Phenotypic characterization of Table Mountain (Pinus pungens) and pitch pine (Pinus rigida) hybrids along an elevational gradient in the Blue Ridge Mountains, Virginia

Hybridization has played a long-standing role in the evolution of both plant and animal species and allows for the sharing of genetic information between lineages. Here, potential hybridization of a species endemic to the Appalachian Mountains, Table Mountain pine (Pinus pungens), and pitch pine (Pinus rigida) was investigated along an elevational gradient, through the use of phenotypic measurements: cone length, cone width, and needle length. Phenotypes were used to identify hybrids in a three-tiered elevational sampling method at two sites in Shenandoah National Park with the use of linear discriminant analysis. It was found that hybridization between Table Mountain and pitch pine is relatively rare and varied by site and elevation. It was hypothesized that this lack of hybridization is due to environmental factors, which was further tested through use of climate data. The site where hybridization was highest was cooler and wetter. These factors may impact the pollen release of the focal species, causing overlap in pollen release timing and female cone receptivity, leading to increased instances of hybridization