Species Circumscription Research Articles

Updated Taxonomy of Iris scariosa (Iridaceae) Inferred from Morphological and Chloroplast DNA Sequence Data with Remarks on Classification of Iris subg. Iris.

Iris scariosa is a rhizomatous perennial whose taxonomy and distribution range still remain unclear. The results of our examination of literature, specimens, and wild plants have shown that I. glaucescens, described from Kazakhstan, and I. timofejewii, considered to be endemic to the Republic of Dagestan, Russia, are very closely related to I. scariosa. We have carried out molecular phylogenetic analyses for the first time to clarify the taxonomy of I. scariosa. For this, we sequenced six chloroplast DNA regions of an extended sampling that comprised the accepted species I. glaucescens and I. timofejewii, which has revealed their strong affinity to the accession of I. scariosa from the vicinity of Astrakhan, Russia. A thorough revision of the morphological characters has confirmed the lack of evident differences between I. scariosa and I. timofejewii. Thus, the analyses support a broad species circumscription of I. scariosa. We here reduce I. timofejewii, as well as I. curvifolia, considered to be endemic to Xinjiang, western China, to synonymy of I. scariosa. Color illustrations, updated nomenclature, and data on distribution of I. scariosa are provided. A lectotype for I. astrachanica and a neotype for I. timofejewii are designated here. Also, the phylogenetic relationships within I. subg. Iris are outlined, and an updated classification of the subgenus is proposed. We have recovered six major lineages within four major clades which we recognize as sections. Here, we propose two new nomenclatural combinations, a revised taxonomic treatment, and a new identification key to I. subg. Iris.

Taxonomic revision of the genus Punjuba (Leguminosae, Caesalpinioideae)

Punjuba is a Neotropical genus of the mimosoid clade (Leguminosae). The genus was recently restablished and is recognized by presenting shrubs and trees, with lax racemes or spiciform racemes, leaves with 1–3 pairs of pinnae and 2–7 pairs of leaflets in each pinna, thin and lateraly compressed legumes, curved to spiral, and seeds lacking pleurogram. Recent advances on legumes systematics have been producing great challenges on the circumscription of genera, especially on the mimosoid clade. Molecular phylogenetic studies confirm that Punjuba is monophyletic, and a revision of the genus and species circumscriptions are needed. Here we present a taxonomic revision of Punjuba, providing an identification key for all species currently recognized in the genus, morphological descriptions, and distribution maps. We recognize six species in the genus: P. callejasii, P. centiflora, P. killipii, P. lehmannii, P. racemiflora and P. foreroana, being the last one described here as a new species. Abarema josephi is proposed as a new synonym of P. lehmannii. Morphological characters including the inflorescence, indumentum, leaves and leaflets, besides quantitative characters, were applied as diagnostic to recognize the species.

An integrative taxonomy of Asian Caryodaphnopsis (Lauraceae) based on morphology and phylogenomics

AbstractCaryodaphnopsis is a small genus of the Lauraceae family with disjunct distribution in tropical Asia and tropical America. Taxa from each region form a well­supported monophyletic clade. However, the species circumscription in Asian Caryodaphnopsis remains ambiguous due to few and generally unstable morphological characters used for classification. To address this, we conducted an integrative taxonomy of the Asian clade. We investigated 13 populations, sampled 57 accessions covering the entire taxonomic diversity, geographic range, and morphological variation in Asia, and reconstructed a new phylogeny using single‐nucleotide polymorphisms. We obtained a well‐resolved phylogeny of the Asian Caryodaphnopsis. The first diverged clade consists of three species endemic to lowland forests. The second (largest) clade (eight species in total) mainly occurs in limestone mountain forests and has a double‐layered lower leaf epidermis morphology of type 2 (less complete roomy with closed “roof”) and type 3 (complete roomy with closed “roof”). Based on the diagnostic morphological characters, distinct distributional ranges, and monophyly of each clade, we recognize 12 species in the Asian Caryodaphnopsis, including three new species: C. cangyuanensis sp. nov., C. hekouensis sp. nov., and C. rubrinervis sp. nov. We also reinstate C. latifolia, and re‐circumscribe the widespread C. tonkinensis and other species based on fruit and inflorescence morphology and molecular evidence.

