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.

Adam, J.H., Wilcock, C.C. & Swaine, M.D. (1992) The ecology and distribution of Bornean Nepenthes. Journal of Tropical Forest Science 5 (1): 13–25.

Bauer, U., Di Giusto, B., Skepper, J., Grafe, T.U. & Federle, W. (2012) With a flick of the lid: a novel trapping mechanism in Nepenthes gracilis pitcher plants. PLoS ONE 7 (6): e38951.

https://doi.org/10.1371/journal.pone.0038951

Bauer, U., Paulin, M., Robert, D. & Sutton, G.P. (2015) Mechanism for rapid passive–dynamic prey capture in a pitcher plant. Proceedings of the National Academy of Sciences 112 (43): 13384–13389.

https://doi.org/10.1073/pnas.1510060112

Bianchi, A. (2016) Nepenthes ronchinii, a new pitcher plant species from Central Sulawesi, Indonesia. Unpublished B.Sc. thesis, University of Pavia, Pavia, 36 pp.

Blume, C.L. (1825) Bijdragen tot de flora van Nederlandsch Indië, vol. 8. Ter Lands Drukkerij, Batavia [Jakarta], 80 pp.

https://doi.org/10.5962/bhl.title.395

Cheek, M.R. (2015) Nepenthes (Nepenthaceae) of Halmahera, Indonesia. Blumea 59 (3): 215–225.

https://doi.org/10.3767/000651915X689091

Cheek, M.R. & Jebb, M.H.P. (2001) Flora Malesiana. Series I – Seed plants. Volume 15: Nepenthaceae. Nationaal Herbarium Nederland, Leiden, iv + 164 pp.

Cheek, M.R. & Jebb, M.H.P. (2016a) A new section in Nepenthes (Nepenthaceae) and a new species from Sulawesi. Blumea 61 (1): 59–62.

https://doi.org/10.3767/000651916X691510

Cheek, M.R. & Jebb, M.H.P. (2016b) Nepenthes minima (Nepenthaceae), a new pyrophytic grassland species from Sulawesi, Indonesia. Blumea 61 (3): 181–185.

https://doi.org/10.3767/000651916X693509

Cheek, M.R. & Jebb, M.H.P. (2016c) Nepenthes, three new infrageneric names and lectotypifications. Planta Carnivora 37 (2): 34–42.

Clarke, C.M. (1997) Nepenthes of Borneo. Natural History Publications (Borneo), Kota Kinabalu, xii + 207 pp.

Clarke, C.M. (2001) A Guide to the Pitcher Plants of Sabah. Natural History Publications (Borneo), Kota Kinabalu, iv + 40 pp.

Clarke, C.M. (2018) Nepenthes hamata (errata version published in 2019). The IUCN Red List of Threatened Species 2018: e.T40111A143967359.

https://doi.org/10.2305/IUCN.UK.2018-1.RLTS.T40111A143967359.en

Clarke, C.M., Lee, C.C. & McPherson, S.R. (2006) Nepenthes chaniana (Nepenthaceae), a new species from north-western Borneo. Sabah Parks Nature Journal 7: 53–66.

Clarke, C.M., Schlauer, J., Moran, J.A. & Robinson, A.S. (2018) Systematics and evolution of Nepenthes. In: Ellison, A.M. & Adamec, L. (Eds.) Carnivorous Plants: physiology, ecology, and evolution. Oxford University Press, Oxford, pp. 58–69.

https://doi.org/10.1093/oso/9780198779841.003.0005

Danser, B.H. (1928) The Nepenthaceae of the Netherlands Indies. Bulletin du Jardin Botanique de Buitenzorg, series 3, 9 (3–4): 249–438.

