suprageneric classification was compiled, and character-state distributions for selected traits were mapped against the phylogenetic tree to identify and discuss diagnostic features for clades. Phylogenetic relationships and the monophyly of most groups aligned closely with previous studies. Morphological traits that define key clades varied significantly across Malvales, with differences observed in growth habit, leaf structure, pollen type, floral features, and fruit/seed morphology. In Malvaceae, we resolved uncertainties in the early Malvoideae lineages, and we describe a new tribe, Pentaplareae tr. nov., which clarifies the taxonomic placement of a previously uncertain genus. Additionally, we propose the recognition of a new subfamily, Matisioideae subfam. nov., elevated from its former status as a tribe, and positioned as the sister group to Malvoideae. This study highlights how taxonomic frameworks can be refined even in the face of conflicting phylogenomic data, demonstrating the importance of integrating molecular and morphological evidence in revising classifications.

Angiosperms are the cornerstone of most terrestrial ecosystems and human livelihoods(1,2). A robust understanding of angiosperm evolution is required to explain their rise to ecological dominance. So far, the angiosperm tree of life has been determined primarily by means of analyses of the plastid genome(3,4). Many studies have drawn on this foundational work, such as classification and first insights into angiosperm diversification since their Mesozoic origins(5-7). However, the limited and biased sampling of both taxa and genomes undermines confidence in the tree and its implications. Here, we build the tree of life for almost 8,000 (about 60%) angiosperm genera using a standardized set of 353 nuclear genes(8). This 15-fold increase in genus-level sampling relative to comparable nuclear studies(9) provides a critical test of earlier results and brings notable change to key groups, especially in rosids, while substantiating many previously predicted relationships. Scaling this tree to time using 200 fossils, we discovered that early angiosperm evolution was characterized by high gene tree conflict and explosive diversification, giving rise to more than 80% of extant angiosperm orders. Steady diversification ensued through the remaining Mesozoic Era until rates resurged in the Cenozoic Era, concurrent with decreasing global temperatures and tightly linked with gene tree conflict. Taken together, our extensive sampling combined with advanced phylogenomic methods shows the deep history and full complexity in the evolution of a megadiverse clade.

With a focus on the Millennium Seed Bank of the Royal Botanic Gardens, Kew, this chapter looks at the vital contribution made to conservation by this seed bank and those who work in partnership with it. The role of botanic gardens in seed banking is explored, together with the development of the Millennium Seed Bank Partnership (MSBP). The process of seed collecting and banking is outlined, together with the advantages and disadvantages of this approach to ex situ conservation. The importance of making high-quality collections is emphasized and discussed in relation to nomenclature, genetic diversity, sample size, viability and longevity, and the data associated with a seed collection. The role of the MSBP's program of technology transfer is defined, and the need for access to collections stressed. Ensuring legal access and frameworks are in place for collecting, storing, and using plant material by a third party is explored. Case studies are presented highlighting the important uses to which MSBP collections can be put, both in the UK and overseas, including support for agriculture, forestry, livelihoods, and restoration.

Madagascar’s biota is hyperdiverse and includes exceptional levels of endemicity. We review the current state of knowledge on Madagascar’s past and current terrestrial and freshwater biodiversity by compiling and presenting comprehensive data on species diversity, endemism, and rates of species description and human uses, in addition to presenting an updated and simplified map of vegetation types. We report a substantial increase of records and species new to science in recent years; however, the diversity and evolution of many groups remain practically unknown (e.g., fungi and most invertebrates). Digitization efforts are increasing the resolution of species richness patterns and we highlight the crucial role of field- and collections-based research for advancing biodiversity knowledge and identifying gaps in our understanding, particularly as species richness corresponds closely to collection effort. Phylogenetic diversity patterns mirror that of species richness and endemism in most of the analyzed groups. We highlight humid forests as centers of diversity and endemism because of their role as refugia and centers of recent and rapid radiations. However, the distinct endemism of other areas, such as the grassland-woodland mosaic of the Central Highlands and the spiny forest of the southwest, is also biologically important despite lower species richness. The documented uses of Malagasy biodiversity are manifold, with much potential for the uncovering of new useful traits for food, medicine, and climate mitigation. The data presented here showcase Madagascar as a unique “living laboratory” for our understanding of evolution and the complex interactions between people and nature. The gathering and analysis of biodiversity data must continue and accelerate if we are to fully understand and safeguard this unique subset of Earth’s biodiversity.

