New Combinations in the Pleopeltis macrocarpa Group (Polypodiaceae: Polypodieae)

Abstract

The Pleopeltis macrocarpa group includes the 11 members of Pleopeltis with simple and undivided leaves. The group is predominately neotropical and epiphytic, and the species occur most frequently between 1500 and 2500 m in disturbed habitats of wet forested areas. They are especially common along roadsides, edges of pastures, and on cultivated trees such as coffee and citrus. In addition to their simple leaves, members of the P. macrocarpa group are characterized by anastomosing venation; large sori subtended by a nexus of veinlets; rhizome, leaf, and soral scales that are peltately attached and at least partially clathrate; and a chromosome base number of x=34 or 35. The peltate soral scales (paraphyses), which form a complete covering over young sori, have been the main diagnostic feature for Pleopeltis since its establishment in 1810. Although the genus was established for P angusta, an unusual fern with irregularly pinnatifid leaves, most of the species included in the genus since 1810 have simple leaves and belong to the P macrocarpa group. The P. macrocarpa group has been the focus of recent morphological, cytological, and isozymic studies (Hooper, 1994), which were initiated because of controversies involving generic circumscription of Pleopeltis. Problems have arisen for two reasons. First, because of the reliance on peltate paraphyses as the main diagnostic feature for the genus, several species (e.g., P munchii and P. fallax) have been included in Pleopeltis, despite the fact that they share little else with P. angusta and members of the P macrocarpa group other than paraphyses. Second, hybridization between at least four members of the P macrocarpa group and scaly-leafed members of Polypodium (subg. Marginaria) (Wagner and Wagner, 1975; Anthony and Schelpe, 1985; Mickel and Beitel, 1987) raised initial doubts about the integrity of the generic boundary between these two groups. Furthermore, preliminary isozyme and chloroplast DNA surveys (Andrews and Haufler, 1990; Haufler and Ranker, in press) revealed greater genetic affinity between two scaly Polypodium species and members of the P macrocarpa group than between the former and non-scaly polypodiums. This genetic evidence, coupled with the strong similarities in rhizome, leaf, and soral indumentum between the two (Baayen and Hennipman, 1987), led Windham (1993) to transfer four scaly Polypodium species into Pleopeltis. Whereas this new arrangement more accurately portrays the evolutionary relationships