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Phylogeny of Isodon (Schrad. ex Benth.) Spach (Lamiaceae) and Related Genera Inferred from Nuclear Ribosomal ITS, trnL-trnF Region, and rps16 Intron Sequences and Morphology

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Phylogenetic analyses of Isodon and related genera using the nuclear ribosomal internal transcribed spacer (nrITS), cpDNA regions (trnL-trnF region and rps16 intron), and morphological data are presented. The results clarify the relationships among Isodon and its putative related genera and the question of the monophyly of Isodon and its relationship with Siphocranion. Siphocranion is a monophyletic genus and the sister clade to the remaining species; the new subtribe Siphocranioninae of tribe Ocimeae is described to accommodate it. Isodon , as currently circumscribed, is only monophyletic if Skapanthus oreophilus is included in it. Isodon forms a distinct subtribe Isodoninae within tribe Ocimeae and three strongly supported subclades are identified within the genus. In addition, a close relationship between Hanceola and Hyptis is indicated in the combined nrITS + cpDNA data set with Bayesian inference and this is also supported in morphological analyses, but more studies are needed to confirm this relationship. It is evident that subtribe Hanceolinae is polyphyletic as currently defined, so subtribe Hanceolinae is restricted to accommodate Hanceola alone. The relationships between Isodon and other genera within tribe Ocimeae are still unresolved: the newly erected subtribe Isodoninae is a monophyletic group representing a distinct lineage in subtribe Ociminae. The relationships among the species of the largest subclade C of Isodon are still poorly known. Additional studies of this group with additional data and more intensive taxon sampling might help to resolve these issues.
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... The 25 Himalaya-Hengduan Mountains (HHM) global biodiversity hotspot, which 26 accommodates ca. 70% of the species of Isodon, is considered the distribution and 27 biodiversity center of the genus (Yu et al., 2014;Zhong et al., 2010). Isodon is 28 recognized as the only genus in subtribe Isodoninae (Zhong et al., 2010), and it differs 29 from other genera of Ocimeae by its pedunculate and bracteolate cymes, slightly or 30 strongly 2-lipped (3/2) calyces, strongly 2-lipped (4/1) corollas, and free filaments 31 inserted at the base of the corolla tube (Harley et al., 2004;Li, 1988;Paton and 32 Ryding, 1998). ...
... 70% of the species of Isodon, is considered the distribution and 27 biodiversity center of the genus (Yu et al., 2014;Zhong et al., 2010). Isodon is 28 recognized as the only genus in subtribe Isodoninae (Zhong et al., 2010), and it differs 29 from other genera of Ocimeae by its pedunculate and bracteolate cymes, slightly or 30 strongly 2-lipped (3/2) calyces, strongly 2-lipped (4/1) corollas, and free filaments 31 inserted at the base of the corolla tube (Harley et al., 2004;Li, 1988;Paton and 32 Ryding, 1998). Some species of Isodon have long been used as traditional folk 33 medicine in China and Japan, and contemporary phytochemical studies of Isodon 34 species have so far isolated and identified more than 1200 diterpenoids, some of 35 which have important pharmaceutical functions (Liu et al., 2017;Sun et al., 2006). ...
... 36 Several new species of Isodon have been reported from China during the last 37 decade (Chen et al., 2014(Chen et al., , 2016b(Chen et al., , 2017(Chen et al., , 2019Xiang and Liu, 2012). Recently, we of Isodon were carried out based on our previous field observations, specimen 46 examination, and unpublished mericarp data (Chen, 2017 Yu et al., 2014;Zhong et al., 2010). Thus, for phylogenetic analyses, we used two 63 nuclear ribosomal DNA markers: the nuclear ribosomal internal and external transcribed spacers (ITS and ETS). ...
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Isodon brevipedunculatus, a new species from southern China, is described and illustrated. The phylogenetic position of the new species within the genus was analyzed based on two nuclear ribosomal DNA regions and an ingroup sampling of about 80% of Asian species of Isodon. The results show that I. brevipedunculatus is recovered in a clade that consists of species mainly with glandular mericarps and that are distributed in the Sino-Japanese region. Combining molecular and geographical evidence, our study reveals that I. brevipedunculatus is most closely related to I. amethystoides and I. bifidocalyx, but differs from the former in lamina shape, number of flowers per cyme, and peduncle length, and from the latter in lamina indumentum, calyx morphology, and corolla length.
... The result concerning the monophyly of Hyptidinae agrees with previous studies (Zhong et al. 2010;Pastore et al. 2011;Yu et al. 2014;Li et al. 2016). The sister group relationships of Hyptidinae, Isodon and Hanceola, agree with some of the previous phylogenetic studies Pastore et al. 2011;Li et al. 2016), but also disagree with others (Yu et al. 2014;Chen et al. 2016;Paton et al. 2018). ...
