Species Of Isoetes Research Articles

Isoetes in Rajasthan-a Systematic Study

On the basis of the study of anatomy and morphology of spores, the systematics of the three species of Isoetes found in Rajasthan is discussed. I. tuberculata Gena & Bhardwaja is not distinct from I. coromandelina L. f. Similarly I. rajasthanensis Gena & Bhardwaja and I. reticulata Gena & Bhardwaja are not based on satisfactory and complete descriptions.

Two new diploid species of Isoetes (Isoetaceae: Lycopodiopsida) from Southeastern China based on morphological and molecular evidence

Two new endemic Isoetes from Zhejiang, China, Isoetes changleensis (2n = 22) and Isoetes yuhangensis (2n = 22), are described and illustrated. The morphological characteristics of I. changleensis, such as the presence of tuberculate and irregularly rugulate megaspores having a broad equatorial band with densely rugulate ornamentation, make it easy to distinguish it from Isoetes longpingii. Isoetes yuhangensis has rugulate megaspores with fibrous perispores, which sets it apart from closely related species. To distinguish the new Isoetes species and explore their phylogenetic position, this study employed complete nuclear genomes and plastomes. Both proposed species obtained high support in the phylogenetic analysis as new species. On the basis of morphological traits, chromosome information, and molecular evidence from chloroplast and nuclear DNA, these two taxa are regarded as two new diploid species of Isoetes.

The genus Isoetes (Isoetaceae) in Central Africa (Democratic Republic of the Congo, Rwanda, Burundi) with the description of three new species

Three new species of Isoetes (Isoetaceae) are described from the Democratic Republic of the Congo, Rwanda and Burundi for inclusion in the family treatment for the Flore d'Afrique Centrale. Isoetes hallei sp. nov. is related to I. alstonii and I. schweinfurthii, I. rwandensis sp. nov. to I. abyssinica and I. welwitschii, and I. pichisermollii sp. nov. to I. abyssinica and I. schweinfurthii. The differences between these species are discussed and geographical distribution maps for the new species are presented. The conservation status of the new species is preliminarily assessed. The megaspores of the type specimens of I. abyssinica, I. alstonii, I. schweinfurthii and I. welwitschii were studied using Scanning Electron Microscopy to distinguish the new species from the more similar other ones. Citation: Fischer E. & Lobin W. 2022: The genus Isoetes (Isoetaceae) in Central Africa (Democratic Republic of the Congo, Rwanda, Burundi) with the description of three new species. – Willdenowia 52: 315–334. Version of record first published online on 1 December 2022 ahead of inclusion in December 2022 issue.

Complete chloroplast genome of Isoetes japonica (Isoetaceae)

Isoetes japonica A. Braun is a heterosporous quillwort living in low-altitude areas in Japan. In the present study, the complete chloroplast genome of I. japonica was assembled and annotated. This chloroplast genome is a circular structure of 145,517 bp in length, comprising a pair of inverted repeat (IR) regions of 13,204 bp each, a large single copy (LSC) region of 91,868 bp, and a small single copy (SSC) region of 27,241 bp. The chloroplast genome contains 135 genes, including 78 protein-coding genes, 36 tRNA genes, and 8 rRNA genes. Phylogenetic analysis showed that I. japonica is sister to I. sinensis and I. yunguiensis. These results provide additional resources for the future studies on Isoetes species.

Rediscovery of the Presumed Extinct Philippine Quillwort Isoetes philippinensis Merr. & L.M. Perry (Isoetaceae) and New Insights on its Morphology and Ecology

Isoetes philippinensis, a critically endangered site-endemic lycophyte, was rediscovered after the last collection in 1969. The present study elucidates the morphology and ecology of the species – which have not been fully investigated – by describing the detailed morpho-anatomical characters, collecting water samples for physico-chemical analysis, and providing an in situ description of its habitat. The diagnostic characteristics of the species included long microphylls (up to 63 cm long), cobwebby megaspores and microspores, and the presence of velum. The morphology of I. philippinensis exhibits the features of other aquatic, amphibious and terrestrial species of Isoetes – such as the presence of lacuna in the roots, air chambers in the leaves, reduced stele, and abundance of parenchyma cells throughout the organs. Water-quality values are within the minimum acceptable limit. Threats to the population of I. philippinensis are discussed and characterized as Critically Endangered (CR A1c, B2a). The information presented here is vital for both in situ and ex situ conservation of the species.

