Combining complete chloroplast genome sequences with target loci data and morphology to resolve species limits in Triplostegia (Caprifoliaceae)

• Published in: Molecular phylogenetics and evolution 2018-12, Vol.129, p.15-26
• Main Authors: Niu, Yan-Ting, Jabbour, Florian, Barrett, Russell L., Ye, Jian-Fei, Zhang, Zhu-Zhi, Lu, Kai-Qing, Lu, Li-Min, Chen, Zhi-Duan
• Format: Article
• Language: English
• Subjects: Allopatric speciation; Chloroplast genome; Molecular phylogenetics; Species concept; Triplostegia glandulifera; Triplostegia grandiflora
• ISSN: 1055-7903; 1095-9513
• DOI: 10.1016/j.ympev.2018.07.013

[Display omitted] •Neither Triplostegia glandulifera nor T. grandiflora is monophyletic.•Statistical analyses of morphological traits could not distinguish two species.•The integrative approach suggests treating Triplostegia as a monotypic genus.•Triplostegia may host four lineages currently undergoing allopatric speciation.•Analyses of chloroplast genomes provide insights into species delimitation. Species represent the most basic unit of taxonomy. As such, species delimitation represents a crucial issue for biodiversity conservation. Taxonomic practices were revolutionized in the last three decades due to the increasing availability of molecular phylogenetic data. The genus Triplostegia (Caprifoliaceae) traditionally consists of two species, T. glandulifera and T. grandiflora, distinguishable mainly based on quantitative morphological features. In this study, we sequenced nine chloroplast loci (i.e., accD, psbK-psbI, rbcL-accD, rpoB-trnC, rps16-trnQ, trnE-trnT, trnF-ndhJ, trnH-psbA, trnS-trnG) and one nuclear locus (ITS) of 16 individuals of Triplostegia representing the entire distribution range of both species recognized. Furthermore, we also obtained whole chloroplast sequences for 11 of the 16 individuals for which silica gel-dried leaves were available. Our phylogenetic analyses integrating chloroplast genome sequences and multiple loci data revealed that Triplostegia includes four main clades that largely match geography. Neither T. grandiflora nor T. glandulifera was recovered as monophyletic and no diagnosable differences in leaf, flower, and pollen traits were detected between the two species, indicating the need for a revised species circumscription within Triplostegia. Our study highlights the importance of combining data from different sources while defining species limits.