What can cause Faststructure to produce really high K clusters as optimal (e.g. 12 - 14)

Question

[Drew]

Hi,

I have been using both Admixture and Faststructure to look at a population of 87 fungal isolates, but the results are really weird. Using just K=1-10 for Admixture, K=10 was the best, meanwhile using Faststructure K=1-15, the optimal K's were between 12 and 14. I attached a PCA of the data here. There a few probably clonal or near clonal groups, but I'm not sure why both Admixture and Faststructure indicate that the number of populations is really high. Should I trust a K value that high or are there other tests that may be worth looking into to verify? Any insight would be greatly appreciated!