Tourist vehicle as a selective mechanism for plant dispersal: evidence from a national park in the eastern Himalaya.
It is increasingly recognised that human vehicle may act as a vector to spread species, but research remains sparse to examine vehicle-mediated spread to natural areas, in particular to protected areas by urbanized societies through increasing tourism/recreation traffic. This study assessed the role of tourist vehicle in driving biotic exchange to Laojun Mountain National Park in the eastern Himalaya. A stratified random sampling method was applied to compare plant seeds in muds collected from different vehicles (sedan, SUV and others) entering the park in different seasons (May, August and October) from different regions. Across the 663 mud samples, 3119 seedlings of 124 species germinated which were predominately roadside ruderals and non-native species. The number of vehicle-dispersed flora was found to be correlated with the amount of mud attached on vehicles, with more seed carried by vehicles travelling in autumn, sport utility vehicles and those from local areas. When seed traits were analysed using generalized linear models, vehicles were more likely disperse appendaged and compact seeds, and those released from low-stature plants such as forb or grass. The results highlight the risks of species introduction and homogenization of flora from seeds on tourist vehicles entering protected areas. Strategies like vehicle washing and managing roadside vegetation may help reduce risks from tourism traffic in the eastern Himalayan parks as well as other sensitive ecosystems around the world.