Ghazalli, M.N., A.A. Tamizi, M.I.M. Esa, E.E. Besi, D. Nikong, A.R.M. Nordin & A.Z. Zaini (2019) The systematic significance of leaf epidermal micro-morphology of ten Nepenthes species (Nepenthaceae) from Peninsular Malaysia. Reinwardtia 18 (2): 81–96.

https://doi.org/10.14203/reinwardtia.v18i2.3753

Golos, M.R., Robinson, A.S., Barer, M., Dančák, M., De Witte, J., Limberg, A., Noorhana, M.S. & Tjiasmanto, W. (2020) Nepenthes fractiflexa (Nepenthaceae), a new Bornean pitcher plant exhibiting concaulescent metatopy and a high degree of axillary bud activation. Phytotaxa 432 (2): 125–143.

https://doi.org/10.11646/phytotaxa.432.2.3

Hemsley, W.B. (1905) April 6th, 1905. Proceedings of the Linnean Society of London 117: 11–13.

Hooker, J.D. (1851) [‘1852’] Nepenthes villosa. tab. 888. In: Hooker, W.J. (Ed.) Icones Plantarum, vol. 9. Reeve & Co., London, tabs. 801–900.

Hooker, J.D. (1859) On the origin and development of the pitchers of Nepenthes, with an account of some new Bornean plants of that genus. The Transactions of the Linnean Society of London 22 (4): 415–424.

https://doi.org/10.1111/j.1096-3642.1856.tb00113.x

Hooker, J.D. (1873) Nepenthaceae. In: Candolle, A.P. de (Ed.) Prodromus Systematis Naturalis Regni Vegetabilis, vol. 17. G. Masson, Paris, pp. 90–105.

Hotta, M. (1966) Notes on Bornean plants, I. Acta Phytotaxonomica et Geobotanica 22 (1–2): 1–10.

IUCN (2012) IUCN Red List Categories and Criteria: Version 3.1, 2nd ed. IUCN, Gland, Switzerland and Cambridge, UK, iv + 32 pp. Available from: https://portals.iucn.org/library/node/10315 (accessed 17 May 2019)

Jebb, M.H.P. & Cheek, M.R. (1997) A skeletal revision of Nepenthes (Nepenthaceae). Blumea 42 (1): 1–106.

Korthals, P.W. (1840) Over het geslacht Nepenthes. In: Temminck, C.J. (Ed.) Verhandelingen over de natuurlijke geschiedenis der Nederlandsche overzeesche bezittingen, door de leden der natuurkundige commissie in Indië en andere schrijvers, vol. 2. S. & J. Luchtmans & C.C. van der Hoek, Leiden, pp. 1–44, tabs. 1–4, 13–15, 20–22.

Kurata, S. (1976) Nepenthes of Mount Kinabalu. Sabah National Parks Trustees, Kota Kinabalu, 80 pp.

Kurata, S. (1984a) New species of Nepenthes from Sulawesi, Indonesia. The Journal of Insectivorous Plant Society 35 (2): 41–45.

Kurata, S. (1984b) A new species of Nepenthes from Sulawesi, Indonesia. The Gardens’ Bulletin Singapore 36 (2): 197–200.

Lee, C.C. (2004) New records and a new species of Nepenthes (Nepenthaceae) from Sarawak. Sandakania 15: 93–101.

Lee, C.C., McPherson, S.R., Bourke, G. & Mansur, M. (2009) Nepenthes pitopangii (Nepenthaceae), a new species from Central Sulawesi, Indonesia. The Gardens’ Bulletin Singapore 61 (1): 95–99.

Lee, C.C., Wistuba, A., Nerz, J., Zimmermann, U., Paserang, A.P. & Pitopang, R. (2011) Nepenthes undulatifolia, a new pitcher plant from South East Sulawesi. In: McPherson, S.R. New Nepenthes, vol. 1. Redfern Natural History Productions, Poole, pp. 492–505.

Linnaeus, C. (1753a) Species Plantarum, vol. 1. Impensis Laurentii Salvii, Holmiae [Stockholm], 560 pp.

Linnaeus, C. (1753b) Species Plantarum, vol. 2. Impensis Laurentii Salvii, Holmiae [Stockholm], 640 + [31] pp.

