Notes on the genus Sauvetrea (Orchidaceae, Maxillariinae), with a description of a new species

The genus Sauvetrea Szlach. (Orchidaceae) was segregated from Maxillaria sensu lato in 2007. It embraces a group of from 10 to nearly 20 species, all initially defined as Maxillaria sect. Trigonae. Sauvetrea can be easily distinguished from closely related Rhetinantha M.A.Blanco by the lip callus. During the revision of the materials stored in AMES we came across specimens collected by Vargas in Peru, which were initially identified by Schweinfurth as Maxillaria brachypetala Schltr. We compared Vargas’s discovery with the protologue of the latter species and other Sauvetrea, but it does not fit the description of any genus representatives known so far. We describe it below as a new species, Sauvetrea schweinfurthiana Szlach. & Lipińska.


Introduction
The subtribe Maxillariinae Benth. is one of the most conspicuous and diverse taxa among the orchid family. Since its first formal description by Bentham (1881), many researchers have attempted to create a classification system of Maxillariinae. Those attempts suffered, however, from the insufficient information available at that time. Modern and more comprehensive molecular and morphological research (Ojeda et al., 2005;Blanco et al., 2007;Whitten et al., 2007;Ojeda et al., 2009) resulted in the splitting of Maxillaria sensu lato into 17 genera. Most of them have been accepted in the most recent studies (Szlachetko et al., 2012) with additional generic delimitation within Camaridium and Ornithidium. Most taxonomists (Dressler, 1993;Szlachetko, 1995) recognized the following genera: Anthosiphon Schltr., Cryptocentrum Benth., Mormolyca Fenzl, Pityphyllum Schltr., Scuticaria Lindl., and Trigonidium Lindl. Other taxa, depending on the adopted concept, were often combined in the collective genus Maxillaria sensu lato (e.g., Dressler, 1981Dressler, , 1993Christenson, 2002). All these taxonomic changes were neglected by Schuiteman and Chase (2015), who amalgamated all previously segregated genera once again into Maxillaria sensu latissimo.
The genus Sauvetrea Szlach. was fragmented from Maxillaria sensu lato in 2007. It embraces group of from 10 to nearly 20 species, all initially defined by Christenson (2002) Whitten et al., 2007) revealed that Sauvetrea sensu lato was a polyphyletic taxon. Whitten et al. (2007) believed that among the species that have not been sampled during molecular analysis and that were included in Sauvetrea by Szlachetko and Śmiszek (2007), Maxillaria grandimentum C.Schweinf. actually belongs in Maxillaria sensu stricto and M. planicola C.Schweinf. in Camaridium.
Plants of Sauvetrea are caespitose to moderately long rhizomatous. Pseudobulbs are ellipsoid to ovoid, flattened, unifoliate and frequently ancipitous, subtended by a pair of nonfoliaceous bracts. The rhizome is covered by a few short, acutely triangular, two-ranked, strongly keeled papery bracts exposing the green internodes. Leaf is always single, oblong to elliptic-oblong, membranous to coriaceous. Inflorescences arise from the base of the newly emerging pseudobulbs and are usually as long as leaf. Scapes have strongly ancipitous, two-ranked, strongly keeled bracts. Flowers are usually yellowish-green to tan, medium-sized, covered by imbricating sheaths, with spreading perianth segments, without strong fibers. Floral bracts are as long as or longer than pedicel and ovary. Tepals are dissimilar, narrow. Lip is hanging on the column foot, unequally 3-lobed, with a central, ligulate callus with sulcate depression along its length. Column foot is short. There are no secretions produced by the flowers.
During the revision of the materials stored in AMES we came across specimens collected by Vargas in Peru, which were initially identified by Schweinfurth as Maxillaria brachypetala Schltr. We compered Vargas's discovery with the protologue of the latter species and other Sauvetrea, but it does not fit the description of any genus representatives known so far. We describe it below as a new species.

Materials and methods
Dried herbarium specimens were examined according to the standard procedures. Each studied sheet was photographed and the data from the labels were taken. The standard procedure of preparing herbarium material to facilitate stereomicroscopic observation was applied. Particular parts of the flower were boiled, dissected, measured, and drawn under a stereomicroscope. The results were then analyzed and compared with the type material, diagnoses, and original illustrations.

Result and discussion
3.1. Sauvetrea schweinfurthiana Szlach. & Lipińska, sp. nov. (Figures 1-3) The new species is somewhat similar to its Peruvian congener Sauvetrea brachypetala, with which it shares similar size of flowers, but it can be easily separated by the lip form.
Etymology: Dedicated to Charles Schweinfurth (1890-1970), an eminent American orchidologist and the leading authority on Peruvian Orchidaceae.
Distribution and ecology. The plant was collected in S Peru in the Dept. Cuzco, and we have found no other collection of this species elsewhere. Nothing is known about the ecological requirements of the new entity, except the information provided on collector's label that it is an epiphyte.
Notes. The new species is somewhat similar to its Peruvian congener Sauvetrea brachypetala (see below), with which it shares similar size of flowers, but it differs by having truncate lip base (vs. narrowly cuneate), lateral lobes oblong elliptic-subquadrate (vs. triangular), and oblong elliptic-ovate middle lobe, obtuse at the apex, with strongly undulate margins, irregularly denticulate, except apical margin (vs. middle lobe broadly oblongelliptic with flared transverse apical part, notched at the apex), and sulcate (vs. bisulcate) callus. The other species similar to S. schweinfurthiana is S. machupicchuensis (Christenson & Salinas) M.A.Blanco, described from the Machu Picchu Sanctuary. The latter species has, however, much shorter leaves (ca. 5 cm long), shorter inflorescence (ca. 2.5 cm long), smaller flowers (with tepals ca. 1.5-2 cm long), and different lip form. The lip lateral lobes of S. machupicchuensis are obliquely elliptic, abruptly acute; the middle lobe is strongly undulate; and the callus is longer, ca. half as long as entire lip length.
In the course of the study on Sauvetrea it became obvious that Maxillaria brachypetala Schltr. needed to be transferred to this genus and we validate such a combination below.