﻿Species of Peperomia (Piperaceae) from the Saña River Valley, Peru

﻿Abstract The Saña River Valley in Northern Peru is unusual for the western slopes of the Peruvian Andes because of its nearly year-round regime of precipitation instead of marked seasonal dry winters. This results in unexpected plant diversity. We surveyed the species of Peperomia (Piperaceae), occurring in this valley from 300 to 3000 m elevation, based on the study of specimens from ten herbaria and field collections, resulting in a total of 81 accessions, of which 48 were made by the authors. We found 16 different taxa: Peperomiacacaophila, from Ecuador, is reported for the first time in Peru; P.cymbifolia, P.dolabriformis and P.emarginulata are reported for the first time for the Saña River Valley; other widely distributed species like P.fraseri, P.galioides, P.haematolepis, P.hispidula, P.inaequalifolia, P.microphylla, and P.rotundata were also found. Five species new to science are described: P.pilocarpa, P.riosaniensis, close to P.palmiformis from Amazonas; P.sagasteguii, related to P.trinervis, P.symmankii, close to P.ricardofernandezii from Piura, and P.vivipara, related to P.alata. A key to the species of Peperomia from the Saña River Valley, based on vegetative characters, is provided.


Introduction
Peperomia (Ruiz & Pavón, 1794), was the name chosen to distinguish some species previously described by Linnaeus as Piper, and its first species were described in Peru (Ruiz and Pavón 1798). It is the second largest genus of the family Piperaceae after Piper, with a pantropical distribution of about 1,600 species (Samain et al. 2009;Mathieu et al. 2011;Samain et al. 2011). Most of them occur in the Neotropics, and approximately 400 species can be found in Peru (Trelease 1936). Due to its high species number, subgenera were proposed and used for classification, based only on morphology (Miquel 1843;Dahlstedt 1900) until this century, when their phylogeny was clarified using molecular studies (Wanke et al. 2006;Samain et al. 2007;Samain et al. 2009). Finally, Frenzke et al. (2015) published a new infrageneric classification as a reference for studies in the genus, based on fruit characters, macroscopic features, and molecular data, defining 14 monophyletic groups, and describing 5 new subgenera. Peru hosts representatives of all subgenera (Frenzke et al. 2015), and it also has the highest diversity of species in the world (Ulloa et al. 2017), many of which are still not described, whereas a considerable number of the currently accepted species are possible synonyms (unpublished results of the first author).
While some of the subgenera are highly diverse and widely distributed (e.g., Micropiper (Miq.) Miq., Leptorhynchum (Dahlst.) Trel. ex Samain, Pseudocupula Frenzke & Scheiris), others are small and restricted to the Neotropics, and even to some Andean countries (Colombia, Ecuador, Peru, and Bolivia) (e.g., Perlucida Scheiris & Frenzke, Phyllobryon (Miq.) Scheiris & Frenzke). Among these small groups, two of them were split from the former subgenus Panicularia sensu Dahlstedt, into two well-supported clades that are well characterized by morphological features. (Panicularia Miq. and Fenestratae Pino) with most of their species adapted to seasonal dry periods through succulence and circumscribed to Peru and Ecuador . Due to the lack of information, many species of these two groups need to be reviewed and new species are to be described. In the quest for these novelties, we explored the Saña River Valley, in the north of Peru, where we found many taxa together in a small area, that was not known to be diverse for Peperomia. Therefore, the objective of the present paper is to review the species of Peperomia present in the Saña River Valley, Peru, as a sample of the high diversity of this species existing in the country.

Study area
The Saña (also spelled Zaña) River is a short course (ca. 125 km length) river on the western slopes of the northern Peruvian Andes, with two main tributaries: Udima River and Nanchoc River. Altogether they make up a total drainage area of 1754.7 m 2 (ANA 2010). The river rises in the district Calquis, province San Miguel, department Cajamarca, at approximately 3200 m elevation (ANA 1999), notoriously lower than similar rivers draining the Pacific Ocean basin.