Lloyd, F.E. (1942) The Carnivorous Plants. Chronica Botanica Company, Waltham, xvi + 352 pp.

Macfarlane, J.M. (1908) Nepenthaceae. In: Engler, A. (Ed.) Das Pflanzenreich: regni vegetabilis conspectus, Heft 36. W. Engelmann, Leipzig, pp. 1–92.

Marabini, J. (1987) Eine neue Unterart von Nepenthes edwardsiana Hook.fil. sowie Anmerkungen zur Taxonomie der Gattung Nepenthes L.. Mitteilungen der Botanischen Staatssammlung München 23: 423–429.

Marabini, J. (1988) Zur taxonomischen Klassifizierung von Nepenthes dentata Kurata und Nepenthes hamatus Turnbull et Middleton. Das Taublatt 9: 4–7.

McPherson, S.R. (2009) Pitcher Plants of the Old World, vols. 1–2. Redfern Natural History Productions, Poole, xvi + 1399 pp.

McPherson, S.R. & Robinson, A.S. (2012) Field Guide to the Pitcher Plants of Sulawesi. Redfern Natural History Productions, Poole, 49 pp.

McNeill, J. (2014) Holotype specimens and type citations: general issues. Taxon 63 (5): 1112–1113.

https://doi.org/10.12705/635.7

Meimberg, H. & Heubl, G. (2006) Introduction of a nuclear marker for phylogenetic analysis of Nepenthaceae. Plant Biology 8 (6): 831–840.

https://doi.org/10.1055/s-2006-924676

Meimberg, H., Thalhammer, S., Brachmann, A. & Heubl, G. (2006) Comparative analysis of a translocated copy of the trnK intron in carnivorous family Nepenthaceae. Molecular Phylogenetics and Evolution 39 (2): 478–490.

https://doi.org/10.1016/j.ympev.2005.11.023

Meimberg, H., Wistuba, A., Dittrich, P. & Heubl, G. (2001) Molecular phylogeny of Nepenthaceae based on cladistic analysis of plastid trnK intron sequence data. Plant Biology 3 (2): 164–175.

https://doi.org/10.1055/s-2001-12897

Metcalfe, C.R. & Chalk, L. (1950) Nepenthaceae. In: Metcalfe, C.R. & Chalk, L. (Eds.) Anatomy of the Dicotyledons, vol. 2. Clarendon Press, Oxford, pp. 1105–1111.

Moran, J.A. & Clarke, C.M. (2010) The carnivorous syndrome in Nepenthes pitcher plants. Plant Signaling & Behavior 5 (6): 644–648.

https://doi.org/10.4161/psb.5.6.11238

Mullins, J.T. (2000) Molecular systematics of Nepenthaceae. Unpublished Ph.D. thesis, University of Reading, Reading, ix + 156 pp. + 8 pl.

Murphy, B., Forest, F., Barraclough, T., Rosindell, J., Bellot, S., Cowan, R., Golos, M.R., Jebb, M.H.P. & Cheek, M.R. (2020) A phylogenomic analysis of Nepenthes (Nepenthaceae). Molecular Phylogenetics and Evolution 144: 106668.

https://doi.org/10.1016/j.ympev.2019.106668

Nees von Esenbeck, C.G.D. (1824) Nouvelles observations sur le genre Nepenthes, extraites d’une lettre adressée à M. Ad. Brogniart. Annales des Sciences Naturelles 3: 365–370.

Nerz, J., Wistuba, A., Lee, C.C., Bourke, G., Zimmermann, U. & McPherson, S.R. (2011) Nepenthes nigra, a new pitcher plant from Central Sulawesi. In: McPherson, S.R. (Eds.) New Nepenthes, vol. 1. Redfern Natural History Productions, Poole, pp. 468–491.

