Species Of Isoetes Research Articles

Microspore Morphology of Isoetes Species (Lycophyta) from Southern South America

Microspores of the 24 species ofIsoetes that grow in southern South America were analyzed under a light microscope and scanning electron microscope. The microspores are monolete, elliptic in polar view, 30–40 μm long, and 20–25 μm wide. A background with various characteristics is seen on each surface. A supra-laesural expansion is present. The perispore is ornamented and has a perforated background. In section, it has a lacunose structure. The exospore is smooth, and it has a compact structure in section. The studied species could be divided into three groups by their perispore ornamentation: equinate, rugulate, and tuberculate. Microspore size was positively correlated with increasing ploidy level, and larger microspores were associated with terrestrial habitats. A convergence in ornamentation was found between spores produced by the studied species and those that grow in regions outside of the area under study.

Taxonomic Reassessment of North American Granite Outcrop Isoetes Species with Emphasis on Vegetative Morphology and I. piedmontana (Pfeiffer) Reed sensu lato

A taxonomic study of collections previously identified as Isoetes melanospora, I. piedmontana, and I. tegetiformans was undertaken emphasizing vegetative characters. The taxonomic position of I. piedmontana was also assessed using cytogeography and a cursory examination of the allozyme locus TPI-2. Isoetes melanospora, I. piedmontana, and I. tegetiformans can be sufficiently distinguished using characters derived from leaves and corms. Isoetes piedmontana occurs as diploid, triploid, and allotetraploid entities. Diploids in the western and eastern parts of the geographic range are genetically distinct. Allotetraploids in eastern Alabama are composed of different genomes than those in North Carolina. Isoetes piedmontana is currently interpreted as an assemblage of morphologically indistinguishable species and is undergoing further taxonomic investigation. The typification of I. piedmontana is clarified, and a key with descriptions of the granite outcrop Isoetes species of the southeastern United States Piedmont is provided.

Current status and conservation strategies for Isoetes in China: a case study for the conservation of threatened aquatic plants

There are four known species of Isoetes (Family Isoetaceae) from China: I. hypsophila, I. sinensis and I. yunguiensis on the mainland, and I. taiwanensis on Taiwan. In a 4-year study we documented the distribution and habitat characteristics of all four species and evaluated their conservation status using IUCN criteria. All four species are facing a high risk of extinction and should be categorized as Critically Endangered on the IUCN Red List. Habitat degradation and loss, water pollution and eutrophication, competitive exclusion, and human disturbance are the main factors causing the decline and extirpation of Isoetes. Only I. taiwanensis is protected in situ in Yangmingshan National Park on Taiwan. None of the species or habitats of Isoetes on mainland China are presently protected, although all species have been designated by the government as State Key Protected Wild Plants. Our results suggest that conservation strategies should be implemented urgently, particularly on the mainland.

A new species of Isoetes (Isoetaceae) from Turkey, with a study of microphyll intercellular pectic protuberances and their potential taxonomic value

Isoetes anatolica sp. nov. is described from a population growing in seasonal ponds of a mountain near the southern coast of the Black Sea in Bolu, Turkey. It is a robust, amphibious quillwort, characterized by semiterete, carnose microphylls, semicircular foliar section, smooth cuticle, prominent cuticular pegs, stomata, several collenchymatous strands, abundant pectic filaments and connections in the cells of the translacunar diaphragms, incurved alae, well developed ligula, small carnose labium, no velum, well-formed bulliform megaspores and obscurely muriform microspores. Plants were investigated anatomically and a description with additional diagnostic characters is included. Morphological affinities with other species of the genus are discussed. Intercellular pectic protuberances (IPP) were studied in the cells of the translacunar diaphragms of the microphylls of several species of Isoetes including I. anatolica. The IPP were examined to determine if they could provide diagnostic characters. They were detected with TBO and analysed using light and scanning electron microscopy. Types of IPP and species bearing them were as follows: warts in I. adspersa, I. andina, I. boliviensis, I. duriei, I. engelmannii, I. lechleri, I. longissima, I. melanopoda, I. storkii, I. velata. ssp. velata, and I. velata ssp. asturicense; warts and filaments in I. brochonii, I. lacustris, and I. setacea, and connections in I. anatolica and I. malinverniana. IPP are lacking in I. boryana, I. echinospora, I. histrix and I. novogranadensis. Combination of type, density, and distribution of IPP promises to be a useful vegetative character in a genus in which diagnostic characters are scarce. © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society, 2005, 147, 213–228.

