Effects of biogeographical origin on the flowering phenology of exotic plant communities

Although numerous attempts have been made to clarify traits associated with the invasiveness of exotic species, the effect of the biogeographical origin of exotic species on trait variability in invaded regions at a community level remains poorly understood. In this study, we examined how biogeographical origin at a continental level affects the flowering phenology of exotic herbaceous plant communities. We collected flowering phenology data for herbaceous plants in Japan based on three independent types of data: records from an illustrated reference book covering almost all naturalized plants in Japan; records from field surveys in 1994-2015 conducted using a citizen science approach; and records from a field survey conducted over a 1-year period. We used multiple regression analyses to examine the effects of four attributes (family, lifeform, habitat and biogeographical origin) on flowering phenology. In Japan, exotic plants of European origin flowered significantly earlier than those of North American origin and native plants. Flowering phenology of exotic plant communities from these two continents were same as that of native ones in their native region, respectively. The results indicated that biogeographical origin has a significant effect on the flowering phenology of exotic plant communities and it is assumed no specific biotic or environmental filtering acts on the flowering phenology during the invasion process. The findings of this study highlight the need to consider biogeographical origin when examining functional traits and their interspecific variation in exotic species and provide important implications for management strategies for exotic plants.