Resolving the phylogenetic relationship between Parmotrema crinitum and Parmotrema perlatum populations

Abstract

The widespread species Parmotrema crinitum (Ach.) M. Choisy and Parmotrema perlatum (Huds.) M. Choisy are mainly distinguished by their reproductive strategies. While P. crinitum propagates by isidia, P. perlatum produces soredia. In this study, we aim to evaluate the phylogenetic relationship between both species and to critically examine their species boundaries. To this purpose, 46 samples belonging to P. crinitum and P. perlatum were used in our analysis, including 22 for which we studied the morphology and chemistry, before extracting their DNA. We used 35 sequences of the internal transcribed spacer region of nuclear ribosomal DNA (ITS) of Parmotrema perlatum from Europe and Africa (20 of which were newly generated), and 11 of Parmotrema crinitum from Europe, North America and North Africa (two newly generated). Additionally, 28 sequences of several species from Parmotrema were included in the ITS dataset. The ITS data matrix was analyzed using different approaches, such as traditional phylogeny (maximum likelihood and Bayesian analyses), genetic distances, automatic barcode gap discovery (ABGD) and the coalescent-based method poisson tree processes (PTP), in order to test congruence among results. Our results indicate that all samples referred to P. crinitum and P. perlatum nested in a well-supported monophyletic clade, but phylogenetic relationships among them remain unresolved. Delimitations inferred from PTP, ABGD and genetic distance analyses were comparable and suggested that P. crinitum and P. perlatum belong to the same lineage. Interestingly, two samples of P. perlatum separate in a different monophyletic clade, which is supported as a different lineage by all the analyses.