Among the genera of Zygopetalinae (Orchidaceae) within the Huntleya clade (sensu Whitten et al., 2005), characterized by sympodial plants with shortened stems and leaves arranged fan-like, without pseudobulbs (or, in rare cases, rudimentary and concealed within basal leaf sheaths), Kefersteinia Rchb.f. stands out as the most diverse. With over 80 published names, likely corresponding to slightly more than 50 species, Kefersteinia generally comprises small epiphytic plants. These feature dark green, subcoriaceous- flexuous leaves, often with a prominent central vein on the abaxial side, and basal inflorescences that frequently produce numerous flowers opening simultaneously. The inflorescence peduncle is typically slender, arching under the weight of the flower until the inflorescence becomes pendulous. Flowers are usually resupinate, except for K. carolorum Carnevali & Cetzal and K. universitatis- tolimae Sierra-Ariza. Given the very thin nature of the peduncle in species of Kefersteinia, which is always arched- pendent or completely pendent in natural conditions, it is possible that variations in the position of the flower may depend on the growing conditions of the studied specimens. Kefersteinia carolorum was described from a plant cultivated in pot (Carnevali et al., 2015), and the illustrations of K. universitatis-tolimae show a plant growing almost horizontally (Sierra-Ariza and Harding, 2023), a feature rarely seen in wild specimens of the genus. The non-resupinate condition of Kefersteinia flowers could perhaps be tested through controlled cultivation experiments to better evaluate the hypothesis that this feature is naturally inherent in these two aberrant species and to gain insight into a possible distinct pollination system in the genus. Species of Kefersteinia range from southern Mexico to Bolivia (Pupulin, 2009), with notable presence in the Andes of Ecuador and Peru (over 30 recorded species) and the humid forests along the mountain chains of Costa Rica and Panama (twelve known species; Pupulin and Merino, 2008). In the type species of the genus, Kefersteinia graminea Lindley, the lip lamina is broadly rounded, with a low- laminar callus typically restricted to the proximal third of the blade. About half of Kefersteinia species share this lip morphology, while others exhibit distinctly stalked or highly anomalous calli. However, the genus includes over 40 names that often refer to poorly characterized taxa, making identification challenging. Molecular evidence from Whitten et al. (2005) indicates that informal species groups based on callus structure are not monophyletic and lack formal taxonomic recognition. Costa Rica hosts 12 Kefersteinia species, half described within the last 30 years, and two-thirds endemic to the country (Pupulin, 2001, 2010). Many species feature a prominent, fungus-like callus that forces visiting bees to twist their bodies while collecting floral fragrances, ensuring pollinaria attachment to the basal segment of an antenna (Pupulin, 2009). The function of the callus in species with low, laminar ornaments is less clear, though in some taxa, upturned basal callus margins are evident. It is possible that these species rely on a combination of the callus maintaining a longitudinal position and the column’s prominent central keel, pressing against