Species Of Isoetes Research Articles

Aquatic plants of Peru: diversity, distribution and conservation

Currently 177 vascular plant species are known or presumed to be obligately associated with water in Peru. Their composition and diversity were surveyed in relationship to their distributions among the natural regions of Peru. Despite considerable aridity, the coastal plains of Peru have important aquatic ecosystems, including marshes in river deltas and mangroves in the far north, near the border with Ecuador; 70 species of aquatic plants are found in this coastal region. The Andean highlands include a great variety of wetlands, plus lakes and rivers; 62 species are found, including eight species of Isoetes, some of which are potentially threatened by extinction. The Amazon region of Peru includes both steep montane rivers in the headwaters and wide floodplains formed by meandering rivers in the lowlands; 102 species are found distributed among these ecosystems, although many additional species are semi-aquatic. Research and conservation strategies for Peru's aquatic plants need to take into account these important regional differences.

Megaspores of some Indian species of Isoetes L. and comparable living and fossil forms

Megaspores of five Indian species of Isoetes., viz., I. coromandelina, I. indica, I. panchananii, I. tuberculata and I. rajasthanensis have been studied under light microscope and scanning electron microscope and Sem and compared with those of modern Salaginella and dispersed fossil megaspores.

Diurnal Acid Metabolism in the Submerged Aquatic Plant, Isoetes tuberculata

Diurnal acid metabolism has been studied largely in xerically adapted, terrestrial, succulent plants that carry out Crassulacean Acid Metabolism (CAM) (Kluge and Ting, 1978). In the CAM process, CO2 is fixed into malic acid during the dark and the activity of the enzyme PEP carboxylase is enhanced. During daylight hours, decarboxylation of CO2 fixed in the dark takes place, and it enters into the C3 cycle. Keeley (1981) reported for the first time the diurnal acid metabolism in the aquatic plant, Isoetes howellii Engelm. Since then this physiological process has been noted in 15 species of Isoetes out of the 60 known (Keeley, 1983, 1985, 1987; Keeley and Bowes, 1982; Keeley et al., 1983). In India, the genus Isoetes is represented by several species (Gena and Bhardwaja, 1984; Panigrahi, 1981; Pant and Srivastava, 1962; Sharma et al., 1985), and they occur as terrestrial, amphibious, or submerged aquatic plants. Diurnal acid metabolism has been studied for the first time in a submerged aquatic species, I. tuberculata Gena and Bhardwaja from the Indian subcontinent, using a simplified method of monitoring changes in the pH of leaf contents during a 48 hour period.

Seasonal changes in diel acid metabolism in two Pyrenean Isoetes species: I. setacea from a pool and I. lacustris from an oligotrophic lake

Seasonal changes in diel acid metabolism in two Pyrenean <i>Isoetes</i> species: <i>I. setacea</i> from a pool and <i>I. lacustris</i> from an oligotrophic lake

Biosystematic studies on the genusIsoetes in Japan I. Variations of the somatic chromosome numbers

The somatic chromosome number of three Japanese species ofIsoetes, I. asiatica, I. japonica andI. sinensis, was determined in 199 individuals from 49 populations. The chromosome number ofI. asiatica was 2n=22, confirming previous reports. However,I. japonica andI. sinensis displayed a diversity in chromosome number. Six cytotypes, 2n=66, 67, 77, 87, 88 and 89, were found inI. japonica; 2n=67, 87, 88 and 89 are new counts in the genusIsoetes. The plants with 2n=66 were the most frequent (72% of total individuals examined) and were distributed throughout Honshu and Shikoku. The plants with 2n=88 occurred in western Honshu and a limited region in northeastern Honshu where the plants with 2n=77 were also found. In contrast, four cytotypes, 2n=44, 65, 66 and 68, were found inI. sinensis. The chromosome numbers ofI. sinensis were reported here for the first time. The plants with 2n=44 occurred only in Kyushu, while the plants with 2n=66 were found throughout a large area of western Japan.

