Leading‐edge populations do not show low genetic diversity or high differentiation in a wind‐pollinated tree

Abstract

AbstractClimate changes can shift species’ ranges. Knowledge on genetic variation of the leading‐edge populations provides critical information to understand responses and adaptation of plants to projected climate warming. To date, the research into genetic variation of leading‐edge populations has been limited, particularly in the role of wind‐mediated pollen flow in maintaining high genetic variation. Castanopsis sclerophylla (Fagaceae) is a wind‐pollinated and gravity‐dispersed tree. In the present study, we used seven polymorphic microsatellites to genotype 482 samples from five leading‐edge and 12 non‐edge populations. Significant effects of recent population bottleneck events were found in three of the five leading‐edge populations, indicating that the leading‐edge populations might have been recolonized after the Last Glacial Maximum. Genetic diversity was higher, though not significantly, in leading‐edge than in non‐edge populations. Relationship between genetic diversity and latitude indicated an increasing trend of genetic diversity towards leading‐edge populations. No significant difference in genetic differentiation was found between leading‐edge and non‐edge populations. The inconsistence with the general predictions by leading‐edge colonization model could be explained by high gene flow via pollen grains. Pollen‐mediated gene flow could maintain high genetic diversity within and low differentiation among leading‐edge populations. In response to climate warming, high genetic variation may provide leading‐edge populations raw materials for evolutionary adaptation to future environmental conditions.