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Award Detail

Doing Business As Name:University of Washington
  • Harvey D Bradshaw
  • (206) 616-1796
  • Kelsey Byers
  • Jeffrey A Riffell
Award Date:06/22/2012
Estimated Total Award Amount: $ 14,562
Funds Obligated to Date: $ 14,562
  • FY 2012=$14,562
Start Date:07/01/2012
End Date:06/30/2014
Transaction Type:Grant
Awarding Agency Code:4900
Funding Agency Code:4900
CFDA Number:47.074
Primary Program Source:040100 NSF RESEARCH & RELATED ACTIVIT
Award Title or Description:DISSERTATION RESEARCH: Contribution of specific floral odorants to differential attraction and reproductive isolation in monkeyflowers (Mimulus)
Federal Award ID Number:1209340
DUNS ID:605799469
Parent DUNS ID:042803536
Program:Animal Behavior
Program Officer:
  • Michelle Elekonich
  • (703) 292-7202

Awardee Location

Street:4333 Brooklyn Ave NE
Awardee Cong. District:07

Primary Place of Performance

Organization Name:University of Washington
Street:24 Kincaid Hall
Cong. District:07

Abstract at Time of Award

Much of the biodiversity of flowering plants is due to their coevolutionary relationships with animal pollinators. Each species of pollinator is attracted to a particular flower because of the flower's color, size, shape, nectar reward, or scent. Little is known about the role of specific genes that cause changes in scent that then affect pollinator behavior. The genus Mimulus (monkeyflowers) contains two species that are separated only by the preferences of their pollinators (hummingbirds and bumblebees). The two Mimulus species have marked differences in their floral scents. This proposal focuses on two questions: 1) What are the genes that underlie these scent differences in Mimulus?; and, 2) How will plants that differ in these genetic traits affect the response of hummingbird and bumblebee pollinators in nature? The work proposed here addresses broader evolutionary principles that underlie species diversity. Additionally, since insect pollination is responsible for $225 billion per year in service to agriculture, understanding the genetic and evolutionary basis of plant-pollinator interactions has important implications for food security.

Publications Produced as a Result of this Research

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Kelsey J.R.P. Byers, H.D. Bradshaw, Jr. , and Jeffrey A. Riffell "Three floral volatiles contribute to differential pollinator attraction in monkeyflowers (Mimulus)" Journal of Experimental Biology, v.217, 2014, p.614. doi:10.1242/jeb.092213 

Yuan Y., K.J.R.P. Byers, & H.D. Bradshaw, Jr. "The genetic control of flower-pollinator specificity." Current Opinion in Plant Biology, v.16, 2013, p.422. doi:10.1016/j.pbi.2013.05.004 

Project Outcomes Report


This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.

Why are there so many species of flowering plants?  Some of the most recent estimates of flowering plant diversity suggest that more than 325,000 species of flowering plants populate the earth.  One major factor that is known to play a role in this diversity is the relationship between flowering plants and their pollinators.  Many closely-related species of flowering plants can cross freely in a greenhouse, but in the wild are kept separate by their use of different pollinators.  These pollinators make choices between flowers based on a variety of signals, including color, size, shape, and scent.

The sister monkeyflower species Mimulus lewisii and M. cardinalis are a model system for studying the role that various signals play in keeping these plants isolated from one another via pollinator choice.  Mimulus lewisii is pollinated by bumblebees, while its sister species, M. cardinalis, is pollinated by hummingbirds.  Neither species smells strongly to us, but preliminary research showed that they had differences in what scent compounds were emitted from the flowers, and that some of these were very exciting to bumblebees both neurologically (in the area of the brain that processes smell) and behaviorally (bumblebees liked to visit paper disks soaked with these compounds).  Three compounds in particular stood out: myrcene, limonene, and ocimene.  However, the role of these scent compounds in pollinator choice and isolation in this system was unclear.

This project covered three main goals: (1) discovery of the genetic differences underlying these differences in scent between the two species; (2) generating populations of Mimulus with altered floral scent; and (3) testing these lines with pollinators to discover the role that shifts in flower scent play in pollinator choice in this system, and thus the role that scent might play in keeping these species separate.  Our understanding how the genetics and evolution of traits like floral color is strong, but our understanding of the role of floral volatiles is still fairly basic, and no single system has yet fully investigated floral volatiles from a genetic and evolutionary point of view.

We found that just two genes - LIMONENE-MYRCENE SYNTHASE and OCIMENE SYNTHASE - were responsible for the important scent differences between these two species (Aim 1).  As their names suggest, the first gene produces limonene and myrcene and the second produces ocimene.  Both genes are functional and turned on in Mimulus lewisii, but are not functional in M. cardinalis despite being turned on.  Using transgenesis, we were able to tell M. lewisii plants to turn down their production of limonene, myrcene, and ocimene (Aim 2).  Finally, we tested these plants with bumblebees in a greenhouse to see whether bumblebees preferred normal M. lewisii plants or those with lower amounts of scent (Aim 3). 

The results were surprising - even though bumblebees were excited by limonene and myrcene with paper disks, they were indifferent to the loss of these compounds in the real plants.  However, they definitively rejected plants that were low in ocimene, in agreement with the earlier results.  The effect is very strong; this means that the lack of ocimene in Mimulus cardinalis - due to the non-functional OCIMENE SYNTHASE gene - must have been lost under strong selective pressure in the past.  Most current examples we have of genes that keep species isolated are genes that have regulatory functions - genes that control whether other genes are turned on or off, in what tissues they work, etc.  It's surprising that we found that the critical gene in this case is an enzyme acting at the very end stage...

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