Dear list members, I'd like to perform a glm analysis with a hierarchically nested design. In particular, I have one fixed factor ("Land Use Classes") with three levels and a random factor ("quadrat") nested within Land Use Classes with different levels per classes (class artificial = 1 quadrat; class crops = 67 quadrats; and class seminatural = 30 quadrats). I have four replicates per each quadrats (response variable = species richness per plot) Here some question about: 1) could I analize these data using the class "artificial" (i.e. I have only 1 level)? 2) using R I'd like perfor a glm analysis considering my response variable (count of species) with a Poisson distribution. How can I develop my model considering the nested nature of my design? I'm sorry but I don't know the right package to use. 3) for the Anova analysis I'd like use a post-hoc comparison between pairwise classes. What is the right procedure to do this? Is this analysis performed in R? Thanks Giovanni -- Dr. Giovanni Bacaro Universit? degli Studi di Siena Dipartimento di Scienze Ambientali "G. Sarfatti" Via P.A. Mattioli 4 53100 Siena tel. 0577 235408 email: bacaro a unisi.it