Toward a Revision of the Genus Orthosia (Apocynaceae: Asclepiadoideae: Asclepiadeae)

This paper summarizes the present knowledge of the genus Orthosia Decne., based on the study of herbarium material, type specimens, digital images, field observations, and Sanger sequencing of 101 accessions for six chloroplast markers. The results of these analyses encourage a rather narrow species circumscription in most cases. A total of 55 species are recognized, nine of which are new to science. Additionally, incomplete material from some remote areas points to the existence of a handful of yet undescribed species. For some species, morphological and molecular results are incongruent, also indicating the need for future studies. All accepted species are described and illustrated, and their distributions are provided. Nine species and two subspecies are newly described, 13 new combinations and two new synonyms are proposed, and 12 names are lectotypified and one is neotypified.

Taxonomic Studies on Indian Guttiferae I. the Genus <I>Calophyllum</I> L

This revision of the genus CalophyllumL. is precursory to the treatment of the family of Guttiferae as occurring in India. No particular attention was paid of late years to this important timber plant in India. It was, therefore, thought necessary to undertake taxonomic their studies on the genus.Nine species occur in India, of which three are restricted to the Andaman and Nicobar Islands. The rest occur in Southern and Eastern India. These are described in detail and their synonymy, distribution, uses, vernacular names, etc. are ascertained.The nomenclature of plants have been adjusted to the latest findings in botanical literature, and aims to be completely in accordance with the 1956 edition of the International Code of Botanical Nomenclature. For one species of Calophyllum, viz., C. apetalum Willd. (Syn. C. wighfianum Wall, ex Pl. et Tr.), Wallich 4847 (in Herb. Calc.) is selected as the neotype of the species. This is done in accordance with the provisions of Article 7 of 1956 edition of the Code.The present treatment of the genus differs in some respects regarding the circumscription of species, from that of T. Anderson (1874) in the Flora of British India. T. Anderson has united C. amoenum Wall, with C. retusum Wall., and C. elatum Bedd. with C. tomentosum Wight. However, a careful study leads me to conclude that these species should be kept separate and of these only C. amoenum Wall., and C. elatum Bedd. occur in India. The details are discussed in this paper.

Plastome structure, phylogeny and evolution of plastid genes in Reevesia (Helicteroideae, Malvaceae).

Reevesia is an eastern Asian-eastern North American disjunction genus in the family Malvaceae s.l. and comprises approximately 25 species. The relationships within the genus are not well understood. Here, 15 plastomes representing 12 Reevesia species were compared, with the aim of better understanding the species circumscription and phylogenetic relationships within the genus and among genera in the family Malvaceae s.l. The 11 newly sequenced plastomes range between 161,532 and 161, 945bp in length. The genomes contain 114 unique genes, 18 of which are duplicated in the inverted repeats (IRs). Gene content of these plastomes is nearly identical. All the protein-coding genes are under purifying selection in the Reevesia plastomes compared. The top ten hypervariable regions, SSRs, and the long repeats identified are potential molecular markers for future population genetic and phylogenetic studies. Phylogenetic analysis based on the whole plastomes confirmed the monophyly of Reevesia and a close relationship with Durio (traditional Bombacaceae) in subfamily Helicteroideae, but not with the morphologically similar genera Pterospermum and Sterculia (both of traditional Sterculiaceae). Phylogenetic relationships within Reevesia suggested that two species, R. pubescens and R. thyrsoidea, as newly defined, are not monophyletic. Six taxa, R. membranacea, R. xuefengensis, R. botingensis, R. lofouensis, R. longipetiolata and R. pycnantha, are suggested to be recognized.

