High frequency of character transformations is phylogenetically structured within the lichenized fungal family Graphidaceae (Ascomycota: Ostropales)

ABSTRACT

Graphidaceae is a large family of over 2000 predominantly tropical, lichenized fungal species encompassing a remarkable range of morphological and chemical diversity. The majority of species belongs in subfamily Graphidoideae, which also exhibits the greatest amount of variation. Various phenotype characters have traditionally been used for classification at the genus and species levels, but their correlations with phylogenetic clades are poorly known. Using a multilocus approach, we reconstructed a phylogeny for 224 taxa, representing all main genera within subfamily Graphidoideae, and employed ancestral character reconstruction and character transformation analyses to understand the evolution of morphological, anatomical and chemical characters within this group. In addition, we examined the changes of habitat and photobiont types over the phylogeny. For this purpose, we focused on 10 characters, including thallus and ascoma features and chemistry. Since previous studies have shown that results may differ depending on the reconstruction method used, both Maximum-parsimony and Maximum-likelihood approaches were employed and multistate coding of characters was used. We reconstructed the ancestral states for 64 well-supported major clades in the family and found support for the ancestor of Graphidoideae being a tropical species with a trentepohlioid photobiont, apothecioid, solitary ascomata lacking both a columella and lateral paraphyses, and having non-amyloid ascospores. The frequency of transformations of morphological and chemical characters over the phylogeny of Graphidaceae was computed, resulting in a high frequency of reversible transformations for some characters, such as secondary chemistry, whereas other characters, such as photobiont, hymenial persistence or ascoma aggregation, exhibited low frequency of transformations. However, we found that even in the character with the highest number of transformations, secondary chemistry, the shifts were highly structured phylogenetically, suggesting that the evolution of the character, rather than the character state itself, can be used to predict phylogenetic relationships with certain accuracy.