Variation in cushion traits is determined by feedback effects from beneficiaries

Filazzola, A. & Lortie, C.J.

Facilitation

Filazzola and Lortie 2014. Global Ecology and Biogeography

Alpine facilitation

…but at what cost?

+

-

Beneficiary cover

Schöb et al. 2013. Functional Ecology

Hypothesis

The abundance of beneficiary species negatively co-vary with cushion-plant traits, particularly reproduction, because of a parasitic consumption of microsite resources.

A. Ruttan

A. Ruttan

Methods

Landscape Characteristics

Cushion Traits

Beneficiary Traits

140 cushion9 sites

Statistics

Site Characteristics Cushion Traits Beneficiary Traits

S1

S2

S3

Sn

C1 C12 C13 C1j

C21

C31

Ci1 Cij

B1 B12 B13 B1j

B21

B31

Bi1 Bij

Step 1• PCA of landscape vs. Cushion• Step-wise regression to reduce cushion traits

Step 2• PCA of cushion vs. beneficiary abundance

Step 3• GLM/GLMMs of key variables

Statistics

N.S.Lat x LongExposurePARDisturbance

Step: AIC666.79Benf ~ Surface.area + Pen + Fruit.Den + Fruit.ht

Trait Df F Value Pr(F)

+ Decad 1 1.77 0.18460- Pen 1 2.67 0.10434+ Site 1 0.79 0.37517+ SWC.per 1 0.58 0.44686+ Dx 1 0.39 0.53334+ Concav 1 0.07 0.77806+ Branches 1 0.05 0.81705+ SWC.cen 1 0.00 0.96021- Surface.area 1 5.16 0.02456 *- Fruit.ht 1 5.19 0.02423 *- Fruit.Den 1 5.43 0.02120 *

High cushionFitness

Beneficiary vs. fitness

Surface area

(Beneficiary ~ Fitness) – Surface area

Results summarized

Cushion fitness is not generally effected by site characteristics

The surface area of the cushion is correlated with both cushion fitness and beneficiary cover

Beneficiary cover is the strongest determinant of cushion fitness

Competition for resources

He et al. 2013. Plant Species Biology

Resource Island

Why Fitness?

• Seed set/fitness is associated with competitive strength and availability of soil resources (Cornelissen et al. 2003)

• Competition in nutrient-poor systems strongly determines plant fitness (Aerts 1999)

• Reducing a plants fitness is a form of competition

• Easily measurable response

Liczner & Lortie. NSTP Conference 2014

Implications

Previous studies have examined functional variability of plants because of cushions

Cushion

Open

Almeida et al. 2012. Plant Ecology & Diversity

ImplicationsOther studies have examined functional variability

of strictly cushions

He et al. 2013. Plant Species Biology

Implications

Findings are similar to that of Schöb et al. 2013

Community Ecology TheoryPlant trait researchDominantsi.e. cushions

Plant trait researchSubordinates

i.e. beneficiaries

Extension of methodology

Albert et al. 2010. Journal of Ecology

Conclusions

Further support for the cost-of-facilitation theory (in terms of fitness)

Highlight necessity of treating a plant community as a response surface

Thank you!

Links

Presentationhttp://www.slideshare.net/AFilazzola/filazzola-nstp-presentation-2014

R-Scripthttp://dx.doi.org/10.6084/m9.figshare.1225923

Appendix• Removing surface area effects

Beneficiary effectsnot attributable to surface area

Surface Area m2

Be

nefic

iary

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