I`m fitting a "poisson" MCMC genetic model using MCMCglmm. My response variable is clearly poisson distributed, constituted by count data (integers) ranging from 1 to 120.

I`ve already ran simmilar models in ASREML and variance components range from 0.01 to 0.4, including animal, permanent environment effects and residual.

The question is:

I`ve read in many MCMCglmm documents that priors for G structure are often set to G1=list(V=1, nu=0.002) and the same for the R structure.

But thinking about my specific problem, initial values for the variance of 1 wouldn`t be correct, right?  If yes, what would be a good prior for small variance components?

Am I missinterpreting V and nu ? (which in correct notation would be alpha and beta for the inverse-gamma distribution)

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