Comparative chloroplast genome and transcriptome analysis on the ancient genus Isoetes from China

Isoetes is a famous living fossil that plays a significant role in the evolutionary studies of the plant kingdom. To explore the adaptive evolution of the ancient genus Isoetes from China, we focused on Isoetes yunguiensis (Q.F. Wang and W.C. Taylor), I. shangrilaensis (X. Li, Y.Q. Huang, X.K. Dai & X. Liu), I. taiwanensis (DeVol), I. sinensis (T.C. Palmer), I. hypsophila_GHC (Handel-Mazzetti), and I. hypsophila_HZS in this study. We sequenced, assembled, and annotated six individuals’ chloroplast genomes and transcriptomes, and performed a series of analyses to investigate their chloroplast genome structures, RNA editing events, and adaptive evolution. The six chloroplast genomes of Isoetes exhibited a typical quadripartite structure with conserved genome sequence and structure. Comparative analyses of Isoetes species demonstrated that the gene organization, genome size, and GC contents of the chloroplast genome are highly conserved across the genus. Besides, our positive selection analyses suggested that one positively selected gene was statistically supported in Isoetes chloroplast genomes using the likelihood ratio test (LRT) based on branch-site models. Moreover, we detected positive selection signals using transcriptome data, suggesting that nuclear-encoded genes involved in the adaption of Isoetes species to the extreme environment of the Qinghai-Tibetan Plateau (QTP). In addition, we identified 291–579 RNA editing sites in the chloroplast genomes of six Isoetes based on transcriptome data, well above the average of angiosperms. RNA editing in protein-coding transcripts results from amino acid changes to increase their hydrophobicity and conservation in Isoetes, which may help proteins form functional three-dimensional structure. Overall, the results of this study provide comprehensive transcriptome and chloroplast genome resources and contribute to a better understanding of adaptive evolutionary and molecular biology in Isoetes.

Phylogeny of Merlin\u2019s grass (Isoetaceae): revealing an \u201cAmborella syndrome\u201d and the importance of geographic distribution for understanding current and historical diversity

BackgroundMerlin’s grass (Isoetes, Isoetaceae, Lycopsida), is the extant remnant of the isoetalean wood-producing lycopsids that originated during the Paleozoic, possibly in aquatic or boggy habitats. Modern day species are aquatic, semi-aquatic or terrestrial and occur almost worldwide. They display little morphological variation; the lobed corm has helically arranged leaves with internal air channels and basal sporangia. Genetic variation has also proven limited, which has hampered phylogenetic inference. We investigate evolutionary relationships in Isoetes, using molecular data and an extended sample of species compared to previous work, adding species that have never before been included in a phylogenetic study.ResultsOur results reveal an unexpected discovery of an “Amborella syndrome” in Isoetaceae: a single poorly known species is sister to the remaining family. The species, Isoetes wormaldii, is a rare endemic to the Eastern Cape of South Africa. Its leaves are flattened with a rounded point, which sharply contrasts with the awl-shaped leaves of most other species of Isoetes. The remaining species of Isoetes are resolved in five major clades, also indicated in previous work. While the phylogeny shows geographic structure, the patterns are complex. For example, tropical-southern African species occur in at least five clades, and Indian, Australian and Mediterranean species in at least three clades each.ConclusionThe evolutionary and biogeographical history of Isoetes is not easily explained, and may conceivably include ample extinction and a mixture of ancient and more recent processes. Previously shown difficulties with node age estimation increase the problem. The here demonstrated sister-relationship between the phylogenetically, morphologically and genetically distinct Isoetes wormaldii and the remaining family appears to bridge the morphological gap between Isoetes and its extinct relatives, although further studies are needed. Moreover, it shortens the branch length to its living sister genus Selaginella, and may enhance node age estimation in future studies. Isoetes wormaldii is critically endangered, known only from one (to a few) minor populations. Immediate actions need to be taken if we want to prevent this unique species from going extinct.

Distribution, status, and habitat characteristics of Columbia Quillwort (<i>Isoetes minima</i>, Isoetaceae) in Canada

In Canada, the globally rare lycophyte, Columbia Quillwort (Isoetes minima), is currently known from four subpopulations, all within a 25-km radius of Castlegar in the Selkirk and Monashee Mountain ranges of southern British Columbia. These constitute just over a quarter of all known subpopulations in Canada and the United States. The species is found in Canada in sloping pocket meadows that are naturally fragmented within a larger forested matrix. The plants grow in spring seepage areas in thin soils that discourage the establishment of larger, more vigorous vascular plant competitors. Long combined within Isoetes howellii (sensu lato), I. minima has only recently been confirmed to be a distinct species, and, in 2019, it was assessed as Endangered by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). We build on information in the COSEWIC status report by describing the species’ morphology and ecology in greater detail and provide a comparison of critical identification features of closely related species as well as a dichotomous key for Isoetes species in British Columbia.

