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Navicula similecataracta-rheni sp. nov. and N. aquitanonipponica sp. nov. (Bacillariophyta), two new species from Nouvelle-Aquitaine, Southwestern France - comparison with the related species N. cataracta-rheni Lange-Bertalot, N. cryptotenella Lange-Bertalot and N. sancti-naumii Levko et Metzeltin
Environmental factors and diatoms were studied in 151 stations in Cypriot streams. Since Navicula simplex Krasske [new combination: Craticula simplex (Krasske) Levkov] is based on the small–scale drawing of a single valve and the type material is no longer available, we provide additional ecological, morphological, and ultrastructural data, and an epitype for C. simplex, which is distinguished by valve outline and stria density, and occurs in small, nutrient–enriched streams. Two other symmetric biraphid species are proposed as new to science based on light and scanning electron microscopy, careful comparison with similar established taxa, and on the analysis of our multi–annual databases. Mastogloia cyprica Lange–Bert. et Cantonati sp. nov. differs from similar species by raphe undulation, stria density, and rare occurrence in oligo– to slightly–eutrophic streamlets and lakes with medium–high conductivity. Navicula loumatensis Lange–Bert. et Cantonati sp. nov. is characterized by the combination of valve outline, central area, and by a high areola density, and occurs in medium–high conductivity, low–N but P–enriched streams. In–depth knowledge of Mediterranean stream diatoms is of pivotal importance in these critical decades of climate change.
The new species Navicula meulemansii Mertens, Witkowski et Lange-Bertalot sp. nov. is described after study by light microscopy and scanning electron microscopy. Based on new morphological information, the relationship with other taxa is discussed. Navicula meulemansii has a wide geographical distribution in coastal brackish waters (The Netherlands and Germany), European estuaries (Tagus, Portugal), and the San Francisco Bay in California (U.S.A.). Evidence suggests that N. meulemansii has a very broad ecological tolerance, similar to other cosmopolitan species such as Planothidium delicatulum, Navicula gregaria and Nitzschia palea.
Type material of Navicula exilis and Navicula cryptocephala from the Kützing collection at the Natural History Museum, London, was re-investigated in light and electron microscopy. The morphology of these species was studied in detail using original materials and the nomenclature and previous studies of type material summarized. Navicula exilis is compared with Navicula cryptocephala, Navicula cryptocephala var. exilis, Navicula lothargeitleri and Navicula adversa.
Autoecological traits of aquatic organisms are well known to provide crucial information on hydrosystems and
are good complements to biotic indices for evaluating surface water ecological quality. In France, as in many
other European countries, autoecological approaches concerning diatoms are based on a checklist developed in
the Netherlands. While this work was pioneering and suited to the conditions of study, ecological indicators
developed in such small scales and such specific natural environments often show reduced efficiency when used
in other conditions.
France is a vast and highly biogeographically diversified region with many situations that are not to be found
in the Netherlands, such as limestone substrate rivers and torrents in mountainous areas. Consequently, the
elaboration of a better suited autoecological reference system has been long requested by French water managers
to support ecological diagnosis.
In this study, we elaborated a new autoecological reference system gathering knowledge on environmental
optima, tolerance and range values for 809 French diatom taxa, along with an ordinal classification for 7 au-
toecological traits: water acidity, water mineralisation, oxygen requirements, saprobity, trophic state, organic
nitrogen and nitrates. By combining weighted averaging and regression tree techniques we also produced a
simple, statistically robust and reproducible approach to study univariate taxa-environment relationships in a
given region.
This new trait matrix, in addition to providing autoecological attributes for over 200 French diatom taxa that
had no correspondence in previous reference systems, also takes into account French specificities such as the
scarcity of acidic situations and mineral nitrogen issues. On the basis of this new matrix, 3 autoecological
functional groups have been identified in French diatom flora, mainly related to traits linked to anthropogenic
disturbance. This revised autoecological classification will provide much more reliable information on French
stream benthic diatoms ecology, and should therefore allow better ecological diagnosis if accompanied by rig-
orous management of synonyms and taxonomic levels.
During an extensive survey of the diatoms of Swedish rivers, four new Navicula species (Bacillariophyceae) were found: Navicula antonioides sp. nov., N. ireneae sp. nov., N. scaniae sp. nov. and N. ceciliae sp. nov. The new species are described formally using light and scanning electron microscopy. All four species possess a unique set of morphological characters including the structure of the central raphe endings, the striation pattern, the valve dimensions and outline, which make it possible to separate them from similar Navicula taxa such as N cryptocephala, N radiosafallax or N. antonii. The ecological preferences of each species are briefly discussed. Finally, the distribution of Navicula s.s. taxa in European inland waters is briefly discussed.
During a survey of some springs in the French Central Massif, a new Navicula species (Bacillariophyceae) was found: Navicula sanctamargaritae Beauger sp. nov. A second new Navicula species was observed during a routine biomonitoring project in Flanders: Navicula flandriae Van de Vijver & A.Mertens sp. nov.. The new species are formally described using light and scanning electron microscopy. Both species present a unique set of morphological characters including the structure of the central raphe endings, the striation pattern, the valve dimensions and outline, which allows their separation from similar Navicula taxa such as N. korzeniewskii, N. recens or N. cincta. The ecological preferences of each species are briefly
discussed.