Two new species of the genus Isoetes L. (Isoetaceae­Lycopsida) from India

AbstractTwo new, primitive quillwort species, I. udupiensis and I. divyadarshanii, are described from peninsular India. Cytologically both species are diploid and unique for India in having 22 chromosomes without fragments. Megaspores of both species are monomorphic, whereas in the previously described species, they are di­to polymorphic. Isoetes udupiensis is unique in having deltoid­shaped megaspores and dominant microspory. The similarity in morphology of both species to sub­genus Euphyllum and to the remaining Indian species of subgenus Isoetes, suggests that they may be connecting links between primitive and derived forms within the genus in India.

Taxonomic Reassessment of North American Granite Outcrop Isoetes Species with Emphasis on Vegetative Morphology and I. piedmontana (Pfeiffer) Reed sensu lato

Taxonomic Reassessment of North American Granite Outcrop Isoetes Species with Emphasis on Vegetative Morphology and I. piedmontana (Pfeiffer) Reed sensu lato

Chromosome Behavior During Meiosis and Development of Spore Mother Cells in the Chinese Quillwort Isoetes sinensis T. C. Palmer (Isoetaceae)

Abstract Chromosome behavior during meiosis of the tetraploid Isoetes sinensis was observed to be similar to that of basic diploid Isoetes species. This observation was consistent with the previous report that polyploid species of Isoetes are allopolyploids. Meiosis was generally similar in both megaspore and microspore mother cells, but differences were observed. Due to the smaller size of the microspore mother cells, during prophase I, chromosomes are not as dispersed as those in megaspore mother cells. Cytomixis was observed in all stages of meiosis in microspore mother cells, but it was not seen at any stage of meiosis in megaspore mother cells. Cytomixis, lagging chromosomes, chromosome bridges, chromosome fragments, and micronuclei, observed during meiosis in I. sinensis, can affect sexual reproduction, but it does not appear to be a major cause of population decline in this species. The major cause of decline is habitat degradation from human disturbance. The few remaining populations of the Chines...

Phylogenetic Relationships of Isoëtes (Isoëtaceae) in China as Revealed by Nucleotide Sequences of the Nuclear Ribosomal ITS Region and the Second Intron of aLEAFYHomolog

Abstract Isoetes is an ancient lycopod lineage with a highly conserved morphology that provides few morphological characters to resolve the phylogeny of its species. Species appear to have evolved by divergence and allopolyploidy. The basic diploids I. hypsophila, I. taiwanensis, and I. yunguiensis and the tetraploid I. sinensis occur in China. Analysis of ITS sequences indicates that the Chinese Isoetes species are part of an Australasian clade including I. brevicula from Western Australia and I. kirkii from New Zealand. Two distinct cloned sequences of the second intron of a LEAFY homolog were recovered from I. sinensis supporting the hypothesis that I. sinensis is an allotetraploid. One of the I. sinensis cloned sequences was similar to the I. taiwanensis sequence and the other cloned sequence was similar to the I. yunguiensis sequence identifying I. taiwanensis and I. yunguiensis as the likely parents of I. sinensis. Other cloned sequences recovered from I. sinensis were recombined parts of the two di...

