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Anthropogenic climate change is projected to become a major driver of biodiversity loss, destabilizing the ecosystems on which human society depends. As the planet rapidly warms, the disruption of ecological interactions among populations, species and their environment, will likely drive positive feedback loops, accelerating the pace and magnitude of biodiversity losses. We propose that, even without invoking such amplifying feedback, biodiversity loss should increase nonlinearly with warming because of the non-uniform distribution of biodiversity. Whether these non-uniformities are the uneven distribution of populations across a species' thermal niche, or the uneven distribution of thermal niche limits among species within an ecological community, we show that in both cases, the resulting clustering in population warming tolerances drives nonlinear increases in the risk to biodiversity. We discuss how fundamental constraints on species' physiologies and geographical distributions give rise to clustered warming tolerances, and how population responses to changing climates could variously temper, delay or intensify nonlinear dynamics. We argue that nonlinear increases in risks to biodiversity should be the null expectation under warming, and highlight the empirical research needed to understand the causes, commonness and consequences of clustered warming tolerances to better predict where, when and why nonlinear biodiversity losses will occur. This article is part of the discussion meeting issue 'Bending the curve towards nature recovery: building on Georgina Mace's legacy for a biodiverse future'. [ABSTRACT FROM AUTHOR]

Unraveling the spatiotemporal dynamics of communities is critical to understand how biodiversity responds to global changes. However, this task is not trivial, as these dynamics are quite complex, and most studies are limited to few taxa at small local and temporal scales. Tropical mountains are ideal indicators of biodiversity response since these endangered and complex ecosystems include many distinct habitats within small geographical areas, harboring a megadiverse fauna, especially insects. Indeed, while insects are particularly sensitive to environmental and climatic changes, the extent of the impact of climate variability on mountain tropical insect diversity remains poorly understood. Here we present time‐series data from a decade of studying the spatiotemporal dynamics of ants, butterflies and dung beetles. We assessed patterns of species richness change along the elevational gradient for each taxonomic group per sampling year and cumulatively over years. We then quantified community changes over time by measuring the variation in species richness across sampling years (temporal trends in α‐diversity), and the temporal variation in species composition (temporal β‐diversity) evaluating species gains and losses over time. We also evaluated the variation of air temperature and humidity through meteorological stations within the sampling years. We detected a classical pattern of species richness decline with elevation, albeit with a noticeable increase in species richness variation with increasing elevation. The temporal β‐diversity exhibited considerable variability across elevations, taxa, and time. Only dung beetles presented a positive relationship with humidity variation over the years. Critically, both rare and common species drove extirpations and colonizations, and we found no trend of temporal decline of insect species at local and regional scales. Our study shows that insect metacommunity responses to elevation and global changes are rather complex, and stresses the importance of long‐term studies that incorporate multiple sampling periods and different groups of organisms in tropical mountains. [ABSTRACT FROM AUTHOR]

Competing Interests: Competing interests: The author declares no competing interests.