Brazilian montane rainforest expansion induced by Heinrich Stadial 1 event

www.nature.com/scientificreports OPEN Brazilian montane rainforest expansion induced by Heinrich Stadial 1 event Jorge L. D. Pinaya1*, Francisco W. Cruz2, Gregório C. T. Ceccantini4, Pedro L. P. Corrêa 1, Nigel Pitman3, Felipe Vemado 5, Maria del Carmen S. Lopez5, Augusto J. Pereira Filho 5, Carlos H. Grohmann 6, Cristiano M. Chiessi 7, Nicolás M. Stríkis8, Ingrid Horák-Terra9, Walter H. L. Pinaya 10, Vanda B. de Medeiros2, Rudney de A. Santos2, Thomas K. Akabane2, Maicon A. Silva4, Rachid Cheddadi11, Mark Bush12, Alexandra-Jane Henrot13, Louis François13, Alain Hambuckers14, Frédéric Boyer15, Matthieu Carré16, Eric Coissac15, Francesco Ficetola15, Kangyou Huang17, Anne-Marie Lézine16, Majda Nourelbait11, Ali Rhoujjati18, Pierre Taberlet15, Fausto Sarmiento 19, Daniel Abel-Schaad 20, Francisca Alba-Sánchez 20, Zhuo Zheng17 & Paulo E. De Oliveira2,3,4* The origin of modern disjunct plant distributions in the Brazilian Highlands with strong floristic affinities to distant montane rainforests of isolated mountaintops in the northeast and northern Amazonia and the Guyana Shield remains unknown. We tested the hypothesis that these unexplained biogeographical patterns reflect former ecosystem rearrangements sustained by widespread plant migrations possibly due to climatic patterns that are very dissimilar from present-day conditions. To address this issue, we mapped the presence of the montane arboreal taxa Araucaria, Podocarpus, Drimys, Hedyosmum, Ilex, Myrsine, Symplocos, and Weinmannia, and cool-adapted plants in the families Myrtaceae, Ericaceae, and Arecaceae (palms) in 29 palynological records during Heinrich Stadial 1 Event, encompassing a latitudinal range of 30°S to 0°S. In addition, Principal Component Analysis and Species Distribution Modelling were used to represent past and modern habitat suitability for Podocarpus and Araucaria. The data reveals two long-distance patterns of plant migration connecting south/southeast to northeastern Brazil and Amazonia with a third short route extending from one of them. Their paleofloristic compositions suggest a climatic scenario of abundant rainfall and relative lower continental surface temperatures, possibly intensified by the effects of polar air incursions forming cold fronts into the Brazilian Highlands. Although these taxa are sensitive to changes in temperature, the combined pollen and speleothems proxy data indicate that this montane rainforest expansion during Heinrich Stadial 1 Event was triggered mainly by a less seasonal rainfall regime from the subtropics to the equatorial region. 1 Politechnical School, University of São Paulo, São Paulo, SP, Brazil. 2Institute of Geosciences, University of São Paulo, São Paulo, SP, Brazil. 3Science Action, The Field Museum of Natural History, Chicago, Illinois, US. 4Institute of Biosciences, University of São Paulo, São Paulo, SP, Brazil. 5Institute of Astronomy and Geophysics and Atmospheric Sciences, University of São Paulo, São Paulo, SP, Brazil. 6Institute of Energy and Environment, University of São Paulo, São Paulo, SP, Brazil. 7School of Arts, Sciences and Humanities, University of São Paulo, São Paulo, SP, Brazil. 8Federal Fluminense University, Niteroi, RJ, Brazil. 9Institute of Agricultural Sciences, Federal University of Jequitinhonha and Mucuri Valleys, Unaí, MG, Brazil. 10Center of Mathematics, Computation, and Cognition, Federal University of ABC, Santo André, SP, Brazil. 11ISEM, Université de Montpellier, Centre National de la Recherche Scientifique, IRD, EPHE, Montpellier, France. 12Department of Biological Sciences, Florida Institute of Technology, Melbourne, FL, US. 13Unité de Modélisation du Climat et des Cycles Biogéochimiques, UR-SPHERES, University of Liège, Liège, Belgium. 14Unité de Biologie du comportement, UR-SPHERES, University of Liège, Liège, Belgium. 15 Laboratoire d’Ecologie Alpine, Centre National de la Recherche Scientifique, Université Grenoble Alpes, Grenoble, France. 16LOCEAN Laboratory, Sorbonne Universités (UPMC), CNRS, IRD, MNHN, Paris, France. 17School of Earth Science and Geological Engineering, Sun Yat-Sen University, Guangzhou, China. 18Laboratoire Géoressources, Unité de Recherche Associée CNRST (URAC 42), Faculté des Sciences et Techniques, Université Cadi Ayyad, Marrakech, Morocco. 19Neotropical Montology Collaboratory, Department of Geography, University of Georgia, Athens, GA, US. 20Departamento de Botánica, Facultad de Ciencias, Universidad de Granada, Granada, Andalucia, Spain. *email: ; Scientific Reports | (2019) 9:17912 | https://doi.org/10.1038/s41598-019-53036-1 1 www.nature.com/scientificreports/ www.nature.com/scientificreports The origin of disjunct vegetation types in mountain landscapes of southeastern and central Brazil that display a strong affinity to wet montane floras of northern South America remains unknown. Earlier hypotheses1,2 suggested cold and wet migration corridors possibly in the Eocene or Miocene, later affected by the Quaternary climatic change, might have allowed ancient contact between plant populations now isolated on distant mountaintops. In this study we investigate the impact on tropical montane vegetation of an enhanced South American Summer Monsoon (SASM) regime between 18.1 and 14.7 kcal yr BP in synchrony with glacial episodic iceberg discharge in the North Atlantic, known as Heinrich Stadial 1 (HS1), as indicated by speleothem isotope records3–7. Oxygen isotopes in the Botuverá cave speleothems have indicated that wet phases prevailed during the last glacial cycle in southern Brazil8. Additional support for this scenario comes from calcite deposits at lake margins within caves and expansion of wet forests in the HS1 of northern Bahia, currently covered by semi-arid vegetation (caatinga), suggested by abundant plant megafossils in calcareous tufas, belonging to arboreal and herbaceous taxa presently found in the Atlantic and Amazon rainforests9. We hypothesize that the intensified precipitation within the area climatologically affected by the South Atlantic Convergence Zone (SACZ) and the Intertropical Convergence Zone (ITCZ) promoted conditions suitable for the establishment of north-south migration corridors for the expansion of montane forest. These possible former connections between southeast and central Brazil, from 31° to 22°S lat. and southeastern Amazonia could, therefore, explain much of the modern occurrence of disjunct humid and cold-adapted taxa in elevated areas of cerrado and semi-arid caatinga reaching 4°S, with counterparts in the tepuis of the Guyana Shield, including those in Roraima (northern Brazilian Amazonia) and in Venezuela. Methods We infer vegetational and correlated climatic changes during the HS1 event by analyzing selected arboreal pollen taxa, in most cases with abundance higher than 5%, in Brazilian Late Quaternary pollen records, with morphological features that allow identification to genus level and in some cases only to family10, the exception (...truncated)