Distribution and taxonomy of two closely related Nychiodes species in southern Italy (Lepidoptera, Geometridae, Ennominae)

We investigated the distribution and species circumscription of Nychiodes obscurariaVillers (1789) and Nychiodes ragusaria Millière (1884). The morphology of male and female genitalia of Calabrian populations (southern Italy) revealed them to belong to N. ragusaria while specimens from Basilicata, Molise and the rest of Italy turned out to be N. obscuraria. Although the DNA barcodes showed a divergence of 1.55% between typical N. obscuraria and N. ragusaria, 9 out of 28 Calabrian specimens of N. ragusaria shared the N. obscuraria haplotype, and sometimes both haplotypes were found at the same site. Genetic introgression appears as the most probable scenario to explain the observed pattern. A correct identification for the investigated species pair should be based on morphology instead of DNA barcode analysis because of the observed mitonuclear discordance at mountain sites. Further studies are needed to clarify the occurrence of this discordance at high elevations only.

Holocarpic oomycete parasites of red algae are not Olpidiopsis, but neither are they all Pontisma or Sirolpidium (Oomycota)

Oomycetes are ubiquitous heterotrophs of considerable economic and ecological importance. Lately their diversity in marine environments has been shown to be greatly underappreciated and many lineages of intracellular holocarpic parasites, infecting micro- and macro-algae, remain to be fully described taxonomically. Among them, pathogens of marine red algae have been studied extensively as they infect important seaweed crops. Throughout the 20th century, most intracellular, holocarpic biotrophic oomycetes that infect red algae have been assigned to the genus Olpidiopsis Cornu. However, 18S rRNA sequencing of Olpidiopsis saprolegniae, the species considered the generitype for Olpidiopsis, suggests that this genus is not closely related to the marine pathogens and that the latter requires a nomenclatural update. Here, we compile and reanalyze all recently published 18S rRNA sequence data for marine holocarpic oomycetes, with a particular focus on holocarpic pathogens of red algae. Their taxonomy has been revised twice over the past four years, with suggestions to transfer them first into the genus Pontisma and then Sirolpidium, and into a monogeneric order, Pontismatales. We show however, that previously published topologies and the proposed taxa Pontisma, Sirolpidium, and Pontismatales are unsupported. We highlight that name changes that are unfounded and premature create confusion in interested parties, especially concerning pathogens of marine red algae that infect important seaweed crops. We thus propose that the names of these holocarpic biotrophic parasites of red algae are retained temporarily, until a supported topology is produced with more genetic markers to enable the circumscription of species and higher-level taxa.

A taxonomic revision of Neotropical Connarus (Connaraceae)

AbstractThe pantropical genus Connarus is the largest within Connaraceae and comprises ca. 80 species, most of which occur in the Neotropics. The genus is potentially economically important as several taxa produce metabolites of medicinal interest. Morphologically, Connarus differs from other members of the family mainly by the punctate perianth, the single carpel and follicular and relatively broader fruits than in the other genera. In the decades after the publication of the Flora Neotropica monograph of Connaraceae, new botanical collections have become available, especially in American herbaria, allowing identification of overlooked characters and, hence, redefinition of species circumscriptions. In addition, a significant number of typifications were outdated and taxonomic novelties have recently been proposed – all elements that justify a revisional work. After intensive examination of herbarium specimens and field expeditions, the present study recognizes 57 species, 2 varieties and 2 subspecies of Connarus in the Neotropics; about 100 specific names were evaluated, 39 of which are here considered heterotypic synonyms, 11 of them are new synonyms. The distribution of Neotropical Connarus ranges from south Mexico to south Brazil and, although most species occur in dense wet forests, especially in the Amazonia and Atlantic Forest, some are dispersed in savannas from Brazil, Colombia and Venezuela, in Brazilian coastal vegetations or in montane formations; wide distributions are commonly seen in wet forests from Central America to northern South America, while restricted occurrences or endemism are mainly observed in the Atlantic Forest, Peru and Venezuela. Complete morphological descriptions of the species of Neotropical Connarus are provided here, as well as illustrative images, identification keys, and detailed discussions of their taxonomy, nomenclature, distribution and habitat.

