Nepenthes spp. is a unique carnivorous plant with the modified leaf lamina as a pitcher to trap insects. Nepenthes usually produce lower traps near the base of the plant, and upper pitchers form a loop in the tendril, allowing it to wrap around the nearby plant. Pitcher plants, being insectivorous plants, can grow in nitrogen-deficient soils. In the Riau Archipelago Province, the intense land conversion to establish ecotourism in national parks disturbed the pitcher plant habitat, even though the pitcher plants have great potential as ornamental plants. Therefore, for in situ conservation, the existing endemic flora may benefit tourist attractions to support local ecotourism efforts. Based on the above discussion, the presented study aimed to characterize the pitcher plants’ diversity and analyze the relationship among its species using morphological markers in the islands of Bintan, Karimun, and Lingga, Indonesia. Based on the collection and identified pitcher plants, the study discovered that the genus Nepenthes comprises 25 accessions belonging to six different species, i.e., N. gracilis, N. × trichocarpa, N. reinwardtiana, N. ampullaria, N. rafflesiana, and N. × hookeriana. The cluster analysis grouped two main clusters that have a similarity coefficient of 31%–97% based on morphological characteristics among Bintan, Karimun, and Lingga accessions. However, the cluster constructions were more on the traits’ similarity than locality based. For principal component analysis (PCA), 19 morphological traits can benefit as diagnostic features to distinguish the pitcher groups. The study revealed that pitcher plants have diverse phenotypic plasticity in the Riau Archipelago, which is experiencing land conversion for tourism activities. The pitcher plants diversity has the genetic potential for ornamental plants development and is a biological wealth that requires conservation for research, tourism activities, and future generations.

Keywords: Nepenthes spp., pitcher plants, genetic diversity, morphological characters, cluster analysis, principal component analysis, Riau Archipelago

Key findings: Pitcher plant exploration transpired on three large islands (Bintan, Karimun, and Lingga) of the Riau Archipelago, with ongoing development as tourist centers. The existing diversity of the pitcher plants is a biological wealth and has the potential to flourish as ornamental plants through in situ conservation to support research and tourism activities.