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context-dependent interactions
inspired by Chamberlain et al 2014
@cjlortie
context dependency in one of the most interesting& important elements
of many ecological subdisciplines
context dependence = variation
variation for interactions = magnitude & sign changes
magnitude of variation best captured by coefficient of variation (CV)
CV = measures the amount of total variation with respect to the mean outcome
sign changes measure outcome ignoring magnitude
positive (+)negative (-)neutral (0)
most powerful form of synthesis is arguablymeta-analyses
effect size
quantitative measure of strength of evidence or difference
Rii = relative interaction index
[-1, +1]
very useful effect size measure in ecology
Armas 2004
Rii = (with - without)/(with + without)
Armas 2004
the metric matters
Chamberlain et al 2014
247 studies
interaction class context-dependency gradient
location ecosystem
predation, competition, mutualism
magnitude sign change
location: lab and greenhouse were the most variablein both magnitude and sign changes
variation in interactions by ecosystem
depends on gradient,& interaction typebut marine varied
less than terrestrial orfreshwater
mutualisms were most likely to change signhowever the magnitude of variation between
mutualisms & competition did not differ
spatial contexts: mutualisms change sign > competition
temporal contexts: competition change sign > mutualisms
frequency & variationare powerful tools to model context
in ecology
the mean outcome does not mean importance
competition, facilitation, and predation are
separate classes of interactionsbut
also interact within a system
context is opportunityin ecology