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Kaplan Z., Fehrer J. & Hellquist C. B. (2009): New hybrid combinations revealed by molecular analysis: The unknown side of North American pondweed diversity (Potamogeton). – Syst. Bot. 34: 625–642.
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The occurrence and diversity of Potamogeton hybrids was investigated in eastern North America, the region of the highest diversity of Potamogeton species in the world. For various reasons, however, the existence of hybrids in this area has been largely overlooked. ITS direct sequencing and RFLPs revealed four previously unknown hybrids, which are described as Potamogeton ×aemulans (P. bicupulatus × P. epihydrus), P. ×mirabilis (P. gramineus × P. oakesianus), P. ×versicolor (P. epihydrus × P. perfoliatus), and P. ×absconditus (P. perfoliatus × P. richardsonii). These are the first confirmed hybrids involving P. bicupulatus, P. epihydrus, P. oakesianus, and P. richardsonii. Another hybrid, P. ×nitens (P. gramineus × P. perfoliatus), is for the first time confirmed for North America with molecular markers. The hybrids’ maternal parents were revealed by cpDNA sequencing. Phenotypically, two of the hybrids more closely resemble other taxa than their parents. Hybrid diversity and recognition in North America and in Europe are compared. Morphological versus molecular identification of hybrids, occurrence of hybrids in the absence of their parents, parental species relationships, long-term persistence of hybrid clones, vegetative dispersal, frequency of hybridization events, and hybrid distribution patterns are discussed.
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Kaplan Z. & Fehrer J. (2009): An orphaned clone of Potamogeton ×schreberi in the Czech Republic. – Preslia 81: 387–397.
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A Potamogeton hybrid found growing in the absence of parental species in a South Bohemian stream, Czech Republic, was subjected to molecular analyses to identify its exact identity. RFLP of the ITS region confirmed its previous morphological identification as P. natans × P. nodosus (= P. ×schreberi). A comparison of its RFLP pattern with those of P. gramineus, P. lucens and P. polygonifolius unambiguously excluded the possibility that the investigated plants are specimens of other similar hybrids (P. ×fluitans, P. ×sparganiifolius, P. ×gessnacensis). The discovery of P. ×schreberi in South Bohemia is the first record of this hybrid for the Czech Republic. So far, it is known only from five countries and the Czech clone is one of a few extant clones of this hybrid in Central Europe. Chloroplast DNA sequencing identified P. nodosus as the maternal parent although at present this species neither occurs at the locality, nor upstream, nor in the entire drainage basin. The other species, P. natans, only occurs downstream of the locality in isolated side pools in a former stream bed and fishponds in an adjacent drainage basin. The available data indicate that this hybrid has persisted vegetatively at this locality for some time in the absence of its parents.
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Zalewska-Gałosz J., Ronikier M. & Kaplan Z. (2009): The first European record of Potamogeton ×subobtusus identified using ITS and cpDNA sequence data. – Preslia 81: 281–292.
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A combined study of morphology, stem anatomy and DNA sequencing data (nuclear ribosomal ITS region and rpl32-trnL and rps12-rpl20 intergenic spacers of chloroplast DNA) was used to identify a putative Potamogeton hybrid from a river in NE Poland. Based on the morphological and anatomical characters the plants were tentatively identified as P. ×subobtusus Hagstr., a hybrid between P. alpinus Balb. and P. nodosus Poir. This identification was independently confirmed by the presence in hybrid individuals of an additive ITS sequence pattern from these two parental species. In all plants peaks corresponding to nucleotide states of both parents were clearly distinguishable, however the variants from P. nodosus dominated over those from P. alpinus. P. nodosus was also identified as the maternal parent of the hybrid based on cpDNA data and dominated the expression of morphological features in hybrid individuals. A detailed morphological description of P. × subobtusus and the typification of the name are provided. As P. nodosus rarely hybridizes with other species, existence of other hybrids, as well as possible difficulties in recognizing these taxa are also discussed.
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Kaplan Z. (2008): A taxonomic revision of Stuckenia (Potamogetonaceae) in Asia, with notes on the diversity and variation of the genus on a worldwide scale. – Folia Geobot. 43: 159–234.