After crossing the districts of Calquis and La Florida in the province of San Miguel and the district of Catache in the province of Santa Cruz (both provinces of the Cajamarca department), it enters the Oyotún district of the province of Chiclayo, Lambayeque department, after which it crosses the districts Nueva Arica, Cayaltí, Zaña, and Lagunas, as it flows to the sea across the coastal desert of the southernmost part of the Lambayeque department, close to the border with the department of La Libertad (Fig. 1). Unlike the Chancay-Reque River system located just north and the Jequetepeque River Valley South of it-both with typical coastal desertic valleys-the Saña River Valley is more humid on average, due to the influence of the Amotape-Huancabamba Zone (AHZ) (observation of the first author). This zone has been proposed as a biodiversity hotspot for its higher diversity levels more than adjacent zones (Weigend 2002). Its boundaries have been set from Río Jubones and Río Zamora systems in Ecuador to the Río Chicama system in Peru (La Libertad). Thus, its influence reaches the highlands of Lambayeque and particularly the Saña River Valley, where the humid forests on the western slopes of the Andes can only be explained by the relatively low elevation of the Andes in the AHZ, which allows the flow of moisture from the rainforests of the Amazon Basin on the east to the desert coasts of western Peru. Plants and animals typical of the Amazon Forest e.g. military macaws (Ara militaris L.) were reported here at the highest altitudes of the Saña River Valley (Taulis) before the anthropogenic deforestation of recent decades, (Koepcke 1961). Native forests of its middle elevations have been displaced by cultivated patches of the tropical bamboo Guadua angustifolia Kunth (Caña Guayaquil) which is extensively cultivated in northern Peru, but not in the adjacent valleys.
From the coast to the Andes, close to the riverbanks of the Saña River, from west to east, we find the localities of Lagunas, Mocupe, Zaña, Cayaltí, La Viña, Culpón, and Nueva Arica. After a detour of the road to the town of Nanchoc in the South, the river flows northwards to the town of Oyotún and Pan de Azúcar, turning later southeastward to El Espinal and La Florida, where a detour to the South moves the road away from the river to El Naranjo and Niepos. Beyond Nanchoc, there is a small relict forest called "La Oscurana" after the town of Bolívar, with four species of Peperomia reported, although only one was found in the Herbaria (Juárez et al. 2005). From La Florida, another small road continues east and then southwards along the Saña River leading to the former Taulis Estate, now a hamlet and no longer a cloud forest due to intense cultivation. From El Espinal on a short walk northwards, we find the Velo de Novia waterfall. Before reaching La Florida, after the bridge El Papayo over the Saña River, a detour to the northeast leads to the town of Monteseco, a former estate located south of a relict forest. From here, a trail leads to El Chorro Blanco waterfall and the former Udima Estate crossing the forest. River Udima, a northeastern affluent of Saña River, crosses the forest from east to west and flows into it at El Espinal.
The fauna and flora of the remaining forest North of Monteseco have been published by Cadle (1989), Cadle and McDiarmid (1990), and Sagástegui and Dillon (1991). The latter report 88 families, 200 genera, and over 326 species of ferns and flowering plants, among them nine species of Peperomia, in a cloud forest where native trees are covered with mosses, ferns, orchids and vines, and humidity is maintained by multiple streams and a waterfall. The forest has been partially destroyed by logging that occurred until the 1960s, and only patches of natural vegetation are left (Sagástegui and Dillon 1991). The Peruvian government has protected this area since 2010, declaring it as a reserved zone: "Zona Reservada Udima" (El Peruano 2010), and categorizing it as "Zona Reservada Udima en Refugio de Vida Silvestre, Bosques Nublados de Udima" (El Peruano 2011).
From 30 to 500 m elevations, the warm desertic climate with temperatures of up to 35 °C in summer (Clima.com) favors the abundance of cactus steppes intermingled with densely irrigated rice and sugar cane cultivation that almost dry up the river at this altitude. From 500 m upwards, the climate changes abruptly to temperate and humid with an annual average temperature of 18 °C. Most cacti grow below 500 m, but some species reach 1000 m of elevation. The unexpected diversity of species of cacti in such a coastal valley was described first by Mischler (1988) and more recently by Alomía (2020) (Sagástegui and Dillon 1991). From this altitude up to 2500 m, as precipitation increases, dense forests are seen, a combination of dry western Andean forests and eastern montane forests (observation by the first author). During the summer months (December to May), increased rain can cause downstream floods, that occasionally reach the lower basin, such as the one that wiped out the city of Zaña in 1720 (Angulo 2011).
