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Taxonomic Categories (taxonomic + category)
Selected AbstractsTaxonomic significance of pollen morphology in some taxa of ResedaceaeFEDDES REPERTORIUM, Issue 7-8 2002S.M. El Naggar Pollen morphology of 13 species and two subspecies belonging to five genera: CayluseaSt.-Hil., OchradenusDelile, RandoniaCoss., OligomerisCambess., and Reseda L. of Resedaceae in Egypt were investigated by light and scanning microscopy. The pollen grains were examined and separated into three pollen types and six subtypes representing the different taxonomic categories on the basis of pollen morphological characters, principally pollen shape, size and exine sculpture. The palynological results are discussed with respect to current systematic treatments of Resedaceae. According to the present palynological results, Resedaceae is a eurypalynous and not a stenopalynous family. In addition, this work came to the conclusions that further studies on the pollen of Resedaceae will be useful in establishing a phylogenetic relationship. Zur taxonomischen Bedeutung der Pollenmorphologie bei einigen Taxa der Familie Resedaceae Mittels Licht- und Rasterelektronen-Mikroskopie wurde die Morphologie der Pollen von 13 Arten und zwei Unterarten aus fünf Gattungen der Familie Resedaceae Ägyptens untersucht: CayluseaSt.-Hil., OchradenusDelile, RandoniaCoss., OligomerisCambess. und Reseda L. Die untersuchten Pollen wurden in drei Typen mit sechs Subtypen unterteilt. Auf der Basis dieser Pollenmorphologie repräsentieren sie verschiedene taxonomische Kategorien: Pollenform, Größe und Skulptur der Exine. Die erzielten Ergebnisse werden in Bezug auf die gegenwärtige Systematik der Resedaceen diskutiert. Entsprechend den hier vorgelegten Daten sind die Resedaceae eine eury- und nicht stenopalynologische Familie. Zusätzlich ergibt sich aus dieser Studie, dass weitere Untersuchungen an Resedaceen-Pollen sinnvoll sind, um phylogenetische Beziehungen aufzufinden. [source] Power law relationships among hierarchical taxonomic categories in algae reveal a new paradox of the planktonGLOBAL ECOLOGY, Issue 5 2006Sophia I. Passy ABSTRACT Aim, In this continental-scale study, the biodiversity of benthic and planktonic algal communities was explored. A recent analysis of extinct and extant tree communities by Enquist et al. (2002) showed that richness of higher taxa was a power function of species richness, invariant across temporal and spatial scales. Here we examined whether the relationships between algal richness at hierarchical taxonomic levels conform to power laws as seen for trees, and if these relationships differ between benthic and planktonic habitats. Location, Streams from more than 50 major watersheds in the United States. Method, A total of 3698 samples were collected from 1277 locations by the National Water-Quality Assessment Program. Three types of stream habitat were sampled: richest targeted habitats, depositional targeted habitats, and phytoplankton. The relationships between taxonomic richness at the species level vs. all higher categories from genus to phylum across the three habitats were examined by ordinary least squares (OLS) regressions after ln-transformation of all variables. The slopes, b, of these regressions represent the exponents of the power functions that scaled the richness of higher taxonomic levels (T) to species richness (S) in the form: T,Sb. Results, Algal richness at hierarchical taxonomic categories (genus to phylum) is a power function of species richness. The scaling exponent of this function, which captures the diversification of higher taxa, i.e. the rate of increase of their richness with the increase of species richness, is significantly different across environments. Main conclusions, The differential algal diversification in the three studied habitats emphasizes the fundamental role of the environment in structuring the communities of simple organisms such as algae. The finding that the diversification of higher taxa is greater in the seemingly homogeneous planktonic environment, when compared to benthic habitats, encompassing an array of ecological niches, poses a new paradox of the plankton. [source] Species concepts and species reality: salvaging a Linnaean rankJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 2 2003M. S. Y. Lee Abstract The validity of the species category (rank) as a distinct level of biological organization has been questioned. Phenetic, cohesion and monophyletic species concepts do not delimit species-level taxa that are qualitatively distinct from lower or higher taxa: all organisms throughout the tree of life exhibit varying degrees of similarity, cohesion, and monophyly. In contrast, interbreeding concepts delimit species-level taxa characterized by a phenomenon (regular gene flow) not found in higher taxa, making the species category a distinct level of biological organization. Only interbreeding concepts delimit species-level taxa that are all comparable according to a biologically meaningful criterion and qualitatively distinct from entities assigned to other taxonomic categories. Consistent application of interbreeding concepts can result in counterintuitive taxonomies , e.g. many wide polytypic species in plants and narrow cryptic species in animals. However, far from being problematic, such differences are biologically illuminating , reflecting differing barriers to gene flow in different clades. Empirical problems with interbreeding concepts exist, but many of these also apply to other species concepts, whereas others are not as severe as some have argued. A monistic view of species using interbreeding concepts will encounter strong historical inertia, but can save the species category from redundancy with other categories, and thus justify continued recognition of the species category. [source] Genetic divergence between morphological forms of brown trout Salmo trutta L. in the Balkan region of MacedoniaJOURNAL OF FISH BIOLOGY, Issue 5 2010S. Lo Brutto The objective of this study was to characterize the genetic structure of two Balkan brown trout morphotypes, Salmo macedonicus and Salmo pelagonicus, and to test whether molecular traits support the species' status proposed by traditional morphological identification. The mitochondrial DNA 12S-rDNA, cyt b and control region genes were sequenced in 15 specimens collected from three localities in the Former Yugoslav Republic of Macedonia. The results of these markers did not support the taxonomic category of species but confirmed the existence of two morphotypes, Salmo trutta macedonicus and Salmo trutta pelagonicus, in the Aegean,Adriatic lineages of the Salmo trutta species complex. [source] Phylogenetic position of Salmo(Platysalmo)platycephalus Behnke 1968 from south-central Turkey, evidenced by genetic dataJOURNAL OF FISH BIOLOGY, Issue 4 2004S. Su To determine whether the current classification of the flathead trout Salmo (Platysalmo) platycephalus, endemic to the upper reaches of the Zamanti River system, Turkey, based solely on morphology, is in congruence with molecular phylogeny, the nucleotide sequence variation in mitochondrial (control region and cytochrome b gene) and nuclear (internal transcribed spacer of rRNA genes) DNA for the flathead trout and various representatives of the genus Salmo was studied. On the basis of pair-wise genetic distance estimates, the highest differences were found to exist between the flathead trout and S. salar, S. ohridana and S. obtusirostris, whereas the differences between the flathead trout and S. trutta were minimal. All the analyses performed firmly positioned the flathead trout within the Adriatic phylogeographic lineage of S. trutta; however, the exact position of the flathead trout within the Adriatic cluster was irresolvable. Accordingly, classifying the flathead trout as a subgenus of Salmo is unjustifiable and its reclassification in a lower taxonomic category is suggested by the present study. [source] | ||||||||||