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A taxonomic revision of the Asian species of Stuckenia, a segregate of Potamogeton, is presented. Six species are recognized and their morphological descriptions, nomenclature and typification of relevant names are given. Distributions of all species are described and lists of representative specimens and distribution maps provided. Lectotypes are designated for 24 names and nomenclatural types are listed for 22 additional names. The correct name for the species known as Potamogeton recurvatus is Stuckenia pamirica (Baagöe) Z. Kaplan, comb. nova. Morphological variation at different levels within the genus is described and compared with different concepts of its taxonomic interpretation. Instructions on examination of key characters are given, together with a key to species. Colour photographs illustrate the general appearance of species as well as many identification details. The pattern of variation and taxonomic validity of the Siberian morphotypes S. subretusa and S. austrosibirica are analyzed. The plasticity of diagnostic characters of P. juncifolius and of P. helveticus from the European Alps, the infraspecific classification of S. filiformis in North America, and the taxonomic status of S. punensis described from Peru are also discussed.
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Kaplan Z. & Fehrer J. (2007): Molecular evidence for a natural primary triple hybrid in plants revealed from direct sequencing. – Ann. Bot. 99: 1213–1222.
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Molecular evidence for natural primary hybrids composed of three different plant species is very rarely reported. An investigation was therefore carried out into the origin and a possible scenario for the rise of a sterile plant clone showing a combination of diagnostic morphological features of three separate, well-defined Potamogeton species. The combination of sequences from maternally inherited cytoplasmic (rpl20-rps12) and biparentally inherited nuclear ribosomal DNA (ITS) was used to identify the exact identity of the putative triple hybrid. Direct sequencing showed ITS variants of three parental taxa, P. gramineus, P. lucens and P. perfoliatus, whereas chloroplast DNA identified P. perfoliatus as the female parent. A scenario for the rise of the triple hybrid through a fertile binary hybrid P. gramineus × P. lucens crossed with P. perfoliatus is described. Even though the triple hybrid is sterile, it possesses an efficient strategy for its existence and became locally successful even in the parental environment, perhaps as a result of heterosis. The population investigated is the only one known of this hybrid, P. × torssanderi, worldwide. Isozyme analysis indicated the colony to be genetically uniform. The plants studied represented a single clone that seems to have persisted at this site for a long time.
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Kaplan Z. (2007): First record of Potamogeton × salicifolius for Italy, with isozyme evidence for plants collected in Italy and Sweden. – Pl. Biosystems 141: 344–351.
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Potamogeton × salicifolius, a hybrid between P. lucens and P. perfoliatus, is identified as a new taxon for Italy. This is the first record of this hybrid from southern Europe. The Italian sample was studied in cultivation and compared with a living specimen of P. × salicifolius from Sweden, where the hybrid is rather widespread. In addition to morphological features, the most compelling evidence for the hybrid origin of these plants came from the isozyme analysis. The additive “hybrid” banding patterns of the five enzyme systems studied indicate inheritance from P. lucens and P. perfoliatus. The distribution of this hybrid in Europe coincides with the areas most severely affected by the Late Pleistocene glaciation. The relationships between environmental conditions, history of the habitat and rise of hybrids are discussed.
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Kaplan Z. & Fehrer J. (2006): Comparison of natural and artificial hybridization in Potamogeton. – Preslia 78: 303–316.
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The first attempt to artificially hybridize species of Potamogeton resulted in the hybrid P. perfoliatus × P. gramineus. The morphological features, reproductive behaviour and molecular markers of the offspring of this experimental hybridization were compared with those of the parental species and natural hybrids of the same assumed parentage. A phenotype corresponding to that of the natural hybrid P. × nitens was acquired from an experimental cross between P. perfoliatus and P. gramineus. All plants, both natural and artificial, of this hybrid were consistently sterile. They showed the ITS variants of both parental taxa, which is consistent with biparental inheritance of nuclear DNA. The experimental hybrid was used to test the maternal inheritance of chloroplast DNA in Potamogeton. Sequences of a chloroplast intergenic spacer (rpl20-rps12) were identical with those of the female parent. Then, the directions of the crosses resulting in the natural hybrids were investigated. Of five natural populations of P. × nitens, P. gramineus was the maternal parent of two and P. perfoliatus of three populations. The frequency of hybridization events and rise of hybrids are discussed.
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Kaplan Z. (2005): Potamogeton schweinfurthii A. Benn., a new species for Europe. – Preslia 77: 419–431.
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The occurrence in the Mediterranean part of Europe of the African species Potamogeton schweinfurthii is recorded for the first time. So far, this native but overlooked species has been found on five major Mediterranean islands: Corsica, Sardinia, Malta, Kefallinía (Ionian Islands, Greece) and Crete. The species is most similar and presumably closely related to the mainly Eurasian P. lucens, with which it has been partly confused. The nomenclature and a description of P. schweinfurthii are provided, and its taxonomy and how it differs from similar taxa discussed. All known localities are listed, together with voucher specimens preserved in the major European herbaria. A distribution map of P. schweinfurthii in the Mediterranean region is presented.
