Predicting occupancy area expansion by Latrodectus hasseltii using a migration kernel function considering anthropogenic transportation.
The range of the invasive redback spider (Latrodectus hasseltii) in Japan has expanded over the past 20 years, since its introduction in Osaka Prefecture, and monitoring and prediction of its occupancy area expansion are required. We predicted occupancy area expansion by this species in Kinki District, Japan, using a migration kernel function integrating random walk migration and anthropogenic transportation. The probability of random walk migration was estimated using the logistic function of annual migration distance, where a random walk distance upper limit of 9 km provided the optimum estimation. We determined the probability of anthropogenic migration according to the geographic attributes of transportation centres (airports, ports, roads, and truck depots) and traffic intensity (for journeys by rail, bus, car, and bicycle). The predicted probability of migration successfully simulated the rate of discovery until 2013. Finally, we used a Monte Carlo simulation to predict redback spider habitat expansion until 2045; our results suggest occupation of its entire potential habitat will occur by 2045.