Additions to the taxonomy of the Hypolepis rugosula complex (Dennstaedtiaceae) in Africa: corrections, two new subspecies and new distribution maps

Abstract

This paper presents complementary data to the recently published taxonomic treatment of the Hypolepis rugosula complex around the world, with special reference to Africa and surrounding islands. Here we present a new subspecies from South Africa (H. rugosula subsp. rouxii) and another from Bioko, Equatorial Guinea (H. rugosula subsp. formosa). We present an updated nomenclatural paragraph for H. rugosula subsp. africana, along with the lectotypification of one heterotypic synonym (Phegopteris boryana) and comments regarding similar but unrelated names (e.g. Aspidium boryanum). We also transfer H. goetzei to the synonymy of H. rugosula subsp. pichi-sermolliana, choosing a new lectotype for it. The population of H. rugosula from South Africa (= subsp. rouxii) is likely to be the source population for populations of Saint Helena (= subsp. viscida) and Ascension Island (= subsp. brownseyana), based on morphological comparisons and on the anticlockwise wind direction. Based on the latitude, H. rugosula subsp. formosa would be expected to be found only at the higher elevations in Bioko (above 2,000 m a.s.l.), but it is also found at mid-elevations (ca 700 m a.s.l.). Apparently, this is a natural pattern of islands and is increased by deforestation. We also offer further taxonomic and ecological comments on the complex, additional examined specimens and maps of distribution in Africa with real occurrences and modelled distributions. The modelled distribution map (based on climatic data) confirms the disjunction of the African subspecies.