Although the abovementioned studies have identified nine species of Peperomia in the relict humid forest north of the town of Monteseco and four species of Peperomia in the forest of La Oscurana, so far no research has been carried out for the rest of the valley, especially the drier areas where fewer species are supposed to occur. This study aims to assess the diversity of Peperomia species along the whole Saña River valley, adding new reports of already known species and describing new ones.

Plant material
This research was approved by the Bioethics Committee of the Facultad de Ciencias Biológicas de la Universidad Nacional Mayor de San Marcos, document 009-2021-CBE-FCB-UNMSM. Collections were enabled by the Servicio Nacional Forestal y de Fauna Silvestre (SERFOR) permit numbers 009-2009-AG-DGFFS-DG-EFFS, 0124-2011-AG-DGFFS-DGEFFS and authorization n° AUT-IFL-2018-064 issued by RDG N° 491-2018-MINAGRI-SERFOR-DGGSPFFS extended by RD N° D000170-2021-MIDAGRI-SERFOR-DGGSPFFS-DGSPF. Fieldwork was carried out by the teams of the Ghent University Botanical Garden (Belgium) and the Technische Universität Dresden (Germany) in 2009, and later by the Museo de Historia Natural -Universidad Nacional Mayor de San Marcos in the years 2020-2022, along the Saña River Valley starting from Zaña city up to Niepos, including the departments of Lambayeque (prov. Chiclayo) and Cajamarca (prov. San Miguel, La Florida, and Santa Cruz). No collections were made in the protected zone of Udima.
Field observations were complemented with the study of herbarium specimens of ten herbaria: F, GB, HAO, HLL, HUA, HUT, NY, UC, US, and USM, checking the types online. (acronyms following Thiers 2022). A total of 81 collections were included, of which 48 were made by the authors.
Photographs with either Sony DSC-HX400V or Olympus TG-6 cameras were taken of plants in habitat and plants ex-situ (vegetative, reproductive, and young plants). Flowers and seeds were photographed either with macro lenses, OPPO Reno-7, or stereomicroscopes. Measurements were taken from fresh plants, photographs, and dry herbarium specimens. Whenever possible, three or more measurements per structure. Floral organ measurements were based on photographs using ImageJ 1.53t. Colors were based on photographs of living plants and notes on herbarium labels.
All localities were georeferenced using GPS coordinates (https://www.gps-coordinates.net/) and Google Maps. For herbarium specimens without coordinates, approximate coordinates were calculated using Google Earth. Maps of distribution were drawn using the same set of coordinates using QGIS v.3.26 Buenos Aires (Official website QGIS: https://www.qgis.org/en/site/).
Finally, the subgenus to which each species belongs is mentioned according to the infrageneric classification of the genus Peperomia by Frenzke et al. (2015), who assigned all species described until then to their respective subgenus based on morphological and/or molecular data. The subgeneric placement of the new species described in this paper was defined based on morphological characters.

Taxonomy
The present study found 81 accessions of 16 different taxa of Peperomia in the Saña River Valley (Fig. 2). We here present an identification key for these taxa. Peperomia crystallina, P. hispiduliformis, and P. hartwegiana are included in the key due to the high probability of occurrence in the region. Characteristics of the species were taken from the present study as well as Pino (2004), Scheiris (2013), Steyermark (1984), and Trelease and Yuncker (1950).
Key to the species of Peperomia from the Saña River Valley   Distribution and habitat. Plants were known only from central Ecuador, prov. Los Ríos, Guayas, Esmeralda, and Pichincha, epiphyte on Theobroma or similar trees, in shaded warm forests from 200-1500 m. This is the first report for Peru.
Notes. The closest species we could compare to is P. topoensis Yunck., also from Ecuador, which is similar in its epiphytic, pendent, or assurgent habit with small, succulent, alternate ovate leaves, cordulate at the base and 7-plinerved, compared to the obtuse, subtruncate based and noticeable 3-nerved leaves of P. cacaophila. Peperomia nitida Dahlst. from Brazil, São Paulo (Campinas), a widely cultivated species, is similar but with larger, light green cordulate-based leaves, only stems slightly reddish. Peperomia portobellensis Beurl. from Panama is also similar in shape but with slightly larger leaves. No material other than the types of these species was available for further comparison.
