Human-Mediated Dispersal of Plantago asiatica Mucilaginous Seeds in Urban Environments

Seed dispersal by humans plays an important role in determining vegetation structure. The seeds of Asian plantain (Plantago asiatica L.) form adhesive mucilage upon hydration, facilitating their attachment to shoes and subsequent dispersal via epizoochory. We investigated the efficacy of this mechanism under various urban environmental conditions. After trampling wild P. asiatica stands, the number of seeds attached to shoe soles was counted. The remaining seeds were then counted after walking at designated distances (1, 2, 5, 10, 20, 50, 100, 200, 500, and 1000 m). The following results were obtained: (1) The retention rate after walking 1000 m varied by shoe type (slip-on (kakkusu) work shoes, 15.4%; leather shoes, 3.4%; rubber boots, 2.7%; running shoes, 13.5%; and sandals, 12.4%). (2) Within the first 50 m of walking, on average more than half of the attached seeds fell off under all investigated conditions. Significantly fewer seeds remained after walking 50 m on asphalt (30.9% of the initial seeds) than on grass (48.2%), whereas after walking 1000 m, similar proportions (15.4% on asphalt and 15.7% on grass) remained on the work shoes. These results indicate that human-mediated short- and long-distance dispersal of mucilaginous seeds of this species is effective in diverse urban environments.