Did Native Americans influence the northward migration of plants during the Holocene?

Long-distance plant dispersal explains the rapid northward migration of plant species during the Holocene but the mechanisms by which it occurred are poorly understood. Given that Native Americans spread numerous cultigens over thousands of kilometres during the late Holocene, I examined historical literature for evidence of non-cultigen dispersal or cultivation in North America's eastern woodlands. Cultivation references are included because a strong relationship between dispersal and indigenous flora husbandry is assumed. Sixty-seven texts describing Native American lifestyle, cultural activities, and land management reported some form of plant use. Most accounts, however, focus on cultigen production or the use of indigenous flora for medicine or food without mention of dispersal. Twenty-four of the texts described the trade, transport, or cultivation of plants indigenous to eastern North American woodlands. Most accounts focus on the informal production of food plants, especially trees and shrubs. Confounding these reports was clear evidence of observer bias, limited botanical knowledge, acculturation, and secrecy by Native American informants. Because of these shortcomings, the likelihood of widespread long-distance plant dispersal by Native Americans could not be determined using historical literature. This activity was either not widespread or was not observed by, or revealed to, Europeans. To adequately test the Native American plant dispersal hypothesis, direct evidence from other sources (e.g. archaeobotancial data) will be required.