Dicranum shennongjiaense W.Z.Huang & R.L.Zhu (Dicranaceae, Bryophyta), a new species from Central China supported by morphological and molecular evidence

ABSTRACT Introduction Dicranum Hedw. is one of the most taxonomically challenging genera of mosses, having 93 accepted species worldwide. Although recent integrative taxonomic revisions have clarified the delimitation of most species within this genus, the circumscriptions of some Dicranum species remain unsolved. During our recent survey of Dicranum in China, an intriguing species with an unknown combination of morphological traits was discovered in the Shennongjia National Nature Reserve, Central China. We carried out a study to provide morphological and phylogenetic evidence with which to determine the taxonomic status of this Chinese species. Methods The phylogenetic evidence was obtained through the combined analysis of five loci (rps4–trnT, trnL–trnF, trnH–psbA, rps19–rpl2 and rpoB) and one nuclear region (nrITS1–5.8S–ITS2). Morphological characteristics were investigated by microscopic examination of specimens. Key results and conclusions A new moss species, Dicranum shennongjiaense W.Z.Huang & R.L.Zhu, is described and illustrated based on molecular and morphological evidence. This new species is characterised by its falcate leaves, rectangular and elongated laminal cells with strongly protruding upper angles on the dorsal side in the upper leaf portion, irregularly bistratose laminal cells above the midleaf, one layer of guide cells in the costa, and sharp serrations on the dorsal side of the costa in the upper leaf portion. Additionally, D. baicalense Tubanova, previously known only from Russia, is newly reported for China. A key for identification of the Chinese species of Dicranum sect. Dicranum is provided.

Integrative approaches to a revision of the liverwort in genus Aneura (Aneuraceae, Marchantiophyta) from Thailand.

The genus Aneura Dumort. is a simple thalloid liverwort with cosmopolitan distributions. Species circumscription is problematic in this genus due to a limited number of morphological traits. Two species are currently reported from Thailand, including A. maxima and A. pinguis. At the global scale, A. pinguis is considered a cryptic species, as the species contains several distinct genetic groups without clear morphological differentiation. At the same time, the identity of A. maxima remains unclear. In this work, we examined the level of diversity of Aneura species found in Thailand using both morphological and molecular data. We measured the morphological traits and generated the molecular data (four markers: trnL-F, trnH-psbA, rbcL, and ITS2) from the Thai specimens. The concatenated dataset was then used to reconstruct phylogeny. Species delimitation with GMYC, bPTP, ASAP, and ABGD methods was performed to estimate the number of putative species within the genus. The samples of A. pinguis formed several clades, while A. maxima sequences from Poland were grouped in their clade and nested within another A. pinguis clade. We could not recover a sample of A. maxima from Thailand, even from the reported locality. Two putative species were detected among Thai Aneura samples. However, no morphological trait could distinguish the specimens from the two observed genetic groups. The previously observed paraphyletic nature of A. pinguis globally was also found among Thai samples, including several putative species. However, we could not confirm the identity of A. maxima from Thai specimens. The previous report could result from misidentification and problematic species circumscription within Aneura. The results highlighted the need to include multiple lines of evidence for the future taxonomic investigation of the group.

A New Species and a New Synonym in Senecio (Compositae) from Madagascar

We describe and illustrate the new species Senecio basipectinatus J. Calvo & Callm. (Compositae) endemic from the Befotaka-Midongy du Sud Protected Area in southeastern Madagascar. The new species is compared with the morphologically most similar taxon S. vaingaindrani Scott Elliot. The taxonomic circumscription of the latter species is further revised and its variety concolor Humbert is newly synonymized.

