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