- October 18, 2018
Bees busy buzzing, bumbling, or burrowing are captivating visitors in a garden. As a wildlife landscaper, there are few things as thrilling as watching the bustling bee-activity in flower beds. This has led some bee-enthusiasts to wonder: are native (a.k.a wild) bees and honey bees at odds with one another?
The science tells us, as it often does, it’s complicated.
We’d be remiss not to remind readers, before diving into this topic, that competition is a healthy aspect of natural systems that leads to specialization and co-existence. Some of the issues facing bees are human-induced, however, and lead researchers to ask how we might be applying pressure at rates that could be detrimental to some bee species’ populations. Read on for more…
Bee research has become critical as there is mounting evidence that pollinators are on the decline.open_in_new The pollination services provided by bees are of enormous economic and environmental value.open_in_new Bees pollinate numerous crops in our food supply, like the above cherry orchard, and help maintain genetic diversity in our plant communities.open_in_new Bee vitality is, arguably, linked to that of many other species, including our own.
Brief Background on Bees
The lifestyle of honey bees (Apis) is very different from the thousands of species of bees native to North America. We have discussed the biology of honey bees in this article and the biology of some native bees in this article. In short, honey bees consist of seven species of non-native bees introduced to North America during colonial times for the valuable honey and wax they produce. They provide large-scale pollination services to commercial farms and orchards. Honeybees are eusocial, colonial nesters, and can be fiercely territorial.
Native bees, like the Augochloropsis metallica pictured, in contrast, are predominantly solitary nesters, with the exception of some species of bumblebees. There are upwards of 4,000 native bee species in North America, including about 50 different bumblebee species.open_in_new Native bees are generally docile, go-about-my-business bees. Many native bees do not have a stinger or very rarely use their stingers because they are not defending a collective hive filled with honey, where such drastic life-threatening defense strategies make sense. Their pollination services, however, are critical for trees, flowers, and shrubs.
These questions are often raised about the dynamics between native and honeybees:
- Do honey and native bees spread diseases or parasites to one another?
- Are the pressures facing native and honey bees the same?
- Should I be planting or doing different things to support different bees?
Let’s start with some good news. There is clear evidence that native and honey bees cohabitate–the presence of one does not imply a lack of the other, as many of us witness in our gardens. Recent research documented that farmers who increase the diversity of foraging areas such as grasslands, wetlands, forest etc., available to pollinators near their farmers, successfully increased both honey and native bee populations.open_in_new A clear case of diversity begets diversity.open_in_new
Likewise, where native and honey bees are living and pollinating side-by-side, overall fruit-set is improved compared to similar fields where only one or the other is found.open_in_new This is great news for farmers and orchardists, where pollination services are critical for a viable crop. The reason for this phenomena is hypothesized to be linked to subtle differences in feeding behavior. Honey bees prefer LOTS of flowers in ONE area.open_in_new They will gravitate towards plants that are loaded with flowers and and feed until the pollen and nectar are depleted.
Native bees, such as bumblebees, mason bees, and carpenter bees, etc., are less concerned about aggregated flower availability and will visit flowers just as efficiently regardless of flower density. In the fields where increased pollination results from the presence of both native and honey bee populations it is likely that the honey bees effectively pollinate the mass flowering areas while native species specialize in out-of-the-way blooms and those blooming later or earlier than the primary bloom period. There is some evidence, however, that native bees will avoid the areas honey bees gravitate towards possibly because honey bees can be more aggressive and territorial than native bees.open_in_new The presence of both, however, is a winning combination for maximizing pollination services.
Do bees spread diseases or parasites to one another?
The simple answer is, yes, they can. The more complicated answer is, diseases and parasites are as diverse, if not more so, than the thousands of bee species that exist. There is also limited research that has been conducted on native bees. As the image above depicts, the existing corpus research is heavily biased towards honey bees leaving a fair amount unknown about disease in native bee populations.
The transmission of disease or parasites is dependent on the bees coming in contact with each other or each others’ environments.open_in_new When bees land on flowers they can leave behind pathogens (viruses, bacteria, etc.) or other parasites through their feces.open_in_new The next visitor can be exposed to those microbes or parasites and contract the associated disease(s), even if that next bee is of a different species. The Deformed wing virus (DWV)open_in_new, an RNA virus, has been shown to affect both disease-exposed honey and bumblebees.open_in_new
DWV causes deformities in the wings and appendages of bees. Bees with the virus do not live long. In honey bees, the severity of this virus on a population is also linked with varroa mites who can transmit the virus to developing pupae in hives.open_in_new The impact of this virus on native wild bee populations is not fully understood, but there is concern that the virus has decreased the populations of bees that are vulnerable to it.open_in_new
Another family of fungal pathogens that have been linked to declines is the Nosema. Nosema apis and Nosema ceranae are common pathogens in honey bee colonies. Nosema ceranae can be transmitted to certain species of bumblebees giving rise to speculation about the role this fungus might be playing in diminishing native bumblebee populations.open_in_new
Nosema bombi, a different fungal infection in the Nosema genus, has likely influenced the decline of the pictured Rusty-patched bumble bee (Bombus affinis) that is now on the Endangered Species List. This pathogen is suspected of being transmitted from escaped greenhouse bumblebees to wild bee populations.open_in_new Though this is not an example of honey bee to native bee transmission, it does allude to the potential fragility of wild bee populations exposed to domestic bee populations raised for pollination services.
