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1. High exposure of global tree diversity to human pressure

   https://doi.org/10.1073/pnas.2026733119  

   Guo, Wen-Yong; Serra-Diaz, Josep M.; Schrodt, Franziska; Eiserhardt, Wolf L.; Maitner, Brian S.; Merow, Cory; Violle, Cyrille; Anand, Madhur; Belluau, Michaël; Bruun, Hans Henrik; et al (June 2022, Proceedings of the National Academy of Sciences)

   Safeguarding Earth’s tree diversity is a conservation priority due to the importance of trees for biodiversity and ecosystem functions and services such as carbon sequestration. Here, we improve the foundation for effective conservation of global tree diversity by analyzing a recently developed database of tree species covering 46,752 species. We quantify range protection and anthropogenic pressures for each species and develop conservation priorities across taxonomic, phylogenetic, and functional diversity dimensions. We also assess the effectiveness of several influential proposed conservation prioritization frameworks to protect the top 17% and top 50% of tree priority areas. We find that an average of 50.2% of a tree species’ range occurs in 110-km grid cells without any protected areas (PAs), with 6,377 small-range tree species fully unprotected, and that 83% of tree species experience nonnegligible human pressure across their range on average. Protecting high-priority areas for the top 17% and 50% priority thresholds would increase the average protected proportion of each tree species’ range to 65.5% and 82.6%, respectively, leaving many fewer species (2,151 and 2,010) completely unprotected. The priority areas identified for trees match well to the Global 200 Ecoregions framework, revealing that priority areas for trees would in large part also optimize protection for terrestrial biodiversity overall. Based on range estimates for >46,000 tree species, our findings show that a large proportion of tree species receive limited protection by current PAs and are under substantial human pressure. Improved protection of biodiversity overall would also strongly benefit global tree diversity. 

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2. Madagascar’s extraordinary biodiversity: Evolution, distribution, and use

   https://doi.org/10.1126/science.abf0869  

   Antonelli, Alexandre; Smith, Rhian J.; Perrigo, Allison L.; Crottini, Angelica; Hackel, Jan; Testo, Weston; Farooq, Harith; Torres Jiménez, Maria F.; Andela, Niels; Andermann, Tobias; et al (December 2022, Science)

   BACKGROUND The Republic of Madagascar is home to a unique assemblage of taxa and a diverse set of ecosystems. These high levels of diversity have arisen over millions of years through complex processes of speciation and extinction. Understanding this extraordinary diversity is crucial for highlighting its global importance and guiding urgent conservation efforts. However, despite the detailed knowledge that exists on some taxonomic groups, there are large knowledge gaps that remain to be filled. ADVANCES Our comprehensive analysis of major taxonomic groups in Madagascar summarizes information on the origin and evolution of terrestrial and freshwater biota, current species richness and endemism, and the utilization of this biodiversity by humans. The depth and breadth of Madagascar’s biodiversity—the product of millions of years of evolution in relative isolation —is still being uncovered. We report a recent acceleration in the scientific description of species but many remain relatively unknown, particularly fungi and most invertebrates. DIGITIZATION Digitization efforts are already increasing the resolution of species richness patterns and we highlight the crucial role of field- and collections-based research for advancing biodiversity knowledge in Madagascar. Phylogenetic diversity patterns mirror that of species richness and endemism in most of the analyzed groups. Among the new data presented, our update on plant numbers estimates 11,516 described vascular plant species native to Madagascar, of which 82% are endemic, in addition to 1215 bryophyte species, of which 28% are endemic. Humid forests are highlighted as centers of diversity because of their role as refugia and centers of recent and rapid radiations, but 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 important despite lower species richness. Endemism in Malagasy fungi remains poorly known given the lack of data on the total diversity and global distribution of species. However, our analysis has shown that ~75% of the fungal species detected by environmental sequencing have not been reported as occurring outside of Madagascar. Among the 1314 species of native terrestrial and freshwater vertebrates, levels of endemism are extremely high (90% overall)—all native nonflying terrestrial mammals and native amphibians are found nowhere else on Earth; further, 56% of the island’s birds, 81% of freshwater fishes, 95% of mammals, and 98% of reptile species are endemic. Little is known about endemism in insects, but data from the few well-studied groups on the island suggest that it is similarly high. The uses of Malagasy species are many, with much potential for the uncovering of useful traits for food, medicine, and climate mitigation. OUTLOOK Considerable work remains to be done to fully characterize Madagascar’s biodiversity and evolutionary history. The multitudes of known and potential uses of Malagasy species reported here, in conjunction with the inherent value of this unique and biodiverse region, reinforce the importance of conserving this unique biota in the face of major threats such as habitat loss and overexploitation. The gathering and analysis of data on Madagascar’s remarkable biota must continue and accelerate if we are to safeguard this unique and highly threatened subset of Earth’s biodiversity. Emergence and composition of Madagascar’s extraordinary biodiversity. Madagascar’s biota is the result of over 160 million years of evolution, mostly in geographic isolation, combined with sporadic long distance immigration events and local extinctions. (Left) We show the age of the oldest endemic Malagasy clade for major groups (from bottom to top): arthropods, bony fishes, reptiles, flatworms, birds, amphibians, flowering plants, mammals, non-flowering vascular plants, and mollusks). Humans arrived recently, some 10,000 to 2000 years (top right) and have directly or indirectly caused multiple extinctions (including hippopotamus, elephant birds, giant tortoises, and giant lemurs) and introduced many new species (such as dogs, zebu, rats, African bushpigs, goats, sheep, rice). Endemism is extremely high and unevenly distributed across the island (the heat map depicts Malagasy palm diversity, a group characteristic of the diverse humid forest). Human use of biodiversity is widespread, including 1916 plant species with reported uses. The scientific description of Malagasy biodiversity has accelerated greatly in recent years (bottom right), yet the diversity and evolution of many groups remain practically unknown, and many discoveries await. 