This   Notes. The samples collected were determined as P. cymbifolia (Pino 2004) However, comparing the plants of the Saña River Valley and the plants from the type locality we found some differences summarized in Table 1. These differences do not support the description of a new species but are sufficient to describe a new variety of this species. Moreover, while previous collections grow from 1800 to 2800 m in colder and moister places, this variety seems to be adapted to low altitudes of 500 to 600 m with higher temperatures and drier periods. It is easy to cultivate outdoors in the city of Lima, quite different from var. cymbifolia, which requires a cool greenhouse. This species belongs to Peperomia subg. Fenestratae Pino (Frenzke et al. 2015). Diagnosis. Peperomia cymbifolia var. occidentalis differs from the type variety mainly in size, plants are smaller and more compact; Leaves are slightly longer (4 cm maximum compared to 3.6 cm long), their lateral faces are not as high (7-10 mm compared to 9-13 mm), and they are more constantly convex than concave, its abaxial side is less convex, sometimes even straight; Its fruits are smaller and narrower, (0.6-0.8 × 0.45-0.55 mm compared to the 0.7-0.8 × 0.6-0.7 mm), light olive green instead of yellowish green, and with a relatively larger stylopodium. Populations of this variety are not only separated geographically from the type variety but mostly by altitude and climate: they grow 1200 m below the lowest occurrence of the type variety, at least 10 °Celsius warmer. The epithet reminds the localization of this variety, the most occidental of all three varieties of P. cymbifolia. (P. cymbifolia var. cymbifolia, var. goodspeedii, and var. occidentalis).  Mathieu and Callejas (2006: 351; isolectotype: E, K!)).
Distribution and habitat. Plants are reported from Ecuador and Peru, in montane forests from 300 to 1500 m.
Notes. We compared the three species with features closer to our findings (   . Peperomia species that can be found in the Saña River Valley A P. dolabriformis B P. fraseri C P. galioides D P. haematolepis E P.hispidula F P.inaequalifolia G P. microphylla H P. rotundata. Table 2. Comparison of some features of the descriptions of P. angularis, P. emarginulata, and P. caucana with the specimens of P. emarginulata studied. All data according to Trelease and Yuncker (1950), complemented with Steyermark (1984) for P. angularis and Trelease (1936)  Leaf (length in cm) 3.5-6 2-6 (-9) 3-6 (-11) 4-6.5 Leaf (width in cm) 2.5-4 1-2.5 2.5-4.5 2-3.5 Peduncle (length in cm)  Diagnosis. Perennial, semi-succulent, prostate caespitose herb similar in habit to P. cacaophila, but differs mainly in leaf shape, which is widely obovate to elliptic or rotundate and sometimes slightly acuminate, compared to the ovate lamina and constantly acuminate apex of this species, leaves are flatter and less succulent, slightly puberulous compared to the canaliculate, glossy leaves of P. cacaophila. Stems are not terete as in this species but with two low prominent wings. Seeds are dimorphic, normal seeds are very similar in shape to the seeds of P. sagasteguii, modified seeds (probably galls) are conspicuous, large up to 2.5 mm long, bright green to brownish, densely covered with white trichomes.
Distribution and habitat. Plants grow from 1500 to 1600 m of the middle course of the Saña River valley, in the remnants of montane forest, mostly epiphytic.

Phenology. Inflorescences appear from October to March; fruits ripen from November to April.
Etymology. The epithet recalls the hairy surface of the modified fruits of this species, from the Latin pilus (hair) and Greek καρπός (fruit).
Notes. This specimen at first was considered a probable hybrid because it shows intermediate features between P. emarginulata and P. cacaophila. However, although those two species share their habitat to some extent they are found at lower altitudes and never close to P. pilocarpa. Instead, this species appears within the range of P. vivipara, but it seems not to be related to it. Another interesting fact is that most fruits are modified to form hairy galls. The etiology of these galls remains unknown.
Distribution and habitat. Plants grow from 450 to 600 m, the lowest and driest layer of the area studied, along the Saña valley between the towns of Oyotún and La Florida in the departments Lambayeque and Cajamarca, on rocky soil, in thickets shaded by shrubs and supplied with moisture from nearby water courses.
Phenology. Inflorescences appear from June to August; fruits ripen from July to September.
Etymology. The epithet was coined by Hutchison in 1967 after the Saña river, "Río Saña" in Spanish, which is Latinized to "riosaniensis" in the same way Rauhocereus riosaniensis was described by Backeberg. As Hutchison only labeled the herbarium sheets and never published this name it has been considered a nomen herbariorum (Mathieu 2007).