Phylogeny and Biogeography of Morus (Moraceae)

The mulberry genus, Morus L. (Moraceae), has long been taxonomically difficult, and its species circumscription has only been defined recently. This genus comprises ca. 16 species distributed across Asia and the Americas, yet its biogeographic history remains poorly understood. In this study, we reconstructed the phylogeny and explored the biogeographic history of Morus using a combination of newly generated and previously published Hyb-Seq data. Our nuclear phylogeny recovered three well-supported geographic clades of Morus and showed that M. notabilis (China) is sister to the American clade plus the Asian clade. Multiple reticulation events among species of Morus and extensive incomplete lineage sorting (ILS) likely explain the difficulties in inferring phylogenetic relationships within the genus. Divergence time estimation indicated that Morus originated at the Eocene–Oligocene boundary, and current lineages started to diverge during the early Miocene, there is ambiguity surrounding the ancestral area with the two most likely regions being Sino-Himalaya or the Americas. Biogeographic inference and the fossil record suggest that Morus might have experienced extensive local extinction events during the Tertiary. Morus has expanded its distributional range through two dispersals from the Sino-Himalayan and Sino-Japanese regions to Southeast Asia. In summary, our new phylogenetic scheme and the biogeographic history presented here provide an essential foundation for understanding species relationships and the evolutionary history of Morus.

Target capture sequencing for phylogenomic and population studies in the Southeast Asian genusPalaquium(Sapotaceae)

AbstractThe first phylogenomic study using a custom target capture bait panel within the Isonandreae tribe in Sapotaceae is presented. The combination of taxon-specific and universal loci from the Angiosperms353 probe set achieved high species resolution within the genus Palaquium and provides the first phylogenomic insights into Malesian representatives of Sapotaceae, where relationships between taxa often remain poorly understood. The results highlight that generic and some species circumscriptions require further investigation and possible revision: Aulandra longifolia is found to be nested in Palaquium, and P. rostratum within P. microphyllum. Population structure analysis produced limited resolution between and within species, but the bait set was able to recover parameters that are potentially useful in population genomic studies.

Ensifer canadensis sp. nov. strain T173T isolated from Melilotus albus (sweet clover) in Canada possesses recombinant plasmid pT173b harbouring symbiosis and type IV secretion system genes apparently acquired from Ensifer medicae.

A bacterial strain, designated T173T, was previously isolated from a root-nodule of a Melilotus albus plant growing in Canada and identified as a novel Ensifer lineage that shared a clade with the non-symbiotic species, Ensifer adhaerens. Strain T173T was also previously found to harbour a symbiosis plasmid and to elicit root-nodules on Medicago and Melilotus species but not fix nitrogen. Here we present data for the genomic and taxonomic description of strain T173T. Phylogenetic analyses including the analysis of whole genome sequences and multiple locus sequence analysis (MLSA) of 53 concatenated ribosome protein subunit (rps) gene sequences confirmed placement of strain T173T in a highly supported lineage distinct from named Ensifer species with E. morelensis Lc04T as the closest relative. The highest digital DNA-DNA hybridization (dDDH) and average nucleotide identity (ANI) values of genome sequences of strain T173T compared with closest relatives (35.7 and 87.9%, respectively) are well below the respective threshold values of 70% and 95-96% for bacterial species circumscription. The genome of strain T173T has a size of 8,094,229 bp with a DNA G + C content of 61.0 mol%. Six replicons were detected: a chromosome (4,051,102 bp) and five plasmids harbouring plasmid replication and segregation (repABC) genes. These plasmids were also found to possess five apparent conjugation systems based on analysis of TraA (relaxase), TrbE/VirB4 (part of the Type IV secretion system (T4SS)) and TraG/VirD4 (coupling protein). Ribosomal RNA operons encoding 16S, 23S, and 5S rRNAs that are usually restricted to bacterial chromosomes were detected on plasmids pT173d and pT173e (946,878 and 1,913,930 bp, respectively) as well as on the chromosome of strain T173T. Moreover, plasmid pT173b (204,278 bp) was found to harbour T4SS and symbiosis genes, including nodulation (nod, noe, nol) and nitrogen fixation (nif, fix) genes that were apparently acquired from E. medicae by horizontal transfer. Data for morphological, physiological and symbiotic characteristics complement the sequence-based characterization of strain T173T. The data presented support the description of a new species for which the name Ensifer canadensis sp. nov. is proposed with strain T173T (= LMG 32374T = HAMBI 3766T) as the species type strain.