... Future samplings with more terminals and more data will be required to ascertain with greater support the position of Hyptidinae within tribe Ocimeae. Subtribe Hanceolinae as recognized by Harley et al. (2004) was shown not to be monophyletic, contrary to the findings of Zhong et al. (2010). Future studies with more terminals in tribe Ocimeae are desired to redefine the taxonomy of the subtribes that compose it. ...
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Hyptidinae, ca. 400 species, is an important component of Neotropical vegetation formations. Members of the subtribe possess flowers arranged in variously modified bracteolate cymes and nutlets with an expanded areole and all share a unique explosive mechanism of pollen release, except for Asterohyptis. In a recent phylogenetic study, the group had its generic delimitations rearranged with the recognition of 19 genera in the subtribe. Although the previous phylogenetic analysis covered almost all the higher taxa in the subtribe, it lacked a broader sampling at the species level. Here we present a new expanded phylogenetic analysis for the subtribe comprising 153 accessions of Hyptidinae sequenced for the nuclear nrITS, nrETS, and waxy regions and the plastid markers trnL-F, trnS-G, trnD-T, and matK. Our results widely support the previous phylogenetic results with some changes in the support and relationship between genera. It also uncovers the need for a new combination of Eriope machrisae in Hypenia and the phylogenetic position of Hyptis sect. Rhytidea, which was demonstrated to be part of Mesosphaerum. The generic delimitation in Hyptidinae is discussed, and we recommend that further studies with more markers are needed to confirm the monophyly of Hyptidendron and Mesosphaerum, as well as to support taxonomic changes on the infrageneric delimita-tion within Hyptis s. s.
... However, the two genera Hanceola and Siphocranion were not included in their analysis. The phylogenetic relationships within Ocimeae were further elucidated based on more comprehensive sampling by Zhong et al. [106], who demonstrated that Siphocranion, Hanceola, and Isodon each formed a distinct lineage within Ocimeae. The subtribes Siphocranioninae and Isodoninae were thus described to accommodate Siphocranion and Isodon, respectively, while subtribe Hanceolinae only includes Hanceola [106]. ...
... The phylogenetic relationships within Ocimeae were further elucidated based on more comprehensive sampling by Zhong et al. [106], who demonstrated that Siphocranion, Hanceola, and Isodon each formed a distinct lineage within Ocimeae. The subtribes Siphocranioninae and Isodoninae were thus described to accommodate Siphocranion and Isodon, respectively, while subtribe Hanceolinae only includes Hanceola [106]. ...
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Background: A robust molecular phylogeny is fundamental for developing a stable classification and providing a solid framework to understand patterns of diversification, historical biogeography, and character evolution. As the sixth largest angiosperm family, Lamiaceae, or the mint family, consitutes a major source of aromatic oil, wood, ornamentals, and culinary and medicinal herbs, making it an exceptionally important group ecologically, ethnobotanically, and floristically. The lack of a reliable phylogenetic framework for this family has thus far hindered broad-scale biogeographic studies and our comprehension of diversification. Although significant progress has been made towards clarifying Lamiaceae relationships during the past three decades, the resolution of a phylogenetic backbone at the tribal level has remained one of the greatest challenges due to limited availability of genetic data. Results: We performed phylogenetic analyses of Lamiaceae to infer relationships at the tribal level using 79 protein-coding plastid genes from 175 accessions representing 170 taxa, 79 genera, and all 12 subfamilies. Both maximum likelihood and Bayesian analyses yielded a more robust phylogenetic hypothesis relative to previous studies and supported the monophyly of all 12 subfamilies, and a classification for 22 tribes, three of which are newly recognized in this study. As a consequence, we propose an updated phylogenetically informed tribal classification for Lamiaceae that is supplemented with a detailed summary of taxonomic history, generic and species diversity, morphology, synapomorphies, and distribution for each subfamily and tribe. Conclusions: Increased taxon sampling conjoined with phylogenetic analyses based on plastome sequences has provided robust support at both deep and shallow nodes and offers new insights into the phylogenetic relationships among tribes and subfamilies of Lamiaceae. This robust phylogenetic backbone of Lamiaceae will serve as a framework for future studies on mint classification, biogeography, character evolution, and diversification.
... This is consistent with the conclusion we proposed. Isodon grandifolius and Isodon nervosus were clustered together, which is also consistent with previous molecular phylogenetic studies [44][45][46][47]. ...
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... ex Benth.) Spach (from subtribe Isodoninae J.S.Zhong, J.Li & H.W.Li, tribe Ocimeae) was selected as outgroup based on broader phylogenetic analyses (Zhong et al. 2010). The sampling included genera of Hyptidinae used in Pastore et al. (2011) and a set of species of Cyanocephalus, including the new species C. glocimarii. ...
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