Notes. The closest species of Peperomia riosaniensis is P. palmiformis Pino & Samain (Pino et al. 2012) The web page "Peperomia.net" (http://www.peperomia.net/ repertorysearch.asp) indicates that this taxon is merely a synonym of the latter. We compared both species in detail and the main differences between P. riosaniensis and P. palmiformis are resumed in Table 3.
While P. palmiformis grows from 800 to 900 m along the Utcubamba valley from Bagua to Pedro Ruiz in department Amazonas, Peru, P. riosaniensis grows 300 m lower. Nevertheless, the temperatures in the habitats of both species average 25-30 °C during the day and 18-22 °C at night, P. riosaniensis grows at 200 km distance from P. palmiformis, on the dry, xerophytic western slopes of the Andes, with 25 mm rain per month average in summer and 0-4 mm in winter (Clima.com: https://www. clima.com/peru/cajamarca/florida). Peperomia palmiformis lives on the flatter eastern slopes of the Andes, along the lower basin of the Utcubamba river, in a dry valley but already under the influence of the Amazon Forest, with nearly 60 mm rain per month in summer and 5 mm monthly in winter (Clima.com). Both species look similar from far away, but P. riosaniensis is slightly shorter when vegetative; its inflorescences have relatively wider panicles, with more horizontal branches and more spadices that are relatively shorter. Although leaves look very much alike when pressed, the new species has longer and thicker petioles, longer leaves that are not as narrow and succulent, wider at the proximal third, making its margin convex, compared to the concave margin of P. palmiformis at this segment. The new species also has induplicate or canaliculate leaves, adaxially slightly darker and glossier, frequently carinate beneath and slightly recurved at the distal third, compared to the straight, flat, mostly biconvex succulent leaves of P. palmiformis, mainly due to its more developed fenestra. The serrate distal margin of the leaves observed in P. palmiformis similar to P. erosa Hutchison ex Pino (Pino et al. 2012) has never been observed in the new species. Fruits are entirely different, more globular, larger, thicker, and papillate in P. riosaniensis, fre- Table 3. Comparison of the main differences between P. riosaniensis and P. palmiformis.
Mainly flat, occasionally slightly convex on both sides, very narrowly obovate. Leaf (length in cm) 6-9 5-7 Leaf (thickness in mm) 1.2-2.4 0.5-3 Leaf (width) 2-3 cm wide at distal third 2-2.5 cm wide at distal third 1.8-3 cm wide at the middle 1-2 cm wide at the middle 1.4-1.8 cm wide at proximal third 0. quently with dry anthers attached, and lacking the conspicuous bright orange persistent basal pedicel. Peperomia palmiformis fruits also have a larger, bright orange style, with a bulge that is sometimes even thicker than the fruit itself. These morphological differences are supported by the fact that in a recent phylogenetic study, P. riosaniensis is located in a different branch from P. palmiformis that is more related to P. columella, P. ferreyrae, P. mathieui, and P. columnaris from the Utcubamba valley (Frenzke et al. 2015). All these species mentioned belong to Peperomia subgenus Fenestratae Pino (Frenzke et al. 2015). Additional specimens were examined. PEru, dept. Lambayeque, prov. Chiclayo, dist. Oyotún: road from Oyotún to El Espinal, on the trail to waterfall Velo de la Novia, 515 m, 06°48'30.  Diagnosis. Perennial, semi-succulent, terrestrial, epiphytic, or saxicolous herb similar to P. trinervis, differs in stems more pubescent, dark red to olive green instead of bright red, leaves with a longer and wider petiole (7-17 long × 1.8-2 wide compared to 3-10 long × 1.2-1.5 wide), lamina more succulent, green adaxially and light green-pinkish abaxially instead of olive green with gray nerves adaxially and red-purple abaxially; spadices longer (4-20 cm compared to 10 cm long), but narrower.
Distribution and habitat. Plants have only been found from 1200 to 1500 m of the middle course of the Saña River valley, in the remnants of montane forest, epiphytic or on rocks, always in shaded places. Peperomia sagasteguii is endemic to the Saña River valley.
Phenology. Inflorescences appear from October to November; fruits ripen from January to March.
