The distribution expansion factors of Papaver dubium (Papaveraceae) in urban area

We investigated the distribution pattern of Papaver dubium in Setagaya ward and in Inagi city of Tokyo metropolis. P. dubium was firstly naturalized in Setagaya area in 1961, but in Inagi area, its distribution has been rapidly expanding from the 1990s. The number of P. dubium population was largest at planting curb of main road, and decreased in the following order: parking lot, residential place facing the roadside. These facts indicate that the transportation of seeds by automobile may influence the distribution expansion of P. dubium. We conducted the logistic regression analysis, where the response variable was the existence of P. dubium and the explanatory variables were distance from parking lot to planting curb along main road, pavement of parking lot, and their interaction. As the results of model selection by AIC, any explanatory variable was not selected in Setagaya area, but in Inagi area, distance (P = 0.07) and interaction of distance and pavement (P = 0.04) negatively influenced the existence of P. dubium. These results suggest that in Setagaya area, where P. dubium naturalized approximately 50 years ago, habitat expansion may be completed and at the present stage, the distance from main road and the pavement of parking lot do not influence its distribution. In contrast, in Inagi area where P. dubium recently naturalized, both the distance and the pavement of parking lot regulate the process of expansion.