Meeting Abstract
145.1 Monday, Jan. 7 Differential pollinator attraction and processing of flower scent by bumblebees BYERS, K.J.; RIFFELL, J.A.*; BRADSHAW, H.D.; Univesity of Washington, Seattle; Univesity of Washington, Seattle; Univesity of Washington, Seattle jriffell@uw.edu
Flowering plants attract the attention of insect pollinators using a wide variety of signals, including scent, which can recruit pollinators at a distance and draw them into visual range. We have investigated the role of floral scent in mediating differential attraction between two species of monkeyflowers (Mimulus) reproductively isolated by pollinator preference. The bumblebee-pollinated Mimulus lewisii and the hummingbird-pollinated M. cardinalis are significantly different both in the chemical composition of the volatile bouquet and in the rate of scent production. M. lewisii flowers produce a bouquet of at least 11 monoterpenes, dominated by limonene, β-myrcene, and cis-β-ocimene. Of these 11 monoterpenes, M. cardinalis flowers produce only limonene, released at just ~1% the rate of M. lewisii flowers. Bumblebees respond more strongly to M. lewisii as measured by gas-chromatograph-coupled multi-unit recording from antennal lobe (AL) neurons, and by wind tunnel and two-choice behavioral assays. Three monoterpenes – limonene, β-myrcene, and cis-β-ocimene – are necessary and sufficient to ensure the neural and behavioral response of bumblebees to M. lewisii. These volatiles are also found in the tergal gland of bumblebees, which mediates recruitment and foraging activation of worker bees. Indeed, AL recordings reveal that the M. lewisii floral scent and tergal gland extracts are represented similarly in the bee AL, hinting at a possible signaling co-option between the recruitment pheromone in bumblebees and floral scent in M. lewisii. In this system, floral scent alone is sufficient to elicit differential visitation, implying a strong role of scent in the origin and maintenance of reproductive isolation between M. lewisii and M. cardinalis.