Madagascar's unique biota is heavily affected by human activity and is under intense threat. Here, we review the current state of knowledge on the conservation status of Madagascar's terrestrial and freshwater biodiversity by presenting data and analyses on documented and predicted species-level conservation statuses, the most prevalent and relevant threats, ex situ collections and programs, and the coverage and comprehensiveness of protected areas. The existing terrestrial protected area network in Madagascar covers 10.4% of its land area and includes at least part of the range of the majority of described native species of vertebrates with known distributions (97.1% of freshwater fishes, amphibians, reptiles, birds, and mammals combined) and plants (67.7%). The overall figures are higher for threatened species (97.7% of threatened vertebrates and 79.6% of threatened plants occurring within at least one protected area). International Union for Conservation of Nature (IUCN) Red List assessments and Bayesian neural network analyses for plants identify overexploitation of biological resources and unsustainable agriculture as themost prominent threats to biodiversity. We highlight five opportunities for action at multiple levels to ensure that conservation and ecological restoration objectives, programs, and activities take account of complex underlying and interacting factors and produce tangible benefits for the biodiversity and people of Madagascar.

Extinction has increased as human activities impact ecosystems, yet relatively few species have conservation assessments. Novel approaches are needed to highlight threatened species that are currently data-deficient. Many Madagascan plant species have extremely narrow ranges, but this may not have always been the case—it is unclear how the island's diverse flora evolved. To assess this, we generated restriction-site associated DNA sequence data for 10 Madagascan plant species, estimated effective population size ( N e ) for each species and compared this to census ( N c ) sizes. In each case, N e was an order of magnitude larger than N c —signifying rapid, recent population decline. We then estimated species' demographic history, tracking changes in N e over time. We show that it is possible to predict extinction risk, particularly in the most threatened species. Furthermore, simulations showed that our approach has the power to detect population decline during the Anthropocene. Our analyses reveal that Madagascar's micro-endemics were not always rare, having experienced a rapid decline in their recent history. This casts further uncertainty over the processes that generated Madagascar's exceptional biodiversity. Our approach targets data-deficient species in need of conservation assessment, particularly in regions where human modification of the environment has been rapid.

Tropical grassy biomes have variable tree cover and are often characterized by a flammable grassy ground layer where the dominating grass species have strategies to persist and proliferate with frequent fire. However, there is limited understanding of how grass growth and flammability traits respond to light availability. We experimentally grew 14 grass species characteristic of the Malagasy Central Highlands for one year with four treatments of light exclusion ranging from 0 – 60%. Eight plant functional traits and four leaf flammability traits were measured: plant height, bulk density, aboveground biomass, belowground biomass, ratio of root to shoot biomass, specific leaf area, leaf length, leaf width, leaf heat release capacity, temperature of maximum decomposition, total heat release and peak heat release rate. Belowground biomass, the ratio of root to shoot biomass, and bulk density were all negatively affected by decreasing light availability. Surprisingly, aboveground biomass showed no significant change with changing light availability, although there was a trend toward shorter plants in low light. At a leaf level, declining light availability increased specific leaf area, leaf length, and leaf width. In terms of leaf flammability, of the four traits measured, unexpectedly, only leaf total heat release was significantly positively related to declining light availability. These results suggest field alterations in grass flammability may be primarily related to plant architecture and microclimates. The shifts in allometry and substantial reduction in belowground biomass suggest that grasses would be rapidly lost from shaded environments with a diminished competitive capacity to resprout.

