an examination of the spatial dimensions of pollination facilitation in an arid ecosystem

An examination of the spatial dimensions of pollination facilitation in an arid ecosystem.

Jenna BraunThesis Proposal – 1st Committee Meeting November 16 2016

Positive Interactions

Pollination Facilitation

Mechanisms

Increased size of co-flowering display

Increased diversity of floral display

Pollinator support: Sequential Mutualism/Community Stability

Magnet species

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

Shrubs and cacti as magnets

ScaleGrain – 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?

Landscape

Neighborhood

Plot

Plant

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

Hypothesis:

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

CH1

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)

Scre

enin

g In

clud

ed

Elig

ibili

ty

Iden

tifica

tion

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-pollinated

Include in synthesis (n = )

Extract data: Location

Ecosystem Experiment type:(manipulative, mensurative)

Hypothesis tested Relative/Absolute Scale

Number of scales Scale dependence

CH1

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=869CH2

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

Phenology

Floral surveys every 8 -10 daysFl

oral

Abu

ndan

ce

Time

Shrubs

Annuals

Cacti

CH2

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

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

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

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.

CH2Seed

set,

polle

n de

posit

ion

Open Understory

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

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

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

Low HighLow High

Annual Density

Shrub Density

4 replicates (1.5 hours) * 4 treatments * 8 days

CH3

Pollin

ator

Visi

tatio

n Ra

te

Low LowHigh HighAnnual Density

Low Shrub Density High Shrub Density

CH3