Diel acid fluctuations in pyrenean Isoetes species: The effects of seasonality and emersion

Diel acid fluctuations in pyrenean Isoetes species: The effects of seasonality and emersion

Isoetes hawaiiensis: A Previously Undescribed Quillwort from Hawaii

The pteridophytes of Hawaii have received relatively little attention from botanists during the past half-century. However, intensive recent studies in the islands have revealed a number of previously undescribed species, including the quillwort named here. Quillworts have been found in Hawaii several times since early this century. Between 25 September and 17 October 1917, Charles N. Forbes discovered Isoetes from pools atop Mt. Eke on the island of Maui (Forbes 682. M. BISH). Forbes did not recognize his collection to be Isoetes. It was not until 17 October 1977, when F. R. Warshauer collected Isoetes from the east slope of Mauna Kea on the island of Hawaii (Warshauer & McEldowney 1500 BISH), that Hawaiian botanists realized there was a native quillwort in the flora. Robert W. Hobdy again discovered Isoetes in pools on the summit of Mt. Eke on 23 October 1980 (Hobdy 931 BISH), and he collected it once more from the same site on 21 October 1982 (Hobdy 1705-1710 BISH). Study of these specimens and three later collections from Mt. Eke (Taylor 5332, 5658 MIL and Palmer 672 BISH) indicates that these Hawaiian quillwort acquisitions represent a previously undescribed species of Isoetes.

MEGASPORE WALL ULTRASTRUCTURE IN ISOETES

In Selaginella, megaspore wall ultrastructure (unit morphology and arrangement) is correlated with taxonomic position. In some Pennsylvanian lycopods there is a correlation with dispersal strategy. This study was designed to assess any correlation between habitat preference and wall ultrastructure in Isoetes. Except for a few minor structural correlations, wall ultrastructure appears to be constant in terrestrial, amphibious, and aquatic species of Isoetes. Several distinct sizes of megaspores occur in some megasporangia and correspond to 1) full-size megaspores with siliceous coatings, 2) small megaspores with siliceous coatings, and 3) full-size megaspores without siliceous coatings. The uniformity in wall ultrastructure within modem Isoetes together with the lack of uniformity of fossil isoetalean megaspore wall ultrastructure suggest that the modem species of Isoetes are closely related.

Megaspore Wall Ultrastructure in Isoetes

In Selaginella, megaspore wall ultrastructure (unit morphology and arrangement) is correlated with taxonomic position. In some Pennsylvanian lycopods there is a correlation with dispersal strategy. This study was designed to assess any correlation between habitat preference and wall ultrastructure in Isoetes. Except for a few minor structural correlations, wall ultrastructure appears to be constant in terrestrial, amphibious, and aquatic species of Isoetes. Several distinct sizes of megaspores occur in some megasporangia and correspond to 1) full-size megaspores with siliceous coatings, 2) small megaspores with siliceous coatings, and 3) full-size megaspores without siliceous coatings. The uniformity in wall ultrastructure within modem Isoetes together with the lack of uniformity of fossil isoetalean megaspore wall ultrastructure suggest that the modem species of Isoetes are closely related.

Allozyme Electrophoresis and the Taxonomy of Two Species of Isoetes in the Southeastern Appalachians

Recent research in the genus Isoetes has included both a continued effort to locate and describe new and little understood taxa as well as a new effort to understand their population biology and mechanisms of speciation. Gel electrophoresis has only recently been used to aid in the latter research. Taylor et al. (1985) and Taylor and Luebke (1988) have compared North American taxa using several enzyme systems, and Hickey et al. (1989b) have used electrophoresis to examine species relationships and population biology in Isoetes. Although electrophoresis may be utilized to distinguish taxa of Isoetes, practical methods of species sorting and identification in the genus continue to utilize characters of spore morphology, habitat preference, and geographical location. The purpose of the present study was to utilize the techniques of gel electrophoresis to explore the relationship between I. engelmannii A. Br. var. engelmannii and var. caroliniana Eaton (1900a). Data gathered as part of this study were also used to better understand the population biology of both taxa and to investigate the usefulness of electrophoresis for examining relationships between presumably closely and more distantly related taxa. Braun (1846) originally described I. engelmannii (Engelmann's quillwort) from specimens collected by Engelmann in 1842 from a Missouri pond near St. Louis. Later Engelmann (1867, 1882) described several varieties of the species: var. valida from Pennsylvania and Delaware, var. gracilis for small plants from southern New England, and var. georgiana for extremely large and robust plants from Floyd County, Georgia. Eaton (1905) recognized var. fontana for plants with accessory bast bundles in the leaves, spotted sporangia, and larger spores with broken reticulations. Isoetes engelmannii var. caroliniana was described by Eaton (1900) from Mitchell County, North Carolina, based on a wide velum covering up to two-thirds of the sporangia and megaspores with jagged crests to a broken reticulate pattern. This variety of I.

