Delimiting floristic biogeographic districts in the Cerrado and assessing their conservation status

This is the author accepted manuscript. The final version is available from Springer via the DOI in this recordThe Cerrado is a biodiversity hotspot in central Brazil that represents the largest expanse of savanna in the Neotropics. Here, we aim to identify and delimit biogeographic districts within the Cerrado, to provide a geographic framework for conservation planning and scientific research prioritisation. We used data from 588 sites with tree species inventories distributed across the entire Cerrado. To identify districts, we clustered sites based on their similarity in tree species composition. To investigate why districts differ in composition, we 1) determined the proportion of tree species in different districts that derive from other biomes, to assess the influence of neighbouring biomes upon geographically marginal districts and 2) assayed key climatic differences between districts, to test the effect of environmental factors upon compositional differences. We found seven biogeographic districts within the Cerrado. Marginal districts have a large proportion of tree species characteristic of Amazonia and Atlantic Forest, but the Cerrado endemic species are also important. Further, districts differed significantly for multiple climatic variables. Finally, to provide a preliminary conservation assessment of the different districts, we assessed their rate of land conversion and current coverage by protected areas. We found that districts in the south and southwest of the Cerrado have experienced the greatest land conversion and are the least protected, while those in the north and northeast are less impacted and better protected. Overall, our results show how biogeographic analyses can contribute to conservation planning by giving clear guidelines on which districts merit greater conservation and management attention.Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorConselho Nacional de Desenvolvimento Científico e Tecnológic

Freezing and water availability structure the evolutionary diversity of trees across the Americas

The historical course of evolutionary diversification shapes the current distribution of biodiversity, but the main forces constraining diversification are still a subject of debate. We unveil the evolutionary structure of tree species assemblages across the Americas to assess whether an inability to move or an inability to evolve is the predominant constraint in plant diversification and biogeography. We find a fundamental divide in tree lineage composition between tropical and extratropical environments, defined by the absence versus presence of freezing temperatures. Within the Neotropics, we uncover a further evolutionary split between moist and dry forests. Our results demonstrate that American tree lineages tend to retain their ancestral environmental relationships and that phylogenetic niche conservatism is the primary force structuring the distribution of tree biodiversity. Our study establishes the pervasive importance of niche conservatism to community assembly even at intercontinental scales

Shade alters savanna grass layer structure and function along a gradient of canopy cover

This is the author accepted manuscript. The final version is available from Wiley via the DOI in this recordData availability statement: Data used for this study are available as supporting information.Aim: In savannas, a grass-dominated ground layer is key to ecosystem function via grass–fire feedbacks that maintain open ecosystems. With woody encroachment, tree density increases, thereby decreasing light in the ground layer and potentially altering ecosystem function. We investigated how light availability can filter individual grass species distributions and whether different functional traits are associated with response to a shade gradient in a landscape experiencing woody encroachment. Location: Savanna–forest mosaic in the Cerrado domain, southeastern Brazil. Methods: Along an encroachment gradient of increasing tree leaf area index (LAI) and shade, we determined how changing light availability alters grass diversity and ground layer structure relative to grass cover and grass functional traits (photosynthetic pathway, underground storage organs, bud protection and traits related to grass shape, size and leaf dimensions). Results: Increasing shade led to a decrease in grass cover and grass species richness, and also compositional and functional changes. We found that where tree LAI reached 1, grass cover was reduced by 50% and species richness by 30%. While C4 grass species abundances decreased with increasing shade, the opposite pattern was true for C3 grasses. There were only small differences in light preferences among C4 subtypes, with phosphoenolpyruvate carboxykinase (PCK) species tolerating slightly more shaded conditions. Persistence of some C4 species under more shaded conditions was possible, likely due to an ability to store starch reserves via underground storage organs. Conclusions: Woody encroachment changes diversity and structure of the grassy layer that is critical to the functioning of savanna ecosystems, highlighting the dependence of the diverse grass layer on open and sunny conditions. Our results suggest a threshold of tree cover close to LAI ≈ 1 as being critical to cerrado grassy layer conservation.National Science Foundation (NSF)São Paulo Research Foundation (FAPESP)National Council for Scientific and Technological DevelopmentCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Pre‐adaptation and adaptation shape trait‐environment matching in the Neotropics

