Adaptive and neutral variation in Psilopeganum sinense

Natural selection and genetic drift are important evolutionary forces in determining genetic and phenotypic differentiation in plant populations. Ye et al. study population differentiation at five quantitative traits (Q_ST) in Psilopeganum sinense (Rutaceae), an endangered species with fragmented distribution and small population sizes, and compare this with differentiation at putatively neutral microsatellite markers (F_ST). The results show that Q_ST < F_ST and thus provide no evidence of local adaptation in well-differentiated populations at a relatively large spatial scale, and instead suggest a role of stabilizing selection and drift leading to phenotypic differentiation among small populations.