biostudies-literatureFarfan-Rios WNational Aeronautics and Space Administration (NASA)Gordon and Betty Moore Foundation (GBMF)European Research CouncilNational Science Foundation (NSF)National Geographic Society (NGS)UKRI | Natural Environment Research Council (NERC)e2425619122https://www.ebi.ac.uk/biostudies/studies/S-EPMC12402989biostudies-literatureUnknown122(34)Climate change is shifting species distributions, leading to changes in community composition and novel species assemblages worldwide. However, the responses of tropical forests to climate change across large-scale environmental gradients remain largely unexplored. Using long-term data over 66,000 trees of more than 2,500 species occurring over 3,500 m elevation along the hyperdiverse Amazon-to-Andes elevational gradients in Peru and Bolivia, we assessed community-level shifts in species composition over a 40+ y time span. We tested the thermophilization hypothesis, which predicts an increase in the relative abundances of species from warmer climates through time. Additionally, we examined the relative contributions of tree mortality, recruitment, and growth to the observed compositional cProceedings of the National Academy of Sciences of the United States of AmericaAmazonian and Andean tree communities are not tracking current climate warming.PMC12402989NGS 7754-04 NGS 8047-06GBMFAAMRS1NNH08ZDA001N-TE/ 08-TE08-0037291585NE/F005806/1 NE/D005590/1 NE/N012542/1DEB 0101775 DEB 0743457 DEB 1836353LTREB - 1754647DEB 0743666Terborgh JWBaker TRSaatchi SSCayola LSalinas NPhillips OLMonteagudo Mendoza ALFarfan-Rios WNunez Vargas PFeeley KJPitman NCANina-Quispe ALoza MISilman MRTello SGarcia-Cabrera KFuentes Claros AMalhi YMyers JASallo-Bravo JVasquez RfalseAmazonian and Andean tree communities are not tracking current climate warming.Climate change is shifting species distributions, leading to changes in community composition and novel species assemblages worldwide. However, the responses of tropical forests to climate change across large-scale environmental gradients remain largely unexplored. Using long-term data over 66,000 trees of more than 2,500 species occurring over 3,500 m elevation along the hyperdiverse Amazon-to-Andes elevational gradients in Peru and Bolivia, we assessed community-level shifts in species composition over a 40+ y time span. We tested the thermophilization hypothesis, which predicts an increase in the relative abundances of species from warmer climates through time. Additionally, we examined the relative contributions of tree mortality, recruitment, and growth to the observed compositional c2025-01-01T00:00:00Z2025 Aug2026-07-16T06:38:27.28Z2026-07-09T10:39:46.201ZS-EPMC124029894082801710.1073/pnas.2425619122