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| Nepenthes megastoma A.S.Rob., R.Bustam. & Altomonte. in Altomonte, Collantes, Mangussad, Bustamante et Robinson, 2025. |
Abstract
Nepenthes megastoma is described and illustrated as a new species from the Puerto Princesa Subterranean River National Park, a UNESCO World Heritage Site in Palawan Philippines. This carnivorous tropical pitcher plant is currently known from just three locations in the Mount Saint Paul karst formation, where it grows on vertical limestone walls. Morphologically, N. megastoma is characterised by its highly branched stems, campanulate pitchers, peltate tendril exsertion, dimorphic upper pitchers, and unidirectionally upturned female flowers. It is assessed as Critically Endangered under the IUCN Red List criteria, based on its restriction to three subpopulations comprising few total individuals. Pitcher morphology suggests a degree of ecological-functional convergence with N. campanulata of Borneo, though overall morphology indicates a probable close affinity with the widespread Palawan endemic N. philippinensis.
Taxonomy, non-core Caryophyllales, Malesia, new species, Eudicots
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| Drone views of Nepenthes megastoma Location 1 with red arrows indicating plants. a. Habitat on vertical limestone walls at c. 250 m elevation. b. Clumps of plants appear to follow vertical seams in the rock wall c. On approach the yellowish green pitchers become apparent, as do co-occurring plants like Dracaena sp. At both locations, the plants appear associated with dark rock that has become encrusted and discoloured over time through accumulation of organic matter. Note that this is the same subpopulation featured in Clarke et al. 2014: fig. 6, confirming a decline in total individuals. d. Closest possible approach without digital magnification. Photographs by J. Altomonte. |
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| Nepenthes megastoma characteristics. a. Lower-intermediate pitcher with strong colouration. b. Stout form of upper pitcher with mediolateral flaring. c. Elongate form of upper pitcher. d. Magnification of stem showing winged phyllode bases with slight basal swelling. e. Suberect terminal growth showing peltate phyllode tips. f. Female inflorescence demonstrating universally upturned flowers with fruit in advanced development. Photographs by J.P. Collantes (a) and A. Robinson (b–f). |
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| Nepenthes megastoma A.S.Rob., R.Bustam. & Altomonte. a. Habit, suberect terminal growth bearing upper pitchers and female inflorescence. b. Section of stem showing characteristic phyllode bases which are shortly decurrent and slightly swollen. c. Abaxial view of phyllode with most prominent venation indicated. d. Attached elongate form of upper pitcher. e. Lower surface of lid showing general distribution of glands. f. Profile section through peristome and upper wall of pitcher. g. Magnification of trichomes, with stellate trichomes and peltate scales (lepides) shown. h. Dissected lower pitcher in profile. i. Stout form of upper pitcher in profile. j. Elongate form of upper pitcher in profile. k. Female flowers with developing fruit (above) and male flowers at anthesis (below). Based on Collantes & Langbao 1 and supplemented with photographs and measurements made of material in situ. Illustration by A. Robinson. |
Nepenthes megastoma A.S.Rob., R.Bustam. & Altomonte, sp. nov.
Type:—PHILIPPINES. Palawan, Barangay Cabayugan: Mount St Paul, on limestone cliffs, 200 m a.s.l., 23 June 2023, Collantes & Langbao 1 (holotype PNH 259144 [one sheet, barcode 01-001582]; isotypes PNH 259145 [three sheets, barcodes 01-001583 (sheet 1 of 6), 01-001584 (sheet 2 of 6), 01-001585 (sheet 3 of 6)]; MEL 2541012A [sheet 4 of 6], MEL 2541013A [sheet 5 of 6], MEL 2541014A [spirit collection from sheet 5 of 6], MEL 2541015A [sheet 6 of 6]).
– Nepenthes campanulata sensu Clarke et al. (2014: 7–13, fig. 6).
– Nepenthes sp. ‘Saint Paul Cliffs’ sensu McPherson (2023: 1988–1991, figs. 2395–2398).
Diagnosis:—Nepenthes megastoma superficially resembles N. campanulata but differs in the production of (differences in parentheses): large growths, individual stems to 2.8 m long and 1.2 cm in dia., branching basally or medially to form pendent clumps to 10 m long (to ~35 cm, mostly basally branching to form short clumps, stems to 0.4 cm dia.), phyllodes elliptic-subobovate and 20–38 cm long with shortly decurrent base and slight abaxial basal swelling (spathulate-lanceolate, to 9 cm long, base amplexicaul without swelling), pitchers trimorphic, comprising uniform lower pitchers and two forms of upper pitcher (pitchers monomorphic), pitchers brittle, peristome pronounced, to 5.5 mm wide, lid ±suborbicular, to 5 cm dia. (pitchers flexible, peristome very narrow, typically ≤ 2 mm, lid ovate-elliptic, to 2 cm long), inflorescences to 48 cm long, partial peduncles dense, mostly 2-flowered, female flowers ascending, unidirectionally upturned (Fig. 6f) but borne on pedicels evenly distributed about rachis (inflorescences ≤ 20 cm long, lax with few flowers, partial peduncles mostly 1-flowered, female flowers spreading, not unidirectionally upturned), and an indumentum of dimorphic trichomes present on most surfaces (almost entirely glabrous except below peristome and around spur).
Etymology:—The epithet megastoma is constructed from the Greek-derived prefix mega- (large) and the Greek word stoma (mouth), meaning ‘large mouth’, a reference to the diameter of the pitcher opening, which is greater than that of the rest of the pitcher in all pitcher forms.
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| Nepenthes megastoma a. Generalised view of the type of habitat that comprises Location 2. b. Individual clumps of N. megastoma (red arrows) growing overhead on sheltered cliff walls. c. Groups of ants (red arrows) were frequently observed feeding beneath the lids. d. Large clump of plants observed from below, comprising what appeared to be two multibranched males and one female e. Female plant viewed from below, showing various inflorescences and pitchers with uncommon single coils. Photographs by A. Robinson. |
John Charles A. ALTOMONTE, John Paul R. COLLANTES, Vernaluz MANGUSSAD, Rene Alfred Anton BUSTAMANTE and Alastair S. ROBINSON. 2025. Nepenthes megastoma (Nepenthaceae), A micro-endemic Pitcher Plant from Puerto Princesa Subterranean River National Park, Palawan, Philippines. Phytotaxa. 728(2); 93-107. DOI: doi.org/10.11646/phytotaxa.728.2.1 [2025-11-12]