Funder: PRONEX-MCT/CNPq/FAPEAM “Tipologias alágaveis 2007”,Universal (479599/2008-4) and PELD/MAUA Áreas Úmidas, additional funding was provided by the ATTO Project (German Federal Ministry of Education and Research, BMBF funds 01LK1602F, and 01LK2101D, Brazilian Ministry of Science, Technology, Innovation and Communication; FINEP/MCTIC contract 01.11.01248.00), UEA and FAPEAM, LBA/INPA and SDS/CEUC/RDS-Uatumã, and the EU Project BiodivERsA—Clambio (BMBF 16LC2025A);Funder: CNPq/CAPES/FAPS/BC-Newton Fund #441244/2016-5 and FAPEMAT/0589267/2016Funder: “Investissement d’Avenir” grant managed by the Agence Nationale de la Recherche (CEBA: ANR-10-LABX-25-01);Funder: CNPQ Grant 308040/2017-1Funder: PVE - MEC/MCTI/CAPES/CNPq/FAPs Reference #407232/2013-3 -Funder: MCT/CNPq/CT-INFRA/GEOMA #550373/2010-1 and # 457515/2012-0 CAPES/PDSE # 88881.135761/2016-01 CAPES/Fapespa #1530801Funder: MCT/CNPq/CT-INFRA/GEOMA #550373/2010-1 and # 457515/2012-0Funder: PVE - MEC/MCTI/CAPES/CNPq/FAPs Reference #407232/2013-3Funder: National Science Foundation grant DEB-1556338Funder: FAPESP grant 2016/25086-3Funder: FAPESP 95/3058-0 - CRS 068/96 WWF Brasil - The Body ShopAmazonia's floodplain system is the largest and most biodiverse on Earth. Although forests are crucial to the ecological integrity of floodplains, our understanding of their species composition and how this may differ from surrounding forest types is still far too limited, particularly as changing inundation regimes begin to reshape floodplain tree communities and the critical ecosystem functions they underpin. Here we address this gap by taking a spatially explicit look at Amazonia-wide patterns of tree-species turnover and ecological specialization of the region's floodplain forests. We show that the majority of Amazonian tree species can inhabit floodplains, and about a sixth of Amazonian tree diversity is ecologically specialized on floodplains. The degree of specialization in floodplain communities is driven by regional flood patterns, with the most compositionally differentiated floodplain forests located centrally within the fluvial network and contingent on the most extraordinary flood magnitudes regionally. Our results provide a spatially explicit view of ecological specialization of floodplain forest communities and expose the need for whole-basin hydrological integrity to protect the Amazon's tree diversity and its function