First record of two urotsylid ciliates (Protozoa: Ciliophora: Spirotrichea) from Japan expanding the circumscription of species

ABSTRACT Two urostylid ciliates, Trichototaxis marina Lu et al., 2014 and Uncinata bradburyae (Gong et al., 2001) Luo et al., 2015, new to Japan, were collected from coastal water in Nagasaki. Both were identified based on live and protargol-stained specimens. Morphologically, two new populations of T. marina correspond well with the type population in the live morphology and ciliature, especially a very flexible body having a long elliptical shape, and reddish cell colour caused by irregularly shaped pigments, multiple left marginal rows and marine habitat. A few morphological features were supplemented for the species. The Japanese population of Uncinata bradburyae presents the diagnostic features, especially the presence of an anterior snout-like procession and the elongated membranelles in the proximal portion of adoral zone, orientation of the anterior portion of the left marginal row, highly developed transverse cirri, and high number of dorsal kineties derived from two unique, de novo formed anlagen. Additionally, greenish pigments were first documented for the species. The new record suggests U. bradburyae might be a eurythermal species. The overall pattern of the divisional events resembles that of the Qingdao population described previously. Part of the reorganisation was also first revealed for U. bradburyae, which corresponds to the divisional processes in the opisthe. The present study corroborates the wide distribution of both species, and contributes to circumscribe the species by expanding the range of some morphometric data.

Corynebacterium guaraldiae sp. nov.: a new species of Corynebacterium from human infections.

Non-diphtheria Corynebacterium species (NDC) belonging to the human skin and mucosa microbiota are frequently neglected as contaminants. However, reports of human infections by Corynebacterium spp. have increased considerably in recent years. In this study, a group of six NDC isolates of urine (n = 5) and sebaceous cyst (n = 1) from two South American countries were identified at genus level or misidentified based on API® Coryne and genetic/molecular analyses. The 16S rRNA (99.09-99.56%) and rpoB (96.18-97.14%) gene sequence similarities of the isolates were higher when compared with Corynebacterium aurimucosum DSM 44532T. Multilocus sequence analysis (MLSA) indicated that these six NDC isolates compose a distinctive phylogenetic clade. Genome-based taxonomic analysis with the whole-genome sequences was able to separate these six isolates from other known Corynebacterium type strains. Average nucleotide identity (ANI), average amino acid identity (AAI), and digital DNA-DNA hybridization (dDDH) values between closely related type strains and the six isolates were considerably lower than the currently recommended threshold values for species circumscription. Phylogenetic and genomic taxonomy analyses indicated these microorganisms as a novel Corynebacterium species, for which we formally propose the name Corynebacterium guaraldiae sp. nov. with isolate 13T (= CBAS 827T = CCBH 35012T) as type strain.

Phylogeography of Ramalina farinacea (Lichenized Fungi, Ascomycota) in the Mediterranean Basin, Europe, and Macaronesia

