Ghosts of cultivation past: Native American dispersal legacy persists in tree distribution
A simplifying ecological assumption is that species are present in suitable habitat and absent from unsuitable habitat. This assumption is undermined, however, when populations persist in suboptimal conditions for centuries. Most evidence connecting indigenous cultures with plant dispersal is anecdotal, but historical records suggest that Native Americans may have transported and cultivated trees, including Gleditsia triacanthos ("Honey locust"). This study tests the hypothesis that regional G. triacanthos distributions better reflect a Cherokee (southeastern U.S. Native Americans) cultivation legacy than a G. triacanthos niche limitation in the Southern Appalachian Mountains, U.S. Gleditsia triacanthos occurs in rocky uplands and xeric fields, as well as in the riverine corridors and floodplains where Cherokee once settled and farmed. The present study combined extensive field surveys with field and greenhouse experiments to investigate G. triacanthos recruitment requirements, and to determine whether there is a quantifiable G. triacanthos association with former Cherokee settlements. Moreover, dispersal and dispersal mechanisms, such as stream transport and domestic cattle, were investigated by examining seedling and sapling distances.
A centuries-old legacy of Native American cultivation remains intact as G. triacanthos' current southern Appalachian distribution better reflects Cherokee settlement patterns than G. triacanthos optimal habitat. The data indicate that the tree is severely dispersal limited in the region, only moving appreciable distances where cattle grazing is prevalent. Such patterning indicates that great caution must be exercised when inferring niche requirements from species distributions. Moreover, pre-European activity may be underrated as a factor influencing modern species distributions.