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Kaplan Z. (2005): Neotypification of Potamogeton ×fluitans Roth and the distribution of this hybrid. – Taxon 54: 822–826.
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The identity of the name Potamogeton fluitans Roth has for a long time been uncertain. An analysis of the history of the name and its use is presented and the identity of the extant material ascribed to Roth discussed. The name P. fluitans is neotypified with a specimen from a population of the hybrid P. lucens L. × P. natans L. recently studied morphologically, anatomically and electrophoretically. Nomenclature of the hybrid is summarized and lectotypes for a further four names designated. Distribution of the hybrid is described and a list of representative specimens given.
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Krahulec F., Kaplan Z. & Novák J. (2005): Tragopogon porrifolius × T. pratensis: the present state of an old hybrid population in Central Bohemia, the Czech Republic. – Preslia 77: 297–306.
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A population of a hybrid between Tragopogon porrifolius and T. pratensis (T. ×mirabilis), which occurs in SW part of the town of Roudnice nad Labem, N part of Central Bohemia, was analysed with respect to its morphology, fertility, life history, ploidy level and DNA content. Both parental species vary relatively little morphologically; they are biennials (monocarpic perennials) and diploids. T. pratensis is a native species in the Czech Republic, T. porrifolius was cultivated there in the past. The hybrid plants are extremely morphologically variable, with variation ranges of some characters overlapping those of the parental species (e.g. ligules are often longer than involucral bracts, peduncles are often lanate). Only diploids were found within the hybrid population; however, they have substantially lower DNA content than both parents (18% lower than T. pratensis, 42% lower than T. porrifolius). The plants of the Roudnice hybrid population are polycarpic perennials in contrast to the monocarpic perennial (mostly biennial) parents. The distribution is described in detail; it shows that the hybrid plants are spreading and at present even occur outside the town. The long-persisting population of fertile diploid hybrid plants in Roudnice nad Labem is an alternative evolutionary pathway to that of the allotetraploid Tragopogon species known from North America.
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Kaplan Z. & Symoens J.-J. (2005): Taxonomy, distribution and nomenclature of three confused broad-leaved Potamogeton species occurring in Africa and on surrounding islands. – Bot. J. Linn. Soc. 148: 329–357.
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A taxonomic revision of broad-leaved Potamogeton species ascribed to the ‘P. schweinfurthii–thunbergii complex’ occurring in Africa and on surrounding islands is presented. Three species, P. nodosus, P. richardii and P. schweinfurthii, are recognized in the African mainland. The widespread species P. nodosus has been widely overlooked in sub-Saharan Africa. It is recorded here for the first time from eight countries of tropical and southern Africa and from six surrounding islands. The distribution of P. richardii is critically revised and the species is recorded for the first time from Cameroon, Swaziland and Madagascar. P. schweinfurthii is recorded for the first time from Algeria, Tunisia, Burkina Faso and Niger. The nomenclature of all three species is revised. Lectotypes are designated for six names. All original material of the name P. thunbergii Cham. et Schltdl. actually belongs to P. nodosus Poir. The correct name for the East and southern African species called ‘P. thunbergii’ is P. richardii Solms. The lectotype of P. schweinfurthii designated by Dandy proved to be P. nodosus. A new type is therefore proposed for the species generally named P. schweinfurthii and the name itself is proposed for conservation. The morphology and stem anatomy of P. nodosus, P. richardii and P. schweinfurthii are described. In spite of some overlaps in the morphological variation in their vegetative characters, a detailed analysis of the variation patterns and instructions for reliable identification are given. The distributions of all three species are described, based solely on reliably identified specimens, many of which were also examined anatomically. Distribution maps are provided.
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Kaplan Z. & Zalewska-Gałosz J. (2004): Potamogeton taxa proposed by J. F. Wolfgang and his collaborators. – Taxon 53: 1033–1041.
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In the first half of 19th century Jan Fryderyk Wolfgang (1775-1859) was the outstanding expert on Potamogetonaceae. Twelve of the names he proposed in a manuscript of a monograph on Potamogeton were validly published by Schultes & Schultes (1827). Of these, four names are now the correct names for the respective taxa, one for a species (P. rutilus Wolfg.) and three for hybrids (P. ×nerviger Wolfg., P. ×salicifolius Wolfg. and P. ×undulatus Wolfg.). Ten names of Potamogeton taxa described by Wolfgang are typified in this paper, together with two names proposed by his collaborators, Besser and Gorski. The identity of these names is discussed.
