Morphological disparity in Cladoniaceae: The foliose genus Heterodea evolved from fruticose Cladia species (Lecanorales, lichenized Ascomycota)

Phylogenetic relationships of the genera Cladia and Heterodea were reconstructed using a combined dataset of nuclear ITS, nuclear LSU and mitochondrial SSU rDNA sequences. Based on different analyses (Bayesian approach, maximum parsimony, maximum likelihood), the ingroup (Cladia + Heterodea) is strongly supported as monophyletic. Pilophorus strumaticus has a well supported sister-group relationship to the ingroup and together they form a sister group with a well-supported clade, which includes Metus conglomeratus and Pycnothelia papillaria. The Shimodaira-Hasegawa test and the ELW test significantly rejected monophyly of Cladia excluding Heterodea. Within Cladia three main clades can be distinguished which share morphological and chemical characters. The position of the foliose genus Heterodea within the fruticose Cladia is supported by anatomical and chemical characters. The species of clade II that includes two Cladia species and Heterodea share a similar type of upper cortex and two-layered medulla with an inner or lower medulla consisting of dark pigmented, thick-walled hyphae. Our phylogenetic estimate and the anatomical studies indicate that the foliose thallus of Heterodea originated from pseudopodetia of Cladia. It is discussed that the species currently classified in Cladia and Heterodea need to be placed in the same genus.