*Guest post by Shannon Underwood, a student in Marc's 'Causes and Consequences of Diversity' class.
When you think “Save the Bees”, most likely a Honeybee comes to mind – this is primarily because they have become the flagship species for the current bee crisis. Although responsible for bringing the much-needed attention to the impact humans are having on our bee populations, they greatly misdirect the public, making a large number of people significantly less aware of the other 4,000 diverse bee species we have in North America14 – our wild (native) bees: the ones we should be more concerned about.
Fig 1. Adapted from Wilson, Forister, and Carril 2017. Above figure shows the total amount of bee species survey-participants thought were in the United States.
Pollinators are responsible for supporting 35% of the global agricultural landscapes15. Outside of agriculture, 80-95% of the native flowering plants that are found in natural ecosystems rely on animal pollinators for reproduction11. Pollination is a fundamental ecosystem service provided by a variety of animals, however most efficiently by wild bees. The unique evolutionary histories that bees share with native plants has resulted in the vast diversity of traits seen among them (Photo 1), and communities with greater bee diversity have shown to be more productive than communities with poorer diversity12 - largely because of greater resource partitioning by the wild bees. Their foraging preferences, differences in body shapes and sizes, as well as some species ability to perform a more effective technique of pollination called buzz pollination, make wild bees the most important group of pollinators.
Photo 1: Shows the different body shapes and sizes of some wild bees. This rich diversity reflects their unique coevolution with plants.
Bees are facing substantial reductions in their diversity, range and abundances worldwide1. In North America, there are currently 12 wild bee species that are recognized as ‘threatened’ under the IUCN Red-list. Staggeringly, all 12 of these species belong to the genus Bombus- commonly referred to as the Bumblebee. Over that last 20 years, Bumblebees have become one of the largest victims of decline in North America - with four species that faced a 23-87% shrinkage in their geographic range, and a precipitous 96% reduction in their abundance2. A leading cause of the declines in wild bee populations has been largely attributed to land-use change1. While the human population continues to expand, accumulating amounts of their natural habitat is lost and replaced with agricultural and urban landscapes. The fragmented habitats that remain often have decreased accessibility to green spaces and poorer nesting opportunities for bees. Making it harder for them to grab a foothold in the community – these human-added stressors put our wild bees at a much greater risk for extinction.
Fig 3. Adapted from Szabo et al. 2012. Shows the decline in the occurrence of B. affinis (A), B. terricola (B), B. pensylvanicus (C), and all bumblebee species (D) between the years of 1980-1990 (green) and 2000-2010 (blue).
The second most prominent impact on wild bee abundance and diversity has been greatly linked to invasive species like the common Western Honey bee1. The Honeybee, native to the Old World region, has become an invasive species in all areas outside of its origin3. Their uniquely large colonies and hive formation make them the most valuable pollinator to humans in agriculture management. Wild bee health and productivity is often reduced in agricultural landscapes because of the high use of pesticides and lower foraging opportunities7. To compensate for this, the honeybee has become a highly used technique worldwide because they can be easily transported to a field for crop pollination- many policies and conservation efforts tend to primarily focus on the protection of such managed bee species because of this. But the positive attention that the honeybee receives publicly leaves many people unaware that it is even invasive in North America.
Fig. 4. Adapted from Garibaldi et al. 2013. The figure shows that wild insects increased reproduction (y-axis) in all crops examined than the honeybee alone.
1. Brown, Mark J. F., and Robert J. Paxton. 2009. “The Conservation of Bees: A Global Perspective.” Apidologie 40(3): 410–16.
2. Cameron, Sydney A. et al. 2011. “Patterns of Widespread Decline in North American Bumble Bees.” Proceedings of the National Academy of Sciences 108(2): 662–67.
3. Colla, Sheila R., and J. Scott MacIvor. 2017. “Questioning Public Perception, Conservation Policy, and Recovery Actions for Honeybees in North America.” Conservation Biology 31(5): 1202–4.
4. Dylewski, Łukasz, Łukasz Maćkowiak, and Weronika Banaszak‐Cibicka. 2019. “Are All Urban Green Spaces a Favourable Habitat for Pollinator Communities? Bees, Butterflies and Hoverflies in Different Urban Green Areas.” Ecological Entomology 44(5): 678–89.
5. Garibaldi, Lucas A. et al. 2013. “Wild Pollinators Enhance Fruit Set of Crops Regardless of Honey Bee Abundance.” Science 339(6127): 1608–11.
6. Graham, Kelsey K. “Beyond Honey Bees: Wild Bees Are Also Key Pollinators, and Some Species Are Disappearing.” The Conversation. http://theconversation.com/beyond-honey-bees-wild-bees-are-also-key-pollinators-and-some-species-are-disappearing-89214 (February 20, 2020).
7. Hall, Damon M. et al. 2017. “The city as a refuge for insect pollinators.” Conservation Biology 31(1): 24–29.
8. “Invasive Species | U.S. Climate Resilience Toolkit.” https://toolkit.climate.gov/topics/ecosystem-vulnerability/invasive-species (February 21, 2020).
9. Javorek, S. K., K. E. Mackenzie, and S. P. Vander Kloet. 2002. “Comparative Pollination Effectiveness Among Bees (Hymenoptera: Apoidea) on Lowbush Blueberry (Ericaceae: Vaccinium Angustifolium).” Annals of the Entomological Society of America 95(3): 345–51.
10. Matias, Denise Margaret S. et al. 2017. “A Review of Ecosystem Service Benefits from Wild Bees across Social Contexts.” Ambio 46(4): 456–67.
11. Ollerton J, Winfree R, Tarrant S: How many flowering plants are pollinated by animals? Oikos 2011, 120(3):321-326.
12. Rogers, Shelley R., David R. Tarpy, and Hannah J. Burrack. 2014. “Bee Species Diversity Enhances Productivity and Stability in a Perennial Crop.” PLOS ONE 9(5): e97307.
13. Szabo, Nora D. et al. 2012. “Do Pathogen Spillover, Pesticide Use, or Habitat Loss Explain Recent North American Bumblebee Declines?” Conservation Letters 5(3): 232–39.
14. “The IUCN Red List of Threatened Species.” IUCN Red List of Threatened Species. https://www.iucnredlist.org/en (February 20, 2020).
15. “What Are Pollinators and Why Do We Need Them? (Center for Pollinator Research).” Center for Pollinator Research (Penn State University). https://ento.psu.edu/pollinators/resources-and-outreach/what-are-pollinators-and-why-do-we-need-them (February 21, 2020).
16. “Why bees matter.” Food and Agriculture Organization of the United Nations. 2018. http://www.fao.org/3/I9527EN/i9527en.PDF
17. Wilson, Joseph S., Matthew L. Forister, and Olivia Messinger Carril. 2017. “Interest Exceeds Understanding in Public Support of Bee Conservation.” Frontiers in Ecology and the Environment 15(8): 460–66.