What are the plant reproductive consequences of losing a nectar robber?
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Date
2022
Publication Type
Journal Article
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yes
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Abstract
Pollinator declines worldwide are having strong negative consequences
for plants. In many communities, antagonistic flower visitors, including nectar
robbers, have likely declined in abundance as well. Given the negative effects that
these visitors can sometimes inflict, might declines in their populations benefit
plants? During the 1970s, the floral visitor community of the Colorado columbine,
Aquilegia caerulea (Ranunculaceae), was documented near Gothic, Colorado. At
that time, Bombus occidentalis, the Western Bumble bee, was one of its many
pollinators, but more commonly acted as its only known nectar robber. Bombus
occidentalis abundance has declined precipitously throughout the Western USA
since the 1970s. In 2016, we documented the floral visitor community in sites near
to those used in the original survey. We then experimentally quantified the effects
of nectar robbing, allowing us to estimate the reproductive consequences of losing
B. occidentalis. We also quantified the potential pollination services of muscid flies
(Muscidae, Diptera). The floral visitor community was dramatically different in 2016
compared to the 1970s. Bombus occidentalis, a frequent A. caerulea visitor from
1969-1976, was infrequently observed visiting the plant, and nectar robbing was
negligible. Our experiments suggested that a high level of nectar robbing would
lead to significantly reduced fruit set, although not seeds per fruit. Fly visits to
flowers were dramatically higher in 2016 compared to the 1970s. We show that, in
the absence of bumble bee pollinators, muscid flies significantly reduced fruit set
below the self-pollination rate. The negative effect of the increase in these flies
likely outweighed any positive effects A. caerulea experienced from the absence of
its nectar robber. Although the field observations were conducted in a single year,
when they are interpreted in combination with our manipulative experiments, they
suggest how A. caerulea may fare in a changing visitation landscape.
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Publication status
published
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Book title
Journal / series
Volume
31 (10)
Pages / Article No.
97 - 109
Publisher
Enviroquest
Event
Edition / version
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Software
Geographic location
Date collected
Date created
Subject
Bombus occidentalis; bee declines; nectar robbing; floral larceny; Aquilegia caerulea; Muscidae
Organisational unit
09716 - Hille Ris Lambers, Janneke / Hille Ris Lambers, Janneke