Nine Navicula species observed in European rivers and lakes are discussed using light and scanning electron microscopy. Four of them are described as new species: Navicula antverpiensis Van de Vijver & Lange-Bertalot sp. nov., N. wendlingii Lange-Bertalot, Hofmann & Van de Vijver sp. nov., N. lacuum Lange-Bertalot, Hofmann, Werum & Van de Vijver sp. nov. and Navicula suecicarum Van de Vijver, Jarlman & Lange-Bertalot. The taxonomy of five other, already established, taxa is investigated: Navicula neomundana(Lange-Bertalot) Van de Vijver, Jarlman & Lange-Bertalot stat. nov., Navicula simulata Manguin syn. Navicula symmetrica Patrick, Navicula schroeteri Meister s. str. and N. escambia (Patrick) Metzeltin & Lange-Bertalot. The ecological preferences and distribution for each species are briefly discussed. Navicula veneta Kützing is formally lectotypified.
Ultrastructural variation in valve morphology between members of Navicula “sensu stricto” is reviewed. Central and polar external raphe fissure paths, internal raphe features, the type and arrangement of the areolae, and girdle band morphology are documented and compared with these features in the generitype, Navicula tripunctata. Although the latter is the nomenclatural type, it is not required by the Botanical Code to be morphologically typical of the genus, although the generic circumscription must encompass it. Thus morphological variation across a genus should be expected to be wider than that shown by the generitype and taxonomic decisions should not be based on comparisons with the generitype only. The observed morphological variation within Navicula is discussed in relation to the recognition and definition of characters, particularly those used as the basis of some recent taxonomic revisions. It is argued that there is a continuum of variation in many morphological features within Navicula, and that, unless clear discontinuities in characters can be demonstrated, separation at the generic level is undesirable. The generic description is amended to reflect the observed range of morphology and structure.
Based on examination of a clay sample comprising part of the type material of diatoms described by Skvortzow in 1936 from Lake Biwa, lectotypes of the following 14 pennate diatom taxa were designated: Caloneis nipponica Skvortzow; Cocconeis disculus var. nipponica Skvortzow; Cymbella nipponica Skvortzow; Cymbella turgidula var. nipponica Skvortzow; Gomphonema lingulatum var. elongatum Skvortzow; Navicula costu-lata var. tenuirostris Skvortzow; Navicula gastrum fo. nipponica Skvortzow; Navicula hasta var. gracilis Skvortzow; Navicula lambda var. nipponica Skvortzow; Navicula lanceolata var. nipponica Skvortzow; Navicula radiosa fo. nipponica Skvortzow; Navicula rostellata var. biwaensis Skvortzow; Navicula similis var. nipponica Skvortzow; and Navicula undulata Skvortzow. Navicula lanceolata var. nipponica, N. costulata var. tenuirostris, N. undulata, G. lingulatum var. elongatum and N. lambda var. nipponica are probably later synonyms of other taxa. Navicula lambda var. nipponica and N. similis var. nipponica are given the new combinations Sellaphora lambda var. nipponica (Skvortzow) Ohtsuka and Placoneis clementis var. nipponica (Skvortzow) Ohtsuka, respectively. Cymbella turgidula var. nipponica, N. hasta var. gracilis, and N. rostellata var. biwaensis are each elevated to the independent species under the names Cymbella rhe-ophila Ohtsuka, Navicula subhasta Ohtsuka and Navicula biwaensis (Skvortzow) Ohtsuka, respectively.
Across the world there is a prevailing view that freshwater algae are cosmopolitan. The notion has seldom been tested and is unlikely to be true in genetic terms. Nonetheless, some morphospecies of several groups of algae do have a worldwide distribution. Others have restricted distributions and may be regarded as endemic to a region. However there is always the possibility that they will be discovered in far away places. Australia has a rather large element of endemicity in its algal flora. From the early days of Australian phycology many new genera and species of freshwater algae have been described. Some are of such distinctive appearance or novelty as to be regarded as ‘flagship’ taxa. There is little doubt about their endemicity and their existence increases the probability of less-distinguished species also being endemic. The degree of endemicity is probably masked by the ‘force-fitting’ of European names to Australian species.
Some Australian endemics are robust and are widely distributed in a variety of types of water body. Others, the frail endemics, the ones of greatest novelty and phylogenetic significance, have a very restricted range with their strongholds in dystrophic coastal lagoons where tracts or remnant patches of native vegetation survive. Their survival and the conservation of their biodiversity depends on recognition of the significance of coastal lagoons and swamps.
Diatom Flora of Marine Coasts 1
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Navicula sensu stricto, 10 Genera separated from Navicula sensu stricto, Frustulia
- Lange-Bertalot
Diatoms of Lakes Prespa and Ohrid - About 500 taxa from ancient lake system. -
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Diatoms from the Aono-gawa River
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Mayama, S. & Kobayashi, H. (1982): Diatoms from the Aono-gawa
River. -Bull. Tokyo Gakugei Univ. Sect 4. 34: 77-107. (in
Japanese).
New species and nomenclatural changes in the genus Navicula (Bacillariophyceae). -
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Diatoms of the Andes
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Atlas des diatomées de la région Languedoc Roussillon
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Asconit Consultants (2013): Atlas des diatomées de la région
Languedoc Roussillon. -561 pp., DREAL Languedoc
Roussillon, Montpellier.
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Lange-Bertalot, H. (1993): 85 New Taxa and much more than 100
taxonomic clarifications supplementary to Süßwasserflora
von Mitteleuropa Vol.2/1-4. -Bibliotheca Diatomologica
27: 1-454.