Notes on XPleopodium and Pleopeltis in Tropical America

Interpretation of the polypodioid ferns has been a classic problem for pteridologists. The groupings are, with some exceptions, fairly clear, but whether they should be treated as subgenera of Polypodium or as distinct genera is a matter of considerable disagreement. There seems to be growing acceptance of their recognition as distinct genera (Smith 1981, 1985; Tryon & Tryon, 1982; Lellinger, 1985; Mickel & Beitel, in press), although some authors continue to recognize Polypodium in a broad sense (Proctor, 1977, 1985; Stolze, 1981). Some of the splinter genera in America (e.g., Campyloneurum, Niphidium) stand well apart from Polypodium s.s., but others are apparently very closely allied to Polypodium. This is especially so in regard to Pleopeltis, some members of which hybridize with species of Polypodium s.s. The best known example of this is Polypodium x leucosporum (=Polypodium lanceolatum x P. thyssanolepis), which was pointed out by Vareschi (1969) and described in detail by Wagner and Wagner (1975), who treated it and its parents within Polypodium. Recently, Anthony and Schelpe (1985) described a similar case in southern Africa, in which Pleopeltis macrocarpa (Bory ex Willd.) Kaulf. (=Polypodium lanceolatum) crosses with Polypodium polypodioides var. ecklonii (Kunze) Schelpe. The authors gave a hybrid intergeneric name to their hybrid species, x Pleopodium simianum Anthony & Schelpe. In our studies on the ferns of Oaxaca, Mexico (in press), we have seen specimens from various parts of Mexico that involve several members of these two genera. Most of the hybrids have binomials under Polypodium. The purpose of this paper is to make several new combinations under x Pleopodium and Pleopeltis, and to clarify the putative parentage of the hybrids.