A Palynological Study of Isoetes taiwanensis DeVol

Isoetes contains approximately 150 species (Tryon & Tryon, 1982). Plants are diverse in habitat, ranging from evergreen hydrophytes to deciduous xerophytes (Pfeiffer, 1922). In Taiwan, I. taiwanensis DeVol grows submersed, but becomes emergent during short dry seasons. There are accounts of Isoetes plants being eaten by fish, birds, pigs, ducks, muskrats, cattle and humans (Pfeiffer, 1922), but in Taiwan, only ducks or other migratory birds are known to eat Isoetes (Chang & Hsu, 1977). In 1971, K. S. Hsu and H. C. Chang collected I. taiwanensis in Dream Lake, in the vicinity of Taipei's Yang Ming Shan National Park, at an altitude of 700m. Eight papers concerning this discovery have been published since 1972 (DeVol, 1972a, b, 1975; Chang & Hsu, 1977; T. C. Huang, 1981; S. E Huang, 1982; Huang & Chen, 1988). As part of a study on I. taiwanensis, spores were examined using a scanning electron microscope. Spores of three geographically proximate Isoetes species were also studied for comparison. A strategraphic pollen analysis was also made in Dream Lake sediments to determine the time of appearance of I. taiwanensis. MATERIALS AND METHODS

Morphology, ecology and distribution of Isoetes L. in Tasmania

Five species of Isoetes are known in Tasmania. I elatior, 1. humilior and 1. gunnii are endemic, whilst I. drummondii and l. muel/f'ri are also widespread in mainland Australia. Distinguishing morphological characteristics, distribution and ecology of the species are discussed. I muelleri is much more common and widespread than originally thought, and many new records have been made for I drummondii, 1. elatior and I humilior, enabling a better understanding of the ecology and conservation status of the genus in Tasmania.

Habitat, Evolution, and Speciation in Isoetes

Species of Isoetes are notorious for the difficulties they present in identification. These difficulties are attributable to a series of habitat adaptations that have resulted in morphological simplicity, homoplasy, and reticulate evolution. Internal air chambers in the leaves of all taxa indicate that primitive Isoetes was aquatic. During the breakup of Gondwana, ancestors of modern taxa appear to have passed through a terrestrialization phase, which was accompanied by development of several morphological novelties and reductions including the evolution of sclerotic phyllopodia. This adaptation appears to have evolved after separation of the Indian subcontinent (...)

Three New Species of Isoetes for the Southeastern United States

Three New Species of Isoetes for the Southeastern United States

On the phytosociology and ecology of Iso�tes asiatica (Makino) Makino in oligotrophic water bodies of South Sakhalin

In 1989, in the southeast of the Sakhalin Island and south of the village Okhotskoye, Isoetes asiatica (Makino) Makino and I. beringensis Kom. were detected in 24 oligotrophic lakes for the first time on Sakhalin. These are stands of the community of Isoetetum asiaticae ass. nov. which in the majority of the lakes form a characteristic pioneer vegetation of the shallow littoral zones. In addition to poor-species dominance stands of both of the Isoetes species, penetration stages of both of these species as well as stages rich in Comarum palustre, Eleocharis acicularis and Potamogeton species can be differentiated. Besides the structure of the species, the site conditions, particularly of the water bodies are described. The ion content is represented by absolute and relative ion field diagrams exemplified by 7 selected water bodies. The ion content is characterized by sodium and chloride which are prevailing, while calcium and magnesium as well as hydrogen carbonate and sulphate exist in low quantitative proportions only. The indicator values of individual characteristics and the complex characteristics of the Isoetes lakes are discussed. The hydrochemical characteristics of the Sakhalin, Kuriles and Kamchatka Isoetes waters are compared with the Isoetes water bodies of North America and Europe. The danger to Isoetes water bodies is discussed, necessary protective measures are defined.