Etymology. This species is dedicated to Abundio Sagástegui (1932Sagástegui ( -2012, collector of the type, a notable botanist, who worked at both Universidad Nacional de Trujillo and Universidad Privada Antonio Orrego, author of many books and articles, director of the journals "Bulletin of the Society of Botany of the UNT" and Arnaldoa, author of four genera and 97 species (Rodríguez and León 2012).
Notes. Most collections were determined initially as P. trinervis Ruiz & Pav., a species that seems to be very close, (see Table 4). The main differences are stem color, which is dull dark red and greenish in P. sagasteguii compared to the bright red of P. trinervis. The indumentum of P. sagasteguii seems to be denser and longer, like that of P. rotundata. Leaf petioles of P. trinervis are shorter and of similar color to its stems. The leaf color of P. sagasteguii is bright green adaxially with depressed nerves, while P. trinervis has a high color contrast between the dark olive green and the bright silver gray of the nerves. Abaxially leaf color of P. sagasteguii is light green, while P. trinervis  Table 4. Comparison of the main differences between P. sagasteguii and P. trinervis. Data of P. trinervis taken from Trelease and Yuncker (1950) and from live cultivated plants.
Diagnosis. Perennial, succulent, caulescent, terrestrial herb, similar to P. ricardofernandezii Pino & Samain, but shorter, less branched, and with more tortuous stems. Leaves are smaller (2.5-4.5 cm long compared to 4.5-8 cm long), more widely ovate, with an obtuse or rounded apex instead of acute-acuminate. Petioles are shorter (0.3-3.5 cm long compared to 2-4 cm), lighter in color, and attached closer to the cordate base, which is sometimes auriculate and overlapping compared to the truly peltate insertion of P. ricardofernandezii. The inflorescence is narrower and longer but otherwise very similar, with longer spadices (3-20 mm compared to 2-4 mm).

Distribution and habitat.
Plants are rare and have been found only at four spots from 700 to 2400, semi-shaded on soil accumulated among huge rocks, on moist places near watercourses.
Phenology. Inflorescences appear from December to March; fruits ripen from February to April.
Etymology. The epithet is dedicated to Lars Symmank, a botanist from Dresden, Germany, who together with Guido Mathieu collected the specimen of this new species in the first expedition to Peru organized by Ghent University in 2009. He worked in several studies of subgenus Tildenia Samain et al. 2011;Symmank et al. 2011).
Notes. The closest species to P. symmankii is P. ricardofernandezii from Piura. This species is mainly terrestrial, taller, and many branched with a bush-like appearance contrasted to the creeping habit of P. symmankii. The main difference is the leaf size and shape: P. symmankii has relatively smaller leaves, more widely ovate, with an obtuse to round apex, compared to the narrow ovate, acute-acuminate leaves of P. ricardofernandezii. Petioles of the new species are shorter, lighter in color, attached closer to the leaf base, which is truly cordate, even sometimes auriculate and overlapping, compared to the more peltate insertion in P. ricardofernandezii. The inflorescence of P. symmankii is narrower and longer but otherwise very similar, with slightly longer spadices (  Narrowly ovate, apex acute to subacuminate, base subcordate; adaxially light green, abaxially reddish to burgundy red. Leaves (size) 2-4.5 cm long 4.5-8 cm long 2.5-4 cm wide at distal third 1.5-3 cm wide at distal third 2.5-5 cm wide at the middle 2.5-6 cm wide at the middle 2-4.5 cm wide at proximal third 2.5-5.5 cm wide at proximal third Vegetative stem Perennial, usually one branch from subterminal bud.
