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Strategies for 21st-century environmental management and conservation under global change require a strong understanding of the biological mechanisms that mediate responses to climate- and human-driven change to successfully mitigate range contractions, extinctions, and the degradation of ecosystem services. Biodiversity responses to past rapid warming events can be followed in situ and over extended periods, using cross-disciplinary approaches that provide cost-effective and scalable information for species' conservation and the maintenance of resilient ecosystems in many bioregions. Beyond the intrinsic knowledge gain such integrative research will increasingly provide the context, tools, and relevant case studies to assist in mitigating climate-driven biodiversity losses in the 21st century and beyond., (Copyright © 2020 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

Knowledge of global patterns of biodiversity, ranging from intraspecific genetic diversity (GD) to taxonomic and phylogenetic diversity, is essential for identifying and conserving the processes that shape the distribution of life. Yet, global patterns of GD and its drivers remain elusive. Here we assess existing biodiversity theories to explain and predict the global distribution of GD in terrestrial mammal assemblages. We find a strong positive covariation between GD and interspecific diversity, with evolutionary time, reflected in phylogenetic diversity, being the best predictor of GD. Moreover, we reveal the negative effect of past rapid climate change and the positive effect of inter-annual precipitation variability in shaping GD. Our models, explaining almost half of the variation in GD globally, uncover the importance of deep evolutionary history and past climate stability in accumulating and maintaining intraspecific diversity, and constitute a crucial step towards reducing the Wallacean shortfall for an important dimension of biodiversity.

Societal Impact Statement: Native medicinal plants contribute essential health benefits to populations globally, constituting a major natural resource that human societies rely on. Being an integral part of terrestrial biodiversity, medicinal plants are detrimentally affected by ongoing climate and land‐use change, yet comprehensive studies on the risk that extinction will pose to medicinal biodiversity are lacking. Responding to ongoing scientific calls for conserving medicinal biodiversity, this study provides an integrated assessment of the impacts of environmental change on ironwort (Sideritis), a group of closely related endemic plants of great cultural significance as local medicinal resources in the Balkan Mountains. Summary: Mountain habitats harbour unique biodiversity and provide vital resources for human well‐being, including natural medicinal resources, yet they are amongst the environments most impacted by global change. While there is ample evidence of recent rapid climate and land‐use change on mountain ecosystems, the impacts of these processes on the habitats of culturally important medicinal plants are still poorly understood. Here, we assess the potential loss of mountain habitats for medicinal plant resources over the past four decades using the culturally important ironwort, a group of endemic medicinal plants of the Balkan Mountains extensively used by local human populations and the pharmaceutical industry for treating cough and cold and gastrointestinal disorders.We used information collected from major European natural history museums to guide extensive field campaigns across 15 separate mountain ranges. We integrate field data with thousands of satellite images, station‐validated climate reanalysis data and habitat suitability modelling. We finally used machine learning to assess the relative roles of climate and vegetation rates of change in driving rates of habitat suitability change.We show that rising temperatures and 'mountain greening' erode the habitats of ironwort at alarming rates. About 50% of the total habitat area across all considered mountain ranges shows a significant decline in habitat suitability.These past trends will most likely continue in the future and could lead to widespread local extinction of the species and other medicinal plants that share similar ecological preferences, threatening their future contributions to societal well‐being. [ABSTRACT FROM AUTHOR]

