Together with the islands of Sumatra (Indonesia) and Borneo (Indonesia, Malaysia), the Philippines are the main center of diversity for carnivorous pitcher plants of the genus, Nepenthes L. Nepenthes are the largest of all carnivorous plants, and the species with the biggest pitchers are capable of trapping and digesting small amphibians and even mammals. The central cordillera of Mindanao Island in the south of the Philippines is mostly covered with old, primary forest and is the largest remaining cohesive, untouched area of wilderness in the Philippines. In a recent field exploration of two areas of the central cordillera, namely Mount Sumagaya and a section of the Pantaron range, four new taxa of Nepenthes were discovered. These four remarkable new species, N. pantaronensis, N. cornuta, N. talaandig and N. amabilis, are described, illustrated and assessed.

With 50 species of the genus Nepenthes L. currently described from the Philippines, it is without doubt that the country, along with the islands of Sumatra (Indonesia) and Borneo (Indonesia, Malaysia, Brunei), should be considered the center of diversity of the genus. In this work, we describe two new species. One species, N. aenigma sp. nov., is from Ilocos Norte province on Luzon Island and has the—for Nepenthes—unusual ecological preference to grow in dense vegetation in deep shade. The other new species is from Mount Hamiguitan in Davao Oriental province on Mindanao Island. With this new entry, Mount Hamiguitan is now home to four endemic species (N. peltata, N. micramphora, N. hamiguitanensis, N. justinae sp. nov.). Furthermore, we provide an emended description of N. ramos based on field data. Nepenthes kurata is synonymized here with N. ramos.

A species of Nepenthes endemic to Peninsular Malaysia and distinctive for its extremely developed lid hairs is described and illustrated. Nepenthes berbulu is a highland species known only from a handful of peaks in the Titiwangsa Range. It is classified here within the recently defined N. macfarlanei group, for which a dichotomous key is provided. The description of this taxon brings the total number of Nepenthes species recognised from Peninsular Malaysia to eighteen.

Nepenthes diabolica, a new species of tropical pitcher plant from Central Sulawesi, is described and illustrated. It is a high-montane, terrestrial to epiphytic taxon, distinguished by its elaborately flanged peristome and rufous, woolly pitcher indumentum. N. diabolica is a member of section Tentaculatae, showing morphological affinities with N. hamata. Nevertheless, the two species can be distinguished by morphological characters as well as by ecology and geography. A diagnostic key to the species of section Tentaculatae is provided. Owing to its highly restricted range, small number of recorded individuals, and desirability among plant collectors, the conservation status of N. diabolica is assessed as Critically Endangered under the IUCN criteria. Finally, N. hamata, until now based on lost types and mixed paratypes, is lectotypified using recently uncovered original material.

Nepenthes limiana, a pitcher plant from the northern Titiwangsa Range of Peninsular Malaysia, is described as new. It is the northernmost known species of the recently defined N. macfarlanei group, whose members are characterised by the presence of conspicuous hairs on the lower surface of the lid. It differs from other members of this group in exhibiting adaptations to seasonal drought in the form of thickened roots and narrow laminae that are reminiscent of those produced by the pyrophytic Nepenthes of Indochina and northernmost Malaysia. Coupled with the presence of decurrent leaf bases, which are not present in any other N. macfarlanei group species but which are present in the pyrophytic Nepenthes, these characters could indicate either morphological convergence or an as yet uncharacterised relationship between N. limiana and the Nepenthes species of Indochina.