This is the final version. Available from Wiley via the DOI in this record. Phylogenetic data (BEAST configuration file, MCC tree and posterior set of trees), trait, environment, and occurrence data, and R script to extract trait data from monographs can be found in the supplementary files in Dryad repository: https://doi.org/10.5061/dryad.vhhmgqnzq.Aim: Functional traits shape the distribution of taxa across environments. However, it remains unclear whether trait and environmental niche evolution are correlated, and what happened first: trait change facilitating environment shifts (pre-adaptation) or environmental change leading to trait change (adaptation). We focus on a species-rich Neotropical legume radiation to shed light on this enigma. Location: Neotropics. Time Period: Cenozoic. Major Taxa Studied: Fabaceae: Papilionoidae: Swartzia. Methods: We assembled leaflet, fruit and petal size data from monographs and herbarium collections for 86 to 96% of the c. 180 Swartzia species, inferred a dated Swartzia phylogenetic tree from existing DNA sequences covering 38% of the species and integrated these with distribution, soil and climate data. We used phylogenetic linear regression to quantify trait–environment relationships and applied comparative methods to evaluate modes of correlated evolution between traits and environments. Results: Leaflet and petal size were strongly linked to climate, while fruit size was not associated with climate or soil characteristics. Evolutionary transitions to relatively low rainfall and low temperature environments were conditional on the evolution of small leaflets, whereas transitions to wet and warm environments were preceded by the evolution of larger leaflets. In contrast, transitions to the warmest or coldest environments were followed, rather than preceded, by petal loss. Main Conclusion: Our results show that the macroevolution of functional traits has influenced the broad-scale distribution of Swartzia across Neotropical rainforest, seasonally dry, montane and inundated habitats. We suggest that trait evolution is conditional on environmental change but both pre-adaptive and adaptive processes may occur. These processes are important to understand the distribution of diversity at both regional (e.g. Amazonia) and global biogeographical scales.German Research Foundation (DFG

Savannahs of Asia: Antiquity, biogeography, and an uncertain future

The savannahs of Asia remain locally unrecognized as distinctive ecosystems, and continue to be viewed as degraded forests or seasonally dry tropical forests. These colonial-era legacies are problematic, because they fail to recognize the unique diversity of Asian savannahs and the critical roles of fire and herbivory in maintaining ecosystem health and diversity. In this review, we show that: the palaeo-historical evidence suggests that the savannahs of Asia have existed for at least 1 million years, long before widespread landscape modification by humans; savannah regions across Asia have levels of C4 grass endemism and diversity that are consistent with area-based expectations for non-Asian savannahs; there are at least three distinct Asian savannah communities, namely deciduous broadleaf savannahs, deciduous fine-leafed and spiny savannahs and evergreen pine savannahs, with distinct functional ecologies consistent with fire- and herbivory-driven community assembly. Via an analysis of savannah climate domains on other continents, we map the potential extent of savannahs across Asia. We find that the climates of African savannahs provide the closest analogues for those of Asian deciduous savannahs, but that Asian pine savannahs occur in climates different to any of the savannahs in the southern continents. Finally, we review major threats to the persistence of savannahs in Asia, including the mismanagement of fire and herbivory, alien woody encroachment, afforestation policies and future climate uncertainty associated with the changing Asian monsoon. Research agendas that target these issues are urgently needed to manage and conserve these ecosystems. This article is part of the themed issue ‘Tropical grassy biomes: linking ecology, human use and conservation’

DNA Barcoding for Community Ecology - How to Tackle a Hyperdiverse, Mostly Undescribed Melanesian Fauna

Trigonopterus weevils are widely distributed throughout Melanesia and hyperdiverse in New Guinea. They are a dominant feature in natural forests, with narrow altitudinal zonation. Their use in community ecology has been precluded by the "taxonomic impediment". We sampled >6,500 specimens from seven areas across New Guinea; 1,002 specimens assigned to 270 morphospecies were DNA sequenced. Objective clustering of a refined dataset (excluding nine cryptic species) at 3% threshold revealed 324 genetic clusters (DNA group count relative to number of morphospecies = 20.0% overestimation of species diversity, or 120.0% agreement) and 85.6% taxonomic accuracy (the proportion of DNA groups that "perfectly" agree with morphology-based species hypotheses). Agreement and accuracy were best at an 8% threshold. GMYC analysis revealed 328 entities (21.5% overestimation) with 227 perfect GMYC entities (84.1% taxonomic accuracy). Both methods outperform the parataxonomist (19% underestimation; 31.6% taxonomic accuracy). The number of species found in more than one sampling area was highest in the Eastern Highlands and Huon (Sørensen similarity index 0.07, 4 shared species); ⅓ of all areas had no species overlap. Success rates of DNA barcoding methods were lowest when species showed a pronounced geographical structure. In general, Trigonopterus show high α and β-diversity across New Guinea. DNA barcoding is an excellent tool for biodiversity surveys but success rates might drop when closer localities are included. Hyperdiverse Trigonopterus are a useful taxon for evaluating forest remnants in Melanesia, allowing finer-grained analyses than would be possible with vertebrate taxa commonly used to date. Our protocol should help establish other groups of hyperdiverse fauna as target taxa for community ecology. Sequencing delivers objective data on taxa of incredible diversity but mostly without a solid taxonomic foundation and should help pave the road for the eventual formal naming of new species

Biogeographic distributions of neotropical trees reflect their directly measured drought tolerances

