The following is a general background into my data analysis problem:

 - I am working with count data that is non-normal.
 - Data was collected at 2 time periods.
 - I am interested in comparisons of species counts between treatments.
 - There are 4 treatments.

Data were initially analyzed using the Kruskal-Wallis rank sum test (a non-parametric ANOVA counterpart).  A reviewer of my manuscript suggested using a Poisson distribution.  How can I perform a repeated measures ANOVA with a Poisson distribution in R?