1.
An examination of the spatial
dimensions of pollination
facilitation in an arid ecosystem.
Jenna Braun
Thesis Proposal – 1st Committee Meeting November 16 2016

2.
Positive Interactions

3.
Pollination Facilitation

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

6.
Shrubs and cacti as magnets

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?

8.
Landscape
Neighborhood
Plot
Plant

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?
CH1

10.
Hypothesis:
Pollinator facilitation neglects scale but the spatial
component of plant-pollinator interactions is an
important research gap.
CH1

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
CH1

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
CH2

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
CH2

14.
Phenology
 Floral surveys every 8 -10 daysFloralAbundance
Time
Shrubs
Annuals
Cacti
CH2

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
CH2

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
CH2

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
CH2

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.
CH2
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.
CH2

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
CH2
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?
CH3

22.
Low High
Low High
Annual Density
Shrub Density
4 replicates (1.5 hours) * 4 treatments * 8 days
CH3

23.
PollinatorVisitationRate
Low LowHigh High
Annual Density
Low Shrub Density High Shrub Density
CH3