An examination of the spatial dimensions of pollination facilitation in an arid ecosystem
1. An examination of the spatial
dimensions of pollination
facilitation in an arid ecosystem.
Jenna Braun
Thesis Proposal – 1st Committee Meeting November 16 2016
4. Mechanisms
Increased size of co-flowering display
Increased diversity of floral display
Pollinator support: Sequential Mutualism/Community Stability
Magnet species
5. Magnet Hypothesis
Presence of a more attractive species increases pollination of
a less attractive species or to a mixed assembly of species
Predicts that the effect is greater than only increasing floral
abundance
7. Scale
Grain – size of the sampling unit. Can be pixel, focal plant, plot, patch.
Extent – total area over which sampling occurs.
Data vs. model
Do individual interactions matter at larger
scales?
What is the effect of a magnet species on
its neighbours?
Neighborhood? Patch? Landscape?
9. A systematic review contrasting pollinator
facilitation in desert shrubs and cacti.
Determine support for current hypotheses and identify any
research gaps.
Is current literature is reporting scale in a meaningful,
replicable way?
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11. Figure 1: PRISMA diagram (Moher et al, 2009) of workflow for pollination facilitation
systematic review.
Papers obtained through database
searching (Web of Science), Keywords:
Pollinat* facilitat* shrub
Pollinat* facilitat* cact*
Pollinat* competit* shrub
Pollinat* competit* cact*
(n = 169)
ScreeningIncludedEligibilityIdentification
Papers obtained from other sources,
such as book chapter bibliographies
Records after duplicates removed
(n = 169)
Records screened by
abstract (n = )
Records excluded for:
Relevance
Review, opinion or idea
paper
Full-text articles assessed
for eligibility
(n = )
Full-text articles excluded:
Not testing facilitation or
competition (n = )
Not testing interspecific
interactions (n = )
Focal species wind-pollinatedInclude in synthesis (n = )
Extract data:
Location
Ecosystem
Experiment type:(manipulative, mensurative)
Hypothesis tested
Relative/Absolute Scale
Number of scales
Scale dependence
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12. A spatially explicit survey of pollination
facilitation between Mojave Desert perennials
and annuals.
Does the strength of
pollination facilitation vary with
guild (annual/perennial)?
How does shrub and cacti
density and spatial distribution
interact to influence pollinator
behavior?
Kelso DunesUC, Riverside http://granite.ucnrs.net/?page_id=869
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13. All shrubs and cacti will be georeferenced using high-
resolution GPS, tagged and identified to species.
Determine a natural replacement series of shrub:cacti
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15. Seed Collection:
Shrubs:
3 * 10cm
diameter circle -
mean
Cacti:
3 per cacti – Will
need to weigh
Annuals:
3 seed heads * 3 species per
paired microsite: Microsite
species should match
understory
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16. Pollen
As visitation by shared pollinators increases, heterospecific
pollen transfer may also increase
A “cost” of pollinator sharing
Can create a pollen transfer network
Hub donors with positive effects on receivers – magnets
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17. Predictions:
Cacti will be non-randomly distributed
around shrubs
Association of shrubs with cacti will be
species-specific
Hypothesis:
Shrubs facilitate cacti through stress-amelioration
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18. Annuals growing under shrubs or cacti will have greater seed
set and pollen deposition than annuals growing in paired
open site
Hypothesis:
Shrubs facilitate cacti and annual plant
reproduction by attracting shared pollinators.
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Seedset,pollendeposition
Open Understory
19. Hypothesis: Pollination facilitation shows scale-dependence because
pollinators make different foraging decisions at different scales
Prediction:
Seed set and pollen transfer to understory and open annuals will
decrease with increasing distance from cacti or shrubs.
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20. Prediction:
At small scales higher floral densities will lead to increased
pollinator visits, pollen deposition and seed set but at larger
scales the interaction will change to neutral or negative
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Distance
21. A contrast of local and regional density
effects on pollinator facilitation.
• How does the density and distribution of shrub-annual complexes
(magnets) affect visitation to low and high densities of annuals?
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22. Low High
Low High
Annual Density
Shrub Density
4 replicates (1.5 hours) * 4 treatments * 8 days
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