Aim: Late Quaternary glaciations left an enduring imprint on the distribution of species and their genetic structure. The responses of plants endemic to the Alps can be summarized in three major demographic hypotheses: (i) post‐glacial expansion hypothesis; (ii) post‐glacial contraction hypothesis; and (iii) long‐term stability hypothesis. Here we test these hypotheses and reconstruct the time and extent of demographic responses of an endemic plant to the Late Quaternary climate dynamics. Location: European Alps. Taxon: Berardia subacaulis Vill. (Asteraceae). Methods: We used species distribution models to estimate the paleodistribution of B. subacaulis (Asteraceae) throughout the last 28 Ky and generated genome‐wide sequences to estimate current patterns of spatial structure of genetic diversity. We tested five demographic models by integrating the results of the two independent approaches in an Approximate Bayesian Computation framework. Results: The species has weak genetic differentiation among populations, with two main genetic groups. Species distribution models showed a reduction in potentially suitable areas for B. subacaulis during the post‐glacial climate warming and demographic models identified a recent split (2.46 Kya) between the two genetic groups and they slightly supported the post glacial contraction hypothesis. Main conclusions: Taken together, our results support the post‐glacial contraction of an endemic plant, differing from the main pattern observed for endemics species in the European Alps during the Late Quaternary. The different pattern observed in B. subacaulis might be due to several factors, including the less severe effects of glaciations and the environmental heterogeneity of the South Western Alps, combined with some features of the species (i.e. poor dispersal ability, slow growth and microhabitat preferences). Future research in areas where the ice cover was less extensive will contribute to a more complete understanding of the role of climatic changes in shaping the endemics of the European Alps. [ABSTRACT FROM AUTHOR]

Accelerating climate and land‐use change are rapidly transforming Earth's biodiversity. While there is substantial evidence on the exposure and vulnerability of biodiversity to global change at the species level, the global exposure of intraspecific genetic diversity (GD) is still unknown. Here, we assess the exposure of mitochondrial GD to mid‐21st century climate and land‐use change in terrestrial mammal assemblages at grid‐cell and bioclimatic region scales under alternative narratives of future societal development. We used global predictions of mammal GD distribution based on thousands of georeferenced mitochondrial genes for hundreds of mammal species, the latest generation of global climate models from the ongoing sixth phase of the Coupled Model Intercomparison Project (CMIP6), and global future projections of land‐use prepared for CMIP6. We found that more than 50% of the genetically poorest geographic areas (grid‐cells), primarily distributed in tundra, boreal forests/taiga and temperate bioclimatic regions, will be exposed to mean annual temperature rise that exceeds 2°C compared to the baseline period under all considered future scenarios. We also show that at least 30% of the most genetically rich areas in tropical, subtropical and montane regions will be exposed to an increase of mean annual temperature > 2°C under less optimal scenarios. Genetic diversity in these rich regions is also predicted to be exposed to severe reductions of primary vegetation area and increasing human activities (an average loss of 5–10% of their total area under the less sustainable land‐use scenarios). Our findings reveal a substantial exposure of mammal GD to the combined effects of global climate and land‐use change. Meanwhile the post‐2020 conservation goals are overlooking genetic diversity, our study identifies both genetically poor and highly diverse areas severely exposed to global change, paving the road to better estimate the geography of biodiversity vulnerability to global change. [ABSTRACT FROM AUTHOR]

Cold‐adapted taxa are experiencing severe range shifts due to climate change and are expected to suffer a significant reduction of their climatically suitable habitats in the next few decades. However, it has been proposed that taxa with sufficient standing genetic and ecologic diversity will better withstand climate change. These taxa are typically more broadly distributed in geographic and ecological niche space, therefore they are likely to endure higher levels of populations loss than more restricted, less diverse taxa before the effects of those losses impact their overall diversity and resilience. Here, we explore the potential relationship between intraspecific genetic and ecological diversity and future resilience, using the cold‐adapted plant Primula farinosa. We employ high‐throughput sequencing to assess the genomic diversity of phylogeographic lineages in P. farinosa. Additionally, we use current climatic variables to define niche breadth and niche differentiation across lineages. Finally, we calibrate species distribution models (SDMs) and project the climatic preferences of each lineage on future climate to predict lineage‐specific shifts in climatically suitable habitats. Our study predicts relative persistence of future suitable habitats for the most genetically and ecologically diverse lineages of the cold‐adapted P. farinosa, but significant reduction of them for two out of its four lineages. While we do not provide specific experiments aimed at identifying the causal links between genetic diversity and resilience to climate change, our results indicate that greater genetic diversity and wider ecological breadth may buffer species responses to rapid climatic changes. This study further highlights the importance of integrating knowledge of intraspecific diversity for predicting species fate in response to climate change. [ABSTRACT FROM AUTHOR]