Distribution of basic diploid and polyploid species of Isoetes in East Asia

AbstractAims Isoetes L. is an ancient, primitive genus of heterosporous lycopsids characterized by a strongly reduced plant. The genus occupies a unique position in plant evolution as the closest relatives of the famous tree lycopods. Hybridization and allopolyploid speciation as well as habitat preference are regarded as having played an important role in the evolution of the genus Isoetes. However, it is still uncertain what factors have impacted upon hybridization and allopolyploid speciation of the genus Isoetes. Our understanding of the origin, evolution and modern distribution pattern of Isoetes in East Asia would benefit from investigations into the relationship between the unique geographical location and topographic features and the existing fossil record in the region.Methods The chromosome number was determined from known 81 populations of 10 species of Isoetes in East Asia. The altitude was obtained in location of every population. T‐test was used to evaluate the altitude difference between diploid and polyploid populations. Data of Japanese Isoetes from Takamiya et al. was used in the study.Results There are 10 known species of Isoetes with four diploids and six polyploids in East Asia. The four diploid species (2n = 22) are found at high altitudes (mean altitude = 2649.67 ± 1396.16 m, n = 18) and isolated from each other. In contrast, the six polyploid species widely occur in low altitude regions (mean altitude = 182.62 ± 181.44 m, n = 63) and are partially sympatric. Highly significant differences (P < 0.001) were observed between the mean altitude of locations of populations of diploids and polyploids.Main conclusions The polyploidy speciations of Isoetes in East Asia might originate and develop from Holocene (Quaternary). The present pattern of distribution of Isoetes in East Asia is the result of allopatric speciation derived from vicariance, dispersal and combinations of both, and significantly correlative with the geological history and geographical changes. The change of altitude might have played an important role in allopolyploid speciation and the pattern of distribution of the genus Isoetes in East Asia by exerting a considerable influence on dispersal and hybridization opportunities of Isoetes species.

Caracteres diagnósticos foliares en táxones ibéricos de <i>Isoetes L.</i> (Isoetaceae, Pteridophyta)

This is a comparative study of foliar morphology of the species of Isoetes L. growing in the Iberian Peninsula. The taxa included are /. durieui and /. histrix (terrestrial), /. setaceum, and /. velatum subsp. Velatum (amphibious), and /. brochonii, I. echinosporum, I. x hickeyi, I. lacustre, I. longissimum and /. velatum subsp. Asturicense (aquatic). Material of an undescribed amphibious tetraploid taxon related to /. velatum was also included in this study and referred as Isoetes sp. until proper description. Several Iberian collections, together with European and American specimens of some of the taxa were analyzed. Selected diagnostic characters of the microphylls are: cuticular ornamentation (striae, ridges and warts), cuticular flanges, epidermal patterns, stomata distribution and dimensions, foliar transverse sections outline, degree of development of the mesophyll, presence or absence, and distribution of the mechanical tissues (collenchyma), diaphragms, and presence or absence and type of intercellular pectic protuberances. All characters are stable, and do not vary with the age of the plants or the microphylls. Cuticular striae, ridges and warts, as well as stomata develop early in plantlets. Stomata present in the microphylls of two aquatic taxa ( /. longissimum, I. velatum subsp. asturicense ) suggest that their absence is not entirely due to influence of aquatic environment. Collenchyma occurs, also, in species growing in different habitats. Restored herbarium material proved to be as useful as fresh or fixed material, an important advantage in the case of Isoetes species, many of which grow in vulnerable areas or are known only through herbarium specimens due to destruction of their pristine habitats.

