Primary Article: Jaffé R. et al. (2019), Landscape genomics to the rescue of a tropical bee threatened by habitat loss and climate change. Evolutionary Applications, 12: 1164-1177. https://doi.org/10.1111/eva.12794.
Featured Image: The study species, Melipona subnitida. Source: Wikipedia
Brazilian bees and a blueberry breakfast
This morning, I microwaved a bowl of oatmeal and topped it with a handful of blueberries, a spoonful of flax seed, and a dollop of honey. Without the toppings, my breakfast would have been a bland bowl of mush. Who should I thank for providing my breakfast’s extra protein and fiber, sweet flavor, and juicy berries, transforming it into a delicious, well-rounded meal? Bees!
Bees produce honey and are key pollinators for a variety of plants, including food crops like berries and flax. Pollinators, including bees, are responsible for 35% of the world’s crops- that’s about one in three bites that you take. Throughout history until today, many families around the world have earned at least part of their income through either farming or beekeeping.
Bees are threatened around the world by habitat degradation and climate change. Deforestation breaks up the bees’ habitat, which gives populations fewer choices for mates. This can reduce genetic diversity.
Climate change affects the availability of the plants that bees need for habitat and food. As changes in the environment cause plants to move or perish, bee populations will likely follow similar patterns.
Jaffe and colleagues (2019) used genomic tools to study how climate change and habitat loss are affecting the tropical bee Melipona subnitida. This species is native to northeastern Brazil and is very important to the region. It is a source of income for rural beekeeping families, and a key pollinator of local crops which feed people in the region.
The bee inhabits a range of climates, altitudes, and latitudes within the region of northeast Brazil. Because the species lives in so many different places, we would expect it to adapt to each set of environmental conditions, and therefore have high levels of genetic diversity.
As the climate changes, we expect that the bees will migrate to higher elevations. However, their migration may be limited. Stingless bee queens do not have wings, so they don’t travel far from their original colonies when they establish new ones. Additionally, deforestation and development have reduced available habitat and migration pathways.
Because of these challenges, and because the bees have social and economic importance, humans may help them migrate. In order to do this effectively, we need more information about the distribution of genetic diversity and adaptation. The study aimed to identify barriers to mating between populations and to piece together the distribution of adaptive traits through geographical space.
Researchers asked two main questions:
- Are genetic diversity and gene flow affected by the availability of forests that have not been cut or turned into farmland?
- Where has genetic adaptation to local environments occurred?
Beekeepers and scientists worked together to collect samples. Scientists collected bees that were distributed throughout the entire region in varying environments from beekeepers who could verify the origin of their bees. They extracted DNA to look for evidence of adaptation to different environments.
The researchers expected that areas with more natural habitat would contain greater genetic diversity. They also expected that landscape features, such as rough terrain, waterways, or developed areas, would lead to isolation of populations. Finally, they expected to find evidence of adaptation to temperature, precipitation, and forest cover in varying locations.
Forests provide pathways, temperature variation builds walls
The researchers identified four genetically distinct groups, supporting their prediction that the species would contain high genetic diversity from local adaptation.
They were surprised to find that the amount of available undeveloped forest did not influence genetic diversity. However, this may be because it is too early to detect effects, so we should continue genetic monitoring and studies in the future.
Temperature fluctuations were the largest obstacle to bee dispersal, compared to other environmental factors. Previous studies showed that temperature affected bee bodily structure and functions, but this is the first to show that temperature affects the ability of the bees to migrate and establish new colonies.
Lack of forest cover also posed a significant dispersal obstacle. Higher amounts of mating between populations were correlated with low annual temperature variation, more forest cover, lower elevations, and flatter terrain.
Even though the bees typically don’t travel far to establish new colonies, researchers were surprised to find genetically related colonies over distances up to 300 km.
DNA analyses showed that bees have adapted in response to varying local environmental conditions such as temperature, precipitation, and forest cover. This study was the first to show that stingless bees are genetically distinct in highland vs lowland environments.
Scientists have predicted that as climate change progresses, highlands will become more similar to current lowland areas. When this occurs, lowland bee populations will likely move to the highlands. However, highland bee populations won’t have anywhere to go. Because these genetically unique highland populations are at risk, we should prioritize their protection.
The connectivity between highlands and lowlands should also be protected so that migration can occur. This can be done by preserving or restoring forests in the foothills and on mountains.
Finally, if humans assist in bee migration by establishing new colonies, we should ensure that the colonies we establish are within 300 km of natural populations in order to maintain connectivity.
The ecological and evolutionary discoveries made through this study can help us to more effectively face environmental challenges and better sustain family livelihoods, tasty honey, and food crops.