For bees (and flowers), tongue size matters

For bees and the flowers they pollinate, a compatible tongue length is essential to a successful relationship. Some bees and plants are very closely matched, with bee tongue sized to the flower depth. Other bee species are generalists, flitting among flower species to drink nectar and collect pollen from a diverse variety of plants. Data on tongue lengths can help ecologists understand and predict the behavior, resilience and invasiveness of bee populations.

But bee tongues are hard to measure. The scarcity of reliable lingual datasets has held back research, so Ignasi Bartomeus of the Estación Biológica de Doñana (EBD-CSIC) in Sevilla, Spain, and his colleagues at Rutgers University (New Brunswick, N.J.)  looked for a more easily measured proxy, like body size. Bee tongues are proportional to body size, but modulated by family adaptations—bee families typically have characteristic tongue shapes and proportions. The research group came up with an equation to predict tongue length from a combination of body size and taxonomic relationships.

Bartomeus will explain the equation and the usefulness of tongue length data for ecology at the 99^th Annual Meeting of the Ecological Society of America in Sacramento, Cal., this August during the “Pollination I” oral session on Thursday afternoon, August 14. The meeting lasts five days and draws roughly 3,500 environmental scientists from around the world.

A bee collects pollen on its body as it laps sugar-rich nectar from within the cupped interior of the flower’s petals, and carries the flower’s genetic heritage away with it to fertilize the next flower of the same species that it visits. In most species, the bee’s tongue is guarded by a long, two-sided, beak of a sheath, which folds under the body when the bee flies.

A lovely Augochlora pura extends part of its tongue. A. pura is a member of the relatively short-tongued Halictidae family, uprettily known as the sweat bees. The small, solitary bee is one of the most common bees of forests and forest edges in the eastern United States, and a promiscuous attendant to many flower species. Collected by Phillip Moore in Polk County, Tennessee. Photograph by Phillip Moore. Photo courtesy of the USGS Bee Inventory and Monitoring Lab.

Perched at the mouth of a flower, the bee unfolds the beaky maxilla and extends its tongue into the corolla of the flower, dipping and retracting it to lap up the nectar. If its tongue is too short to reach the nectar, the bee has a problem. Long flowers like honeysuckle or columbine are too deep for short-tongued bees.

But longer isn’t always better; long tongues are harder to wrangle into short flowers. Long-tongued bees are often specialists, favoring a few deep-throated flower species. In the bumblebee-sparse southern tip of Argentina, for example, Bombus dahlbomii, the native long-tongued giant of Patagonia, has lost ground to a new bumblebee from Europe, the short-tongued generalist Bombus terrestris, imported to help pollinate tomatoes. Although disease has likely played a role in the retreat of the long-tongued giant, B. terrestris also appears to be out-competing an earlier European immigrant, the long-tongued Bombus ruderatus.

Because specialists depend on just a few flowers, they can be more vulnerable to change. Tongue length can thus be intertwined with a species’ risk of extinction, as well as specialization.

Presentation:

Contributed talk 122-4 – The allometry of bee tongue length and its uses in ecology Thursday, August 14, 2014: 2:30 PM Room 315, Sacramento Convention Center

Speaker:

Ignasi Bartomeus , Estación Biológica de Doñana (EBD-CSIC), Sevilla, Spain nacho.bartomeus@gmail.com

Session:

Contributed talks 102: Pollination I. Thursday, August 14, 2014: 1:30 PM-5:00 PM. Room 315.

Additional reference:

Carolina L Morales, Marina P Arbetman, Sydney A Cameron, and Marcelo A Aizen (2013). Rapid ecological replacement of a native bumble bee by invasive species. Frontiers in Ecology and the Environment 11: 529–534. http://dx.doi.org/10.1890/120321

More bees, butterflies, birds and other pollinators at ESA’s 2014 Annual Meeting, August 10-15, 2014, at the Sacramento Convention Center in Sacramento, Cal.:

• Poster session 17-133: Landscape drivers of pollination services in urban gardens
• Monday, August 11, 2014. Exhibit Hall.
• Workshop 30: Intergovernmental Platform on Biodiversity and Ecosystem Services Thematic Assessment of Pollination and Food Production. Tuesday, August 12, 2014: 11:30 AM-1:15 PM. 203.
• Organized talks 19-4: Nectar microbial community assembly and plant-pollinator mutualism. Tuesday, August 12, 2014: 2:30 PM, 308.
• Organized talks 31-4: Can pollinator habitat plantings restore both biodiversity and ecosystem services? Wednesday, August 13, 2014: 2:30 PM. Room 307.
• Organized talks 31-5: Native bee community functional diversity explains sentinel plant pollination in an intensive agricultural landscape. Wednesday, August 13, 2014: 2:50 PM. Room 307.
• Cointributed talks 77-8: Do ecosystem service-providers and rare bees prefer the same plant species? A three-year experimental field study. Wednesday, August 13, 2014: 4:00 PM. Regency Blrm B, Hyatt.
• Poster session 41: Pollination. Wednesday, August 13, 2014: 4:30 PM-6:30 PM. Exhibit Hall.
• Contributed talks 97-1: Abundance, not species richness, drives ecosystem service delivery at large spatial and temporal scales.Thursday, August 14, 2014: 8:00 AM. Regency Blrm D, Hyatt. 
• Contributed talks session 122: Pollination I. Thursday, August 14, 2014: 1:30 PM-5:00 PM. Room 315.
• Organized talks 46-5: Investigating the effects of production-scale harvesting on pollination and biocontrol services in bioenergy grasslands. Thursday, August 14, 2014: 2:50 PM. Room 308.
• Contributed talks 115-10: More pollinator species are required for pollination function at larger spatial scales, but high regional dominance can suppress this effect. Thursday, August 14, 2014: 4:40 PM. Regency Blrm D, Hyatt Regency Hotel.
• Contributed talk session 140: Pollination II. Friday, August 15, 2014: 8:00 AM-11:30 AM. 314.

The Ecological Society of America is the world’s largest community of professional ecologists and a trusted source of ecological knowledge. ESA is committed to advancing the understanding of life on Earth. The 10,000 member Society publishes five journals, convenes an annual scientific conference, and broadly shares ecological information through policy and media outreach and education initiatives. Visit the ESA website at http://www.esa.org.