A taxonomic reassessment of lithophyllum (corallinaceae, rhodophyta) based on studies of R. A. Philippi’s original collections

Abstract

Critical studies of the original collections upon which Lithophyllum Philippi (Corallinaceae, Rhodophyta) is based have revealed that only two of the four species included in the initial presentation conform to any modern concept of the genus. Early concepts of Lithophyllum based on characters associated with external morphology have given way to more modern concepts based on anatomical features, and since 1943 at least six different concepts have been employed. Of the four species originally included in the genus, Philippi’s specimens of L. decussatum Philippi are too fragmentary to allow for any firm determination, while lectotype material of L. expansum Philippi is considered conspecific with Mesophyllum lichenoides (Ellis) Lemoine. The lectotype collection ofLithophyllum incrustans Philippi (which also is the generitype specimen of Lithophyllum) and the lectotype specimen of L. lichenoides Philippi conform to some modern concepts of Lithophyllum but not to others. Based on detailed morphologicalanatomical studies of Philippi’s collections, the six modern concepts of Lithophyllum are reassessed in relation to a series of hypotheses concerning thallus ontogeny and hypothallial attributes, but no single concept can be supported unequivocally based on the evidence available currently. Relevant historical data on the genus and on the various species studied also are presented. © 1983 British Phycological Society.