Native and exotic plant invasions vary across habitat types and anthropogenic disturbances in a tourism-heavy protected area

Biological invasions are among the leading drivers of global biodiversity loss and are responsible for impaired ecosystem structure and function. Underpinning the mechanisms and patterns of biological invasions, particularly how both exotic invasions and native-weed expansion vary across different habitats and variable degrees of human-induced disturbances, is a key scientific endeavor at the crossroads of conservation biology and ecology. In this study, we explored the diversity of both invasive and native weeds across different habitat types and levels of tourism at Ruhuna (Yala) National Park of southern Sri Lanka. Species richness as well as abundance of both invasive and native weeds varied in response to habitat type and extent of tourism. The effects of habitat type and tourism were modulated by the distance from the nearest safari road. Therefore, no habitat type consistently remained either most or least encroached by invasive or native weeds. The physical disturbances and variable niche opportunities presented by safari roads have a potentially strong but non-linear effect on exotic invasions and native-weed encroachment. Co-occurrence of invasive and native weeds at plot level was infrequent. At the plot level, the type of invasion (native-weed only, invasive-weed only, both, none) varied significantly among habitat types as well as levels of tourism. Our findings on drivers of biological invasions can provide useful insights to implement management actions and biosecurity measures in protected areas that are subject to intensive tourism.