The Other Domesticated Bee
It is all about the bumblebee buzz pollination. Since the 1980s, bumblebees have been used to pollinate greenhouse tomatoes and other crops. Originally practiced in Europe, it is now widespread throughout North America.open_in_new When a bumblebee lands on a flower they will vibrate their bodies to break the pollen free as they gather it, incidentally releasing some of the previously collected pollen-grains they are carrying on their fuzzy thorax . This activity makes bumblebees excellent pollinators for crops such as tomatoes, blueberries, and strawberries. Other features such as their effectiveness at pollinating inside and pollinating across wide temperature ranges, make them an excellent choice for greenhouses.
Are the pressures facing native and honey bees the same?
Yes. Disease, pesticide exposure, loss of habitat or habitat fragmentation, and climate change are all threats that bees are facing.open_in_new How these pressures specifically influence native and honey bee populations, however, is complicated.
Climate change, for example, may threaten honey bees sooner than some bumblebees. In Norway, researchers found that bumblebee feeding correlated with warmer temperatures. As it became warmer, the feeding activity of bumblebees actually increased. This was not true for the honey bee. Honey bees preferred temperatures around 24.1 degree Celsius (75 degree Fahrenheit).open_in_new When temperatures started to rise above this, honey bee foraging decreased leading to concerns that perhaps honey bees will be more sensitive to the temperature pressures imposed by climate change.open_in_new
Lack of habitat and fragmentation affect numerous species, including bees. But, unlike some species, there is evidence that native and honey bees can both thrive in the urban, built environments that often replace larger tracks of native landscape. In fact, because honey and native bees may favor slightly different foraging opportunities in these landscapes, they might even be compatible members of an urban community.open_in_new
Researchers in Germany found honey bees in urban environments were more likely to be regular pollinators in smaller, residential, or commercial gardens. Wild bees, however, were more commonly found in green spaces, pollinating trees and plants in less developed areas.open_in_new Both are present and vital components of urban pollinator services.open_in_new
Another consideration for pressures facing bees are the kinds of plants made available in their habitat. Honey bees are considered generalistsopen_in_new, like the one pictured above about to feed on a squash family flower. They are capable of foraging on a wide range of plants, many of which are not native. Native bees, however, are sometimes specialists, preferring specific species of plants and flowers.
One study found that among the hundreds of bees in the northeast, 15% of them are specialists for specific plants.open_in_new Similar to Monarch butterflies that require milkweed plants to complete their reproduction cycle, some bees seek-out specific plants to satisfy specific nutritional needs, flower timing, or morphological relationships that determine their ability to successfully access pollen and nectar. If those plants are eliminated in their habitats, the bee populations that depend on them will suffer.
Finally, bees are often sensitive to pesticide exposure. Neonicotinoids, for example, are a kind of pesticide that has been found to negatively affect honey bees and populations of bumblebees and mason bees.open_in_new There is limited research on other species of native bees and their responses to neonicotinoids or other pesticides has not been studied, but given the functional and biological similarities between bee species, it seems expeditious to hypothesize that these pesticides also negatively impact many species of bees. Thus, we recommend minimizing extraneous use of pesticides to help all bees.
Should I be planting or doing different things to support different bees?
Yes. If you want to help native bees thrive in your region, help to protect native biodiversity by keeping wild green spaces thriving, removing invasive species, and adding a diversity of native plants to your landscape.
Jacob Johnston (pictured in the field above), Project Assistant for Habitat Network, and Masters student in Natural Resources Management at Cornell University has unpublished research suggesting a yard comprised of approximately 75% native plant species and 25% nonnative plant varieties can result in an increased abundance of bee visits per hour to the gardens (Johnston and Dickinson, unpublished). A diversity of native and non-native flower types provide overlapping bloom times and variations in nectar and pollen accessibility that may extend the flowering season and reduce competition between specialist and generalist speciesopen_in_new, attracting an overall greater number and diversity of pollinating visitors to your landscape.
Bees can have their preferences.open_in_new Some bees simply cannot reach the pollen or nectar of certain flowers due to their anatomy. Leafcutter bees, with their short tongues and large bodies cannot access long tubular flowers like penstemon and will stick to visiting upright flowers with short clustered florets, like native sunflowers. This leaves the penstemon for the small resin bees (Heriades), shown above, who can land on the bottom elongated petal and crawl deep inside for their sweet treat. When we have landscapes that are predominantly native, we help provide a little something for everyone, including the honey bee.
If you are a beekeeper, who is also concerned about native bee populations, you can safely raise your honey bees in a place where you provide a diversity of habitatsopen_in_new–flower gardens, vegetable gardens, orchards, meadows, forests, wetlands, etc. Habitat diversity helps to provide vital resources to a diversity of bee species and thus strengthens pollination services in general. This is especially true in more urban environments where the landscape tends to be homogenized.open_in_new
Landscape homogenization, where many of the floral resources are similar, or where resources are scarce, is the one area where direct competition between honey bees and bumblebees has been observed. In one study, honey bee hives were added to areas where bumblebee populations were present. In the areas with simple, homogeneous vegetative resources (i.e. not many kinds of plants) where hives were set, honey bees outcompeted bumblebees for limited resources. The same was not found to be true for heterogeneous landscapes where a diversity of foraging opportunities were available for both honey bees and bumblebees.open_in_new
Other Bee-Friendly Habitat Features
Besides offering a diversity in flowering plant habitats, the following are features you can add to support bees at home and in your community:
…additional research measuring direct, long-term, and population-level effects of managed bees is needed to understand their potential impact on wild bees.
More time and researchopen_in_new is needed to fully understand the conditional competition that may exist between honey bees and native bees. In the meantime, we know there are pressures facing all bees. And, we can do something about it. To help bees, create diverse native landscapes, eliminate the use of pesticides, and spread the word to neighbors and communities that they can be a part of the solution for our struggling bee populations.
Thank you to Mia Park, Postdoctoral Fellow at North Dakota State University for reviewing this content. Her research lab can be followed on Twitter @ColdBugLife.