Study of ants investigates recovery of the Atlantic Forest

Insects are considered biomarkers of an ecosystem’s health; researchers conducted analyses in areas previously planted with eucalyptus trees.

By Ivonete Lucirio

Agência FAPESP – One way to determine the health of an ecosystem is to examine the variety of species that live in it. Researchers at the University of Mogi das Cruzes (UMC) have used this premise to quantify the species of leaf litter ants in a region between the Alto Tietê and Rio Itatinga river basins in the city of Mogi das Cruzes, on the border of Bertioga (SP).

The leaf litter layer consists of a mixture of fragments of leaves, twigs and other decomposing organic matter found on the forest floor and forms humus. This material shelters a rich ecosystem composed of a large variety of arthropods, fungi and bacteria. Many species of ants that build nests on the ground visit the leaf litter region to collect food.

Unlike generalist ants, which are mostly found in urban environments, those that live in leaf litter are normally specialists. In the forest leaf litter, with no interference from humans, several ecological interactions occur to support the existence of other small animals that serve as food for the ants.

In the case of the study “Structure of litter ant communities in extensive Eucalyptus grandis dunnii Maiden culture in Atlantic Forest areas,” coordinated by Maria Santina de Castro Morini of UMC, the leaf litter ants were used as a biological marker to establish the recovery capacity of areas once covered by native Atlantic Forest.

Three types of environments were studied in the region selected for the analysis: areas in which the Atlantic Forest was removed for the planting of eucalyptus, and still underway; areas in which planting was discontinued 28-30 years ago owing to conservationist pressures or management difficulties; and conservation units (CUs) with native forest.

In areas that had never been deforested, it was possible to find nearly 25 of the 200 existing species of leaf litter ants per square meter. In the eucalyptus forests, however, the number of species did not exceed five per square meter. “This difference is due to several factors, but the primary reason is that eucalyptus leaves decompose more slowly and have high levels of tannin, which is toxic to many organisms that serve as food for the ants,” said Morini, professor in the Biological Sciences program at UMC.

However, in regions where plantations were discontinued nearly 30 years ago and where the Atlantic Forest has re-established, an average of 18 species were found per square meter – a sign that the region’s forest and fauna were able to recover. The researcher had decided to study regions where plantations had been discontinued for nearly 30 years – and there are several of them - because these sites allowed her to obtain the most reliable data (because these data were collected in more than one area).

To perform the counts, Morini worked from July 2010 to July 2013, specifically in the region of the Alto Tietê River Basin. Her group of researchers demarcated areas of one square meter of leaf litter – in eucalyptus plantation areas, native forest or abandoned plantations – and took the material to her laboratory, where the ants were counted. For each area studied, six samples were removed, and a total of 120 samples of leaf litter were collected.

Morini worked together with a group of researchers from the Museum of Zoology of the University of São Paulo (USP) as they conducted the projects “Richness and diversity of Hymenoptera and Isoptera along a latitudinal gradient in the Mata Atlântica – the eastern Brazilian rainforest” and “Biodiversity of Isoptera and Hymenoptera,” coordinated by professors Carlos Roberto Ferreira Brandão and Eliana Cancello. “All the methodology that I used was discussed so that the results could be compared. I took part in meetings to learn how to design samples and to learn the techniques they use for collecting so that I could do the same in mine,” said Morini.

Study of the microbiota

In another study, entitled “Diversity of bacteria and invertebrates and its influence on the structure of the communities of litter ants in areas of Atlantic Rainforest,” also conducted between 2010 and 2013, the researcher examined the diversity of bacteria and invertebrates and their influence on the structure of the ant communities.

The Atlantic Forest in the Alto Tietê region is protected in dam areas, CUs and on private property. The research was conducted in sections of these areas in an attempt to assess the number of fungi and bacteria in the samples.

The forest areas protected by the public agencies responsible for the dams and on private properties that value conservation are as diverse as the CUs themselves, which indicates, according to the researcher, how important the sections in dam areas and on private property actually are in protecting the biodiversity of the Atlantic Forest. “My research shows that it is not only the CUs that are important to the Alto Tietê but also the other areas, so it’s important to establish incentives to keep them from being deforested,” Morini said.

The microbiota, through the decomposition of organic matter, allows the existence of other invertebrates (acari and springtails, for example) that serve as food for the ants. It is expected that where there are more microorganisms, there are also more species of ants. That hypothesis remains to be proven, however.

“We cannot yet make any assertions about the relationship between the microbiota and the richness of the ants. We soon hope to complete the model proposed in the project,” Morini told Agência FAPESP.

The findings from the two studies led by Morini are scheduled to be published by the end of this year. “Right now, we’re preparing a manuscript for publication in the journal Biological Conservation,” Morini said.

Partial findings have already resulted in the following publications: “Characterization of ant communities (Hymenoptera: Formicidae) in twigs in the leaf litter of the Atlantic Rainforest and eucalyptus trees in the southeast region of Brazil,” by Morini and others, available in Psyche; and “Occurrence and natural history of Myrmelachista Roger (Formicidae: Formicinae) in the Atlantic Forest of southeastern Brazil,” by Morini and others, published in Revista Chilena de Historia Natural.

Images

During her research, Morini photographed in the laboratory then catalogued 235 species of ants that live in the Alto Tietê as part of the project “The ant fauna biological collection of the Alto Tietê: organizing a photographic collection.”

The findings will be available in a catalogue that is scheduled to be published in April 2014. In addition to the photos, there are texts that describe the environment in which these ants live, written by several colleagues, such as Ramon Luciano de Melo of the Federal University of Mato Grosso (UFMT) and Jacques Delabie of the Executive Commission of the Cocoa Farming Plan (CEPLAC).

The publication will touch upon the biological collections and the conservation of their biodiversity. The catalogue is being edited by Morini, Silvia Sayuri Suguituru, also of UMC, Rodrigo Feitosa of the Federal University of Paraná (UFPR) and Rogério Rosa Silva, researcher at the Museu Paraense Emílio Goeldi. “I want to show everyone, not just scholars, that ants are morphologically beautiful. They aren’t pests, and they help the forest. Once society is aware of this, I hope it also helps to protect them,” Morini says.

Morini has studied the leaf litter ants for more than a decade, and some of the conclusions she has reached through other projects are also found in the book Serra do Itapeti: aspectos históricos, sociais e naturalísticos (Itapeti Forest: historical, social and naturalistic aspects) (Canal 6 Editora), edited by her and Vitor Fernandes Oliveira de Miranda and published in 2012.

A total of 1,500 copies of the book have been distributed free of charge to academic institutions of the Alto Tietê and NGOs. It is available for download at www.canal6.com.br/site/download. The book is helping to promote new discussions about the subject. According to the researcher, the biodiversity information in the book is being used to establish the Serra do Itapeti Environmental Protection Area (APA) in the Mogi das Cruzes region.