Isoetes prototypus, a new diploid species from eastern Canada

A new species of Isoetes, I. prototypus from eastern Canada, is described. The morphology of the megaspores shows some similarity to those of acadiensis and I. hieroglyphica, but the microspores have a spinulose network on their surface. The plants have straight and rigid leaves that resemble some forms of I. macrospora. The species is diploid (2n = 22) and is found deep (± 2 m) in cool lakes in New Brunswick and Nova Scotia. Key words: Isoetes, new species, diploid, Canada, SEM.

The Species Concept in Pteridophyta with Special Reference to Isoetes

The definition, description, and identification of Isoetes species has always been difficult. This is primarily the result of an overall morphological simplicity and extreme phenotypic plasticity that combine to reduce the number of stable and therefore diagnostic characters. Such aspects of the biology of Isoetes have, historically, resulted in rather diverse specific treatments and circumscriptions. Recent studies in the genus have tended to emphasize previously overlooked characters and to apply both modern experimental techniques and the principles of population genetics in order to resolve many of these inconsistencies. Investigations utilizing cytological data, germination and hybridization studies, and protein electrophoresis have shown that over the range of a species its boundaries vary due to clinal variation, non-patterned geographical variation, interspecific hybridization, and the production of fertile allopolyploids. Such approaches have greatly increased our understanding of the dynamics of this genus. At the outset, it should be stated that it is not the objective of this paper to discuss the theoretical implications, or the limitations and benefits of the various species concepts that are currently in existence. Such discussions are numerous and can be found throughout the pages of many of the major systematic journals such as Systematic Botany, Systematic Zoology and Biology and Philosophy. Rather, this paper is designed to illustrate both the current and the historical application of the various species concepts in pteridophytes with particular reference to Isoetes. It is hoped that the reader will come away with an appreciation of the progressive nature involved in the elucidation of species and for the (practical) necessity of applying multiple species concepts during any given systematic inquiry (see also Zander, 1985). To illustrate such processes the following examples will be presented: the I. storkii aggregate of Costa Rica; the I. melanopoda complex of the southeastern United States; and the Isoetes species of northeastern North America. As a prelude to these examples, a brief review of the species concept and a discussion of the role of herbarium material will be presented. Species concepts.-For the purposes of this paper, the species concepts of consequence are: the typological species concept (TSC), the morphological species concept (MSC) and the biological species concept (BSC). The TSC is associated with all poorly known groups. Typically it is associated with rare or at least rarely collected species and is almost always employed when only a single collection is known for the species; i.e., simply, the species is circumscribed upon the only materials available-the type. The MSC, the traditional concept of

EVIDENCE FOR POST‐TRANSLATIONAL MODIFICATION OF TRIOSE PHOSPHATE ISOMERASE (TPI) IN ISOËTES (ISOËTACEAE)

