Molecular Species Delimitation in the Racomitrium canescens Complex (Grimmiaceae) and Implications for DNA Barcoding of Species Complexes in Mosses

Abstract

In bryophytes a morphological species concept is still most commonly employed, but delimitation of closely related species based on morphological characters is often difficult. Here we test morphological species circumscriptions in a species complex of the moss genus Racomitrium, the R. canescens complex, based on variable DNA sequence markers from the plastid (rps4-trnT-trnL region) and nuclear (nrITS) genomes. The extensive morphological variability within the complex has led to different opinions about the number of species and intraspecific taxa to be distinguished. Molecular phylogenetic reconstructions allowed to clearly distinguish all eight currently recognised species of the complex plus a ninth species that was inferred to belong to the complex in earlier molecular analyses. The taxonomic significance of intraspecific sequence variation is discussed. The present molecular data do not support the division of the R. canescens complex into two groups of species (subsections or sections). Most morphological characters, albeit being in part difficult to apply, are reliable for species identification in the R. canescens complex. However, misidentification of collections that were morphologically intermediate between species questioned the suitability of leaf shape as diagnostic character. Four partitions of the molecular markers (rps4-trnT, trnT-trnL, ITS1, ITS2) that could potentially be used for molecular species identification (DNA barcoding) performed almost equally well concerning amplification and sequencing success. Of these, ITS1 provided the highest species discrimination capacity and should be considered as a DNA barcoding marker for mosses, especially in complexes of closely related species. Molecular species identification should be complemented by redefining morphological characters, to develop a set of easy-to-use molecular and non-molecular identification tools for improving biodiversity assessments and ecological research including mosses.

Ecological niche comparison and molecular phylogeny segregate the invasive moss species Campylopus introflexus (Leucobryaceae, Bryophyta) from its closest relatives

“…With the exception of the C. catarractilis specimen, all analyzed specimens originally identified as other Campylopus species could be assigned to one of the three species. Similar percentages of misidentified specimens in Campylopus (15%, present study) and the Racomitrium canescens species complex (20%; Stech et al., ) indicate that a percentage of 15%−20% may be expected when analyzing morphologically identified specimens of closely related bryophyte species in an integrative approach.…”

Species delimitations in theDicranum acutifoliumcomplex (Dicranaceae, Bryophyta) using molecular markers

“…Sukkharak et al, 2011;Carter, 2012;Medina et al, 2012;Stech et al, 2013; the present study illustrates the importance of molecular data for clarifying species circumscriptions, resolving taxonomical issues and for the re-evaluation of morphological characters in bryophytes and Dicranum in particular. …”

How to fail at species delimitation

“…Some researchers interpret phenotypical variation in the context of delimitations from genetic data (e.g. Setiadi et al 2011;Esselstyn et al 2012;Stech et al 2013) as a way to buttress the results of delimitation analysis. In some systems, morphological differences serve as the basis for taxonomic hypotheses that are validated using genetic data (e.g.…”