Description. Perennial, semi-succulent, caespitose herb, growing terrestrial, epiphytic, or saxicolous in the shade of other plants, 30-45 cm tall. Roots fibrous, emerging from the base of plants, 0.7-1 mm diam., light brown. Stem stoloniferous at the base, from which 3-10 deciduous branches emerge, straight erect, sometimes in zig-zag towards the apex, terete at the base, then prominently winged towards the apex with a triangular section, dark olive green, slightly puberulous at the base, then glabrescent towards the apex, 0.7-1 cm diam. At the base, gradually tapering to 0.3-0.5 mm at the apex, rarely branched close to the base, internodes 2.5-5 cm at the base gradually descending to 0.5-0.7 cm towards the apex, wings prominent at the distal half of the stems, from below the node towards the node after the next, semitransparent, 1-2 mm tall. Leaves alternate, distichous, glabrous, elliptic to elliptic ovate; petiole short, decurrent to next opposite node, reniform in section, channeled above, reddish green-pinkish, 0.2-0.4 (-1) cm long, 1.5-2 mm wide; lamina 3-6.5 cm long, 0.5-1.5 mm thick, 1.8-3.2 cm wide, apex acute to very slightly acuminate, slightly recurvate, base sub truncate; adaxially bright glossy green in young leaves, then very dark army green and even bluish, flat to slightly canaliculate, 3-5-palmatinerved, nerves depressed; margin entire; abaxially very light green with a pink blush, 3-palmatinerved, nerves elevated. Inflorescence simple terminal or up to 3 individually from upper leaf nodes opposite to the leaves; peduncle terete to infundibuliform, bright green, 2-9 mm long, 1.4-1.5 mm diam.; rachis 3-6 cm long, 2-3 mm diam., light green. Floral bracts rotundate, light green, flat, almost inconspicuous, only darker green than rachis, 0.4-0.5 mm diam. Stamens, filaments transparent, 0.2 mm diam., 1.5-3 mm long, anthers white ovoid, 0.4-0.5 mm long, 0.3-0.4 mm wide. Fruit not seen. Propagule developing at the apex of the branch, 1-5 cm tall, persistent until the whole stem dries.
Distribution and habitat. Plants grow from 1500 to 1800 m of the middle course of the Saña River valley, in the remnants of montane forest, epiphytic or on rocks, always in shaded places.
Phenology. Inflorescences appear from December to March; fruits ripen from February to April.
Etymology. The epithet stands for the most striking feature of this plant, the production of offsets directly from the mother plant, bypassing germination, as a method of survival in extreme weather conditions, from the Latin viviparus (that brings forth its young alive).
Notes. The closest species to P. vivipara is P. alata Ruiz & Pav., a species of wide distribution in Mexico, Central America, and all countries of South America except Chile, Argentina, and Uruguay, in tropical forests at lower elevations. Plants are similar in habit and size, they share the zig-zag winged internodes, although P. vivipara is stouter, with thicker and more erect branches with longer internodes. The main difference is in leaves, which are shorter, elliptic with an acute short apex and an obtuse or almost truncate base in P. vivipara compared to the lanceolate, long acuminate, and acute-based leaves of P. alata. A further difference is that P. alata does not produce propagules at the distal stems. (Table 6) These plantlets, that drop readily and root close to the mother plant propagating the plants vegetatively, have not been seen in any other species of Peperomia and give the name to the epithet of the species.

Discussion
This research found 16 taxa of Peperomia in a radius of less than 25 km (Fig. 2). Previous studies had reported nine species of Peperomia in the protected area of Udima, north of the town of Monteseco (Sagástegui and Dillon 1991) and only four in the still unprotected forest La Oscurana in Bolívar (Juárez et al. 2005). It is noticeable that previous studies focus on "relict forests" that represent a sample of the former extension of the natural extents of these woodlands, but neglect to sample semi-arid environments that can also be rich in species, as we show in this article. This species richness could be explained by the influence of the AHZ, but the closest valleys to the north and south of Río Saña, also inside this zone have very scarce collections of this genus. Perhaps they deserve more research to verify if they share the same biodiversity.
We have observed that the highest diversity of Peperomia species occurs between 500 and 1600 m, although more rainfall and vegetation can be expected at higher altitudes. The species found in the upper layers (P. hispidula, P. rotundata. P. microphylla, P. galioides) have a broad distribution in the department of Cajamarca (Pino 2004) and even in the rest of the Americas. The fact that the endemic or rare species are concentrated in the middle range of mountain systems is an observation consistent with other floral studies (Vergara et al. 2017) but has no demonstrated explanation yet.
Another observation is that in the lower range, where more droughts threaten the diversity of species of Peperomia, we have found two species of subgenus Fenestratae and one of subgenus Panicularia. These subgenera are restricted to Ecuador and Peru, and they show an extreme adaptation to prolonged periods of drought through succulence. Other families adapted to this desertic environment, such as Cactaceae, -are also rich in diversity in this lower layer (Mischler 1988;Alomía 2020). Finally, our findings support the hypothesis that there are still many species of Peperomia in Peru awaiting their discovery.