Description, distribution and ecology of endemic Tasmanian quillwort, Isoetes jarmaniae, sp. nov. (Isoetaceae; Lycopodiopsida)

Isoetes jarmaniae sp. nov. is described as a new lycophyte endemic to Tasmania, Australia, where it is confined to peat-bound karstic wetlands in several river valleys in the south-west wilderness. While seemingly morphologically closest to I. drummondii, this quillwort has features that are globally uncommon in Isoetes and unknown in other Australasian taxa. Most notable are its markedly flattened, strongly recurved leaves and disproportionately large sporangium ligules that are more suggestive of South American than Australian taxa. As well, the exceptionally thin and wide (alate) megaspore equatorial ridge is swollen at suture intersections, presenting a slightly triangular shape suggestive of the Indian taxon I. udupiensis. The microspores of I. jarmaniae exhibit exceptionally, perhaps uniquely, fine-papillate ornamentation. An original key placing I. jarmaniae in context with the other Tasmanian Isoetes species is provided. This diminutive, apparently diploid species is evidently maintaining a self-sustaining population within a regionally unique habitat and small geographic range.

Rediscovery, resurrection and lectotypification of endemic Isoetes sampathkumarnii L. N. Rao from India

An interesting species of Isoetes was collected from Jambughoda, Wildlife Sanctuary, Gujarat. After a review of literature and comparison of the morphological characters with type specimens, it was identified as I. sampathkumarnii L. N. Rao. It is endemic species of south India and rediscovered after a lapse of 63 years. The species shows several features that make it unique in the genus. Earlier, I. sampathkumarnii was also treated as synonym of I. coromandelina L.f. and I. sahyadrii Mahabala. However, it has an idiosyncratic velum character and spore ornamentation that makes it different from other species. Hence, the authors resurrected it as a distinct species. The original material is ambiguous hence, a lectotype of I. sampathkumarnii has been designated here.

Transplanting experiment and transcriptome sequencing reveal the potential ecological adaptation to plateau environments in the allopolyploid Isoetes sinensis

Relatively high frequencies of polyploidy are generally found in high-altitude regions. However, more diploid than polyploid species of Isoetes are distributed in plateau environments in China. The low-altitude species Isoetes sinensis originates from the allopolyploidization between a plateau parent and another low altitude species. To study potential ecological adaptation to plateau environments in the allopolyploid I. sinensis, we transplanted individuals of I. sinensis to different altitudes. RNA sequencing was performed to elucidate the molecular response of this species’ ecological adaptation to plateaus. More unique differentially expressed genes (DEGs) were detected in individuals transplanted to the Qinghai–Tibet Plateau (QTP) than elsewhere, such as genes for ribosomal proteins (RPs) and succinate dehydrogenase (SDH), which helped them adapt to higher altitudes under both terrestrial and submerged conditions. In both terrestrial and submerged conditions, the expression of a large number of genes changed to help plants adapt to exposure to the high levels of ultraviolet (UV) radiation on plateaus, such as the genes associated with the accumulation of flavonoids, decreasing chlorophyll content, and reducing light harvesting activity. The expression of vacuolar-type H+-transporting ATPase (V-ATPase) and phosphoenolpyruvate carboxylase (PEPC) increased with altitude, revealing that the intensity of the crassulacean acid metabolism (CAM) of I. sinensis might be positively associated with altitude. In general, our results reveal that although I. sinensis only lives at low altitudes, it can still adapt to plateau stress by regulating the expression of certain key genes. The potential ecological adaptation to plateau environments in the allopolyploid I. sinensis may have been inherited from the plateau parent.

Plastid Genomes of the Early Vascular Plant Genus Selaginella Have Unusual Direct Repeat Structures and Drastically Reduced Gene Numbers.

