Dispersal of Araucaria trees in Atlantic Rainforest was influenced by pre-Columbian people

A study conducted as part of a Thematic Project by Brazilian and US researchers investigates how plants and animals in the Atlantic Rainforest biome have reacted to climate change in past millennia.

By Karina Toledo  |  Agência FAPESP – Intensive logging in South Brazil since the nineteenth century has been largely responsible for the near-disappearance of the Paraná pine (Araucaria angustifolia), now listed as a critically endangered species. However, data from an ongoing study suggests that human action in the more distant past may have benefited the conifer’s expansion in the Atlantic Rainforest biome, contributing to the formation of the Araucaria forest (or mixed ombrophilous forest) domain that now spans parts of all three Southern Brazilian states (Paraná, Santa Catarina and Rio Grande do Sul).

“The current distribution of this species appears to have been influenced by both climate and human activity, but we don’t know if it came about by chance or deliberate human action to expand the Paraná pine population and thereby increase the food supply,” Mariana Vasconcellos, postdoctoral fellow at City University of New York (CUNY) and the New York Botanical Garden (NYBG) in the United States, told Agência FAPESP.

Archeological research, she added, has shown that at least 4,300 years ago, the first indigenous people who lived in what is now the South of Brazil used the Paraná pine’s nut-like seeds as food.

Vasconcellos collaborates with fellow researchers Ana Carolina Carnaval (CUNY) and Fabian Michelangeli (NYBG) on a Thematic Project funded by FAPESP and the US National Science Foundation (NSF) under the aegis of the FAPESP Research Program on Biodiversity Characterization, Conservation, Restoration and Sustainable Use (BIOTA-FAPESP).

The goal of their research is to map the distribution of animal and plant species in the Atlantic Rainforest, understand how they have reacted to climate change in the past millennia, and use the resulting data to help predict the impact of current climate change on the biome in order to establish key areas and species for conservation policy purposes.

Findings from several research lines linked to the Thematic Project were presented on July 12, 2019, at FAPESP during a symposium called “Dimensions US-BIOTA São Paulo: A multidisciplinary framework for biodiversity prediction in the Brazilian Atlantic Forest hotspot”.

Vasconcellos’s postdoctoral research aims to discover how the Araucaria forest remnants have behaved, that is, whether they have expanded or contracted, since the Last Glacial Maximum (LGM) approximately 20,000 years ago. The group analyzed the genomes of A. angustifolia samples from areas of native vegetation in the Serra da Mantiqueira region of São Paulo State and in the three states of the south. They then cross-referenced the genomic data with the pollen fossil record available in the scientific literature and data from models of past climate change.

“We knew a cold wet climate is ideal for the species. We modeled its distribution during the LGM [when it was very cold and dry] and during the middle Holocene [a relatively warm and wet period that occurred about 6,000 years ago] and compared these findings with the distribution of Paraná pine in the present [warm like the middle Holocene but drier]. Generally speaking, we concluded that as the temperature rose, the size of the area containing these trees decreased. However, the pollen fossil record shows that the population of A. angustifolia exploded about 4,000 years ago,” Vasconcellos said.

The genomic analysis reinforced the hypothesis that humans influenced this phenomenon. “The population of this species is more genetically differentiated in Serra da Mantiqueira and appears to have evolved naturally with little anthropic interference, whereas the Araucaria forest remnants contain highly similar trees distributed over a large geographic area, which is characteristic of violent population growth. Given the longevity of the species, which takes 20-40 years to start reproducing, it’s unlikely that climate alone can explain such a rapid dispersal,” Vasconcellos said.

Her current work involves reanalyzing the data with models capable of supplying more continuous information on climate change in the past 20,000 years. “The new analysis will confirm whether the expansion of the species was influenced by human activity, and if so, when,” she said.

According to Cristina Miyaki, a professor at the University of São Paulo’s Bioscience Institute (IB-USP) and coprincipal investigator for the Thematic Project (with Carnaval), the influence of pre-Colombian communities on shaping the Amazon Rainforest and the propagation of species of interest such as the Brazil nut tree (Bertholletia excelsa) has been extensively studied. “In the case of the Atlantic Rainforest, however, this question hasn’t been discussed much,” she said.

“This is the only study in the project that explored anthropic impacts in terms of species dispersal in the Atlantic Rainforest. It’s a special case and wasn’t part of our initial scope,” said Carnaval, a professor in CUNY’s Biology Department.

New species

Another study presented to the symposium that has been conducted in the last four years by Lucas Bacci as part of his PhD research at the University of Campinas (UNICAMP) in São Paulo State, Brazil, practically doubled the number of known species in the genus Bertolonia, which is endemic to the Atlantic Rainforest and is characterized by large leaves and scorpioid inflorescences (coiled in buds resembling a scorpion’s tail or the neck of a violin, uncurling as the flowers develop alternately on opposite sides of the peduncle).

Twelve new species were described, mostly in the central and northern portions of the biome. “The genus is found throughout the Atlantic Rainforest, but only five species are widely distributed. Most are microendemic, especially in the north,” Bacci said.

In reconstructing the history of these species, he concluded that the genus is monophyletic and evolved from a common ancestor approximately 30 million years ago.

Other presentations included data on the diversity and phylogeny of birds, harvestmen (Opiliones) and butterflies and discussed the influences of climate, temperature and rainfall on the biome’s evolution.

“One of the things discovered by the research we’ve been conducting since 2014 is that the Atlantic Rainforest didn’t evolve on its own. Its connections with the Amazon and the Andes are among the reasons it became so diverse. We found several links among these forest biomes, all of which have been mediated by climate over time,” Carnaval said.

Now that the data collection part is being finalized by the 16 associated researchers and their students involved in the initiative, a major multidisciplinary knowledge integration effort will begin as the basis for developing predictive models.

“One of the proposals is to monitor temperature variations by satellite and produce models to estimate the diversity that’s being lost and show where this loss is happening,” Carnaval said.

According to Miyaki, bringing together such a diverse group of scientists to collaborate has been a major challenge. “The team comprises biologists in different specialties – systematics, ecology, genetics, paleobotany – with geologists, paleoclimatologists, model designers and remote sensing engineers. A regular research funding program wouldn’t allow us to be so ambitious. All this has been made possible by the partnership between FAPESP and NSF,” she said.