Researchers reveal plant diversity in the Amazon

International work listed 14,003 species of plants, with 6,727 species of trees. Study led by Brazilians was published in Proceedings of the National Academy of Sciences

Diversity

Image: Domingos Cardoso

What is the number of plants in the largest and most diverse rainforest on the planet? A study led by Brazilians has just reached the following result: the diversity of plants in the Amazon comprises 14,003 species of plants with seeds (angiosperms and gymnosperms). The majority (52%) is composed of shrubs, vines, vines, epiphytes and underbrush, but the majestic trees are represented among the 6,727 cataloged species.

These numbers are not estimates but the result of accurate counting and verification by an international team of taxonomists. The work was conceived and coordinated by botanist Domingos Cardoso, from the Biology Institute of the Federal University of Bahia, and published in Proceedings of the National Academy of Sciences .

The species inventory covers the regions of the Amazon Forest at elevations between sea level and one thousand meters of altitude, in the following countries: Brazil, Bolivia, Peru, Ecuador, Colombia, Venezuela, in the two Guianas and in Suriname.

The finding that there are 6,727 species of native Amazon trees represents a phenomenal reduction compared to recent estimates based on statistical extrapolation, according to which the Amazon was thought to have up to 16,200 tree species.

However, in the new study, researchers investigated whether 9,346 species in 55 plant families were actually Amazonian, as listed in a previous study, and detected no less than 40% (3,794 species) as improper entries.

The fact that the total number of tree species revealed by the taxonomy is less than half of what was previously estimated from ecological data does not mean that the Amazon rainforest biome is less diverse than previously assumed.

“On the contrary, the differences between the previous estimates and the numbers presented in this new study only underscore the huge gap in taxonomic knowledge that we still need to fill. The Amazon has extraordinary plant richness, and our count of 6,727 tree species provides a reliable number that reflects what we know so far about some of the biodiversity in the world's largest tropical rainforest,” said Cardoso, whose specialty is taxonomy and molecular phylogeny of plants, that is, the cataloguing, classification and understanding of the evolutionary history of species.

“Knowing the precise amount of tree species native to the Amazon is of great importance to guide the formulation of conservation initiatives. Without this scientific basis, we may be putting at risk our biodiversity, a unique and irreplaceable heritage, simply for lack of really qualified knowledge”, he said.

The two previous surveys, published by another multinational group, estimated that, of the more than 40,000 tree species in the world's tropical forests, the Amazon Forest would be home to around 16,000 tree species (according to the 2013 study), number corroborated by a recent attempt to assemble an updated catalog of Amazon tree species that listed 11,676 species (see 2016 study).

The first estimate was statistical based on ecological data compiled from 1,170 plant inventories, while the second survey was based on information from more than 200 museums, universities, herbaria and botanical gardens, gathered in two large databases, the Global Biodiversity Information Facility it's the SpeciesLink (which has support from FAPESP) but without the same scientific rigor as a taxonomic verification.

Cardoso is a taxonomist specializing in the study of the large legume family (Fabaceae). It is the third largest family of terrestrial plants in number of species (over 19 thousand). In the new list, within the total universe of 14,003 species of native Amazonian plants, legumes have the highest representation, with about 1,380 species.

But the biome that is Cardoso's main focus of study is not the Amazon, but seasonally dry tropical forests, which include the Caatinga. It was also thanks to this specific knowledge and his taxonomic training that he began to suspect that something was wrong with the previous survey of the diversity of trees in the Amazon.

“When I looked at the species list from that 2016 compilation, I quickly identified around 400 species names that only occur in the Caatinga or that were completely outdated or duplicated,” he said.

The finding of such inaccuracy led Cardoso and his colleague Tiina Särkinen, from Royal Botanic Gardens Edinburgh from Scotland, in addition to his colleague and former supervisor, botanist Luciano Paganucci de Queiroz, from the State University of Feira de Santana, to begin a thorough check on the validity of the names on that list, a long-term work with the collaboration of 44 scientists from eight Amazonian nations, as well as researchers from the United States and Europe.