As part of an electrophoretic study on Isoites, a number of Neotropical and North American species were examined for allozyme variation in TPI. Three of these species-L storkii, L flaccida, and L mexicana-exhibit three distinct zones of TPI activity. The two most anodally migrating zones are comparable to the two zones found in most angiosperms and in several other species of Isoetes. The single or three-banded phenotypes produced at these loci correspond, respectively, to the homozygous and heterozygous pattems typical of a dimeric enzyme. The most cathodal zone (zone III) differs in producing either single or two-banded phenotypes. Analyses of these three zones indicate a nearly perfect correlation between zones II and III in putative allelic constitution and relative allelic mobility. Explanations involving TPI gene duplications and/or null alleles fail to account for the peculiar banding characteristics and origin of activity zone III. An altemative hypothesis involving a protease duplication and differential post-translational modification is postulated. This hypothesis adequately explains the zone III phenotypes and fixation of the third activity zone in the species examined. Amino acid sequencing is suggested as the most direct test of this hypothesis. The taxonomic distribution of TPI III generally supports a previous, morphologically-based, hypothesis on species relationships in Isoetes. The presence of this zone is regarded as an independent synapomorphy for a major clade of Neotropical Isoetes. TRIOSE PHOSPHATE ISOMERASE (TPI) is a glycolytic enzyme mediating the interconversion of dihydroxyacetone phosphate and glyceraldehyde 3-phosphate. A majority of diploid angiosperms and certain pteridophytes typically exhibit two zones of banding activity on starch gels indicating that TPI is encoded by two loci. Genetic studies (Gottlieb, 1982) have shown that these two zones do in fact represent discrete loci, both of which are nuclear. Additional studies employing pollen exudates and cell fractionations (Gottlieb, 1982; Gastony and Darrow, 1983; Soltis, 1986) have shown that the products of these two genes are differentially expressed in the cytosol and the plastids. Because this enzyme is dimeric, individuals heterozygous at a TPI locus normally resolve as a three-banded pattern using standard starch gel electrophoretic techniques; individuals I Received for publication 1O November 1987; revision accepted 6 June 1988. This research was supported by NSFgrant BSR 86-0672. The authors thank Drs. Susan Bamum, Jan Jaworski, and Jack Vaughn for comments and assistance during the formulation of this paper. We also thank Elizabeth Southworth for her help in the laboratory. The authors are grateful to the three reviewers who provided helpful suggestions on and insights into novel interpretations of the TPI phenotypes observed. homozygous at TPI loci produce only a single band at each locus. Interlocus heterodimers are not known to occur in plants between TPI loci in different compartments (Gottlieb, 1982). Although TPI is normally encoded by two loci, a number of cases are known in which at least one of these TPI loci has been duplicated. Gottlieb (1982), for example, has shown that both cytosolic and plastid TPI have been duplicated subsequent to the origin of the genus Clarkia and that one or both of these duplications represent distinguishing features for most species in the genus. A characteristic of gene duplications in TPI and in other dimeric enzymes is the presence of one or more sets of three nonsegregating bands: a case of apparent fixed heterozygosity. Examples ofthis apparent fixed heterozygosity have been found in a large number of pteridophytes including Lycopodium (Soltis and Soltis, 1988), Equisetum (Soltis, 1986), and nearly all members of the Polypodiaceae sensu lato examined to date (see Haufler and Soltis, 1986). In Lycopodium and Equisetum, the additional TPI bands are compartmentalized in the plastids, whereas the extra bands of the polypodiaceous ferns are cytosolic. Three hypotheses have been put forth to explain the peculiar three-banded pattern

Isoetes X hickeyi: A Naturally Occurring Hybrid between I. echinospora and I. macrospora

Speculation about the occurrence of interspecific hybrids in Isoetes began as early as 1896 when Dodge noted that some New England species of Isoetes intergrade at times. Jeffrey and Hicks (1925) and Jeffrey (1937) attributed variation in size and shape of megaspores, lack of protoplasmic content in microspores, and lagging chromosomes during microsporogenesis to hybridization in Isoetes from Nova Scotia. Boom (1980) artificially crossed several Isoetes species. Subsequently, he proposed six interspecific hybrids from southeastern United States (Boom, 1982). However, Kott and Britton (1983) believed that there was insufficient evidence to support interspecific hybridization in northeastern North American Isoetes, and that either ethological or sterility barriers exist among most taxa. Data are presented here to document the natural occurrence of an interspecific hybrid in Isoetes. Hybrids between Isoetes echinospora and I. macrospora were discovered in Neva Lake, Langlade County, Wisconsin. These plants possess megaspores that are more variable in size, shape, and surface ornamentation than typical megaspores of I. echinospora and I. macrospora. The origin of I. echinospora x macrospora is supported by evidence from spore morphology and viability, chromosome counts made from root tip squashes, and electrophoresis of leaf enzymes.

TertiaryIsoetesfrom Tasmania

Leaves and megaspores for the Late Oligocene — Early Miocene Monpellyata flora are assigned to the new species Isoetes reticulata. This represents the first Tertiary macrofossil evidence for the genus in Australia. The species is distinct from all extant species of Isoetes in southern Australia and does not closely resemble any extant species so far examined. The lack of stomates on the leaves of I. reticulata suggests that the species grew wholly submerged in water, and this, along with the excellent state of preservation, adds to evidence indicating that the depositional site was equivalent to an extant alpine or sub-alpine lake with Isoetes growing in situ.