Character and Variation of Chemical Properties of the Water in the Natural Habitats of Three Species of Isoetes in China

Habitat preference has played an important role in the evolution of the genus Isoetes. Aquatic Isoetes species are generally distributed in oligotrophic softwater. However, it is still uncertain if chemical properties of the water have an impact on the pattern of distribution of Isoetes species. Investigation of habitat preference with regard to water chemistry in natural habitats of species would contribute significance to our understanding of evolution in the genus. Four species of Isoetes are known to occur in China: Isoetes taiwanensis in Taiwan island and /. hyp-sophila, I. yunguiensis and I. sinensis in the mainland, and their distribution regions do not overlap. All four species are endangered aquatic plants throughout their distribution range in the country. In this paper, 20 parameters of water chemistry in the natural habitats, of three species of Isoetes in mainland China were measured, using HANNA Pocket-sized pH Meter HI98107 (resolution = 0.1 pH, accuracy = ±0. 1 pH), HANNA Conductivity Meter Dist4/HI983004 (resolution = 0. 1 m S · cm-1, accuracy = ±0.1 m S·cm-1) and HANNA C200 Multiparameter Ion Specific Photometer (resolution of NO3-N, NO3- , P, Mn and Mo =0.1mg·L-1, accuracy = ±0.1 mg·L-1; resolution of other factors = 0.01 mg·L-1, accuracy = ±0.01 mg· L-1 ). The character and variation of the chemical properties of the water were analyzed using mean, coefficient variability and difference significance tests (ANOVA and Kruskal-Wallis). Results showed a common character in that there were bigger variations in average and coefficient variability of the 20 parameters. Average Ni was overwhelmingly greater than the other factors, and lower conductivity indicated there was litter pollution in the water. However, of the 20 factors assessed, except for pH (p 0.05), P (p 0.05), NO3-N (p 0.05) , NO3- (p 0.05) and Al (p 0.01) , the rest displayed no significant difference among habitats of the three species. This indicated that most of the factors (75% ) were relatively stable. pH had an identically positive correlation with NO3-N and NO3- (p 0.05) ; on the contrary, P had an identically negative correlation with NO3-N and NO3- (p 0.05). pH and P were also negatively correlated (p 0.05). Only Al had a positive correlation with P (p 0.05). An analysis, according to data from other research and this study, suggested the significant difference of chemical nature of the water among the three Isoetes species could be due to differences in physiological characters among them, and has no impact on their distribution.

The geographic distribution and habitat of the Isoetes plants in China

Isoetes is a genus of primitive vascular plants classified in the subdivision Lycopsida and occupies a very important position in the evolutionary history of the pteridophytes. In recent years, Isoetes has declined rapidly in population quantity (number) and has even disappeared from many locations in Mainland China. The genus is now considered to be rare and threatened or endangered in China and is listed among first category protected plants. The progressive decline in populations of Isoetes in Mainland China has been attributed to on-going anthropogenic changes; however, no data have been adduced to support this assumption. In this study, all present locations of Isoetes populations and locations where the genus had been previously recorded but is now extinct were investigated in Mainland China. The habitat characteristics, including elevation, water pH value and the conditions of substrate were measured at each site. Associated plants growing together with Isoetes were collected from each population. The result indicated that the geographic distribution of Isoetes in Mainland China is discontinuous and that every population of Isoetes is insulated from other populations. The three species of Isoetes in Mainland China occur at different elevations. The current populations showed no obvious differences in water pH and other characteristics. But habitats where Isoetes plants had been extirpated currently have higher water and substrate pH values compared to the period when the sites supported Isoetes populations. These sites also had higher readings than the current locations of remaining Isoetes populations. This study indicates that populations of Isoetes growing in marshy areas close to farmland are faced with intense competition from other hydrophyte species whose proliferation is encouraged by the use of fertilizers in adjacent farmland. The populations of Isoetes growing in the freshwater intertidal zone avoid competition with other hydrophytes because of the periodic fluctuation of water level and thus grow comparatively well. The results indicate that the geographic distribution and occurrence of Isoetes plants in Mainland China is closely correlated with elevation, water pH, competition with other species, and water depth.