Ramalina farinacea is an epiphytic lichen-forming fungus with a broad geographic distribution, especially in the Northern Hemisphere. In the eighties of the last century, it was hypothesized that R. farinacea had originated in the Macaronesian–Mediterranean region, with the Canary Islands as its probable southernmost limit, and thereafter it would have increased its distribution area. In order to explore the phylogeography of this emblematic lichen, we analyzed 120 thalli of R. farinacea collected in 38 localities distributed in temperate and boreal Europe, the Western Mediterranean Basin, and several Macaronesian archipelagos in the Atlantic Ocean. Data from two nuclear markers (nrITS and uid70) of the mycobiont were obtained to calculate genetic diversity indices to infer the phylogenies and haplotype networks and to investigate population structure. In addition, dating analysis was conducted to provide a valuable hypothesis of the timing of the origin and diversification of R. farinacea and its close allies. Our results highlight that phylogenetic species circumscription in the “Ramalina farinacea group” is complex and suggests that incomplete lineage sorting is at the base of conflicting phylogenetic signals. The existence of a high number of haplotypes restricted to the Macaronesian region, together with the diversification of R. farinacea in the Pleistocene, suggests that this species and its closest relatives originated during relatively recent geological times and then expanded its range to higher latitudes. However, our data cannot rule out whether the species originated from the Macaronesian archipelagos exclusively or also from the Mediterranean Basin. In conclusion, the present work provides a valuable biogeographical hypothesis for disentangling the evolution of this epiphytic lichen in space and time.

Solanum malmeanum, a promising wild relative for potato breeding.

Crop wild relatives are gaining increasing attention. Their use in plant breeding is essential to broaden the genetic basis of crops as well as to meet industrial demands, for global food security and sustainable production. Solanum malmeanum (Solanum sect. Petota, Solanaceae) is a wild relative of potatoes (S. tuberosum) from Southern South America, occurring in Argentina, Brazil, Paraguay and Uruguay. This wild potato has been largely mistaken for or historically considered as conspecific with S. commersonii. Recently, it was reinstated at the species level. Retrieving information on its traits and applied uses is challenging, because the species name has not always been applied correctly and also because species circumscriptions and morphological criteria applied to recognize it have not been consistent. To overcome these difficulties, we performed a thorough literature reference survey, herbaria specimens' identification revision and genebank database queries to review and update the information available on this potato wild relative, contributing to an increase in research on it to fully understand and explore its potential for potato breeding. Scarce studies have been carried out concerning its reproductive biology, resistance against pests and diseases as well as tolerance to abiotic stresses and evaluation of quality traits. The scattered information available makes it less represented in genebanks and genetic studies are missing. We compile, update and present available information for S. malmeanum on taxonomy, geographical distribution, ecology, reproductive biology, relationship with its closest relatives, biotic and abiotic stresses resistance and quality traits and discuss ways to overcome sexual barriers of hybridization and future perspectives for its use in potato breeding. As a final remark, we highlight that this species' potential uses have been neglected and must be unlocked. Thus, further studies on morphological and genetic variability with molecular tools are fundamental for an efficient conservation and applied use of this promising genetic resource.

Delimitation of Some Taxa of Ulnaria and Fragilaria (Bacillariophyceae) Based on Genetic, Morphological Data and Mating Compatibility

Fragilaria and Ulnaria are two closely related diatom genera for which the delimitation and circumscription of several species is unclear. We studied strains isolated from Lake Baikal and compared them with the species from freshwater reservoirs in Europe and Asia using phylogenetic and species delimitation methods, microscopy and interclonal crossing experiments. The results of the phylogenetic analyses of the fragments of rbcL and 18S rRNA genes revealed that baikalian F. radians clade was independent from the representatives of the genus from other localities. Among Ulnaria we found the following 18S rRNA phylogenetic tree groups at species level: U. acus, U. ulna and U. danica. Genetic distance between genera varied between 3.9–10.2% substitutions in rbcL gene and 3.2–11.5% in 18S rRNA. The boundary between intraspecies and interspecies polymorphism for studied species of Ulnaria and Fragilaria in these marker genes was around 0.8% substitutions. Morphometric characters of individual strains showed their variability and division into F. radians, U. acus and U. ulna together with U. danica. Strains of U. acus and U. danica from different localities of Europe and Asia were sexually compatible inside the species. Sexual reproduction has never been observed in monoclonal cultures, either between this species or with strains of the Fragilaria.