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Kaplan Z. & Fehrer J. (2004): Evidence for the hybrid origin of Potamogeton ×cooperi (Potamogetonaceae): traditional morphology-based taxonomy and molecular techniques in concert. – Folia Geobot. 39: 431–453.
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The identity of plants morphologically intermediate between Potamogeton crispus and P. perfoliatus from two recently discovered sites, one in Moravia, Czech Republic and another in Wales, United Kingdom, was investigated with molecular markers. Evidence from restriction fragment length polymorphism analysis of the nuclear internal transcribed spacer region of ribosomal DNA and of the trnK-trnQ chloroplast DNA intergenic spacer confirmed the morphology-based determination of two putative hybrid samples as P. ×cooperi. The hybrids showed the ITS variants of both parental taxa, consistent with the expected biparental inheritance of nuclear DNA. The chloroplast DNA markers indicate P. crispus as the female parent in both hybridization events. The hybrid origin of another dubious sample was excluded by the molecular data, in accordance with previous detailed morphological examination. This plant represented an extreme, narrow-leaved form of P. perfoliatus, imitating P. ×cooperi in some characters. The results of the molecular analyses are discussed in relation to the morphology of the plants. They underline that some Potamogeton hybrids could indeed be identified by careful and detailed morphological examination and also that these identifications were reliable and confirmed by molecular markers. This study exemplifies that long-term taxonomic expertise usually generates very well-founded specific questions suitable for straightforward treatment by appropriate molecular methods. The process and ecological implications of hybrid formation are also discussed.
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Kaplan Z. & Wolff P. (2004): A morphological, anatomical and isozyme study of Potamogeton ×schreberi: confirmation of its recent occurrence in Germany and first documented record in France. – Preslia 76: 141–161.
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A combined study of morphology, stem anatomy and isozyme patterns was used to reveal the identity of sterile plants from two rivers on the Germany/France border. A detailed morphological examination proved that the putative hybrid is clearly intermediate between Potamogeton natans and P. nodosus. The stem anatomy had characteristics of both species. The most compelling evidence came from the isozyme analysis. The additive “hybrid” banding patterns of the six enzyme systems studied indicate inheritance from P. natans and P. nodosus. In contrast, other morphologically similar hybrids were excluded: P. ×gessnacensis (= P. natans × P. polygonifolius) by all the enzyme systems, P. ×fluitans (= P. lucens × P. natans) by AAT, EST and 6PGDH, and P. ×sparganiifolius (= P. gramineus × P. natans) by AAT and EST. All samples of P. ×schreberi are of a single multi-enzyme phenotype, suggesting that they resulted from a single hybridization event and that the present-day distribution of P. ×schreberi along the Saarland/Moselle border was achieved by means of vegetative propagation and long-distance dispersal. Neither of its parental species occur with P. ×schreberi or are present upstream, which suggests that this hybrid has persisted vegetatively for a long time in the absence of its parents. The total distribution of this hybrid is reviewed and a detailed account of the records from Germany is given. P. ×schreberi appears to be a rare hybrid. The risk of incorrect determination resulting from the identification of insufficiently developed or inadequately preserved plant material is discussed.
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Kaplan Z. & Štěpánek J. (2003): Genetic variation within and between populations of Potamogeton pusillus agg. – Plant Syst. Evol. 239: 95-112.
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Patterns of isozyme variation were examined in 17 populations of P. pusillus and P. berchtoldii, together with 1 population of P. trichoides taken for comparison. Both P. pusillus and P. berchtoldii displayed low levels of variation within populations associated with high levels of interpopulation differentiation. This pattern of partitioning of genetic variation within and between populations is attributed to the founder effect, frequent vegetative propagation by turions, dominant self-fertilization and limited seedling recruitment. The mechanism of pollen transfer was investigated in cultivation. Effective pollination takes place in air above the water surface (autogamy, geitonogamy, anemogamy), on the water surface (epihydrogamy) or below water surface (hydroautogamy). The species are self-compatible. The low level of infra-population variation together with rare occurrence of heterozygotes suggest that selfing is the most frequent mode of pollination, although the protogynous flowers may occasionally permit some cross-pollination. Unique enzyme markers were found for P. pusillus and P. berchtoldii, and also for the single population of P. trichoides. All multienzyme phenotypes were species-specific. Isozyme data support the separate position of P. pusillus and P. berchtoldii. UPGMA dendogram based on enzyme data of 133 plant samples revealed three distinct main enzymatic entities perfectly corresponding to the three morphologically defined species.
