Assessing the invasion risk of botanical garden’s exotic threatened collections to adjacent mountain forests: A case study of Cibodas Botanical Garden

A primary objective of botanical gardens is to conserve threatened plant species from different regions and countries. However, such ex-situ conservation practices for exotic plant species may pose a significant plant invasion risks. In this study, we predict the naturalization probability of exotic threatened plant species of Cibodas Botanical Garden (CBG) collections based on leaf trait (specific leaf area, SLA) or as a function of invasion risk assessment scoring system (Tropical Weed Risk Assessment Protocol, TWRAP). We found that SLA and TWRAP were positively correlated with naturalization probability. The TWRAP model produced higher predictive probabilities with larger uncertainty compared to SLA model. Parmentiera cereifera and Burretiodendron hsienmu are two species that have highest naturalization probability based on SLA model. Chamaedorea oblongata has the highest naturalization probability based on TWRAP model. From practical and management point of view, we recommend the simultaneous use of SLA-based and TWRAP-based invasive species risk assessment to estimate the naturalization risk of exotic threatened collections of botanical gardens to adjacent mountain forests. Finally, given the important conservation value of threatened exotic collection of botanical garden, we need to be aware with the invasion risks of these species. The threatened condition of a plant species is not only caused by its natural characteristics but also may be caused (in fact mostly confounding with) by external disturbance either natural catastrophic or human related activities. Thus, a threatened species may not necessarily a non-invasive species outside their natural distribution ranges.