Native Brazilian bee is resilient enough to offset decline of other pollinators

Research shows that Trigona spinipes can disperse over long distances and flourish in degraded areas.

By Elton Alisson

Agência FAPESP – Trigona spinipes is a species of stingless bee native to Brazil but found almost everywhere in South America. It is shiny, black and quite aggressive, and scientists are interested in its resilience to habitat degradation.

A study performed at the University of São Paulo’s Bioscience Institute (IB-USP) in Brazil in collaboration with the University of Texas at Austin in the United States found that the presence of this species throughout South America may be due to the ability of its drones to fly long distances and colonize degraded habitats.

Popularly called irapuá in Brazil, the species is capable of surviving in significantly altered environments and can be considered a “rescue” pollinator that offsets the decline of other native pollinators.

These findings, resulting from postdoctoral research supported by a scholarship from FAPESP and a Thematic Project also funded by FAPESP, are described in a paper published in the journal Conservation Genetics.

“We already knew that the Africanized honey bee, Apis mellifera, is a rescue pollinator, but this is the first time a native bee species has also been found to play this role,” Rodolfo Jaffé, first author of the paper, told Agência FAPESP. Jaffé’s postdoctoral research was supervised by Vera Lucia Imperatriz-Fonseca, Full Professor at IB-USP and a researcher at the Vale Sustainable Development Technology Institute (ITVDS) in Belém, Pará State.

According to Jaffé, who also works at ITVDS, T. spinipes is an opportunistic and generalist pollinator, foraging in flowers of many native plants as well as crops, such as carrot, sunflower, orange, mango, strawberry, squash, bell pepper and coffee. It is dominant in most bee-plant interaction networks and equivalent to Africanized bees in Brazil.

To find out whether the loss or fragmentation of forest areas influences the distribution and population dynamics of T. spinipes, the researchers collected specimens of this bee species in coffee plantations associated with fragments of Atlantic rainforest and in urban areas of Poços de Caldas, a city in southern Minas Gerais.

Using next-generation gene sequencing tools, the researchers developed new microsatellite markers, which they used to genotype the collected specimens. Microsatellites, also called simple sequence repeats, are short segments of DNA containing repeated sequences of base pairs that indicate the most recent evolutionary variations of an individual organism. The technique is useful to assess the magnitude and directionality of gene flow between populations.

Deploying computer software run by a laboratory that specializes in landscape genetics at the University of Texas at Austin, where Jaffé worked for a period with funding from a scholarship awarded by FAPESP under its Research Internship Abroad Program (BEPE), the researchers estimated the impact of landscape structure on genetic differentiation in the bees collected from environments with varying degrees of degradation.

They superimposed this genetic data on high-resolution relief maps showing land use and plant cover in the corresponding areas to assess the influence of these factors on gene flow among the bees collected.

“We wanted to investigate the influence of forest cover, land use and elevation on the dispersal and genetic differentiation of T. spinipes,” Jaffé said.

The results of the statistical analysis showed that this stingless bee species is capable of dispersing over remarkably long distances: no genetic differentiation was detected across bees collected in a radius of 200 km, meaning that bees found in São Paulo and Poços de Caldas belonged to the same population.

Moreover, gene flow was not affected by forest cover, land use or elevation, indicating that reproductive individuals are able to disperse well through both preserved and deforested areas and across different altitudinal gradients.

“The species maintains high levels of gene flow in several different kinds of environment,” Jaffé said. “This is why it can be considered a rescue pollinator. It compensates for the decline in other native pollinators that are more sensitive to deforestation.”

The researchers also found evidence of recent growth in the population of T. spinipes, probably as a reflection of its resilience despite ongoing destruction of Atlantic rainforest areas.

“This recent population growth suggests it’s capable of colonizing degraded habitats such as deforested areas,” Jaffé said.

Another group of Brazilian researchers compared bee-plant interaction networks throughout Brazil in a study published in early September by the journal PLoS One and conducted under the aegis of another Thematic Project supported by FAPESP.

The findings showed that T. spinipes flourishes more in degraded areas than in well-preserved environments.

“The species has a high capacity to colonize degraded habitats,” Jaffé said.

High reproduction rate

The researchers do not yet know why T. spinipes survives so well in degraded areas and is so widely distributed throughout the continent. They are considering the hypothesis that the species has a very high rate of reproduction.

“Every year, this species produces a daughter colony with 90,000 workers on average, or even several colonies, and they’re able to disperse over large areas,” Jaffé said.

Another hypothesis is that males are able to fly long distances and mate with queens from other colonies.

In addition, the species builds “annex” nests outside the main colony but does not need hollows in trees to do so. Hence, it has the ability to disperse over large areas with many new nests.

“These factors combined explain the unusually wide distribution of the species,” Jaffé said.

The article entitled “Landscape genetics of a tropical rescue pollinator” (doi: 10.1007/s10592-015-0779-0) by Jaffé et al. can be read in the journal Conservation Genetics at link.springer.com/article/10.1007/s10592-015-0779-0.

The article entitled “Native and non-native supergeneralist bee species have different effects on plant-bee networks” (doi: 10.1371/journal.pone.0137198) by Tereza Giannini et al. can be read in the journal PLoS One at journals.plos.org/plosone/article?id=10.1371/journal.pone.0137198.