Variation in species interaction outcomes

Collaborators

Jennifer Rudgers - (website)

rudgers

Judith Bronstein - (website)

bronstein

Bronstein 1994 TREE

Species interactions

Interaction outcomes are important for:

Mean interaction outcomes

gurevitch bolnick morris schmitz

What about variation in outcomes?

Species interaction outcomes vary a lot

thompson Thompson & Cunningham 2002

Within a species interaction, outcomes are not just +, 0, or -

sppintout

Outcomes within a species interaction can range from - to +

What is meant by variation in interaction outcomes?

Variation in interaction outcomes - example

Images from Todd Palmer

Two points:

  1. Variation in outcomes is common

  2. Variation in outcomes is important

Variation in outcomes is common

Mutualism


Herbivory outcome for Acacia trees varies with ant species identity (Palmer et al. 2008)

mutualism

Variation in outcomes is common

Competition/facilitation


Outcomes vary from competition at low elevation to facilitation at high elevation (Callaway et al. 2002)

facilitation

Variation in outcomes is important

for populations



Miller et al. 2009

Variation in outcomes is important

for communities



Kokkoris et al. 2002

Variation in outcomes is important

for evolution



Rudgers and Strauss 2004

And people are calling for examination of variation

To the extent that different biotic interactions are important contributors to different population dynamics within a species, variable interactions might be expected to be a powerful such source. - Joseph Travis 1996 AmNat
The full range of natural outcomes...may reveal far more about...ecological and evolutionary dynamics than does the average outcome. - Judith Bronstein 1994 TREE
...understanding context-dependency is critical for such reconciliation [of variation in species interaction outcomes]. - Anurag Agrawal et al. 2007 FREE

Questions

  1. How do different species interaction types differ in variation in outcomes?

  2. What are the relative importance of drivers of variation in outcomes?
  3. Does variation in outcome differ by ecosystem type?

Two major distinctions can be made:

  1. Types of species interactions, and
  2. Gradients along which interaction occur

How do different species interaction types differ in variation in outcomes?

Gradients that drive variation in interaction outcome

Meta-analysis

E.g. Getting data from a single study

Silhouettes from phylopic.org

E.g. Getting data from a single study..cont.

Data analyses

Final dataset - 353 papers

How do different species interaction types differ in variation in outcomes?

How do different species interaction types differ in variation in outcomes?

How do different species interaction types differ in variation in outcomes?

Why is mutualism more variable?

What are the relative importance of drivers of variation in outcomes?

What are the relative importance of drivers of variation in outcomes?

** No difference for sign change

What does this mean?

A few observations




Species identity > third party presence

Spatial tended to be > temporal variation, but not significant

Drivers of variation in outcomes X interaction type? - Sign

Drivers of variation in outcomes X interaction type? - Sign

Mutualism > predation & competition along spatial and 3rd party axes



  • Makes sense at least in some mutualisms, e.g. ->

  • Drivers of variation in outcomes X interaction type? - Sign

    Predation < competition & mutualism along abiotic and temporal axes

    Mobility

    Results qualitatively the same when accounting for mobility

    Does variation in outcome differ by ecosystem type?

    Image: http://people.ucsc.edu/~trlevi/Projects.html

    Reasoning for ecosystem differences




    Oceans buffer abiotic variables more so than freshwater and marine


    Any ideas?









    Reid et al. 2009

    Conclusions

    Future work

    How does variation in outcome vary with latitude?

    How does variation in outcome vary with latitude? - Predation

    Latitude

  • Variation may depend on latitude, or some variable correlated with latitude


  • What about latitude is correlated with variation in interaction outcomes?

  • How can we test these findings in the field?

    Thanks to...

    Taxonomic bias

    Though can't account for it due to lack of replication across levels

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