High levels of species diversity hamper current understanding of how tropical forests may respond to environmental change. In the tropics, water availability is a leading driver of the diversity and distribution of tree species, suggesting that many tropical taxa may be physiologically incapable of tolerating dry conditions, and that their distributions along moisture gradients can be used to predict their drought tolerance. While this hypothesis has been explored at local and regional scales, large continental-scale tests are lacking. We investigate whether the relationship between drought-induced mortality and distributions holds continentally by relating experimental and observational data of drought-induced mortality across the Neotropics to the large-scale bioclimatic distributions of 115 tree genera. Across the different experiments, genera affiliated to wetter climatic regimes show higher drought-induced mortality than dry-affiliated ones, even after controlling for phylogenetic relationships. This pattern is stronger for adult trees than for saplings or seedlings, suggesting that the environmental filters exerted by drought impact adult tree survival most strongly. Overall, our analysis of experimental, observational, and bioclimatic data across neotropical forests suggests that increasing moisture-stress is indeed likely to drive significant changes in floristic composition

Precipitation is the main axis of tropical plant phylogenetic turnover across space and time.

This is the final version. Available from the American Association for the Advancement of Science via the DOI in this record. Data and materials availability: All data needed to evaluate the conclusions in the paper are present in the paper and/or the Supplementary Materials. All phylogenies, both occurrence datasets, and the taxonomic checklist are available as data S1 on Zenodo (https://doi.org/10.5281/zenodo.7568716). GenBank or European Nucleotide Archive accession codes for new genetic sequences generated here are listed in tables S1 and S4 to S10.Early natural historians-Comte de Buffon, von Humboldt, and De Candolle-established environment and geography as two principal axes determining the distribution of groups of organisms, laying the foundations for biogeography over the subsequent 200 years, yet the relative importance of these two axes remains unresolved. Leveraging phylogenomic and global species distribution data for Mimosoid legumes, a pantropical plant clade of c. 3500 species, we show that the water availability gradient from deserts to rain forests dictates turnover of lineages within continents across the tropics. We demonstrate that 95% of speciation occurs within a precipitation niche, showing profound phylogenetic niche conservatism, and that lineage turnover boundaries coincide with isohyets of precipitation. We reveal similar patterns on different continents, implying that evolution and dispersal follow universal processes.Natural Environment Research Council (NERC)Swiss National Science Foundation (SNSF)Swiss National Science Foundation (SNSF)Swiss National Science Foundation (SNSF)Claraz Schenkung Foundation, SwitzerlandU.S. National Science FoundationU.S. National Science FoundationNatural Sciences and Engineering Research Council of Canada (NSERC)Biotechnology and Biological Sciences Research CouncilFAPESB, BrazilFAPESB, BrazilFAPESB, BrazilCNPq, BrazilCNPq, BrazilCNPq, BrazilCNPq, BrazilConsejo Nacional de Investigaciones Científicas y Técnicas (CONICET), ArgentinaAgencia Nacional de Promoción Científica y Tecnológica (ANPCyT), ArgentinaInstituto Nacional de Tecnología Agropecuaria (INTA), ArgentinaInstituto Nacional de Tecnología Agropecuaria (INTA), ArgentinaUniversidad de Morón, ArgentinaCoordination for the Improvement of Higher Education Personnel (CAPES), BrazilEmbrapa Recursos Genéticos e Biotecnologia (CENARGEN), Brazi

Evolutionary diversity in tropical tree communities peaks at intermediate precipitation

This is the final version. Available from Nature Research via the DOI in this record. Time-calibrated molecular phylogenies are deposited at the Dryad Digital Repository (https://doi.org/10.5061/dryad.gf1vhhmk0). A full description with details of data accessibility for Neo-TropTree can be found at http://www.neotroptree.info/.Global patterns of species and evolutionary diversity in plants are primarily determined by a temperature gradient, but precipitation gradients may be more important within the tropics, where plant species richness is positively associated with the amount of rainfall. The impact of precipitation on the distribution of evolutionary diversity, however, is largely unexplored. Here we detail how evolutionary diversity varies along precipitation gradients by bringing together a comprehensive database on the composition of angiosperm tree communities across lowland tropical South America (2,025 inventories from wet to arid biomes), and a new, large-scale phylogenetic hypothesis for the genera that occur in these ecosystems. We find a marked reduction in the evolutionary diversity of communities at low precipitation. However, unlike species richness, evolutionary diversity does not continually increase with rainfall. Rather, our results show that the greatest evolutionary diversity is found in intermediate precipitation regimes, and that there is a decline in evolutionary diversity above 1,490 mm of mean annual rainfall. If conservation is to prioritise evolutionary diversity, areas of intermediate precipitation that are found in the South American ‘arc of deforestation’, but which have been neglected in the design of protected area networks in the tropics, merit increased conservation attention.Natural Environment Research Council (NERC)Conselho Nacional de Desenvolvimento Científico e TecnológicoConselho Nacional de Desenvolvimento Científico e TecnológicoConselho Nacional de Desenvolvimento Científico e TecnológicoNational Science Foundation (NSF)Mohamed bin Zayed Species Conservation FundLeverhulme TrustCoordenação de Aperfeiçoamento de Pessoal de Nível Superio