Spatial analysis
Individual methylation rate and epigenetic variation may be associated
with geographical distance. We used principle components of
neighbourhood matrices (PCNM) implemented in the R package “vegan”
(Oksanen, 2015) to model those relationships. Moran’s eigenvector
mapping(MEM)was used to calculate spatial variables with R. Before
calculating the semivariance, polynomial trend-surface regressions on
each variable were performed using the method described in Chen (Chenet al ., 2016). Residuals from the trend-surface regressions were
used to generate the semivariograms and the confidence envelopes in
spatial autocorrelation analyses. In short, in each lag class, sample
values were randomly selected and a semivariogram was calculated based
on the selected data in 10,000 randomisations. A 95% confidence
envelope was then obtained by calculating the 2.5 and 97.5 percentiles
of the randomly generated semivariance values in each lag class.