Population genetic diversity of the rare hardwood butternut (<Emphasis Type="Italic">Juglans cinerea</Emphasis>) in the northeastern USA

Populations of butternut tree (Juglans cinerea) have undergone range-wide extirpation. A fungal pathogen, Ophiognomonia clavigignenti-juglandacearum, of unknown origin has been recognized as the causal factor. This population collapse has allowed for observations of a broadleaf hardwood in rapid decline. This study made use of six neutral microsatellite markers to describe the present genetic diversity of butternut in the northeastern USA. Our results indicated weak population differentiation (F _ST?=?0.084), further supported by an absence of regional genetic structure. Despite reports of high mortality rates, genetic analysis revealed no sign of a recent bottleneck. Population statistics and Bayesian analysis indicated significant historical gene flow among butternut populations of the northeast. Attention should be given to genetic differences between upland and riparian habitat as riparian populations appear to contain greater allele diversity.