Table 1.

The four dispersal measurements available in European butterflies used in this study

Dispersal element	Description of the measurement	Transfo.	N
Mean dispersal distance	Mean dispersal distance (km) from a of a negative exponential function of the form P(D) = e−α × D with D = distance (km), fitted to dispersal kernel (density probability of dispersal distances) obtained from mark-release-recapture (MRR) surveys. Mean dispersal distance (x) = 1/α.	x′ = ln(x)	29
Frequency of long-distance dispersal	Probability of >5 km dispersal movements, estimated from a inverse power function of the form P(D) = a × D−b with D=distance (km), fitted to dispersal kernel (density probability of dispersal distances) obtained from mark-release-recapture (MRR).	x′ = log(x)	28
Dispersal propensity	Propensity to leave a patch, estimated from the proportion of recaptures of marked individuals that occurred in patch of initial capture (residents) in MRR surveys. Dispersal propensity is [1−proportion of residents], and is averaged over patches of different size.	x′ = −√x	25
Gene flow	Dispersal ability estimated from gene flow across landscapes, as given by the analysis of allozymes spatial redistribution. Corresponds to [1−FST]. FST quantifies the genetic structuring of populations, and hence is inversely related to gene flow. Loci under selection were removed from the calculation.	x′ = 1−√x	26

Transfo. is the function ensuring data normality, and N is the number of European butterfly species for which the measure is given in Stevens et al. (2010b).