The early vascular plants in the genus Selaginella, which is the sole genus of the Selaginellaceae family, have an important place in evolutionary history, along with ferns, as such plants are valuable resources for deciphering plant evolution. In this study, we sequenced and assembled the plastid genome (plastome) sequences of two Selaginella tamariscina individuals, as well as Selaginella stauntoniana and Selaginella involvens. Unlike the inverted repeat (IR) structures typically found in plant plastomes, Selaginella species had direct repeat (DR) structures, which were confirmed by Oxford Nanopore long-read sequence assembly. Comparative analyses of 19 lycophytes, including two Huperzia and one Isoetes species, revealed unique phylogenetic relationships between Selaginella species and related lycophytes, reflected by structural rearrangements involving two rounds of large inversions that resulted in dynamic changes between IR and DR blocks in the plastome sequence. Furthermore, we present other uncommon characteristics, including a small genome size, drastic reductions in gene and intron numbers, a high GC content, and extensive RNA editing. Although the 16 Selaginella species examined may not fully represent the genus, our findings suggest that Selaginella plastomes have undergone unique evolutionary events yielding genomic features unparalleled in other lycophytes, ferns, or seed plants.

Chloroplast genomes of key species shed light on the evolution of the ancient genus Isoetes

AbstractAlthough phylogenetic studies have revealed major clades, the deepest relationships in Isoetes remain unresolved. The use of next‐generation sequencing provides enormous amounts of gene sequences, which allows not only clarification of the basal relationships but also rapid radiations. Plastomes of six key Isoetes species were annotated, revealing a total of 129 or 130 genes, depending on the species. Our phylogenomic analyses comprising representatives of all major clades yielded well‐supported nodes and identical topologies using maximum likelihood and Bayesian inference. The phylogenetic reconstructions detangled the deep relationships in Isoetes and illuminated the more recent radiations in the genus. A basal dichotomy was found that grouped Isoetes spp. from Brazil and South Africa into a clade sister to the remaining Isoetes groups. Interestingly, I. andicola was found to be sister to the North American species complex. Genomic trait mapping analysis showed that the missing introns in the atpF and clpP genes were well conserved in two major clades. The absence of trnK‐UUU was observed in the Brazilian tropical species and in I. velata. Among lycophytes, the gene trnR‐CCG was missing only in I. eludens. In general, genomic traits such as the presence or absence of internal stop codons, a tRNA, and an intron were revealed to be conserved within groups, suggesting that these genomic traits might reveal vital information about the evolution of the genus. This study will contribute to understanding the diversification of Isoetes and the establishment of a better framework to address the evolutionary history of the genus.

The taxonomy and conservation status of Isoetes (Isoetaceae; Lycopodiopsida) in India

ABSTRACT In many cases over the years the diversity of Isoetes in India has been defined by inconsistent morphological analyses and questionable data. This has resulted in substantial confusion, dramatically different taxonomic interpretations and a low level of global acceptance. That in turn has prevented the reliable determination of conservation priorities. The present study reviews the most reliable morphological, distributional and cytological Indian data available with techniques and standards that have guided successful taxonomic investigations of Isoetes elsewhere in the world. This results in the enumeration of nine readily distinguishable species for India. One named hybrid is also discussed as is the probable occurrence of other unnamed hybrids. All Indian Isoetes species except I. coromandelina subsp. coromandelina are endemic. Two possible but unresolved taxa are also discussed. A clearer determination of the highest national priorities for Isoetes conservation has resulted. Most Indian taxa are rare, some qualifying as Endangered and others probably being extinct. Suggestions for conservation strategies and actions to protect and sustain vulnerable Isoetes species and their habitats are offered.

Phylogenomics indicates the "living fossil" Isoetes diversified in the Cenozoic.

The fossil record provides an invaluable insight into the temporal origins of extant lineages of organisms. However, establishing the relationships between fossils and extant lineages can be difficult in groups with low rates of morphological change over time. Molecular dating can potentially circumvent this issue by allowing distant fossils to act as calibration points, but rate variation across large evolutionary scales can bias such analyses. In this study, we apply multiple dating methods to genome-wide datasets to infer the origin of extant species of Isoetes, a group of mostly aquatic and semi-aquatic isoetalean lycopsids, which closely resemble fossil forms dating back to the Triassic. Rate variation observed in chloroplast genomes hampers accurate dating, but genome-wide nuclear markers place the origin of extant diversity within this group in the mid-Paleogene, 45–60 million years ago. Our genomic analyses coupled with a careful evaluation of the fossil record indicate that despite resembling forms from the Triassic, extant Isoetes species do not represent the remnants of an ancient and widespread group, but instead have spread around the globe in the relatively recent past.

