impact of humans, especially in the local areas where they reside. The most important outcome of specialized domestication is the development of a unique ecological niche - the agroecology. Agricultural domestication, the culmination of the other two processes, involves the further evolution of plants in response to the conditions existing with the agroecology... [and] is roughly equivalent to what has simply been termed domestication in the literature of agricultural origins.
Dispersal of the Pawpaw
Many agents have been suggested as being dispersers of the pawpaw, but most are of doubtful importance. Opossum, raccoon, fox, squirrel, skunk, groundhog and turtles have been implicated by Little (1905), Van Dresel3 (1938), and Glaser (1961) but seem too small to swallow the seed dependably. Water transport has been suggested by Bowden and Miller (1951) on account of the seed's buoyancy, but transport by water could play only a minor role4. It appears that humans have been the primary disperser of the pawpaw. Asimina triloba, however, is indigenous to North America, predating the presence of Homo sapiens by tens of thousands of years. Identifiable fossils closely resembling A. triloba date to the Late Miocene from New Jersey, and fossil fruits of Asimina have been recovered from the Eocene in Mississippi (Berry, 1916). Janzen and Martin (1982), pondering the mystery of the many Central American fruits that seem to lack coevolved fruit feeders, hypothesize that they were originally dispersed by the large mammals of the Americas that died out at the end of the Pleistocene (e.g., extinct equids, gomphotheres [which were mastodon-like proboscidians], ground sloths, glyptodonts). They conclude that North American fruits such as the pawpaw, persimmon, and osage orange also fit their hypothesis.
Incidental domestication.
The demise of the mastodons and other frugivorous giants of North America at the end of the Pleistocene might have consigned Asminia triloba to an evolutionary backwater of population decline, inbreeding, and genetic loss. The arrival of humans in North America toward the end of the Pleistocene probably saved A. triloba from such a fateful decline. The spread of pawpaws out of their southern Ice Age refugia into the once glaciated regions north of the Ohio River must have been accomplished primarily by humans. Native Americans expanded the ranges of some other native species which were useful as food and medicine, such as may apple (Podophyllum peltatum) pond nuts (Nelumbo lutea), Kentucky coffee tree (Gymnocladus dioica), and possibly American chestnut (Castanea dentata) (Yarnell, 1964). Given the paw-paw's value as a source of food, fiber and medicine (Millspaugh, 1887; Meijer, 1974; Allard, 1955; Krochmal and Krochmal, 1973), it is reasonable to believe that the early
Opossum and gray fox may be dispersers; Van Dresel reported that stomach records of those two species contain pawpaw, although he did not state whether that was flesh, seed, or skin.
Water will not transport seed above flood levels, however, and pawpaw seed loses its buoyancy as it imbibes water during stratification [unpublished observation].
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