Niche contraction of American chestnut in response to chestnut blight

Invasive pathogens can cause native population declines and change native species distributions, but the spatial limitations posed by disease are rarely explored. This study explored spatiotemporal variation in American chestnut (Castanea dentata (Marsh.) Borkh.) survival over an 80-year period in response to the introduction of an invasive pathogen, chestnut blight (Cryphonectria parasitica (Murrill) Barr), and identified changes in its current realized niche compared with its original niche. A study area in southwestern Virginia, USA, sampled historically for chestnut abundance before blight invasion, was resampled and measured for topography, soil chemistry, and forest composition. Pre-blight chestnut abundance was not significantly correlated to current chestnut abundance, suggesting that chestnut survival rate was not constant across stands. Results indicated that chestnut's niche has shifted toward dry, high disturbance sites on southern- to western-facing slopes. This study provides evidence that chestnut is being constrained to a portion of its former niche following chestnut blight introduction because of spatial heterogeneity in survival rate.