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Floral scent guides bee-flower interactions and explains seasonal patterns in communities

Date: October 21, 2019


Background:

Diverse meadow community in which the effects of floral scent on plant-pollinator webs was examined
Diverse meadow community in which the effects of floral scent on plant-pollinator webs was examined

In diverse communities, insect pollinators – like native bee species – visit flowers of plant species, forming complex webs of interactions. These interaction webs can have special structural characteristics. For example, some plant species are visited by many bee species (generalists), whereas others are only visited by a few (specialists). Also, bee-plant interaction webs often contain subgroups of species that form many connections amongst themselves (“modules”), but rarely mingle outside this group. Another property is “nestedness” in which specialist pollinator species visit plant species that are subsets of those visited by generalist pollinators. Nestedness increases overlap across modules and can stabilize interaction webs. Floral scent – complex mixtures of airborne chemical compounds – is one cue used by bees to locate preferred flowers and avoid others. Pollination biology has largely focused on the role of visual cues for pollinator attraction, like floral color, size and shape, and these traits are known to contribute to patterns in plant-pollinator webs, but if or how floral scent structures plant-pollinator webs is unknown. Understanding seasonal patterns in floral scent and bee visitation could guide selection of plants for use in pollinator restoration and have important implications for plant-pollinator interactions as shifts occur in suites of co‐flowering species due to climate change.

Research:

We sampled the floral scent, phenologies and bee visitors of 47 naturally growing plant species in a montane meadow in Montana in order to acquire a base understanding of how floral scent may structure plant-pollinator interactions across the growing season.

Key Findings and Activities:

  • Species blooming in early spring emitted similar blends of floral odors containing generalist attractants, whereas floral scent complexity was highest in species blooming in mid to late summer.
  • Plant species with unusual floral scents were visited by fewer bee species while plant species emitting more and common compounds were visited by more bee species.
  • Floral VOCs contributed to the nested structure, but not modular structure, of the plant-pollinator network.
  • These findings show that floral scent plays important roles in structuring bee-plant interactions and guiding seasonal patterns in complex communities.

Matrix of flower-bee interactions as filled boxes (PDF) Credit to Laura Burkle and Justin Runyon

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Principal Investigators: 
Principal Investigators - External: 
Dr. Laura Burkle - Montana State University
Research Location: 
Northern Rocky Mountains, Montana