HISTORICAL EVIDENCE ON THE ORIGINS OF EASTERN HELLBENDERS (CRYpToBRANCHus ALLEGANIENsIs) IN THE SUSQUEHANNA RIVER WATERSHED, EASTERN USA

The Eastern Hellbender (Cryptobranchus alleganiensis) is a fully aquatic salamander endemic to eastern North America. Although hellbenders are found primarily in watersheds connected to the Mississippi River, a disjunct population is present in the Susquehanna River Basin. The origin of this population has long been the subject of speculation, with stream capture as the commonly hypothesized mechanism of introduction. We employed a novel approach using historical sources to assess the origin of Susquehanna hellbenders, specifically archaeological, paleontological, and archival evidence. Hellbender remains were absent from all prehistoric assemblages in the Susquehanna River watershed, despite being present in more than 75% of assemblages from sites within other portions of the known hellbender range. Archival records failed to reveal any hellbender occurrences in the Susquehanna River watershed prior to the 1830s, and the spatial and temporal pattern of sightings indicates a slow spread throughout the watershed initiating at two separate points of entry: an initial colonization along the Allegheny divide that may support the hypothesis of a natural range expansion, and a secondary colonization in the lower reaches of the Susquehanna River that suggests anthropogenic transportation of the species. Disjunct populations may have important value for conservation due to the unique ecological and evolutionary conditions they experience. Further study on the role and adaptations of hellbenders to conditions in the Susquehanna ecosystem may provide important insights on their conservation, regardless of their origin.