The variety of structures and forms of the trees in the tropical forests of Amazonia must have wondered humanity since its first contact with the forests more than 12,000 years ago. More recently, in the 18th century, when early European naturalists started to account for the diversity of life in the forests of the Americas and realised the enormous diversity of tree species in there, they wondered when new species would stop coming. From these first accounts to present more than 10,000 tree species have been recorded in Amazonia, and at least 5,000 are still to be discovered among the more than 390 billion trees in forests covering over 6 million square kilometres of land 1–3. Despite appearing as a continuous green carpet from above, the tree species diversity is not evenly distributed across Amazonian forests, soil catena, flood pulses, and climatic seasonality in droughts and temperatures are key for differences in tree species richness assembling the forests along landscapes and regions4–6. Key ecological information is delivered in maps for tree species richness and densities across Amazonia6,7, however, these maps do not address the changes in the identity of the tree species assembling the forests, instead, they show forests with equal number of species that nevertheless can support completely different compositions of species and lineages8. We now provide a detailed scale map for the tree species compositional turnover across tropical forests of Amazonia[Luize, B. G. et al. The biogeography of the Amazonian tree flora. Commun Biol 7, 1240 (2024).].
To advance the knowledge of geographic changes in the composition of tree species, assembling forest communities, the availability and access of ground-based information of forest plot census data is essential. The very first forest inventory plots established in Amazonia were sampled less than a century ago by ecologists of the Oxford University in the forests of the Essequibo river basin at Guyana9. Since then, hundreds of ecologists have been inventorying trees at standard forest plots all across Amazonia. It was just in the beginning of the 21st century that the Amazon Tree Diversity Network (ATDN) was created, thanks to the strategic view of Professor Hans ter Steege anticipating the need for the aggregation and harmonisation of data from the rising number of forests inventories of the Amazonian tree flora. This proved essential and allowed a much better understanding of the distribution of tree diversity in Amazonia
By 2004, I started studying Amazonian trees and forests. Ten years later, I was responsible for sampling over 21 hectares of inventory plots in Amazonian Floodplain Forests – perhaps the most remarkable forests of Amazonia, where trees can remain under water for half a year regularly. It was in 2014 that I had the chance to contribute to the growing wealth of information the ATDN produces, by becoming a member of the network. After defending my PhD thesis about the role of floodplains for Amazonian tree diversity I wrote a research proposal to improve our knowledge on the turnover in tree species and lineages across the forests of Amazonia, an aim that is simple to write in a proposal, but really complex to be achieved. More importantly, the research I was proposing was only feasible because of the existence of a collaborative network of researchers who spent months and years sampling trees under conditions not always as nice as desired, but sometimes as exciting as it can be. By the end of 2020, I received a post-doctoral fellowship from FAPESP supporting the realisation of the study as a researcher associated with the Laboratory of Evolutionary Ecology and Plant Genomics (LEEG) of UNICAMP in Brazil.
The realisation of my post-doctoral studies started during dark days of Covid-19 pandemic, and rising levels of deforestation in Amazonia promoted by a Brazilian government which deliberately neglected socio-environmental concerns, laws, and science. Restricted to one personal computer and locked-down at my house, I was well assisted by other researchers of UNICAMP and the ATDN network. Things started to get better when interactions became easier to realise. In 2022, I received funding from FAPESP to go abroad for an internship at The University of Edinburgh and collaborate with Professor Kyle Dexter for the study on the evolutionary assembly of Amazonian tree flora8. During those months in Scotland, I had the opportunity to participate in a workshop coordinated by Professor Toby Pennington at the Edinburgh Botanical Garden for sharing the results of the Inga project. It was during that workshop, and the week before, that I had the chance to meet personally for the first time Hans ter Steege to start forming the contribution that is now published in Comm. Biol. The history behind the paper is the time and effort it takes to deliver those contributions which was only feasible thanks to the power of networks. Now, you can find more about the gradual change in tree species composition over large geographic extents in Amazonia and confer the geographic zones of sharp tree species turnover. Interestingly, each one of the four major floristic transitional zones in Amazonia is associated with a different edaphic or climatic gradient. Putative biogeographic barriers, as the mighty Amazon-river tributaries and the Amazon river itself, seem not to matter that much for tree species. Floristic changes in southern Amazonia are associated with gradual changes from dryer to moist climate, in western Amazonia floristic transitions are linked with changes in soil pH and fertility, in the central part of the region with floods and soil texture changes, and in the northeastern with a dry diagonal forming a divide between the Amazon river basin and the lowlands of the Guianas. Also, you will find detailed information for the geographical and ecological distribution of over 5,000 tree species, something that should make the first who envisioned the study of the geography of plants proud.
1. ter Steege, H. et al. Hyperdominance in the Amazonian Tree Flora. Science 342, 1243092–1243092 (2013).
2. ter Steege, H. et al. Biased-corrected richness estimates for the Amazonian tree flora. Sci Rep 10, 10130 (2020).
3. ter Steege, H. et al. Towards a dynamic list of Amazonian tree species. Sci Rep 9, 3501 (2019).
4. ter Steege, H. et al. An analysis of the floristic composition and diversity of Amazonian forests including those of the Guiana Shield. Journal of Tropical Ecology 16, 801–828 (2000).
5. ter Steege, H. et al. A spatial model of tree a-diversity and tree density for the Amazon. Biodiversity and Conservation 12, 2255–2277 (2003).
6. ter Steege, H. et al. Mapping density, diversity and species-richness of the Amazon tree flora. Commun Biol 6, 1–14 (2023).
7. ter Steege, H. et al. Continental-scale patterns of canopy tree composition and function across Amazonia. Nature 443, 444–447 (2006).
8. Luize, B. G. et al. Geography and ecology shape the phylogenetic composition of Amazonian tree communities. Journal of Biogeography 51, 1163–1184 (2024).
9. Davis, T. A. W. & Richards, P. W. The Vegetation of Moraballi Creek, British Guiana: An Ecological Study of a Limited Area of Tropical Rain Forest. Part I. The Journal of Ecology 21, 350 (1933).
Please sign in or register for FREE
If you are a registered user on Research Communities by Springer Nature, please sign in