Evolution of Lycopodiaceae Inferred from Spacer Sequencing of Chloroplast rRNA Genes

Nucleotide sequences of a chloroplast rDNA region including 8 bp from the 3" end of 23S rDNA–ITS2–4.5S rDNA–ITS3–5S rDNA–ITS4 (approximately 800 bp) were determined in 25 species of Lycopodiaceae and two species of the genus Isoetes. The rate of molecular evolution of spacers significantly varied in different Lycopsida taxa. A phylogenetic analysis by the neighbor-joining (NJ) method revealed that the family Lycopodiaceae is monophyletic. The topology of phylogenetic trees suggests the isolation of four or probably five genera in family Lycopodiaceae. For these genera, synapomorphic indels were detected. The obtained data were compared with the results of phylogenetic analysis of Lycopsida with regard to other sequences. The relationships of taxa within the family Lycopodiaceae is discussed.

Casparian Strips in the Leaf Intrastelar Canals of Isoetes duriei Bory, a Mediterranean Terrestrial Species

Anatomical observations, using light and fluorescence microscopy, were made on leaves of Isoetes duriei to verify the presence of casparian bands around the intrastelar canals. This peculiar anatomical feature, previously reported for some Isoetes species, is confirmed. The possible role of this endodermis-like structure, in the transport of water due to root pressure or in the accumulation of certain metabolites, is discussed in relation to the ecological and anatomical features of the species.

Isozymes of the Isoetes riparia Complex, I. Genetic Variation and Relatedness of Diploid Species

Abstract Isozymes were examined in the six aquatic (including amphibious) diploid species of Isoetes of eastern North America in order to quantify their levels and patterns of genetic variation, to determine their genetic distinctness, and to evaluate the utility of allozymes in addressing ancestry in the I. riparia complex. Twenty-six populations representing diploid species, I. echinospora, I. engelmannii, I. flaccida, I. mattaponi, I. prototypus, and I. valida were compared for eleven enzymes coded by 16 interpretable loci. Levels of genetic variation in populations tended to be low ranging from none (means: P = 0.0, A = 1.0, H = 0.0) in I. echinospora to moderate (means: P = 22.9, A = 1.4, H = 0.093) in I. flaccida. Genetic variation in polymorphic species tended to be distributed more among than within populations, as indicated by high Fst values (Fst > 0.607 in all polymorphic species except I.mattaponi, for which Fst = 0.272). The genetic identities of conspecific populations were high, with mean v...

Some Observations on the Reproductive Anatomy of Isoetes andicola

The gametophyte generation of Isoetes andicola was investigated anatomically and using microspectrophotometry. Microsporangia, which sometimes additionally contained a few abortive megaspores, produced numerous microspores that developed apparently functional male gametophytes and swimming spermatozoids. In contrast, the female gametophytes produced from functional megaspores were found to contain archegonia lacking neck canals and that mostly did not develop functional embryos. Instead, the megagametophytes were found to contain embryos deeply embedded within somatic tissue. The nuclei of these embryos were about twice the size and contained about twice as much DNA as of those in adjacent gametophytic cells. Such embryos, which were not associated with archegonia, are interpreted to have arisen via some form of apog- amy. Plants that are now referable to Isoetes andicola (Amstutz) L.D. G6mez were originally described as two separate species, Stylites andicola E. Amstutz and S. gemmifera Rauh. Although G6mez (1980) had maintained the latter taxon as a variety of I. andicola, this distinction is dubious (Karrfalt and Hunter, 1980; Karrfalt, 1984), and although Gomez (1980) did not provide any new evidence to support the combination of Stylites with Isoetes, Karrfalt (1984) showed that the elongate, monopolar stem characterizing the genus Stylites is secondarily derived during the ontogeny of each young Stylites plant and that these plants begin life with bipolar corms that are morphologically indistin- guishable from those of any other species of Isoetes. As an adjunct to this study of stem development, plants of I. andicola maintained in cultivation yielded a large number of gametophytes that subsequently produced correspondingly large numbers of new sporophytes. These gametophytes and sporophytes pro- vided an unexpected opportunity to study some aspects of the reproductive anatomy of this taxon. These anatomical observations seem to suggest that apomixis exists in this species.

