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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 the most 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.

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.

Seed size shapes plant evolution and ecosystems, and may be driven by plant size and architecture, dispersers, habitat and insularity. How these factors influence the evolution of giant seeds is unclear, as are the rate of evolution and the biogeographical consequences of giant seeds. We generated DNA and seed size data for the palm tribe Borasseae (Arecaceae) and its relatives, which show a wide diversity in seed size and include the double coconut (Lodoicea maldivica), the largest seed in the world. We inferred their phylogeny, dispersal history and rates of change in seed size, and evaluated the possible influence of plant size, inflorescence branching, habitat and insularity on these changes. Large seeds were involved in 10 oceanic dispersals. Following theoretical predictions, we found that: taller plants with fewer-branched inflorescences produced larger seeds; seed size tended to evolve faster on islands (except Madagascar); and seeds of shade-loving Borasseae tended to be larger. Plant size and inflorescence branching may constrain seed size in Borasseae and their relatives. The possible roles of insularity, habitat and dispersers are difficult to disentangle. Evolutionary contingencies better explain the gigantism of the double coconut than unusually high rates of seed size increase., (© 2020 The Authors New Phytologist © 2020 New Phytologist Trust.)

The establishment of baseline IUCN Red List assessments for plants is a crucial step in conservation planning. Nowhere is this more important than in biodiversity hotspots that are subject to significant anthropogenic pressures, such as Madagascar. Here, all Madagascar palm species are assessed using the IUCN Red List categories and criteria, version 3.1. Our results indicate that 83% of the 192 endemic species are threatened, nearly four times the proportion estimated for plants globally and exceeding estimates for all other comprehensively evaluated plant groups in Madagascar. Compared with a previous assessment in 1995, the number of Endangered and Critically Endangered species has substantially increased, due to the discovery of 28 new species since 1995, most of which are highly threatened. The conservation status of most species included in both the 1995 and the current assessments has not changed. Where change occurred, more species have moved to lower threat categories than to higher categories, because of improved knowledge of species and their distributions, rather than a decrease in extinction risk. However, some cases of genuine deterioration in conservation status were also identified. Palms in Madagascar are primarily threatened by habitat loss due to agriculture and biological resource use through direct exploitation or collateral damage. The recent extension of Madagascar's protected area network is highly beneficial for palms, substantially increasing the number of threatened species populations included within reserves. Notably, three of the eight most important protected areas for palms are newly designated. However, 28 threatened and data deficient species are not protected by the expanded network, including some Critically Endangered species. Moreover, many species occurring in protected areas are still threatened, indicating that threatening processes persist even in reserves. Definitive implementation of the new protected areas combined with local community engagement are essential for the survival of Madagascar's palms.

The distribution of rainforest in many regions across the Earth was strongly affected by Pleistocene ice ages. However, the extent to which these dynamics are still important for modern-day biodiversity patterns within tropical biodiversity hotspots has not been assessed. We employ a comprehensive dataset of Madagascan palms (Arecaceae) and climate reconstructions from the last glacial maximum (LGM; 21 000 years ago) to assess the relative role of modern environment and LGM climate in explaining geographical species richness patterns in this major tropical biodiversity hotspot. We found that palaeoclimate exerted a strong influence on palm species richness patterns, with richness peaking in areas with higher LGM precipitation relative to present-day even after controlling for modern environment, in particular in northeastern Madagascar, consistent with the persistence of tropical rainforest during the LGM primarily in this region. Our results provide evidence that diversity patterns in the World's most biodiverse regions may be shaped by long-term climate history as well as contemporary environment.

Despite long-standing interest in the origin and maintenance of species diversity, little is known about historical drivers of species assemblage structure at large spatiotemporal scales. Here, we use global species distribution data, a dated genus-level phylogeny, and paleo-reconstructions of biomes and climate to examine Cenozoic imprints on the phylogenetic structure of regional species assemblages of palms (Arecaceae), a species-rich plant family characteristic of tropical ecosystems. We find a strong imprint on phylogenetic clustering due to geographic isolation and in situ diversification, especially in the Neotropics and on islands with spectacular palm radiations (e.g., Madagascar, Hawaii, and Cuba). Phylogenetic overdispersion on mainlands and islands corresponds to biotic interchange areas. Differences in the degree of phylogenetic clustering among biogeographic realms are related to differential losses of tropical rainforests during the Cenozoic, but not to the cumulative area of tropical rainforest over geological time. A largely random phylogenetic assemblage structure in Africa coincides with severe losses of rainforest area, especially after the Miocene. More recent events also appear to be influential: phylogenetic clustering increases with increasing intensity of Quaternary glacial-interglacial climatic oscillations in South America and, to a lesser extent, Africa, indicating that specific clades perform better in climatically unstable regions. Our results suggest that continental isolation (in combination with limited long-distance dispersal) and changing climate and habitat loss throughout the Cenozoic have had strong impacts on the phylogenetic structure of regional species assemblages in the tropics.