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Iris sanguinea is conspecific with I. sibirica (Iridaceae) according to morphology and plastid DNA sequence data

ABSTRACT: A taxonomic revision of Iris subser. Sibiricae is provided based on morphological and molecular analyses and the study of protologues and original material. Two to three species have been recognized in this subseries by botanists. To address the question of species delimitations and relationships within this group, we analyzed four non-coding regions of plastid DNA (trnS–trnG, trnL–trnF, rps4–trnSGGA, and psbA–trnH) for samples from 26 localities across the distribution ranges of two currently recognized species, I. sanguinea and I. sibirica. Variance analysis, based on nine characters, revealed no separation between taxa. Moreover, no morphological character could be used to define clear boundaries between taxa. Our results strongly support that I. subser. Sibiricae is monotypic and comprises only I. sibirica, instead of two or three species. Iris sibirica is morphologically variable and one of the most widespread Eurasian species of Iridaceae. Previously accepted taxa, I. sanguinea and I. typhifolia, are synonymised with I. sibirica and also two names, I. orientalis and I. sibirica var. haematophylla, which are typified here, are placed in the synonymy of I. sibirica. Information on the distribution of I. sibirica and the main features used to distinguish between I. sibirica and I. subser. Chrysographes species are provided.

SUBMITTER: Boltenkov E

PROVIDER: S-EPMC7533061 | biostudies-literature | 2020 Jan

REPOSITORIES: biostudies-literature

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Project description:The plastid genome has proven to be an effective tool for examining deep correlations in plant phylogenetics, owing to its highly conserved structure, uniparental inheritance, and limited variation in evolutionary rates. Iridaceae, comprising more than 2,000 species, includes numerous economically significant taxa that are frequently utilized in food industries and medicines and for ornamental and horticulture purposes. Molecular studies on chloroplast DNA have confirmed the position of this family in the order Asparagales with non-asparagoids. The current subfamilial classification of Iridaceae recognizes seven subfamilies-Isophysioideae, Nivenioideae, Iridoideae, Crocoideae, Geosiridaceae, Aristeoideae, and Patersonioideae-which are supported by limited plastid DNA regions. To date, no comparative phylogenomic studies have been conducted on the family Iridaceae. We assembled and annotated (de novo) the plastid genomes of 24 taxa together with seven published species representing all the seven subfamilies of Iridaceae and performed comparative genomics using the Illumina MiSeq platform. The plastomes of the autotrophic Iridaceae represent 79 protein-coding, 30 tRNA, and four rRNA genes, with lengths ranging from 150,062 to 164,622 bp. The phylogenetic analysis of the plastome sequences based on maximum parsimony, maximum likelihood, and Bayesian inference analyses suggested that Watsonia and Gladiolus were closely related, supported by strong support values, which differed considerably from recent phylogenetic studies. In addition, we identified genomic events, such as sequence inversions, deletions, mutations, and pseudogenization, in some species. Furthermore, the largest nucleotide variability was found in the seven plastome regions, which can be used in future phylogenetic studies. Notably, three subfamilies-Crocoideae, Nivenioideae, and Aristeoideae-shared a common ycf2 gene locus deletion. Our study is a preliminary report of a comparative study of the complete plastid genomes of 7/7 subfamilies and 9/10 tribes, elucidating the structural characteristics and shedding light on plastome evolution and phylogenetic relationships within Iridaceae. Additionally, further research is required to update the relative position of Watsonia within the tribal classification of the subfamily Crocoideae.

Project description:BackgroundIris L. s.l. is one of the most diverse and well-known genera in the Asparagales, with approximately 250-300 circumscribed species and significant economic impact. The taxonomy of the genus has suffered dramatic changes in the last century, particularly in the last decades after the application of molecular techniques. As a result several contrasting systematic arrangements are currently available to taxonomists. Many genera that were split from Iris s.str. in the past, on the basis of morphology (e.g., Hermodactylus, Iridodictyum, Juno, Pardanthopsis, and Xiphion, among others), are now a priori re-included in a very widely circumscribed Iris s.l. (incl. Belamcanda). This resulted in a more heterogeneous genus that is more difficult to define on morphological grounds. Testing congruence between taxonomic treatments and the results of recent molecular studies of Iris has never been performed, mostly due to the lack of proper taxonomic context.ResultsWe generated several conventional phylogenies for Iris & outgroups using extensive sampling of taxa (187) and characters (10 plastid loci). We demonstrate that the natural history of Iris, written either as conventional molecular phylogenies or, if viewing in the context of the comparative approach, as a nested most parsimonious hierarchy of patterns, appear to be fully congruent with the narrow taxonomical treatment of the genus, restricted to the rhizomatous "bearded" taxa. The resulting topologies place Belamcanda, Pardanthopsis, and Gattenhofia as sisters to Iris s.str. and genus Siphonostylis as sister to Iris s.l.ConclusionThe present study clearly justifies the splitting of Iris s.l. into at least 23 genera, 18 of which have already been accepted in the past by numerous authorities. These genera are characterized by unique combinations of partly overlapping morphological characters and biogeography. Moreover, nearly the same entities, which we here recognize at a generic rank, were for centuries frequently referred to by horticulturists as "working-name" groups.

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Iris sanguinea is conspecific with I. sibirica (Iridaceae) according to morphology and plastid DNA sequence data

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