Gloeocantharellus andasibensis sp. nov. is recognized by orange-red basidiomata with a convex to plane, innately fibrillose and viscid pileus, ellipsoid to amygdaliform, small, verrucose basidiospores, and a distinct nrITS sequence. This is the first record of the genus from Madagascar. To improve the understanding of the nomenclature of the genus, the type specimen of G. okapaensis and specimens of G. lateritius and G. corneri accessioned in the fungarium of the Royal Botanic Gardens, Kew were also sequenced.

Gloeocantharellus andasibensis sp. nov. is recognized by orange-red basidiomata with a convex to plane, innately fibrillose and viscid pileus, ellipsoid to amygdaliform, small, verrucose basidiospores, and a distinct nrITS sequence. This is the first record of the genus from Madagascar. To improve the understanding of the nomenclature of the genus, the type specimen of G. okapaensis and specimens of G. lateritius and G. corneri accessioned in the fungarium of the Royal Botanic Gardens, Kew were also sequenced.

The genus Hygroaster (Hygrophoraceae, Hygrophorineae) is a small genus with a tropical distribution. Based on morphological and phylogenetic analysis, two new species, H. madagascarensis and H. andasibensis, are described from Madagascar. They are the first species of this genus described from Africa. To stabilize the nomenclature, the type specimens of H. nodulisporus, the type species of the genus, and H. fucatus were studied. The initial combination of the name Hygrophorus nodulisporus in the genus Hygroaster was invalid and is thus validated here. In addition, our study revealed that H. fucatus belongs to the genus Asproinocybe in suborder Tricholomatineae, whose representatives also have nodulose basidiospores. A new combination A. fucata is proposed.

Summary This paper is the fourth part of the taxonomic revision of the genus Phyllanthus in Madagascar and the Comoro Islands. Here we treat Pseudogomphidium Ralim. & Cable sect. nov. consisting of nine species that we misplaced in the subgenus Gomphidium (Baill.) G.L.Webster in our previous paper. Two species are new to science: Phyllanthus razakamalalae Ralim. & Cable, sp. nov. and P. ankirindrensis Ralim. & Cable, sp. nov. We also treat three unplaced species: P. analamerae Leandri, P. coluteoides Müll.Arg. and P. vergens Baill. An identification key, descriptions, distribution maps and IUCN Red List assessments are provided.

SummaryBrexia madagascariensis (Lam.) Ker Gawl is native in East Madagascar. There are at least 25 known subpopulations growing mostly in humid forest (IUCN 2020), particularly in remnant patches of coastal forest. It was listed as ‘Least Concern’ on the IUCN Red Lists in 2007; however, continuing pressure on forests and potential taxonomic changes may require this to be reviewed. Madagascar has very high deforestation rates, primarily caused by logging and widespread shifting cultivation. Germination and cultivation for in‐situ and ex‐situ conservation are easily achievable and this small tree is ideal for education and display in botanic gardens. The leaves of juvenile plants are long and spiny, while the adult leaves tend to be more rounded and lack the spines.

The ecology of Madagascar's grasslands is under-investigated and the dearth of ecological understanding of how disturbance by fire and grazing shapes these grasslands stems from a perception that disturbance shaped Malagasy grasslands only after human arrival. However, worldwide, fire and grazing shape tropical grasslands over ecological and evolutionary timescales, and it is curious Madagascar should be a global anomaly. We examined the functional and community ecology of Madagascar's grasslands across 71 communities in the Central Highlands. Combining multivariate abundance models of community composition and clustering of grass functional traits, we identified distinct grass assemblages each shaped by fire or grazing. The fire-maintained assemblage is primarily composed of tall caespitose species with narrow leaves and low bulk density. By contrast, the grazer-maintained assemblage is characterized by mat-forming, high bulk density grasses with wide leaves. Within each assemblage, levels of endemism, diversity and grass ages support these as ancient assemblages. Grazer-dependent grasses can only have co-evolved with a now-extinct megafauna. Ironically, the human introduction of cattle probably introduced a megafaunal substitute facilitating modern day persistence of a grazer-maintained grass assemblage in an otherwise defaunated landscape, where these landscapes now support the livelihoods of millions of people.