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3. Defaunation and species introductions alter long-term functional trait diversity in insular reptiles

   https://doi.org/10.1073/pnas.2201944119  

   Kemp, Melissa E. (February 2023, Proceedings of the National Academy of Sciences)

   Biodiversity loss poses a major threat to ecosystem function, which has already been severely impacted by global late-Quaternary defaunation. The loss of mammalian megafauna from many insular systems has rendered reptiles into key modulators of many ecosystem services, such as seed dispersal and pollination. How late-Quaternary extinction events impacted reptile functional diversity remains unclear but can provide critical guidance on traits that render reptiles vulnerable to extinction, as well as anthropogenic, environmental, and evolutionary histories that may promote stability and resilience. This study reconstructs the trajectory of functional diversity change in the Caribbean reptile fauna, a speciose biota distributed over a diverse set of islands with heterogeneous histories of human habitation and exploitation. Human-induced Quaternary extinctions have completely removed key functional entities (FEs)—groupings of species with similar traits that are expected to provide similar ecosystem services—from the region, but functional redundancy on large islands served as a buffer to major functional diversity loss. Small islands, on the other hand, lose up to 67% of their native FEs with only a few exceptions, underscoring the importance of a place’s anthropogenic history in shaping present-day biodiversity. While functional redundancy has shielded ecosystems from significant functional diversity loss in the past, it is being eroded and not replenished by species introductions, leaving many native FEs and the communities that they support vulnerable to extinction and functional collapse. This research provides critical data on long-term functional diversity loss for a taxonomic group whose contributions to ecosystem function are understudied and undervalued. 

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4. Highland reptiles of Angola and Namibia

   Bauer, AM; Ceriaco, LMP; Marques, MP; Becker, FS (December 2023, Namibian Journal of Environment)

   Approximately 238 species of reptiles are found in the highlands and escarpments of Angola and Namibia (HEAN). Of the 430 species present in the two countries in total, 46 are strictly endemic (or nearly so) to the HEAN and another 16 have extensive portions of their ranges in these areas. Geckos constitute the majority of HEAN endemics with 32 species; in addition, there are nine cordylids, six skinks, four lacertids and one chameleon, as well as nine snakes (in five families) and a single tortoise comprising the remainder. Many of these species are substrate specialists and therefore rock types and textures may be a more important determinant of their distributions than elevation per se. Reptile diversity is greatest in the larger highland areas of the Khomas Hochland and Angolan Planalto, but many areas support at least some regional highland endemics including the Marginal Mountain Chain and Central Escarpment, and the Serra do Môco and the Serra da Neve in Angola, and the Karasberge, Waterberg and the Otavi, Erongo, Numib, Tiras, Baynes and Otjihipa mountains as well as numerous inselberg clusters (e.g., Huns–Orange and Huab outliers) in Namibia. The vast majority of the highland taxa have been assessed as Least Concern by the International Union for Conservation of Nature (IUCN), with several taxa considered Data Deficient or Near Threatened and only three Vulnerable. Most highland and escarpment areas in Angola and Namibia remain woefully understudied from a herpetological perspective and the description of 20% of the endemics in the last ten years suggests that true reptile diversity remains underestimated. 

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5. A global reptile assessment highlights shared conservation needs of tetrapods

   https://doi.org/10.1038/s41586-022-04664-7  

   Cox, Neil; Young, Bruce E.; Bowles, Philip; Fernandez, Miguel; Marin, Julie; Rapacciuolo, Giovanni; Böhm, Monika; Brooks, Thomas M.; Hedges, S. Blair; Hilton-Taylor, Craig; et al (May 2022, Nature)

   Abstract Comprehensive assessments of species’ extinction risks have documented the extinction crisis 1 and underpinned strategies for reducing those risks 2 . Global assessments reveal that, among tetrapods, 40.7% of amphibians, 25.4% of mammals and 13.6% of birds are threatened with extinction 3 . Because global assessments have been lacking, reptiles have been omitted from conservation-prioritization analyses that encompass other tetrapods 4–7 . Reptiles are unusually diverse in arid regions, suggesting that they may have different conservation needs 6 . Here we provide a comprehensive extinction-risk assessment of reptiles and show that at least 1,829 out of 10,196 species (21.1%) are threatened—confirming a previous extrapolation 8 and representing 15.6 billion years of phylogenetic diversity. Reptiles are threatened by the same major factors that threaten other tetrapods—agriculture, logging, urban development and invasive species—although the threat posed by climate change remains uncertain. Reptiles inhabiting forests, where these threats are strongest, are more threatened than those in arid habitats, contrary to our prediction. Birds, mammals and amphibians are unexpectedly good surrogates for the conservation of reptiles, although threatened reptiles with the smallest ranges tend to be isolated from other threatened tetrapods. Although some reptiles—including most species of crocodiles and turtles—require urgent, targeted action to prevent extinctions, efforts to protect other tetrapods, such as habitat preservation and control of trade and invasive species, will probably also benefit many reptiles. 

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