the scutellum, to direct the bee’s movement and prevent lateral escape (see also discussion on putative pollination mechanisms in Kefersteinia by Carnevali et al. 2015). Kefersteinia nova istHmii americani australis cum generis synopsi Franco PuPulin,1,2,3,4,8 Elvira SalaS-Hidalgo,5 and diEgo Bogarín1,6,7 Abstract. A new species of Kefersteinia (Orchidaceae) from the southern region of the Central American isthmus is described and illustrated, and its affinities with K. elegans are discussed. In Panama, Kefersteinia luteola was previously misidentified as the Colombian K. elegans, but the new species appears to be restricted to the Cordillera de Guanacaste and Talamanca in Costa Rica and Panama. Among Kefersteinia species, K. luteola is distinguished by its small yellowish flowers, broadly extensively excised lip with a depressed laminate, trullate callus, and a column recognized by large, triangular, rounded wings with subciliate margins. The most similar species is Kefersteinia elegans, from which it differs in plant and flower size, with subringent sepals and petals, a sessile entire lip, and minutely glandular-ciliate wings of the column. A synopsis of the genus Kefersteinia is presented, and the species grouped according to their overall similarity. Keywords: floristics, Huntleya clade, New Species, taxonomy, Zygopetalinae We are grateful to the Costa Rican Ministry of Environment and Energy (MINAE) and the National System of Conservation Areas (SINAC) for issuing the scientific permit “R-SINAC-SE-DT-PI-006-2023,” which allowed us to collect the wild species studied. We also thank the Vice-Presidency of Research at the University of Costa Rica for providing support under the project “Inventario y taxonomía de la flora epífita de la región Mesoamericana” (814-A7-015). Additionally, we thank Karol Sandi for inking the illustration of the new species. 1 Centro de Investigación Jardín Botánico Lankester, Universidad de Costa Rica, P.O. Box 302-7050 Cartago, Costa Rica 2 Harvard University Herbaria, Cambridge, Massachusetts, U.S.A. 3 The Marie Selby Botanical Gardens, Sarasota, Florida, U.S.A. 4 Fellow of the American Orchid Society 5 Departamento de Bioquímica, Escuela de Medicina, Universidad de Costa Rica 6 Herbario UCH, Universidad Autónoma de Chiriquí, 0427, David, Chiriquí, Panamá 7 Naturalis Biodiversity Center, Evolutionary Ecology Group, 2333 CR Leiden, The Netherlands 8 Corresponding author: franco.pupulin@ucr.ac.cr Harvard papers in Botany, Vol. 29, No. 2, 2024, pp. 307–315. © President and Fellows of Harvard College, 2024 ISSN: 1938-2944, DOI: 10.3100/hpib.v29iss2.2024.n11, Published online: 31 December 2024 FigurE 1. Lankester Composite Digital Plate of Kefersteinia luteola Pupulin, E. Salas, & Bogarín. A, habit; B, flower; C, dissected perianth; D, column and lip, lateral view; E, column, several views; on the right, emasculate; F, pollinarium, dorsal, ventral, and three quarters views; G, anther cap. Photos and composition by F. Pupulin & D. Bogarín from Karremans 9383. 2024 PUPULIN ET AL., Kefersteinia (ORCHIDACEAE) 309 FigurE 2. Kefersteinia luteola Pupulin, E. Salas, & Bogarín. A, habit; B, flower; C, dissected perianth; D, column and lip, lateral view; E, column, several views; on the right, emasculate; F, pollinarium, dorsal, ventral, and three quarters views; G, anther cap. Drawing by Karol Sandi, based on Karremans 9383. 