Monographs Details: Melpomene xiphopteroides var. acrodontia (Fée) Lehnert
Authority: Lehnert, Marcus. 2013. Grammitid ferns (Polypodiaceae). II. . Fl. Neotrop. Monogr. 112: 1--121. (Published by NYBG Press)
Family:Polypodiaceae
Synonyms:Polypodium acrodontium Fée
Description:Species Description - Plants predominatly epiphytic, sometimes epilithic. Rhizomes short-erect to short-creeping, 0.6-0.8 mm diam. Fronds to 17 cm long, patent, inserted onto the rhizomes at narrow angles or appressed to them, closely arranged (internodes 0.5-1.0 mm), fasciculate. Rhizome scales 1.2—1.4(—4.5) x 0.3-0.8 mm, (8—)10—12 (-14) cells wide across bases, clathrate, dark brown to brown, weakly iridescent, lanceate, cordate to pseudopeltate at bases, long-acute at tips; apical cells 5-10, linearly to furcately arranged. Petioles 15-35 mm long, 0.8 mm thick, usually marginate, rarely weakly alate, with many dark brown hairs 1.2-2.0 mm long; simple and branched clavate hairs often absent even in crosiers and young fronds. Laminae to 140 x 26-29 mm, narrowly to broadly elliptic (broadest in the middle), cuneate to truncate at bases, short-acute to attenuate at tips. Rachises dark brown to black, planar and slightly sunken adaxially, hemispherically protruding abaxially, moderately to abundantly hairy abaxially, sparsely hairy to glabrous adaxially, the hairs to 1.5 mm abaxially, shorter adaxially. Largest segments to 12.0-14.0 x 2.5-3.0 mm (4-5 times longer than broad), weakly ascending (70-80°), segments linear-oblong, bases equilateral, fully adnate, tips obtuse, often with hyaline margins; midveins not visible; proximal segment pairs notably smaller than the subsequent segments but not auriculiform; hairs 0.8—1.5 mm long, brown, with rather flaccid bases; hairs clustered in sori, scattered along midveins, usually also some on the tips and along margins of some segments; stomata often visible as dark spots; hydathodes present. Sori 2-8 pairs per segment, with several ciliform hairs to 1.5 mm long.

Discussion:The general characters distinguishing Melpomene xiphopteroides from M. pilosissima (setiform/ciliform hairs clustered in sori, petioles marginate to alate vs. hairs not clustered in sori, petioles terete or only decurrently marginate) are valid also for var. acrodontia. However, fronds with decurrent laminar bases, which render the majority of specimens of var. xiphopteroides recognizable at a glance, are almost absent in var. acrodontia, and conspicuously alate petioles are less frequent. Therefore, plants of M. xiphopteroides var. acrodontia look superficially more like M. pilosissima, but this is due only to a skewed frequency of morphological traits present in both varieties of M. xiphopteroides, i.e., plants of var. xiphopteroides usually also have fronds with the typical pattern of var. acrodontia but not vice versa. The morphological differences are not considered here as sufficient for separating the Brazilian population from the Andean population on the species level. Melpomene xiphopteroides var. acrodontia includes almost all Brazilian specimens previously determined as M. pilosissima. However, Melpomene pilosissima, as defined here, occurs only in Mesoamerica and the northern Andes. In contrast, M. xiphopteroides forms a continuous population along the eastern Andean slope, reaching the Andean deflection in central Bolivia. Plants from the Parque Nacional Amboro in Central Bolivia are also morphologically closer to the Brazilian population than to Bolivian plants from adjoining areas to the west and, thus, better placed under var. acrodontia. Furthermore, the average elevational ranges of M. xiphopteroides var. xiphopteroides and var. acrodontia match better with each other (900-2400 m and 800-2500 m, respectively) than with that of M. pilosissima (2000-3500 m). A similar biogeo-graphical connection between the Andean deflection and SE Brazil is found in M. albicans.

The name is from the Greek akros- = pointed top and dons = tooth, probably referring to the pinnatifid frond tips. Fée (1873) did not give an explanation for the name, but described the frond tips as dentate.
Distribution:São Paulo Brazil South America| Rio de Janeiro Brazil South America| Santa Catarina Brazil South America| Espirito Santo Brazil South America| Minas Gerais Brazil South America| Paraná Brazil South America| Santa Cruz Bolivia South America|