WITHDRAWN: Rediscovering two Isoetes species in the Brazilian Amazon and Cerrado after ca 167 and 175 years, respectively

Abstract Isoetes amazonica and I. gardneriana were the first two species of the genus to be collected from Brazil. Isoetes amazonica was gathered by Richard Spruce in the Amazon basin near Santarem in the state of Para in 1850. Isoetes gardneriana was collected by George Gardner in current Dianopolis in Tocantins State in 1843. Despite being for a long term known by botanists, these species were not recollected since then, which raise questions about their taxonomic recognition, current distribution ranges and conservation status. Fieldwork efforts lead to rediscover I. amazonica and I. gardneriana after ca 167 and 174 years, respectively. Based on IUCN criteria, Isoetes amazonica and I. gardneriana should be assigned as data deficient (DD) and endangered (EN), respectively. The rediscovering of these species raises hopes that other areas in Amazon and Cerrado biomes harbour I. amazonica and I. gardneriana, respectively. This study will serve as a basis toward the conservation of these species.

Rediscovering two Isoetes species in the Brazilian Amazon and Cerrado after 167 years.

Isoetes amazonica and I. gardneriana were the first two species of the genus to be collected from Brazil. Isoetes amazonica was gathered by Richard Spruce in the Amazon basin near Santarém in the state of Pará in 1850. Isoetes gardneriana was collected by George Gardner in the current Dianópolis in Tocantins State in 1843. Despite being known for a long time by botanists, these species have not been recollected since then, which raised questions about their taxonomic recognition, current distribution ranges and conservation status. Fieldwork efforts led to the rediscovery of I. amazonica and I. gardneriana after 167 years. These collections enrich our understanding of their habitats and morphologies. We provide here re-descriptions for these species. Based on IUCN criteria, Isoetes amazonica and I. gardneriana should be assigned as data deficient (DD) and endangered (EN), respectively. The rediscovery of these species raises hopes that other areas in Amazon and Cerrado biomes harbour I. amazonica and I. gardneriana, respectively. This study will serve as a basis towards the conservation of these species.

Tiny Rhizomorphic Rooting Systems from the Early Permian Abo Formation of New Mexico, USA

Premise of research. Extant Isoetes species, which all develop small pseudoherbaceous habits, are the only living remnants of the once diverse clade of rhizomorphic lycopsids, which included trees ...

Isoetes shangrilaensis, a new species of Isoetes from Hengduan mountain region of Shangri-la, Yunnan

Isoetes shangrilaensis is recognized as a new species in Shangri-la and compared with Isoetes hypsophila, another species in the Hengduan Mountain Region. Spore sizes and ornamentations are useful to distinguish these two species. Isoetes shangrilaensis has tuberculate to rugulate megaspores and echinate to cristate microspores while Isoetes hypsophila has laevigate megaspores and bacculate to rugulate microspores. One nuclear and three chloroplast DNA sequences were used to infer the phylogenetic relationships of I. shangrilaensis, I. hypsophila and two other basic diploid Isoetes species (Isoetes taiwanensis and I. yunguiensis) in China. The phylogenetic tree showed a distinct separation between these two species: I. shangrilaensis was more closely related to other basic diploid species in China whereas I. hypsophila was distantly related. The delineation of Isoetes in this region can contribute to a better understanding of its phylogeny.

A contribution to the phylogeny and biogeography of the genus Isoetes (Isoetaceae, Lycopodiidae) in the Mediterranean region

To better understand the phylogeny of Isoetes species in the Mediterranean region, sequences of the second intron of a LFY-like homolog were determined for six populations of three Mediterranean Isoetes species and analyzed with other LFY and ITS sequences of Euro-Mediterranean species available in GenBank. Nomenclature of selected species was updated according to recent literature. Investigations of voucher specimens from previously sequenced taxa revealed that a specimen of I. histrix from Crete, Greece used in several previous molecular studies is probably I. phrygia. Analysis of the limited LFY and ITS DNA sequence data presented here agrees with the organization of Mediterranean species into three groups as suggested by worldwide phylogenies of the genus: first, an older group, including I. longissima, I. histrix, I. durieui, I. libanotica and similar species in addition to other probably “Laurasian” species; second, an intermediate endemic relict group, including only I. malinverniana and I. anatolica; and third a younger group, including the Mediterranean I. delilei, I. phrygia and I. todaroana, along with the widely-distributed I. echinospora and I. lacustris and other species. Preliminary remarks on the evolution and biogeography of the genus in the Mediterranean region are presented.