310 HARVARD PAPERS IN BOTANy VOL. 29, NO. 2 FigurE 4. Kefersteinia luteola Pupulin, E. Salas, & Bogarín. A, habit; B, flower; C, dissected perianth; D, column and lip, three quarters view; E, column, ventral, and three-quarters view; F, pollinarium and anther cap. Drawn by F. Pupulin from nuñez & olmos 111. 312 HARVARD PAPERS IN BOTANy VOL. 29, NO. 2 a SynoPSiS oF Kefersteinia Species with laminar callus 1. Kefersteinia alba Schltr., Repert. Spec. Nov. Regni Veg. Beih. 19: 228. 1923. TyPE: Costa Rica. 2. Kefersteinia andreettae G. Gerlach, Neudecker, & Seeger, Orchidee (Hamburg) 40(4): 133. 1989. TyPE: Ecuador. = Kefersteinia salustianae D.E. Benn. & Christenson, Brittonia 46(1): 37. 1994. TyPE: Peru. 3. Kefersteinia bismarckii Dodson & D.E. Benn., Icon. Pl. Trop., ser. 2. 1: t. 83. 1989. TyPE: Peru. 4. Kefersteinia candida D.E. Benn. & Christenson, Brittonia 46(3): 238. 1994. TyPE: Peru. 5. Kefersteinia carolorum Carnevali & Cetzal, Phytotaxa 239(2): 166. 2015. TyPE: Venezuela. 6. Kefersteinia delcastilloi D.E. Benn. & Christenson, Brittonia 46(1): 32. 1994. TyPE: Peru. 7. Kefersteinia elegans Garay, Orquideología 4(2): 80. 1969. TyPE: Colombia. 8. Kefersteinia escobariana G. Gerlach & Neudecker, Orquideología 19(3): 46. 1996. TyPE: Ecuador. 9. Kefersteinia forcipata (hort. ex Rchb.f.) P.A. Harding, Huntleyas 165. 2008. TyPE: Unknown. = Kefersteinia laminata (Rchb.f.) Schltr., Gard. Chron. 2: 70. 1885. TyPE: Ecuador. 10. Kefersteinia gemma Schltr., Gard. Chron. 1: 406. 1874. TyPE: Ecuador. = Kefersteinia oscarii P. Ortiz, Orquideología 20(2): 240. 1996. TyPE: Colombia. 11. Kefersteinia graminea (Lindl.) Rchb f., Bot. Zeitung (Berlin) 10: 634. 1852. TyPE: Venezuela. 12. Kefersteinia heideri Neudecker, Orquideología 19(3): 97. 1994. TyPE: Bolivia. 13. Kefersteinia klabochii Schltr., Repert. Spec. Nov. Regni Veg. Beih. 7: 267. 1920. TyPE: Colombia. 14. Kefersteinia lactea (Rchb.f.) Schltr., Repert. Spec. Nov. Regni Veg. Beih. 19: 228. 1923. TyPE: Costa Rica. 15. Kefersteinia lojae Schltr., Repert. Spec. Nov. Regni Veg. Beih. 8: 93. 1921. TyPE: Ecuador. = Kefersteinia pusilla (C. Schweinf.) C. Schweinf., Fieldiana, Bot. 33: 59. 1970. TyPE: Bolivia. = Kefersteinia bertoldii Jenny, Orchideen 36: 184. 1985. TyPE: Peru. = Kefersteinia lindneri Dodson, Icon. Pl. Trop. 5: t. 439. 1982. TyPE: Ecuador. = Kefersteinia vollesii Jenny, Orchideen 36(5): 185. 1985. TyPE: Colombia. = Kefersteinia lafontainei Senghas & G. Gerlach, Orchideen 41: 47 1990. TyPE: ??. = Kefersteinia benvenathar D.E. Benn. & Christenson, Brittonia 46(3): 235. 1994. TyPE: Peru. = Kefersteinia bengasahra D.E. Benn. & Christenson, Brittonia 46(3): 235. 1994. TyPE: Peru. = Kefersteinia jarae D.E. Benn. & Christenson, Brittonia 46(1): 34. 1994. TyPE: Peru. 2024 PUPULIN ET AL., Kefersteinia (ORCHIDACEAE) 313 liTEraTurE ciTEd Bogarín, d., Z. SErracín HErnándEZ, Z. Samudio, r. rincón, and F. PuPulin. 2014. An updated checklist of the Orchidaceae of Panama. Lankesteriana 14, no. 3: 135–364. carnEvali, G., W. cETZal ix, J. L. TaPia, and g. a. romEro- gonZálEZ. 