Dear Colleagues, We have field collected data on one host species that is affected by two parasites, often simultaneously. In a perfect world, we could look at a host trait (e.g., gonad relative size) and see how it varies as a function of each parasite, or their interaction, using a simple 2-way ANOVA with presence/absence of each parasite as fixed factors (which would allow 4 possibilities: - -; - +; + -; + +).
One problem with doing this (as it is often the case with field collections) is that our data are strongly unbalanced. For example, less than 5% of all individuals collected in the samples had neither parasite in them (- -). The other problem is that, not surprisingly, the number of either parasite per host was variable. This might obscure patterns if parasites have additive effects on the host (e.g., is having 3 individuals of parasite A the same as having 1 of parasite B?). We have asked a few people and have received very different opinions on how to analyze these results. We would like to know how other folks have tackled similar issues. Any ideas will be greatly appreciated. Sincerely, Edwin -- Dr. Edwin Cruz-Rivera Assistant Professor of Marine Biology Department of Biology American University in Cairo AUC Avenue, P.O. Box 74 New Cairo 11835, Egypt Tel 20.2.2615.2906 fax 20.2.2795.7565 [email protected] "It is not the same to hear the devil as it is to see him coming your way" (Puerto Rican proverb)