Isoetes in Alaska and the Aleutians

Three species of Isoetes are recognized as present in the study area: echinospora Durieu (diploid, 2n=22), maritima Underw. (tetraploid, 2n=44) and occidentalis L.F. Hend. (hexaploid, 2n=66). Three interspecific hybrids are expected and two are known to be present: xpseudotruncata D.M. Britton & D.F. Brunton (triploid, 2n = 33) and Xtruncata (Eaton) Clute (pentaploid, 2n = 55). The missing hybrid taxon is echinospora (diploid) x occidentalis (hexaploid). The genus Isoetes was largely unknown in Alaska and adjacent areas until recent years. The floristic treatment by Hulten (1968) was a major advance at the time. He recognized three taxa in Alaska, muricata Durieu var. braunii (Durieu) C.F. Reed, muricata ssp. maritima (Underw.) Hulten, and truncata (Eaton) Clute. In the same publication, maritima ssp. maritima received syn- onyms of maritima Underw., macounii A.A. Eaton and beringensis Kom., whereas, truncata, had the query, I. asiatica with respect to Alaskan spec- imens, attached to it. Britton and Brunton (1993) considered Alaskan taxa in an assessment of the pentaploid hybrid xtruncata (A.A. Eaton) Clute in western North America. Further biosystematic studies on Alaska Isoetes are a natural extension of that hybrid investigation. Almost no cytological determinations of Alaskan taxa had been undertaken before Britton and Brunton (1993). Similarly, no Scan- ning Electron Microscope (SEM) studies of spores had been conducted. Britton and Brunton (1993) cited four Alaskan collections of occidentalis L.F. Hend., including a large collection by S. S. Talbot from Auke Lake that was deter- mined cytologically as 2n=66. Our objectives in the present study were to determine the number of species and interspecific hybrids of Isoetes in Alaska and to document their cytology, spore morphology, and distribution. Another longer term objective was to clar- ify the relationship of maritima with macounii and beringensis.

Fungal Associations with Isoetes Species

The fungal associations present in the roots and corms of four species of Isoetes found in Rajasthan, India, are described. Fungal fruiting bodies and chlamydospores are assigned to the mycorrhizal genus Glomus, and the septate branched intracellular mycelium is assigned to the genus Rhizoctonia of the Deuteromycotina.

Fungal associations in the roots of three species of Isoetes L.

A fungal association has been described in the roots of three species of Isoetes which flourish during the rainy season in Rajasthan (India). The mycelium is septate, branched and forms bunches of intracellular hyphae in cortical cells of young roots. The association is symbiotic and is not influenced by habitat, i.e. while the host plant is aquatic, amphibious or terrestrial. This is the first report of a fungal association with the roots of the taxon Isoetes.

Levels and Patterns of Genetic Variation in Isoetes karstenii with Observations on I. palmeri

Genetic variation was surveyed in eleven populations from throughout the range of the diploid Isoetes karstenii, as well as in two populations of a closely related tetraploid, I. pal- meri, using allozyme electrophoresis. Genetic variation was high in I. karstenii and appears to be highly structured, as evidenced by analyses of F-statistics and genetic vs. geographic distance. No fixed unique alleles were found that could distinguish between I. karstenii and I. palmeri, although one allele was observed that was unique to I. palmeri. These analyses confirm earlier observations suggesting low levels of interpopulational gene flow and have implications for sampling strategies. Isoetes karstenii A. Braun was first described based on a collection from the high-altitude paramos of Merida, Venezuela (Braun, 1862). Since that time it has variously been accepted or synonymized by subsequent researchers, yet no detailed discussions of its variation or distribution have been published. As part of continuing research aimed at characterizing the neotropical species of Isoetes, we performed a survey of genetic variation in I. karstenii from throughout its range, as well as in a pair of populations from a single locality of a related species, I palmeri H.P. Fuchs, using allozyme electrophoresis. A taxonomic revision of the species complex to which these taxa belong is cur- rently in preparation (Small and Hickey, in prep.).