Exploring a critically endangered pitcher plant Nepenthes rigidifolia and predicting its distribution habitat in North Sumatra, Indonesia

Nepenthes rigidifolia Akhriadi, Hernawati & Tamin is a critically endangered pitcher plant endemic to Sumatra, Indonesia. This species is at risk of extinction due to anthropogenic activities such as land use and illegal har vesting. Immediate conservation efforts are necessary to prevent the extinction of N. rigidifolia. This study aimed to investigate the occurrence of N. rigidifolia and predict its habitat as a part of conservation efforts. Several forests in four regencies of North Sumatra Province, Indonesia, namely Karo, Dairi, Pakpak Bharat, and Sima lungun, were explored. The area of occupancy (AOO) and extent of occurrence (EOO) of this species were analyzed using the GeoCAT site. In addition, the prediction of habitat suitability was modeled using MaxEnt. A population of N. rigidifolia was found only in Lae Pondom Protected Forest, Karo Regency, which added two new records for this species. The AOO and EOO values are 12 km2 and 4.17 km2 , respectively, located in Karo and Dairi Regencies. According to EOO value, population size, and threat level, we suggest that the new current conservation status of N. rigidifolia is Critically Endangered A2ad + 3d; B1ab(iv,v); C2a(i,ii); D. The AUC value of the MaxEnt model is over 0.9, indicating an excellent performance. An area of 364.18 km2 around Lake Toba is estimated to be a highly suitable area for N. rigidifolia. This area, which overlaps with the EOO, is recommended as a priority area for N. rigidifolia conservation.