Graphis and Allographa (lichenized Ascomycota: Graphidaceae) in Sri Lanka, with six new species and a biogeographical comparison investigating a potential signature of the 'biotic ferry' species interchange

Abstract

We provide an updated survey for Sri Lanka of species of Graphis sensu Staiger, recently divided into Graphis s. str. and Allographa, including brief descriptions and a key to all 124 species currently known. Six new species are described: Allographa bambusicola Weerakoon, Lücking & Aptroot, a bambusicolous Allographa with entire labia, a laterally carbonized excipulum, 80-100 × 15-17 μm large, muriform ascospores and a rather thick, irregularly verrucose lateral thalline margin of the lirellae; A. weerasooriyana Weerakoon, Arachchige & Lücking, a corticolous Allographa resembling A. rustica Kremp. in overall anatomy and chemistry, but with a verrucose thalline margin of the lirellae and labia not distinctly raised above the thalline margin; Graphis flosculifera Weerakoon, Lücking & Aptroot, a corticolous Graphis resembling G. insulana but differing in the unique disposition of the lirellae and the slightly more elongate ascospores; G. rajapakshana Weerakoon, Lücking & Aptroot, a corticolous Graphis resembling G. desquamescens, including in ascospore size, but with lirellae with a distinct lateral thalline margin; G. rimosothallina Weerakoon, Lücking & Aptroot, a corticolous Graphis with a thick, uneven, rimose thallus and Fissurina-like lirellae, a completely carbonized excipulum and transversely 7-septate ascospores, 32-37 × 8-10 μm; and G. thunsinhalayensis Weerakoon, Arachchige & Lücking, a corticolous Graphis resembling G. subalbostriata but with smaller ascospores and lacking white lines between the striae of the labia. We also validate the name G. verrucoserpens Lücking. A total of 106 species are reported here for the first time from Sri Lanka. A biogeographical comparison with two other well-sampled countries (Costa Rica and Thailand) revealed a significantly higher similarity in species composition with Costa Rica than between Thailand and Costa Rica, suggesting a potential signature of the 'biotic ferry' hypothesis, that is the migration of lineages from Gondwana (partly corresponding to the modern Neotropics) via the north-eastwards drifting Indian subcontinent and subsequent interchange with Laurasia (partly corresponding to the modern eastern Paleotropics). However, the evolutionary timeline of the clades involved does not support this hypothesis and suggests an alternative explanation of geologically more recent mid-to long-distance dispersal.