Evaluation of Genetic Structure of Flowering Dogwood In the Great Smoky Mountains National Park

In the past three decades, flowering dogwood (Cornus florida) populations have experienced severe declines caused by dogwood anthracnose. Mortality has ranged from 48 to 98%, raising the concern that the genetic diversity of this native tree has been reduced significantly.  In this study we investigated levels of genetic diversity and population structure of flowering dogwood populations in the Great Smoky Mountains National Park (GSMNP). Understanding the factors influencing geographic distribution of genetic variation is one of the major concerns for preserving biodiversity and conservation of native populations. Nineteen microsatellite loci were used to evaluate the level and distribution of genetic variation of native flowering dogwoods throughout the GSMNP. Significant genetic structure exists at both landscape and local levels. Two genetic clusters exist within the park separated by the main dividing ridges of the Great Smoky Mountains. The differentiation of the clusters is subtle, but statistically significant, with gene flow evident through low-elevation corridors indicating nonrandom mating that occurs between related individuals despite wide dispersal of seeds. Although high mortality rate and reduced fecundity caused by dogwood anthracnose severely affected native flowering dogwood populations throughout the entire GSMNP, this study confirmed that considerable genetic diversity of flowering dogwoods still exists at the population level. It seems unlikely that recent demographic dynamics have resulted in a depletion of genetic variation.