Phylogeny and secondary metabolites of lichen-forming fungi in trypetheliaceae in Thailand

Abstract

Trypetheliaceae is a family of tropical crustose lichenized fungi belonging to the order Trypetheliales (Dothideomycetes). Nine hundred and sixty-five lichen specimens were collected from various localities in Thailand at 28 study sites in 24 provinces, in which species of this family were found in different habitats. Mycobionts were isolated by the ascopore discharge technique and 313 isolates were successfully isolated and cultivated in axenic cultures. In this study the following eight genera have been found in Thailand: Astrothelium, Bathelium, Campylothelium, Laurera, Marcelaria, Polymeridium, Pseudopyrenula and Trypethelium. Phylogenetic analysis of the genera Astrothelium, Laurera, Marcelaria and Trypethelium revealed evolutionary relationships among these lichenized fungi and supported previously unrecognized species, including five new species in the genus Astrothelium. The genus Laurera was found to be closely related to Marcelaria and the two currently accepted species M. benguelensis and M. cumingii were found to be conspecific. Morphological characters and phylogenetic relationships were incongruent within Trypethelium and within the T. eluteriae group a remarkable diversity was found with three species occurring in Thailand, viz. T. eluteriae, T. platystomum and T. subeluteriae. In contrast to morphological characters, secondary metabolites showed better correlation with phylogenetic relationships. Molecular phylogenetic studies of the family Trypetheliaceae based on ITS, nuLSU, mtSSU rDNA and RPB1 showed various genetic relationships, which demonstrated conflict in phylogeny, morphology and chemistry. Most genera in this family were found to be polyphyletic, including Astrothelium, Bathelium, Laurera, Polymeridium and Trypethelium, whereas Campylothelium, Marcelaria and Pseudopyrenula formed monophyletic groups. Although, most morphological characters did not correlate with molecular data, the metabolites produced in mycobiont cultures showed correlation with the phylogeny. Thus, the family requires a taxonomic revision based on molecular phylogeny in combination with the mycobiont substances. In this study, 62 species were recorded of Trypetheliaceae in Thailand, including 18 new records and 5 new species. According to the chemical study, secondary metabolites produced from mycobiont cultures are polar compounds. Crude extracts from eleven species A. neglectum, L. varia, M. cumingii, T. andamanicum, T. eluteriae, T. platystomum, T. subeluteriae, T. ubianense, Trypethelium sp.2, Trypethelium sp.7 and Trypethelium sp.8 showed effective inhibition of Staphylococcus aureus and Candida albicans and reacted to free radical DPPH, while all extracts from these lichens were ineffective against Escherichia coli.