New Approach to the Systematics of the Section Psammiris (Iris, Iridaceae): What Does Chloroplast DNA Sequence Tell Us?

Iris sect. Psammiris comprises rhizomatous perennials distributed in the north temperate zone of Eurasia. The systematics of the section are currently based on morphology, and the phylogenetic relationships within it still remain unclear. In the framework of Iris systematics, we conducted molecular and morphological analyses of the currently recognized I. sect. Psammiris species to elucidate the taxonomic composition and relationships within the section. The phylogenetic reconstructions based on sequence variation of four noncoding chloroplast DNA regions support the monophyly of I. sect. Psammiris, which includes I. tigridia, while I. potaninii var. ionantha belongs to I. sect. Pseudoregelia. The proposed novel classification of I. sect. Psammiris recognizes three series: an autonymic series with I. humilis, I. bloudowii, and I. vorobievii and two unispecific series (I. ser. Potaninia with I. potaninii and I. ser. Tigridiae with I. tigridia). In addition, the taxonomic statuses of I. arenaria, I. ivanovae, I. kamelinii, I. mandshurica, I. pineticola, I. psammocola, and I. schmakovii are clarified herein. We provide a revised taxonomic treatment for I. sect. Psammiris, including notes on the types; updated information on species synonymy, distributions, habitats, and chromosome numbers; and a new identification key to the species. Three lectotypes are designated here.

The species of Oxytropis DC. of section Gloeocephala Bunge (Fabaceae) from Northeast Asia: genetic diversity and relationships based on sequencing of the intergenic spacers of cpDNA and ITS nrDNA.

Phylogenetic relationships within Oxytropis DC. sect. Gloeocephala Bunge from Northeast Asia were studied using plastid intergenic spacers (psbA-trnH + trnL-trnF + trnS-trnG) and ITS nrDNA. Populations of O. anadyrensis Vass., O. borealis DC., O. middendorffii Trautv., O. trautvetteri Meinsh., and O. vasskovskyi Jurtz. were monomorphic or characterised by a low level of chloroplast genetic diversity (h varied from 0.143 to 0.692, and π from 0.0001 to 0.0005). Presumably, the low genetic diversity was a result of the severe bottlenecks during Pleistocene glaciation-interglacial cycles. Twenty chlorotypes were identified; species studied had no shared chlorotypes. Chlorotypes of O. anadyrensis, O. borealis, and O. middendorffii formed two lineages each, while the chlorotypes of O. trautvetteri and O. vasskovskyi formed one separate lineage each in the phylogenetic network. There were specific diagnostic markers of cpDNA in each lineage, excluding O. vasskovskyi. The presence of a species-specific diagnostic marker in O. trautvetteri and specific markers in two lineages of O. anadyrensis support circumscribing these taxa as independent species. Regarding ITS nrDNA polymorphism, five ribotypes were detected. The differences revealed in plastid and nuclear genomes of Oxytropis sect. Gloeocephala confirmed that the Asian sector of Megaberingia was the main centre of diversification of arctic legumes.

Taxonomic Composition of Iris Subser. Chrysographes (Iridaceae) Inferred from Chloroplast DNA and Morphological Analyses.

The species of Iris subser. Chrysographes are herbaceous perennials found mainly in southwestern and central China and also in the Eastern Himalayas. To date, six species have been recognized in this group. In the framework of its taxonomic revision, we have carried out molecular and morphological studies. For this, we have sequenced four chloroplast DNA regions (trnS-trnG, trnL-trnF, rps4-trnSGGA, and psbA-trnH) for 25 samples across the major distribution ranges of the six species. Our phylogenetic analyses evidence that I. subser. Chrysographes is indeed a monophyletic group, which is sister to I. subser. Sibiricae. Within I. subser. Chrysographes, we have recovered four divergent lineages further supported by diagnosable morphological traits and geographical distributions. In this context, our data confirm the recognition of I. clarkei, I. delavayi, and I. wilsonii in their traditional concepts. Furthermore, both molecular and morphological data support the close affinities and similar distribution ranges of I. bulleyana, I. chrysographes, and I. forrestii, which suggests including I. chrysographes and I. forrestii as color forms in I. bulleyana. A revised taxonomic treatment for the group, including the notes on the species distributions and habitats, and also an identification key to the species are provided.

Genetic diversity of Oxytropis section Xerobia (Fabaceae) in one of the centres of speciation.

The genetic diversity and phylogenetic relationships of Oxytropis caespitosa, O. grandiflora, O. eriocarpa, O. mixotriche, O. nitens, O. peschkovae and O. triphylla, section Xerobia subgenus Oxytropis, in one of the main speciation centres of the genus Oxytropis (Baikal Siberia and adjacent territories of Northeastern Mongolia) were studied based on sequence analysis of the psbA-trnH, trnL-trnF and trnS-trnG intergenic spacers of cpDNA, as well as the ITS nrDNA. Most populations are characterized by a high level of chloroplast genetic diversity (h varied from 0.327 to 1.000 and π from 0.0001 to 0.0090) due to the ancient origin for some species and to hybridization and polyploidy for others. 67 haplotypes were identified, of which six were shared. Phylogenetic relationships among species could not be satisfactorily resolved. Only the haplotypes of O. triphylla formed a group with rather high support. Probably, O. caespitosa, O. grandiflora, O. mixotriche and O. nitens constitute a single genetic complex. As regards the ITS nrDNA polymorphism, we detected only two ribotypes (RX1, RX2). Both were found in O. caespitosa, O. eriocarpa, O. mixotriche and O. peschkovae, while RX1 was present in O. nitens and O. triphylla, RX2 in O. grandiflora. The absence of diagnostic species-specific variants for the markers studied, together with the sharing of cpDNA haplotypes and nrDNA ribotypes between species, and the resulting polytomies on the phylogenetic trees, confirm the hypothesis on the hybrid origin of some of them. Obviously, the reproductive barriers within the sect. Xerobia are weak. However, morphological differences between the species of the sect. Xerobia are clearly pronounced, even when they grow in sympatry.

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

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-trnS GGA , 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.

Plastid DNA variation in highly fragmented populations of Microbiota decussata Kom. (Cupressaceae), an endemic to Sikhote Alin Mountains.

Microbiota decussata Kom. (Cupressaceae) is a subalpine species endemic to the Sikhote Alin Mountains with populations scattered throughout the range. We used sequence data for four noncoding regions of chloroplast DNA to characterize the genetic diversity in populations sampled from different parts of M. decussata natural range. No variation was observed in the trnT-trnF region, whereas the trnH-psbA, trnS-trnfM, and trnS-trnG regions showed polymorphisms. At the species level, we found a low nucleotide diversity (pi = 0.0009) and high haplotype diversity (h = 0.981) as well as high differentiation (Phi(ST) = 0.420). N(ST) and G(ST) values suggested the existence of a phylogeographic structure in M. decussata. The observed patterns of diversity could be explained in part by ecological features of the species and its long-term persistence throughout the range with population expansion, successive fragmentation and isolation.