[R-sig-ME] Deviations from normality in MCMC models

Christopher Robinson crobinson19 at cub.uca.edu
Thu Jun 1 16:04:18 CEST 2017

MCMCglmm users,

I am trying to quantify correlated thermal reaction norms using bivariate
MCMCglmm models in R. Unfortunately, one of my variables is highly right
skewed and I cannot get the data to take on a normal (gaussian)
distribution. I've attached a histogram showing how my data look.

The MCMCglmm package in R allows users to specify the distribution family
for each variable. Unfortunately, I cannot fit a gamma distribution to my
data because MCMCglmm currently does not support this family. My question
is how sensitive to deviations from normality is MCMC? That is, if I apply
a gaussian distribution to this variable, will my results be strongly

An example of my code is as follows:


                  rcov = ~us(trait):units,
                  family=c("gaussian", "gaussian"),

Thank you for any advice.

Chris Robinson

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