I am designing a comparative study of life history traits among a small family of flies (Piophilidae, 82 spp worldwide). Seven species are present at my usual field site (Algonquin Park, ON). I suspect his is not a satisfactory sample size. How many should I aim for? In Eastern Canada I can probably collect between 12-15 species. Would that be an appropriate number to compare?
You can only compare what is available at each site, so those numbers are fine. But you could study a number of sites, include the total number of species in your analysis, and have 'site' as one of your factors or variables :)
How many genera are there in this family? It is important to cover for higher taxonomical units, such as at a subfamily, tribe, or genus level. I think it is desired to collect much more samples globally. Some can be found from other museum collections and even from gene-banks.
Anyway I think more than 20 species are desired to construct a phylogenetic tree for it.
Shuhei, there are about 20 genera in this family (though 6 of them belong to a subfamily found only in the old world). The 12 species I referenced above come from 7 genera. (The original 7 spp. are in 5 genera).
To be clear, I'm not trying to create a phylogeny; a recent one already exists. I just want to do a phylogenetically controlled comparison of the correlations between life history traits among species. I am pretty confident I can get 12 species if I go to multiple locations, would that be enough?
Sorry for confusion. I think it depends on the journal you would like to submit (higher number of species could possibly be publishable in higher level journals). In my opinion, 12 species are rather enough, but it would be better to add a few species more (if you could do that!).
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