2015. The world upside down: the first Kefersteinia (Orchidaceae: Zygopetalinae) with non-resupinate flowers. phytotaxa 239, no. 2: 165–173. drESSlEr, R. L. 2023. Kefersteinia. Pages 662–665 in c. ulloa ulloa, H. m. HErnándEZ, g. davidSE, F. r. BarriE, and S. KnaPP, EdS., Flora Mesoamericana 7, parte 2—Orchidaceae. Saint Louis, Missouri. garay, L. A. 1969. El complejo chondrorhyncha. Orquideología 4: 139–152. Harding, P. 2008. Huntleyas and Related Orchids. Timber Press, Portland, Oregon. PuPulin, F. 2001. Contributions to a reassessment of Costa Rican Zygopetalinae (Orchidaceae). The genus Kefersteinia Rchb. f. Annalen des Naturhistorischen Museums in Wien: Serie B: für Botanik und Zoologie 103B: 543–545. –––––––. 2004. Novelties in Mesoamerican Kefersteinia (Orchidaceae: Zygopetalinae). Harvard Papers in Botany 8, no. 2: 161–170. –––––––. 2009. Kefersteinia. Pages 211–220 in a. m. PridgEon, P. J. criBB, m. W. cHaSE, and F. n. raSmuSSEn, EdS., Genera Orchidacearum. Epidendroideae, part II, volume 5. Oxford University, Oxford. –––––––. 2010. Flora Costaricensis. Family #39 Orchidaceae: Tribe Cymbidieae: Subtribe Zygopetalinae. Fieldiana: Botany 49: i– iv, 1–60. PuPulin, F., and G. mErino. 2008. Two new species of Kefersteinia (Orchidaceae: Zygopetalinae). Willdenowia 38: 187–193. SiErra-ariZa, m. a., and P. Harding. 2023. A new species of Kefersteinia (Orchidaceae: Zygopetalinae), with peculiar non- resupinate flowers. Harvard Papers in Botany 28, no. 2: 727– 733. TroPicoS. 2023. Kefersteinia elegans, Collections. Retrieved at: https://www.tropicos.org/name/23508646, consulted 14 Aug. 2023. WHiTTEn, W. M., N. H. WilliamS, R. L. drESSlEr, G. gErlacH, and F. PuPulin. 2005. Generic relationships of Zygopetalinae (Orchidaceae: Cymbidieae): combined molecular evidence. lankesteriana 5: 87–107. a SynoPSiS oF Kefersteinia conT. Species with stalked callus cont. 46. Kefersteinia taurina Rchb.f., Linnaea 41: 5. 1877 [1876]. TyPE: Colombia?. = Kefersteinia lehmannii P. Ortiz, Orquideología 20: 234. 1996. TyPE: Colombia. 47. Kefersteinia trullata Dressler, Native Colomb. Orchids 2: 225. 1991. TyPE: Colombia. 48. Kefersteinia wercklei Schltr., Repert. Spec. Nov. Regni Veg. Beih. 19: 531. 923. TyPE: Costa Rica. Species with anomalous callus 49. Kefersteinia endresii Pupulin, Ann. Naturhist. Mus. Wien, B 103B: 543. 2001. TyPE: Costa Rica. 50. Kefersteinia expansa Rchb.f., Otia Bot. Hamburg. 9. 1872. TyPE: Ecuador. 51. Kefersteinia hirtzii Dodson, Icon. Pl. Trop., ser. 2. 6: pl. 506. 1989. TyPE: Ecuador. 52. Kefersteinia mystacina Rchb.f., Gard. Chron., n.s. 15(382): 530. 1881. TyPE: Colombia. = Kefersteinia lacerata Fowlie, Orchid Digest 32: 145. 1968. TyPE: Colombia. 53. Kefersteinia parvilabris Schltr., Repert. Spec. Nov. Regni Veg. Beih. 19: 52. 1923. TyPE: Costa Rica. = Kefersteinia deflexipetala Fowlie, Orchid Digest 30(4): 117. 1966. TyPE: Costa Rica. Excluded species Kefersteinia bicallosa (Rchb.f.) Rchb.f., Otia Bot. Hamburg. 1: 31. 1878 = Inti bicallosa (Rchb.f.) M.A. Blanco Kefersteinia flaveola (Linden & Rchb.f. ex Rchb.f.) Schltr., Repert. Spec. Nov. Regni Veg. Beih. 7: 266. 1920 = Chondroscaphe flaveola (Linden & Rchb.f. ex Rchb.f.) Senghas & G. Gerlach Kefersteinia leucantha Rchb.f. ex L. Linden, Ill. Hort. 29: 52. 1882, nomen nudum. Kefersteinia sanguinea Pritz., Icon. Bot. Index 2: 161 Orchidaceae, sphalm. Kefersteinia subquadrata Schltr., Repert. Spec. Nov. Regni Veg. Beih. 19: 300. 1923 = Chaubardiella subquadrata (Schltr.) Garay 2024 PUPULIN ET AL., Kefersteinia (ORCHIDACEAE) 315