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Kaplan Z. (2003): Linear-leaved species of Potamogeton in the Czech Republic V. P. pectinatus. – Preslia 75: 165–181.
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The last part of a revision of linear-leaved species of the genus Potamogeton in the Czech Republic focuses on P. pectinatus. This species is the only member of subgenus Coleogeton occurring in this country. Species description, relevant synonyms, illustrations, a list of specimens examined and a distribution map are provided. P. pectinatus is widespread in the Czech Republic; it is the most common Potamogeton species particularly in runningwaters. P. pectinatus still quite often grows in most lowland rivers and their basins.
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Kirschner J. & Kaplan Z. (2002): Taxonomic monographs in relation to global Red Lists. – Taxon 51: 155–158.
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Upon comparison with recent monographs of Juncaceae and Potamogetonaceae, the 1997 IUCN Red List of Threatened Plants is shown to be an inadequate information source for conservation decisions. A substantial proportion of names listed in the IUCN RL represent synonyms, often belonging to widespread taxa, or remain doubtful taxonomically. If a new Red List is derived from the two new monographic accounts, and compared with the 1997 IUCN RL, the correct data from the latter represent 10–25% of the former. It may concluded that the overall accuracy of the IUCN list is rather low. The importance of global taxonomic monographs as a source of basic data for the accurate compilation of Red Lists is stressed.
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Kaplan Z. (2002): Linear-leaved species of Potamogeton in the Czech Republic IV. P. pusillus s.l. and P. trichoides. – Preslia 74: 345–371.
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The fourth part of a revision of linear-leaved species of the genus Potamogeton in the Czech Republic is given, dealing with P. pusillus s.l. and P. trichoides. The appropriate taxonomic concept and species delimitation within P. pusillus s.l. are discussed. Because of still unresolved taxonomic difficulties and high percentage of specimens that cannot be assigned to one of the two traditionally distinguished species, P. pusillus s. str. (syn. P. panormitanus) and P. berchtoldii, the broader concept of P. pusillus s.l. has tentatively been adopted in this revision. This species complex is widespread in the Czech Republic, absent only in relatively small areas of the highest elevations and the driest areas without suitable biotopes. P. pusillus s.l. is the commonest taxon of Potamogeton in standing waters. P. trichoides, a well defined species distinguished by several morphological characters, occurs scattered mainly in S, C and E Bohemia and S and C Moravia, with most localities concentrated in S Bohemia. It is considered as strongly threatened species of the Czech flora. Species descriptions, relevant synonyms, illustrations, a list of specimens examined and distribution maps are provided for both species. P. rutilus was once reported from the Czech Republic in error. No specimen from this country has been found in herbaria.
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Kaplan Z., Plačková I. & Štěpánek J. (2002): Potamogeton ×fluitans (P. natans × P. lucens) in the Czech Republic. II. Isozyme analysis. – Preslia 74: 187–195.
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Evidence from isozyme electrophoresis confirmed previous hypothesis on the occurrence of interspecific hybridization between Potamogeton natans L. and P. lucens L. formulated on the basis of morphology and stem anatomy. Isozyme phenotypes of the morphologically intermediate plants were compared with those obtained from the putative parents growing in the same locality. P. natans and P. lucens differed consistently in at least 12 loci and possessed different alleles at 7 loci. The hybrid had no unique alleles and exhibited an additive “hybrid” isozyme pattern for all 7 loci that could be reliably analysed and where the parents displayed different enzyme patterns. Both true parental genotypes were detected among samples of plants of P. lucens and P. natans from the same locality. The hybrid plants represent a recent F1 hybrid generation resulting from a single hybridization event. Consistent differences in enzyme activity between submerged and floating leaves of P. natans and P. ×fluitans were observed in all interpretable enzyme systems.
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Kaplan Z. (2002): Phenotypic plasticity in Potamogeton (Potamogetonaceae). – Folia Geobot. 37: 141–170.
