Sis, the ITS region that could provide more diagnostic characters for this species than other regions was more suitable for its authentication (S5 8 Tables), which has also been supported by the study of Li et al. [55]. For Illicium verum, ITS and matK were more suitable for its authentication, and they could easily distinguish this species from others using the diagnostic characters through visual examination of the alignments (S5 8 Tables). This result was different from that of Liu M et al. [54], because we used longer sequences of ITS and matK, which included informative positions for distinguishing this species. Our phylogenetic analyses indicated that both Schisandra and Kadsura were not monophyletic, and some species of Schisandra, such as S. plena A. C. Sm. and S. propinqua, consistently nested in the clade of Kadsura, although the topologies varied slightly among different DNA regions (S1 and S2 Figs). This result has also been found in many other molecular studies of Schisandraceae [40?5], which implied that the genus boundary between Schisandra and Kadsura needs to be re- examined based on both comprehensive morphological and molecular data. Furthermore, the single regions and their combinations tested in this study exhibitedPLOS ONE | DOI:10.1371/journal.pone.0125574 May 4,14 /DNA Barcoding for Schisandraceaepoor resolution for the discrimination of some species for Schisandra and Kadsura (S9 Table). These species always formed paraphyletic groups under the tree-based identification, such as Schisandra order CGP-57148B rubriflora and S. grandiflora, and Kadsura heteroclita and K. longipedunculata (S1 and S2 Figs). There are several possible reasons for gene-tree paraphyly in plants, such as imperfect taxonomy due to cryptic species complexes, incomplete lineage sorting among newly diverged species, and hybridization [111]. The unresolved species are mainly from the section Pleiostema of Schisandra and section Eukadsura of Kadsura based on the classification of Smith [17], and the species from these two groups were suggested to have diverged recently during the late Miocene to Pliocene [45]. These newly diverged species had been initially expected to exhibit paraphyletic gene trees because of incomplete lineage sorting. Schisandra rubriflora and S. grandiflora are morphologically very similar, with overlap in geographical distribution ranges, and they have been incorporated into one species by Lin and Yang [51]. In this study, the individuals of these two species always grouped together on phylogenetic trees, such that the two species could not be distinguished (Fig 3 and S10 Table). SP600125 price Therefore, the species boundary between them was indistinct, indicating the need of comprehensive morphological observations and evaluation of additional molecular markers. Our distancebased, tree-based, and character-based analyses all supported a distinct cluster of S. rubriflora and S. grandiflora from the southern Hengduan Mountains region (Fig 3 and S6, S7, S10 Tables). Therefore, a putative cryptic species within S. rubriflora and S. grandiflora was found here. The Hengduan Mountains region, a key biodiversity hotspot in China, could provide different habitats or ecological niches that might drive the cryptic speciation [112,113]. Cryptic diversity of the species from the Hengduan Mountains region was also documented in other studies [105,113]. Further investigations into these species will be needed in order to confirm the cryptic diversity encountered by.Sis, the ITS region that could provide more diagnostic characters for this species than other regions was more suitable for its authentication (S5 8 Tables), which has also been supported by the study of Li et al. [55]. For Illicium verum, ITS and matK were more suitable for its authentication, and they could easily distinguish this species from others using the diagnostic characters through visual examination of the alignments (S5 8 Tables). This result was different from that of Liu M et al. [54], because we used longer sequences of ITS and matK, which included informative positions for distinguishing this species. Our phylogenetic analyses indicated that both Schisandra and Kadsura were not monophyletic, and some species of Schisandra, such as S. plena A. C. Sm. and S. propinqua, consistently nested in the clade of Kadsura, although the topologies varied slightly among different DNA regions (S1 and S2 Figs). This result has also been found in many other molecular studies of Schisandraceae [40?5], which implied that the genus boundary between Schisandra and Kadsura needs to be re- examined based on both comprehensive morphological and molecular data. Furthermore, the single regions and their combinations tested in this study exhibitedPLOS ONE | DOI:10.1371/journal.pone.0125574 May 4,14 /DNA Barcoding for Schisandraceaepoor resolution for the discrimination of some species for Schisandra and Kadsura (S9 Table). These species always formed paraphyletic groups under the tree-based identification, such as Schisandra rubriflora and S. grandiflora, and Kadsura heteroclita and K. longipedunculata (S1 and S2 Figs). There are several possible reasons for gene-tree paraphyly in plants, such as imperfect taxonomy due to cryptic species complexes, incomplete lineage sorting among newly diverged species, and hybridization [111]. The unresolved species are mainly from the section Pleiostema of Schisandra and section Eukadsura of Kadsura based on the classification of Smith [17], and the species from these two groups were suggested to have diverged recently during the late Miocene to Pliocene [45]. These newly diverged species had been initially expected to exhibit paraphyletic gene trees because of incomplete lineage sorting. Schisandra rubriflora and S. grandiflora are morphologically very similar, with overlap in geographical distribution ranges, and they have been incorporated into one species by Lin and Yang [51]. In this study, the individuals of these two species always grouped together on phylogenetic trees, such that the two species could not be distinguished (Fig 3 and S10 Table). Therefore, the species boundary between them was indistinct, indicating the need of comprehensive morphological observations and evaluation of additional molecular markers. Our distancebased, tree-based, and character-based analyses all supported a distinct cluster of S. rubriflora and S. grandiflora from the southern Hengduan Mountains region (Fig 3 and S6, S7, S10 Tables). Therefore, a putative cryptic species within S. rubriflora and S. grandiflora was found here. The Hengduan Mountains region, a key biodiversity hotspot in China, could provide different habitats or ecological niches that might drive the cryptic speciation [112,113]. Cryptic diversity of the species from the Hengduan Mountains region was also documented in other studies [105,113]. Further investigations into these species will be needed in order to confirm the cryptic diversity encountered by.