Understanding the effects of past climatic fluctuations on the distribution and population-size dynamics of cold-adapted species is essential for predicting their responses to ongoing global climate change. In spite of the heterogeneity of cold-adapted species, two main contrasting hypotheses have been proposed to explain their responses to Late Quaternary glacial cycles, namely, the interglacial contraction versus the interglacial expansion hypotheses. Here, we use the cold-adapted plant Primula farinosa to test two demographic models under each of the two alternative hypotheses and a fifth, null model. We first approximate the time and extent of demographic contractions and expansions during the Late Quaternary by projecting species distribution models across the last 72 ka. We also generate genome-wide sequence data using a Reduced Representation Library approach to reconstruct the spatial structure, genetic diversity, and phylogenetic relationships of lineages within P. farinosa. Finally, by integrating the results of climatic and genomic analyses in an Approximate Bayesian Computation framework, we propose the most likely model for the extent and direction of population-size changes in P. farinosa through the Late Quaternary. Our results support the interglacial expansion of P. farinosa, differing from the prevailing paradigm that the observed distribution of cold-adapted species currently fragmented in high altitude and latitude regions reflects the consequences of postglacial contraction processes. [ABSTRACT FROM AUTHOR]

Background:The topographic complexity typical of alpine landscapes creates a variety of (micro)climatic conditions that may mitigate the effects of a warming climate on alpine plants via such mechanisms as cold air pooling (CAP). Aims:Our primary objectives were to (1) assess whether landscape potential forCAPas a predictor improved species distribution models (SDMs) projections and (2) quantify the impact ofCAPon the microclimate experienced by alpine plants compared to the macroclimate. Methods:We selected the Maritime Alps as our study area, located on the French–Italian border, and its rare endemic plant,Saxifraga florulenta, as model taxon. We generated a spatial layer in GIS (Geographic Information System) that reflected the potential of the landscape forCAPand ran five SDM algorithms with and withoutCAPlayer as a predictor. Second, we recorded the microclimate plants experience with temperature loggers. Results:CAPas a predictor decreased the omission error of SDMs, mostly at low and mid elevations, where topography may buffer extreme temperatures, resulting in a more stable microclimate compared to macroclimate. Conclusions:We have shown that plants in an alpine landscape may be less exposed to climate warming than predicted by macroclimate. Topo-climatic GIS layers for SDM projections in mountain environments should integrate such physical mechanisms asCAP. [ABSTRACT FROM AUTHOR]

Ongoing rapid climate change is predicted to cause local extinction of plant species in mountain regions. However, some plant species could have persisted during Quaternary climate oscillations without shifting their range, despite the limited evidence from fossils. Here, we tested two candidate mechanisms of persistence by comparing the macrorefugia and microrefugia ( MR) hypotheses. We used the rare and endemic Saxifraga florulenta as a model taxon and combined ensembles of species distribution models ( SDMs) with a high-resolution paleoclimatic and topographic dataset to reconstruct its potential current and past distribution since the last glacial maximum. To test the macrorefugia hypothesis, we verified whether the species could have persisted in or shifted to geographic areas defined by its realized niche. We then identified potential MR based on climatic and topographic properties of the landscape and applied refined scenarios of MR dynamics and functions over time. Last, we quantified the number of known occurrences that could be explained by either the macrorefugia or MR model. A consensus of two or three SDM techniques predicted absence between 14-10, 3-4 and 1 ka bp, which did not support the macrorefugia model. In contrast, we showed that S. florulenta could have contracted into MR during periods of absence predicted by the SDMs and later re-colonized suitable areas according to the macrorefugia model. Assuming a limited and realistic seed dispersal distance for our species, we explained a large number of the current occurrences (61-96%). Additionally, we showed that MR could have facilitated range expansions or shifts of S. florulenta. Finally, we found that the most recent and the most stable MR were the ones closest to current occurrences. Hence, we propose a novel paradigm to explain plant persistence by highlighting the importance of supporting functions of MR when forecasting the fate of plant species under climate change. [ABSTRACT FROM AUTHOR]