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Sources of the extensive morphological variation of the species and hybrids of Potamogeton were studied, especially from the viewpoint of the stability of the morphological characters used in Potamogeton taxonomy. Transplant experiments, the cultivation of clones under different values of environmental factors, and the cultivation of different clones under uniform conditions were performed to assess the proportion of phenotypic plasticity in the total morphological variation. Samples from 184 populations of 41 Potamogeton taxa were grown. The immense range of phenotypic plasticity, which is possible for a single clone, is documented in detail in 14 well-described examples. The differences among distinct populations of a single species observed in the field were mostly not maintained when grown together under the same environmental conditions. Clonal material cultivated under different values of environmental factors produced distinct phenotypes, and in a few cases a single genotype was able to demonstrate almost the entire range of morphological variation in an observed trait known for that species. Several characters by recent literature claimed to be suitable for distinguishing varieties or even species were proven to be dependent on environmental conditions and to be highly unreliable markers for the delimitation of taxa. The unsatisfactory taxonomy that results when such classification of phenotypes is adopted is illustrated by three examples from recent literature. Phenotypic plasticity was found to be the main source of morphological variation within the species of Potamogeton, having much more influence than morphological differences caused by different genotypes.
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Kaplan Z. (2002): Main sources of taxonomic difficulties in Potamogeton. – Zprávy Čes. Bot. Společ. (Praha) 37: 43–46.
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Main sources of taxonomic difficulties in Potamogeton are identified and described. Prevailing clonal reproduction, autogamy and the founder effect play the principal roles in genetic structure of populations. Genetic variation is higher between than within populations. Extensive phenotypic plasticity and parallel evolution giving rise to shared morphological similarities obscure relationships between evolutionary units and their morphology. Occasionally evolving hybrids are sometimes difficult to distinguish from the respective parent species and some of them may be thus overlooked. In contrast, extreme morphotypes of true species are sometimes misidentified as hybrids. Even though hybridisation does not seem to be frequent event in Potamogeton, once established hybrids can persist in their localities for a long time or even spread vegetatively.
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Kaplan Z. (2002): Linear-leaved species of Potamogeton in the Czech Republic III. P. obtusifolius and P. friesii. – Preslia 74: 267–280.
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The third part of a revision of linear-leaved species of the genus Potamogeton in the Czech Republic is given. Two species, P. obtusifolius and P. friesii, are dealt with in this contribution. Species descriptions, relevant synonyms, illustrations, a list of specimens examined and distribution maps are provided. P. obtusifolius grows almost exclusively in the Bohemian part, particularly in S and E Bohemia, whereas in Moravia it is confined to a few localities mainly in its NE part (Silesia). It is classified as a threatened species of the Czech flora. P. friesii has been collected only in a few localities in C and NE Bohemia. Last time it was seen in 1989 but has not been confirmed in the site since then; thus the species belongs among missing (and probably extinct) taxa in the Czech Republic.
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Kaplan Z. (2001): Potamogeton ×fluitans (P. natans × P. lucens) in the Czech Republic. I. Morphology and anatomy. – Preslia 73: 333–340.
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Potamogeton ×fluitans Roth (P. natans L. × P. lucens L.) was discovered in NE Bohemia as a new taxon for the Czech Republic. In the site, the hybrid grew together with both its parents. The revision of herbarium specimens proved that all previous records of “P. fluitans” from the Czech Republic were erroneous. Morphological and anatomical characters of the hybrid are described, together with those of its parents and other morphologically similar taxa. P. ×fluitans differs from P. natans especially in having submerged leaves with a distinct lamina and petioles of floating leaves without a flexible section at the junction with the lamina. From P. lucens, it is distinguished by the capability of developing floating leaves and by long, narrowly oblong submerged leaves. While stem anatomical pattern of P. ×fluitans is intermediate between those of its parents, it is easily distinguishable from that of morphologically the most similar P. nodosus Poir. The hybrid is sterile and no trace of developed fruits has been found among the Czech material.
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Kirschner J. & Kaplan Z. (2001): Taxonomic and nomenclatural notes on Luzula and Juncus (Juncaceae). – Taxon 50: 1107–1113.
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New taxa and combinations are presented to be included in the prepared treatment of Juncaceae in the Flora of the World. A new section, Luzula sect. Atlanticae, and a new species, Luzula indica, are described, and three new combinations are made: Luzula nipponica (Satake) Kirschner & Miyamoto, L. lutescens (Koidzumi) Kirschner & Miyamoto, and Luzula alpino-pilosa subsp. deflexa (Kozuharov) Kirschner. A new name, Juncus meianthus K. Wilson is proposed for a later homonym, J. gracilis R. Br. The name Luzula acuminata Raf. is neotypified in order to retain its current usage.
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Kaplan Z. (2001): Linear-leaved species of Potamogeton in the Czech Republic: II. P. compressus and P. acutifolius. – Preslia 73: 127–139.