R Core Team (2018) R: a language and environment for statistical computing. R Foundation for Statistical Computing, Vienna. Available from: https://www.R-project.org/ (accessed 27 September 2019)

Robinson, A.S., Zamudio, S.G. & Caballero, R.B. (2019) Nepenthes erucoides (Nepenthaceae), an ultramaficolous micro-endemic from Dinagat Islands Province, northern Mindanao, Philippines. Phytotaxa 423 (1): 21–32.

https://doi.org/10.11646/phytotaxa.423.1.3

Salisbury, R.A. (1807) The characters of several genera in the natural order of Coniferae: with remarks on their stigmata, and cotyledons. The Transactions of the Linnean Society of London 8 (1): 308–317.

https://doi.org/10.1111/j.1096-3642.1807.tb00316.x

Salisbury, R.A. & Hooker, W. (1807) Corybas aconitiflorus. In: Salisbury, R.A. & Hooker, W. The Paradisus Londinensis: or Coloured Figures of Plants Cultivated in the Vicinity of the Metropolis. W. Hooker, London, tab. 83 (figure and notes).

Scharmann, M. & Grafe, T.U. (2013) Reinstatement of Nepenthes hemsleyana (Nepenthaceae), an endemic pitcher plant from Borneo, with a discussion of associated Nepenthes taxa. Blumea 58 (1): 8–12.

https://doi.org/10.3767/000651913X668465

Schlauer, J. & Nerz, J. (1994) Notes on Nepenthes (Nepenthaceae) I. Contributions to the flora of Sumatra. Blumea 39 (1–2): 139–142.

Schmid-Hollinger, R. (1971) Nepenthes-Studien II. Die Haare der Nepenthaceen und ihre phylogenetische Bedeutung. Botanische Jahrbücher für Systematik, Pflanzengeschichte und Pflanzengeographie 91 (1): 61–90.

Schmid-Hollinger, R. (2019) Nepenthes tentaculata I & II. bio-schmidhol.ch. Available from: http://www.bio-schmidhol.ch/site/index.cfm?id_art=137501 and http://www.bio-schmidhol.ch/site/index.cfm?id_art=137923 (accessed 29 September 2019)

Tamin, R. & Hotta, M. (1986) Nepenthes di Sumatera: The genus Nepenthes of the Sumatra Island. In: Hotta, M. (Ed.) Diversity and Dynamics of Plant Life in Sumatra: Forest Ecosystem and Speciation in Wet Tropical Environments. Part 1: Reports and Collection of Papers. Kyoto University, Kyoto, pp. 75–109.

Thiers, B. (2020 [continuously updated]) Index Herbariorum. A global directory of public herbaria and associated staff. New York Botanical Garden’s Virtual Herbarium. Available from: http://sweetgum.nybg.org/science/ih (accessed 6 January 2020)

Turland, N.J., Wiersema, J.H., Barrie, F.R., Greuter, W., Hawksworth, D.L., Herendeen, P.S., Knapp, S., Kusber, W.-H., Li, D.-Z., Marhold, K., May, T.W., McNeill, J., Monro, A.M., Prado, J., Price, M.J. & Smith, G.F. (Eds.) (2018) International Code of Nomenclature for algae, fungi, and plants (Shenzhen Code) adopted by the Nineteenth International Botanical Congress Shenzhen, China, July 2017. Koeltz Botanical Books, Glashütten, xxxviii + 254 pp.

https://doi.org/10.12705/Code.2018

Turnbull, J.R. & Middleton, A.T. (1984) Three new Nepenthes from Sulawesi Tengah. Reinwardtia 10 (2): 107–111.

https://doi.org/10.14203/reinwardtia.v10i2.261

Wickham, H. (2016) ggplot2: Elegant Graphics for Data Analysis, 2nd ed. Springer, New York, xvi + 260 pp.

https://doi.org/10.1007/978-3-319-24277-4

Ziemer, B. (2010) Exciting conservation news: The Rare Nepenthes Collection project! Carnivorous Plant Newsletter 39 (3): 67.

Ziemer, B. (2020) Nepenthes ronchinii. Carnivorous Plant Photo Finder, 21 August 2020. Available from: https://cpphotofinder.com/nepenthes-ronchinii-16682.html (accessed 29 September 2020)