PIPER COMMUTATUM (PIPERACEAE), THE CORRECT NAME FOR A WIDESPREAD SPECIES IN MEXICO AND MESOAMERICA

Piper sanctum, long treated as a distinct species, is here reduced to a synonym of P. auritum, which is a popularly known plant in Mexico. The oldest binomial for the species to which the name Piper sanctum was misapplied is P. commutatum, a taxon ranging from central Mexico south to Costa Rica and occurring in cloud forest, tropical perennial forest, tropical subdeciduous forest and humid canyons in tropical deciduous forest, at elevations from sea level to 2050 m. Synonyms of Piper commutatum include: P. papantlense, P. nudum, P. diandrum, P. membranaceum, and P. venulosum, among others.

As would be expected with such a large taxon, the nomenclatural and taxonomic history of Piper is complex and challenging.This is primarily due to three reasons.First, the flowers are small and morphologically homogeneous across the genus; second, many species have been described on the basis of characteristics of little taxonomic value or sterile specimens; and third, many new species have been proposed for plants occurring in different political regions, despite their similarity with previously described species from other regions (Bornstein, 1989).One problematic name is Piper sanctum (Miq.)Schltdl.ex C. DC.This was first described as Artanthe sancta in 1845, based on specimens housed in the Schlechtendal Herbarium, now at HAL (Miquel, 1845).The material used is referred by Miquel as collection Schiede 1105, from Atlacomulco in the Mexican state of Veracruz.The description is relatively incomplete, and the cited material does not have inflorescences.In fact, the type collection consists of a single leaf with no other structures (Fig. 1) and corresponds precisely with the morphological description provided in the protologue.The combination Piper sanctum was subsequently made by C. de Candolle (1869), citing the Miquel binomial but with a mistake in the collection number (Schiede 105).Furthermore, I am able to confirm that he indeed saw Schiede 1105, because in the herbarium G-DC there is a calc, made on translucid paper, which correspond to the leaf shape of the species.That tracing was made by de Candolle himself, as he did for many species (available in C-DG, G00322955), and is provided with the number 1105.
Piper sanctum was subsequently recognized by Standley (1920), accompanied by many common names and reported from the Mexican states of Oaxaca, Tabasco and Veracruz.Tebbs also treated it as a distinct species (1993) and listed its distribution as ranging from Mexico to Costa Rica.In addition to its basionym, the latter author treated various binomials as synonyms: Piper papantlense C. DC., P. diandrum C. DC., P. venulosum Trel, P. dissimulans Trel., and P. heterophlebium Trel.ex Standl.Apparently Tebbs did not see original material of Piper sanctum, as she cited the type as "Schiede 105 [sic] (?B, holotype)."However, while searching in the database and realizing an extensive revision in the herbarium of the Botanisches Museum Berlin-Dahlem (B) in December 2014, I did not find any material collected by Schiede with this number, and I believe that she was perpetuating C. de Candolle's error.
In conjunction with a revision of the genus in the Mexican state of Michoacán, I reviewed the types of many of the taxa treated by Tebbs, including those of Piper sanctum and the species that she listed as its synonyms.Much to my surprise, I encountered that Tebbs' application of the name was erroneous, and that the type clearly corresponds to the earlier described P. auritum Kunth.Piper auritum ranges from Mexico to Colombia and the Antilles, occurring commonly along edges of rivers in cloud forest, tropical perennial forest, tropical subdeciduous forest and humid canyons in tropical deciduous forest, at elevations from sea level to 2260 m.It also often grows beside agricultural crops or is cultivated in domestic gardens.It is very common in Veracruz, where it is widely employed in traditional medicine and the preparation of various culinary dishes.It has many common names in Spanish, including "Acuyo," "Hoja de Aján," "Hoja Santa," and "Hierba Santa".The word "Santa" means holy in Spanish, as does Miquel's Latin species epithet "sancta," and undoubtedly, he choose the specific epithet in reference to its common name in Veracruz.Apparently, Tebbs did not take into consideration the protologue of Artanthe sancta, and its new combination of Piper sanctum, which clearly indicate that the leaves are membranaceous, punctate pellucid, puberulent along the veins and margin, and with five secondary nerves all originating along the middle part of the leaf (pinnatinerved): "foliis membranaceis pellucido-punctatis utrinque subtus praesertim in nervis et secus margines puberulis rotundato-cordatis... costis usque ad 1/2 alt.utrinque" (Miquel, 1845); "foliis tenuiter membranaceis pellucido-punctatis utrinque praesertim subtus ad nervos et secus margines puberulis rotundato-cordatis... Usque nervos utrinque 5 supremos ad apicem ductos infimos e basi solutos mittente" (de Candolle, 1869).
The synonyms recognized by Tebbs, in contrast, have non-membranaceous leaves that are glabrous along the veins and margin and have seven to nine secondary nerves, all originating from the base of the leaf (palmatinerved).Since this error, a number of authors have followed her misapplication of the name Piper sanctum (e.g., Callejas, 2001;Bornstein and Coe, 2007;Jaramillo et al., 2008).
Piper auritum has dimorphic leaves, as described in detail in the description below.Those of the sympodial axis are different from those of the monopodial axis.It is worth mentioning that the leaf of the type specimen of Piper sanctum is from the monopodial axis, whereas the leaves of the type specimens of P. auritum are from the sympodial axis.However, there is no doubt that both specimens represent the same species.