SummaryThe status of Madagascar's plant diversity is briefly reviewed, together with a consideration of the key threats and approaches used in conserving this unique flora. The role of the Kew Madagascar Conservation Centre is reviewed in relation to species discovery and conservation.

Abstract Madagascar is home to 208 indigenous palm species, almost all of them endemic and >80% of which are endangered. We undertook complete population census and sampling for genetic analysis of a relatively recently discovered giant fan palm, the Critically Endangered Tahina spectablis in 2008 and 2016. Our 2016 study included newly discovered populations and added to our genetic study. We incorporated these new populations into species distribution niche model (SDM) and projected these onto maps of the region. We developed population matrix models based on observed demographic data to model population change and predict the species vulnerability to extinction by undertaking population viability analysis (PVA). We investigated the potential conservation value of reintroduced planted populations within the species potential suitable habitat. We found that the population studied in 2008 had grown in size due to seedling regeneration but had declined in the number of reproductively mature plants, and we were able to estimate that the species reproduces and dies after approximately 70 years. Our models suggest that if the habitat where it resides continues to be protected the species is unlikely to go extinct due to inherent population decline and that it will likely experience significant population growth after approximately 80 years due to the reproductive and life cycle attributes of the species. The newly discovered populations contain more genetic diversity than the first discovered southern population which is genetically depauperate. The species appears to demonstrate a pattern of dispersal leading to isolated founder plants which may eventually lead to population development depending on local establishment opportunities. The conservation efforts currently put in place including the reintroduction of plants within the species potential suitable habitat if maintained are thought likely to enable the species to sustain itself but it remains vulnerable to anthropogenic impacts.

Grassland, woodland, and forest are three key vegetation types that co-occur across the central highlands of Madagascar, where the woodland has historically been considered as degraded forest. Here, we use grass functional traits to inform our understanding of the biogeography of Malagasy vegetation and the differentiation of vegetation types in the region. We sampled grass community composition at 56 sites across the central highlands of Madagascar spanning grassland, woodland, and forest. We selected seven functional traits known to correlate with different aspects of life history collated via GrassBase (habit, culm type, physiology, leaf consistency, plant height, leaf width, and leaf length) for the 71 constituent species. Via analyses of the beta diversity, rank abundance, functional dispersion, functional group richness, and community phylogenetic structure of grassland communities, we differentiate these vegetation types using plant functional traits. Grassland and woodland are highly similar in grass species composition and dominated by the same species (Loudetia simplex, Trachypogon spicatus, and Schizachyrium sanguineum). In contrast, forest grass species composition significantly differs from both grassland and woodland. Consistent with these species composition patterns, the vegetation types can be distinguished based on physiology, culm type, and leaf consistency. Forests harbor primarily C-3 grasses, which are almost invariably laterally spreading with herbaceous leaves. In contrast, both grassland and woodland species are predominantly tall, caespitose C-4 grasses with coriaceous leaves. Forest grasses are phylogenetically clustered and less diverse than the grassland and woodland communities. Further, we sampled bark thickness of the common woody species occurring in the woodland and forest of the region and found that the relative bark thickness of the woodland tree species was significantly greater than that of forest species from the same genus. We found that the functional traits and architecture of grasses diverge strongly between forest and the grassland-woodland mosaic. We conclude that the woodlands, primarily dominated by Uapaca bojeri Baill., are a form of savanna and not forest as has been previously suggested.

Morphological character data are used to show that a distinct morphotype of Dioscorea L. from the Irodo valley (East of Sadjoavato) in Antsiranana Province of Madagascar is an undescribed species, differing in its leaf arrangement, pubescence form and male inflorescence structure from all other taxa. It is described as Dioscorea irodensis Wilkin, Rajaonah & Randriamb., illustrated and a distribution map and ecological information provided. It is known from three sites, but is likely to have been eradicated from one of them. The population that has been studied in the field contains a very low number of adult plants. Tubers have been extracted for use as food at a level that appears to be unsustainable. Thus its provisional IUCN conservation status assessment is that it is critically endangered (CR). Its vernacular name in Irodo is Bemandry.