Abstract
Phylogenetic relationships between Usnea nipparensis and U. sinensis, caperatic acid containing Usnea species, were examined based on ITS rDNA, and the phylogenetic position of U. nipparensis was inferred based on multi-locus gene analysis using ITS rDNA, nuLSU, and MCM7. Although U. nipparensis and U. sinensis have a sorediate and an esorediate shrubby thallus, respectively, and in general look quite different, other detailed morphological and chemical features are similar. Analysis of the ITS rDNA sequences suggests their close relationship, but also confirms the independence of both species, and that they most likely form a ‘species pair’ based on morphological, chemical and molecular phylogenetic data. Phylogenetic trees based on both multi-locus gene and ITS rDNA alone strongly support that U. nipparensis and U. angulata belong to the same clade.
Highlights
IntroductionThe genus Usnea (Parmeliaceae) is known as one of the most difficult genera to identify due to the high morphological variability within species (Clerc 1998), while recent studies with molecular data using correctly identified specimens made big progress to understand the species concept and phylogeny of this difficult group (Ohmura 2002, 2008; Ohmura & Kanda 2004; Wirtz et al 2008; Kelly et al 2011; Lumbsch & Wirtz 2011; Saag et al 2011; Truong et al 2013; Truong & Clerc 2016; Clerc & Otte 2018; Gerlach et al 2017, 2019; Ohmura & Clerc 2019).Among c. 350 species of Usnea worldwide (Lücking et al 2017), clarifying ‘species pairs’ would be an interesting matter to discuss, considering their distribution, dispersal strategy and evolution
The main aim of this study is to examine the relationship between U. nipparensis Asahina and U. sinensis Motyka based on nuclear ITS rDNA
The topology of the molecular phylogenetic tree based on the multi-locus dataset of ITS rDNA, nu LSU and MCM7 obtained in this study (Fig. 1) is not in conflict with the one shown in Truong & Clerc (2016)
Summary
The genus Usnea (Parmeliaceae) is known as one of the most difficult genera to identify due to the high morphological variability within species (Clerc 1998), while recent studies with molecular data using correctly identified specimens made big progress to understand the species concept and phylogeny of this difficult group (Ohmura 2002, 2008; Ohmura & Kanda 2004; Wirtz et al 2008; Kelly et al 2011; Lumbsch & Wirtz 2011; Saag et al 2011; Truong et al 2013; Truong & Clerc 2016; Clerc & Otte 2018; Gerlach et al 2017, 2019; Ohmura & Clerc 2019).Among c. 350 species of Usnea worldwide (Lücking et al 2017), clarifying ‘species pairs’ would be an interesting matter to discuss, considering their distribution, dispersal strategy and evolution. Several other species pairs were proposed in the genus Usnea by Walker (1985) (i.e., U. aurantiacoatra – U. antarctica; U. perpusilla – U. sphacelata; U. trachycarpa – U. subantarctica) and by Shen et al (2012) (i.e., U. orientalis Motyka – U. pygmoidea). Molecular phylogenetic analyses using single- or multi-locus genetic data have not supported most of these relationships and they considered that they are conspecific (Articus et al 2002; Seymour et al 2007; Saag et al 2011; Wirtz et al 2012; Mark et al 2016) except U. aurantiacoatra – U. antarctica that were revealed as independent species by using microsatellite analysis (Lagostina et al 2018) and RADseq (Grewe et al 2018). Since the relationship for U. orientalis – U. pygmoidea was not tested by phylogenetic analysis in Shen et al (2012), these ITS rDNA sequences were incorporated into the analysis in this present study
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