The team found that the incorrect insertion of those hundreds of species from the Caatinga and of duplicate names or synonyms in the Amazonian listing was just the tip of the iceberg. “Careful review showed that 40% of the names cited as Amazon trees contained some kind of error,” said Queiroz.

The inaccuracies found were due to a series of confusions, such as the inclusion of multiple references to the same plants, such as the angico, which entered the list twice, once with its official name (Anadenanthera colubrina) and the other with a synonym that fell into disuse for over 20 years (Anadenanthera macrocarp). “Two species of trees in the guava family (Myrtaceae) were misquoted more than 20 times,” said Cardoso.

primary sources

Another common type of inaccuracy found in the listing was the inclusion of native plants from other regions of Brazil and the world, or even species cultivated in the Amazon, but of different origin.

"There are cases of plants that only occur in eastern Brazil, one of which is well known to us, such as pau-brasil (paubrasilia echinata), and also from plants from other continents such as Australia (Acacia podalyriifolia) or Africa (Vachellia nilotica). There are plants cultivated as ornamentals, such as the North American magnolia (Magnolia grandiflora), or with medicinal uses such as Asian moringa (Moringa oleifera)”, said Cardoso.

In the list of tree species, references that were not even trees were included, "like the burr (Desmodium barbatum), a little plant a few centimeters high,” he said.

According to Cardoso, the errors may have occurred due to the data sources used. “The biological collections, in museums and herbaria, are material testimonies of everything that is known about biodiversity, but the compilation of this data from online databases such as GBIF and SpeciesLink, it should not be done without careful verification of the validity of the names”, he said.

A differential of this new study was the use of up-to-date taxonomic information, verified by hundreds of specialists from around the world during the production of catalogs of national plant species, such as Flora do Brasil 2020.

“This digital platform represents the accumulation of hundreds of years of fieldwork in the Amazon, the effort of hundreds of taxonomists. Taxonomically validated catalogs like this one provide solid foundations for understanding the evolution and ecology of this monumental forest in the face of climate change and other environmental changes”, state Cardoso and Särkinen.

Biology is a science of classification, and since the time of Carolus Linnaeus (1707-1778), the formulator of the taxonomic classification system, names have been given to species in nature. This path was marked by the creation of a profusion of synonyms for previously described species, as only the first description made is valid.

Among the 11,676 species names listed from the compilation of herbarium collections there is much outdated material, hence the vast synonymy.

“Although our article was not written as a criticism of previously published lists, it does not fail to oppose them and in this confrontation point out errors. Fundamentally, the lack of taxonomic expertise has led to the naive assumption that information from data repositories can be consumed in its primary state, leading to an overestimation of diversity,” he said.

The great international collaboration that brought together taxonomists from South America, the United States and Europe was the result of the support of several funding agencies, including FAPESP indirectly, through the project "Northeast: a new science for an important but neglected biome" , in which Cardoso and Queiroz participated.

“Our previous experience in the flora of the Caatinga allowed us to verify the errors in those listings”, said Cardoso. He and Queiroz credit their experience, in part, to their collaboration with Projeto Nordeste.

For the researchers, it is important to highlight that the new list of 6,727 species of Amazonian trees is a good reflection of current knowledge, but that there is still an enormous need for inventories to be carried out in the Amazon.

“There are gigantic collection voids. Some areas where a plant has never been collected are larger than areas in some Brazilian states. Certainly, there are many new species waiting to be known by science”, they add.

The article Amazon plant diversity revealed by a taxonomically verified species list (doi: 10.1073/pnas.1706756114), by Domingos Cardoso, Tiina Särkinen, Luciano Paganucci de Queiroz and others, can be read here .,


Source: FAPESP Agency


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