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A revision of linear-leaved species of the genus Potamogeton in the Czech Republic is given. Two species, P. compressus and P. acutifolius, are dealt with in this paper. Species descriptions, relevant synonyms, illustrations, a list of specimens examined and distribution maps are provided. P. compressus, always an extremely rare taxon in the Czech Republic, is now extinct. P. acutifolius, now strongly endangered in its occurrence, has main centres of its distribution in pond areas in SW and E Bohemia.
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Kubát K. & Kaplan Z. (2001): Arnoseris minima Schweigg. et Koerte in the Czech Republic. – Severočes. Přír. (Litoměřice) 32("2000"): 29–36.
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Arnoseris minima is a scarce and critically endangered species of the Czech flora. Altogether, it has been found on approximately 200 localities but during the last 20 years it has been confirmed to still occur in only 12 sites. These recent localities are confined to N and S Bohemia. A list of specimens examined and a distribution map are provided.
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Kaplan Z. (2001): Taxonomic and nomenclatural notes on Luzula subg. Pterodes (Juncaceae). – Preslia 73: 59–71.
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New taxa and combinations are given resulting from a revision of Luzula subg. Pterodes (Griseb.) Buchenau for the monographic treatment of Juncaceae for Species plantarum: Flora of the world. Luzula jimboi Miyabe et Kudo subsp. atrotepala Z. Kaplan, subsp. nova, and L. plumosa E. Mey. subsp. dilatata Z. Kaplan, subsp. nova, are described. Three new combinations, L. forsteri (Sm.) DC. subsp. rhizomata (Ebinger) Z. Kaplan, comb. nova, L. acuminata Raf. subsp. carolinae (S. Watson) Z. Kaplan, comb. nova, and L. plumosa E. Mey. subsp. reflexa (Ebinger) Z. Kaplan, comb. nova, are proposed for taxa with obvious geographically correlated variations. Identity of L. cechica Domin, a name proposed for the putative hybrid of L. luzuloides × L. pilosa, and that of a misapplied name L. rostrata Buchenau is elucidated. Diagnostic characters of members of taxonomically difficult groups are given. Eight names are lectotypified.
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Kaplan Z. (2000): Linear-leaved species of Potamogeton in the Czech Republic: I. Introduction and key to determination. – Preslia 72: 457–467.
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A revision of linear-leaved species of the genus Potamogeton in the Czech Republic is given. On the basis of field investigation, cultivation experiments and herbarium studies, 8 taxa have been recognized as distinct species. Prevailing clonal reproduction, autogamy, easy dispersal on long distances, and especially extensive phenotypic plasticity are taken for the principal sources of taxonomic difficulties. Description and explanation of special morphologic terms, comments on infrageneric classification, and instructions for collecting and drying of specimens are provided. This first part of a series of papers on linear-leaved species includes also key to determination.
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Kaplan Z. (2000): Lemna turionifera – a new species for the Czech Republic. – Zprávy Čes. Bot. Společ. (Praha) 34("1999"): 135–141.
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Lemna turionifera has been found as a new species for the Czech Republic. It is only known from a single site so far: northern Bohemia, Distr. Turnov, Český ráj Landscape Area, Březina village, small concrete water reservoir in Kurovodice settlement, 0.8 km S–SSE of the Březina railway-station, 255 m a. s. l., 18 September 1997, leg. Z. Kaplan 97/908. Voucher specimens are deposited in the herbarium of the present author at the Institute of Botany, Průhonice, Czech Republic, and in the herbarium of Prof. E. Landolt at the Geobotanisches Institut ETH, Stiftung Rübel, Zürich, Switzerland, who kindly revised the determination. The aim of the present paper is to make current knowledge on the species accessible to Czech botanists in order to stimulate them to look for it in the field. Differential characters of L. turionifera are listed in the paper. A key to the determination to all Central European members of Lemnaceae together with their illustrations are provided as well.
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Kirschner J., Novara L. J., Novikov V. S., Snogerup S. & Kaplan Z. (1999): Supraspecific division of the genus Juncus (Juncaceae). – Folia Geobot. 34: 377–390.
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New classification of the genus Juncus (Juncaceae) is presented. The genus is divided in two subgenera, characterized by the presence/absence of bracteoles and the structure of inflorescence. Lower rank subdivisions, sections, generally correspond to the traditionally recognized subgenera introduced by Buchenau. A new name is introduced for what has been called subg. (sect.) Ensifolii, Juncus sect. Iridifolii. A checklist of supraspecific names in Juncus, with typification and references to the sectional names accepted, is presented in the Appendix.
