DNA Barcoding Study of Representative Thymus Species in Bulgaria.

Ina Aneva,Stiliana Simeonova,Denitsa Kancheva,Georgi Bonchev,Irina Boycheva,Petar Zhelev

doi:10.3390/plants11030270

Abstract

We present a study on the taxonomy of eleven Thymus species, belonging to two sections and occurring naturally in Bulgaria. Four DNA barcoding markers—matK, rbcL, trnH-psbA and ITS—were applied to discriminate the species and to reveal their phylogenetic relationships. The results showed that rbcL has the lowest discriminating power regarding the studied species, while the other markers yielded results fitting better to the existing taxonomic schemes based on morphological traits. However, even in the case of better performing markers, the results were not straightforward—morphologically distinct species belonging to different sections were grouped together, and closely related species appeared genetically distinct. The results are typical for taxonomically complex groups, such as the genus Thymus, characterized in Bulgaria with great diversity, high percentage of endemism and still requiring a full and comprehensive taxonomic study. The results are discussed in the light of unresolved taxonomic problems and application of DNA barcoding methods.

Highlights

IntroductionResolving the problems arising when studying taxonomically complex groups (TCGs) requires a combined approach consisting of classical (morphological, anatomical, cytological) and modern (molecular) methods
Resolving the problems arising when studying taxonomically complex groups (TCGs) requires a combined approach consisting of classical and modern methods
In the genus Thymus, primers used for different barcodes showed 100% amplification and sequencing efficiency among the 15 tested samples

Summary

Introduction

Resolving the problems arising when studying taxonomically complex groups (TCGs) requires a combined approach consisting of classical (morphological, anatomical, cytological) and modern (molecular) methods. The complex systematics of the genus Thymus has been outlined in many studies attempting to resolve the puzzle or a part of it [2,3,4,5,6]. Most of the challenges still stand today, and in many cases, the application of modern molecular methods did not provide a clear solution to taxonomic problems [1,7]. The number of species of the genus Thymus in Bulgaria is 21 [8,9,10,11], and the species list slightly differs from the one in the Euro+Med PlantBase (https://ww2 .bgbm.org/EuroPlusMed/; last accessed 23 December 2021).

Objectives

Methods

Results

Conclusion