Plant Ecology and Evolution 144 (2): 148–176, 2011 doi:10.5091/plecevo.2011.470 The geophytic Peperomia subgenus Tildenia (Piperaceae) in the Andes with the description of new species in a phylogenetic framework Marie-Stéphanie Samain 1,* , Guido Mathieu 1 , Guillermo Pino 2 , Lars Symmank 3 , Nelson Cieza 4 , Christoph Neinhuis 3 , Paul Goetghebeur 1 & Stefan Wanke 3 1 Ghent University, Department of Biology, Research Group Spermatophytes, K.L. Ledeganckstraat 35, BE-9000 Gent, Belgium 2 Universidad Nacional Mayor de San Marcos, Museo de Historia Natural, Av. Arenales 1256, Lima, Perú 3 Technische Universität Dresden, Institut für Botanik, Plant Phylogenetics and Phylogenomics Group, DE-01062 Dresden, Germany 4 Urb. José Sabogal B-22 Cajamarca, Perú *Author for correspondence: MarieStephanie.Samain@UGent.be INTRODUCTION With approximately 1,600 species, the pantropical genus Peperomia described by Ruiz & Pavón in 1794 from Peru belongs to the ten most species-rich genera of angiosperms (Frodin 2004, Samain et al. 2009). Among the 24 Pepero- mia species Ruiz & Pavón described in 1798 are two pecu- liar tuberous species, P. umbilicata and P. scutellifolia, both occurring in ‘loma’ vegetation on very few localities along the Peruvian coast. They belong to what is now to be consid- ered as Peperomia subgenus Tildenia (Miq.) Miq. (hereafter shortened as Tildenia), one of the most easily recognizable infrageneric Peperomia clades. This clade consists of approx- imately thirty currently accepted geophytic species with two easily observable synapomorphies: an entirely or partially underground tuber, and with petioles and peduncles originat- ing directly from the tuber (Wanke et al. 2006, Samain et al. 2009). All these species occur in seasonal habitats of Neo- tropical mountain areas from Mexico to Argentina, with an All rights reserved. © 2011 National Botanic Garden of Belgium and Royal Botanical Society of Belgium – ISSN 2032-3921 REGULAR PAPER Background and aims – The pantropical genus Peperomia consists of approximately 1,600 species with an extremely diverse vegetative morphology, especially in the Neotropics. One of the most startling yet overlooked growth forms is the geophytic one, as in subgenus Tildenia. This group occurs in seasonal Neotropical habitats with its highest diversity in Mexico-Guatemala and Peru-Bolivia with few species known from in between these hot spots. Methods – Recent feldwork in Peru and Bolivia combined with herbarium study and a Bayesian analysis of an aligned sequence matrix of the chloroplast trnK-matK-psbA gene cluster of one accession of each species resulted in new fndings within this subgenus. Key results – Fourteen new species are described, discussed in a phylogenetic framework and illustrated. Two species have a wide distribution and occur from central W. Peru to S. Bolivia: the common P. cerrateae and the rare P. parvisagittata. Three endemic species are described from the Amotape-Huancabamba Zone which is particularly rich in tuberous Peperomia species: P. gigantea, P. jalcaensis and P. klopfensteinii. Two species are only known from their type locality in central W. Peru: P. ocrosensis and P. pugnicaudex. Five other Peruvian species are P. ayacuchoana from Ayacucho, P. querocochana from Ancash, P. wernerrauhii from Huánuco, Peperomia umbrosa from three distant localities, and P. pseudoverruculosa which is relatively common in SE Peru. Two species are Bolivian endemics: the rare P. purpureonervosa from La Paz and the more common P. radiatinervosa from Cochabamba and Chuquisaca. Two former varieties, both endemics of the extreme northern Central Andes, are raised to species rank: P. lilliputiana and P. pseudoperuviana. Finally, basionym rejection and lectotypifcation are proposed for the widespread and commonly collected tuberous Peperomia in the southern Central Andes: P. peruviana. An emended description of Peperomia subgenus Tildenia is also provided. Key words – Peperomia, Peru, Bolivia, Argentina, Ecuador, Colombia, Venezuela, Central Andes, Amotape-Huancabamba Zone, chloroplast trnK-matK-psbA gene cluster.