Abstracts (first author)
Equilibrium and non-equilibrium demographic history and the distribution of FST: deviations from the island model can strongly affect the conclusions of QST and FST outlier tests
Local adaptation predicts that selected alleles and traits will differ in frequencies among populations, as each population adapts to its own optimum. Recently, our field has made increasing use of several methods designed to look for loci or traits that have greater divergence among populations than expected by genetic drift alone. Statistical conclusions from QST approaches (in the case of traits) or FST genome scans (for selected loci) depend on the demographic properties assumed by their null models. Typically an island model or a Dirichlet distribution is assumed. We explored through simulation a number of demographic models that differ increasingly from the island model, including several realistic scenarios out of equilibrium. For both QST and FST, the distribution of differentiation measures sometimes is well described by the island model, but often the differences are profound. We show that the differences can cause a great excess of false positives in QST or FST outlier approaches, and we make several suggestions about how to identify and ameliorate these problems in real biological settings.