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Wiegleb G. & Kaplan Z. (1998): An account of the species of Potamogeton L. (Potamogetonaceae). – Folia Geobot. 33: 241–316.
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An account of the taxonomy of the genus Potamogeton L. with special reference to species description and delimitation is presented. A key to the species is given, based as far as possible on vegetative characters. Detailed descriptions are provided for a total of 69 species which are regarded as sufficiently well known. Special emphasis is laid both on a complete list of relevant characters as well as on the judgement of their respective diagnostic values. All important synonyms are listed allowing direct access to most of the relevant taxonomic and floristic Potamogeton literature. 50 confirmed hybrids are listed and assigned to their putative parent species. Questions with respect to the taxa listed are formulated in notes on each of the species. A more general view and questions on future Potamogeton research are summarized in the conclusions.
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Kaplan Z. & Řehořek V. (1998): Galium parisiense - a new alien species for the Czech Republic. – Preslia 70: 51–56.
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Two specimens of Galium parisiense L. having their origin in the wild in the Czech Republic have been found during the study of the herbaria of PR and BRNM. The species has never been reported for the country before. The earlier collection is from the present-day area of Prague in central Bohemia, the later one from a field near the village of Nedachlebice in southeastern Moravia. Both localities are situated on the northeastern border of the species distribution. No recent occurrence of the species in the wild in the Czech Republic has been reported, except for the single find in a concrete flower-bowl in Brno, southern Moravia. Infraspecific variation and its taxonomic evaluation is discussed in the present paper.
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Kaplan Z. (1998): Relict serpentine populations of Knautia arvensis s. l. (Dipsacaceae) in the Czech Republic and an adjacent area of Germany. – Preslia 70: 21–31.
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Several distinct populations of Knautia arvensis (L.) Coulter s. l. restricted to serpentine outcrops have been found in the Czech Republic and an adjacent area of Germany. They have been determined as diploids or tetraploids despite the fact that only common, non-serpentine tetraploids occur in the area. These plants differ also in their morphology, florogenesis, and in their behaviour within a plant community from all other known taxa within the species. Their origin has been explained by the hypothesis of microevolution of a relict diploid ancestor. The isolated relict populations have not expanded their range, being confined to the place where they originated.
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Kaplan Z. (1997): Names of Potamogeton (Potamogetonaceae) proposed by Bohemian botanists in the period 1819–1902. – Preslia 69: 193–239.
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Names of taxa of the genus Potamogeton proposed by Bohemian authors are discussed and typified. 74 names are listed, proposed by L. Čelakovský, F. X. Fieber, P. M. Opiz, J. S. Presl, K. B. Presl (= C. B. Presl), J. Rohlena, F. J. Ruprecht, D. Sloboda and I. F. Tausch. Three names and their types are of importance for contemporary plant taxonomy: P. berchtoldii Fieber, P. ×angustifolius J. S. Presl [= P. gramineus L. × P. lucens L.] and P. friesii Rupr. The study has also proved the justification of the use of these names. The correct name for the species known as P. malaianus [auct.] or P. mucronatus C. B. Presl is P. wrightii Morong. In order to preserve nomenclatural stability, a justification for the conservation of the name P. maackianus A. Benn. against P. serrulatus Regel et Maack is given.
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Krahulec F. & Kaplan Z. (1995): Diversity of Potamogeton species during 21 years of succession in a new water reservoir. – Preslia 66: 237–241.
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The composition of the Potamogeton flora and its changes during 21 years of vegetation succession in the new water reservoir Rozkoš in East Bohemia are described. Ten species and two hybrids were observed at this locality during this period and in two years preceding the flooding. It seems highly probable that this richness was confined only to a short period during the succession. Diversity was correlated with trophic conditions in the reservoir.
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Kaplan Z. (1995): Genus Potamogeton on the Svjatoj Nos isthmus and in the Barguzinskaja valley, Lake Baikal. – Siber. Nat. (Praha) 1: 73–89.
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Genus Potamogeton was studied in two wetlands in the eastern vicinity of Lake Baikal: on the isthmus of the Svjatoj Nos Peninsula with adjacent parts of Čivyrkujskij Bay and in Barguzinskaja Basin. Distribution of Potamogeton taxa is presented, based on the authors fieldwork and published data. Taxonomical, ecological and syntaxonomical comments are also given. The possibility of the occurrence of Potamogeton taxa recently described from Siberia is discussed.
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