Endemic Peperomia (Piperaceae) novelties from eastern Madagascar

Abstract Mathieu, G. (2020). Endemic Peperomia (Piperaceae) novelties from eastern Madagascar. Candollea 75: 75–82. In English, English and French-abstracts. Three endemic Peperomia Ruiz & Pav. species (Piperaceae) from the eastern Malagasy rainforests are presented as new to science. They are described, illustrated, compared with presumed closest relatives and their conservation status assessments are provided. Peperomia irrasa G. Mathieu seems to be restricted to the Anjanaharibe massif, while Peperomia robusta G. Mathieu is reported from the National Park of Zahamena to the Loky-Manambato Protected Area (Daraina). Peperomia variilimba G. Mathieu is an apparently common species occurring from the Tsaratanana massif to Analamazaotra. These novelties bring the number of accepted Peperomia species on Madagascar to 42.


Introduction
Peperomia Ruiz & Pav. (Piperaceae) is a giant, pantropical genus of terrestrial and epiphytic herbs. As of April 2020 it includes 1625 accepted taxa, 1455 species plus 172 forms and varieties (Mathieu, 2001(Mathieu, -2020. The genus shows its highest diversity in the neotropics. In the paleotropics, its diversity density is striking on the Malagasy Island. With the three novelties here presented, there are currently 42 species recognized (Madagascar Catalogue, 2020), about twice the number known from the entire African continent. However, the Malagasy Peperomia richness remained underestimated for a long time. Field work conducted in 2001 and subsequent scrutinization of herbarium collections already revealed ten new species (Mathieu, 2003a(Mathieu, , 2003b(Mathieu, , 2006. Three more are presented here as new to science. They are described, illustrated, compared with morphologically close taxa and assigned to subgenus. Two of the three newly described species were observed in situ and their type collections were made during the three month Malagasy Peperomia expedition in 2001. The third species is an herbarium finding, discovered during subsequent scrutinization of about 1700 herbarium specimens of Malagasy Peperomias (at B, BM, BR, E, G, GENT, GH, HUA, JE, K, L, LY, M, MO, P, PR, S, TAN, US, W, WAG, Z). The new species have been compared macroscopically and by light microscope with similar taxa.
Digital images of the types of species mentioned in this article can be accessed online by the TRGP (Taxonomic Repertory of the genus Peperomia) (Mathieu, 2001(Mathieu, -2020 and distribution maps by the Madagascar Catalogue (2020). Calculations of extent of occurrence (EOO) and area of occupancy (AOO) have been conducted with Geocat (Bachmann & Moat, 2012).
Etymology. -The specific epithet irrasa ("unshaven") refers to the minute pubescent indument of stem and petioles, resembling a stubble beard (Fig. 1B), a key character of the species.
Distribution and habitat. -The new species is known from only three collections (Cours 3861 being probably a duplicate of one of Humbert's), made during the same expedition in December 1951-January 1952 in the Anjanaharibe massif in the region of SAVA and has apparently not been reported since. It occurs at an altitude of 1600 -1800 m, in the upper part of the medium altitude moist evergreen forest (sensu Gautier et al., 2018) corresponding to the "Sylve à Lichen" of Humbert (1955). It is believed to be endemic from the Anjanaharibe massif. The collections show only young inflorescences without mature fruits.
Conservation status. -Peperomia irrasa is known from three (most likely two) old specimens collected most likely in a single location from Anjanaharibe Sud National Park. Despite the very restricted distribution and the absence of recent collection, there appear to be no current threats, and thus P. irrasa is assigned a status of "Least Concern" [LC] using the IUCN Red List Categories and Criteria (IUCN, 2012).
Etymology. -The specific epithet refers to the quite variable leaves, as well in shape as in succulence and indument density.
Distribution and habitat. -The new species is endemic to the medium altitude moist evergreen forests at an elevation range from 900 to 2300 m. Peperomia variilimba is known from the Tsaratanana massif in the North-East to Analamazaotra in the Centre East. It is apparently common. Notes. -In its general habit P. variilimba resembles P. villilimba. However, the latter species is characterized by an opposite leaf position. The taxonomic concept of P. villilimba has been rather confusing for almost a century due to an inaccurate description of its leaf position in the protologue. The holotype of P. villilimba (Baron 2606, P) was considered by Casimir de Candolle as exhibiting alternate leaves (Candolle, 1911: 48). The specimen concerned is showing only 6 leaves, which were pressed and mounted with considerable superposition. After remounting (straightening of the 2 superposed spadices and turning the specimen so that its former back is in front now) the opposite leaf position became evident. This position is also obvious in the isotype at K, apparently never seen by Candolle. In P. villilimba there is a marked length difference between the indument of the leaf surfaces (long) and of the margin (short). That difference is lacking in P. variilimba. The general habit of P. variilimba also resembles P. rotundilimba C. DC., which shows an opposite (or 3-verticillate) leaf position. P. variilimba is considered as belonging to subgenus Micropiper, as it is the case with P. villilimba (Frenzke et al., 2015).