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, Nepenthes pantaronensis, N. cornuta, N. talaandig and N. amabilis, are described, illustrated and assessed.
Keywords: carnivorous pitcher plants; Nepenthes; biodiversity; Philippines
Nepenthes pantaronensis Gieray, Gronem., Wistuba, Marwinski, Micheler, Coritico, V.B. Amoroso, spec. nov.
Diagnosis: Differs from N. pulchra Gronem. in having 2 longitudinal nerves (N. pulchra: 3–4), 2 non-fringed or barely fringed wings on the lower pitchers and no wings on the upper pitchers (N. pulchra: fringed wings on the lower pitchers and wings reduced to ribs on the upper pitchers) and in having basal stem leaves with a canaliculate petiole (N. pulchra: broad-winged petiole).
Type: Philippines, Mindanao Island, Bukidnon Province, Pantaron mountain range, Mt. Gaka (1,390 m) near Sitio Mahayag (Barangay St. Peter, Malaybalay City, Bukidnon Province, Philippines), 15.08.2012, T. Gronemeyer and F. Coritico, holotype CMUH00008625, Central Mindanao University Herbarium (CMUH), Musuan, Bukidnon, Philippines.
Etymology: The specific epithet denotes that N. pantaronensis was discovered in the Pantaron mountain range.
Nepenthes cornuta Marwinski, Coritico, Wistuba, Micheler, Gronem., Gieray, V.B.Amoroso, spec. nov.
Diagnosis: Differs from N. copelandii Macfarlane in having a narrower lamina, upper pitchers with a distinctive, swollen base and an almost completely cylindrical upper two-thirds (N. copelandii: upper pitchers strongly infundibular with a narrow base and proportionally a much wider opening) and noticeably smaller lower pitchers lacking wings (N. copelandii: wings always present on lower pitchers).
Type: Philippines, Mindanao Island, Bukidnon Province, Pantaron mountain range, trail from Sitio Mahayag (Barangay St. Peter, Malaybalay City) to Sitio Balaudo, 15.08.2012, T. Gronemeyer and F. Coritico, holotype CMUH00008547, Central Mindanao University Herbarium (CMUH), Musuan, Bukidnon, Philippines.
Etymology: The specific epithet, cornuta (lat. cornu = horn), refers to the plant’s horn-shaped upper pitchers.
Nepenthes talaandig Gronem., Coritico, Wistuba, Micheler, Marwinski, Gieray, V.B.Amoroso, spec. nov.
Diagnosis: Differs from N. cornuta Marwinski in having bulbous lower pitchers with a flattened, crenellated peristome (N. cornuta: slender lower pitchers; cylindrical towards the pitcher opening; with cylindrical peristome) and having a winged petiole that clasps the stem (N. cornuta: canaliculate petiole).
Type: Philippines, Mindanao Island, Bukidnon Province, Pantaron mountain range, trail from Sitio Mahayag (Barangay St. Peter, Malaybalay City) to Sitio Balaudo, 15.08.2012, T. Gronemeyer and F. Coritico, holotype CMUH00008624, Central Mindanao University Herbarium (CMUH), Musuan, Bukidnon, Philippines.
Etymology: The specific epithet was chosen to acknowledge the indigenous tribe of the Talaandig. N. talaandig occurs on the ancestral territory of the Talaandig communities of east Bukidnon.
Nepenthes amabilis Wistuba, Gronem., Micheler, Marwinski, Gieray, Coritico, V.B.Amoroso, spec. nov.
Diagnosis: Differs from N. pantaronensis Gieray in having spathulate-ovate, approximately 10 cm long and 3.5 cm wide leaves with an obtuse apex (N. pantaronensis: up to 28 cm long and narrowly acute apex) and having mostly cylindrical to slightly infundibular upper pitchers that are only 10–15 cm tall and distinctly contracted in the region below the peristome (N. pantaronensis: clearly inflated in the lowest quarter and up to 40 cm tall).
Type: Philippines, Mindanao, Mt. Sumagaya, trail from Barangay Mat-I (Municipality of Claveria) to the summit 19.08.2012, T. Gronemeyer and A. Wistuba, holotype CMUH00008635 (male flower), isotype CMUH00008637 (female flower), Central Mindanao University Herbarium (CMUH), Musuan, Bukidnon, Philippines.
Etymology: The specific epithet, amabilis (lat. amabilis = lovely), refers to the extraordinary beauty of the compact specimens with very colorful pitchers and mostly striped peristomes that were observed in situ.
InfaunaAt the type locality of N. cornuta, several ant colonies (Crematogaster sp.) were found in dead or dying pitchers of this species. The ants obstruct the pitcher opening with a greyish matter, probably made out of vegetal detritus and dirt. This ‘lid’ has small entry holes along the pitcher walls. The bottom of the pitchers is pierced with one or two round holes, draining them of their digestive fluid. These holes also serve as “emergency exits” for the ants when disturbed. The presence of those insects on some pierced functional pitchers without a nest might suggest that the ants first pierce and drain functional pitchers before colonizing them. A similar colonization has been observed before in other Nepenthes species, e.g., N. macfarlanei Hemsl. in Malaysia  and N. maxima Reinw. on the lower slopes of the Maoke Mountains in West Papua (personal observation by the authors).
ConclusionsCarnivorous pitcher plants are widespread within the Malesian biogeographical region comprising the Malayan peninsula and the islands of Sumatra, Borneo, Sulawesi and the Philippines. Especially in the Philippines, the majority of species are known from centers of diversity and endemism. Several species are restricted to one single mountain top or a mountain ridge.
A field research trip to the formerly unexplored central cordillera of Mindanao led to the discovery of four new taxa of carnivorous pitcher plants, namely N. amabilis, N. cornuta, N. pantaronensis and N. talaandig.
While N. cornuta and possibly N. talaandig belong to the N. alata group of species, N. pantaronensis is clearly related to N. pulchra and N. petiolata and, thus, belongs to the Reginae group.
N. amabilis stands clearly on its own among the Philippine Nepenthes species.
Other species in the central cordillera include N. ceciliae, N. pulchra, N. surigaoensis and N. truncata. However, the latter two species are widespread and also occur in other regions of Mindanao.
As with many other species of Nepenthes in the Philippines, the future of all species of the central cordillera is highly dependent on habitat conservation. Mt. Kiamo is not currently a protected area and, thus, the conservation status of the two endemic species, N. ceciliae and N. pulchra, needs to be monitored closely in the future.
If the current status “key biodiversity area” for the Pantaron range and the Kimangkil massif, including Mt. Sumagaya, leads to permanent protection combined with careful monitoring of the relevant protective measures, at least the four endemic Nepenthes species we described in this article would be assured preservation in the long term.
Thomas Gronemeyer, Fulgent Coritico, Andreas Wistuba, David Marwinski, Tobias Gieray, Marius Micheler, François Sockhom Mey and Victor Amoroso. 2016. Four New Species of Nepenthes L. (Nepenthaceae) from the Central Mountains of Mindanao, Philippines. Plants. 3, 284-303. DOI: 10.3390/plants3020284