00355nas a2200109 4500008004100000245006600041210005900107300001000166490000900176100002000185856004000205 1875 eng d00aOn the recent progress and present state of systematic botany0 arecent progress and present state of systematic botany a27-540 v18741 aBentham, George uhttps://ubsc.myspecies.info/node/2002128nas a2200193 4500008004100000245006900041210006300110300001200173490000800185520157200193653001801765653002101783653002301804653001701827653002001844653001301864100001701877856004001894 2003 eng d00aProblem of the taxonomic category “species” in cyanobacteria0 aProblem of the taxonomic category species in cyanobacteria a281-2970 v1093 a

Abstract: In Cyanobacteria (cyanophytes, cyanoprokaryotes) “species” has been traditionally defined on the basis of morphological characters (“Geitlerian system”) and these same criteria are still commonly used for identification of natural populations. Modern investigations, based on EM-methods and molecular sequencing have proven the differences between the genotypes which correspond more or less with the traditional phenotypic genera (revised after re-evaluation of morphologial characters). However, within genotypes enormous variability of natural morphotypes and ecotypes has been found and the same diversity has been confirmed in strains in cultures. Genotypically distinct species have not been confirmed, and the separation of them according to morphological criteria is problematic with respect to wide morphological variability. – Because the purely traditional (morphological) concept of cyanobacterial species is frequently in disagreement with modern knowledge of cyanobacteria, the criteria for species delimitation should be changed. Taxonomic classification is always conventional; the definition of “species” in cyanobacteria is possible, if it will be based on rules developed in concordance with modern knowledge of morphology (phenotype variability and stability of different features), physiology, ecology and molecular bases of individual morpho- and ecotypes (e.g. morphospecies belonging to proved and distinct genotypes and characterised by ecological characterization).
 

10acyanobacteria10aCyanoprokaryotes10agenus delimitation10anomenclature10aspecies problem10ataxonomy1 aKomárek, J. uhttps://ubsc.myspecies.info/node/2202060nas a2200133 4500008004100000245007200041210006900113300000800182490000700190520165000197100001901847700002001866856004001886 2012 eng d00aSpecies Delimitation: Inferring Gaps in Morphology across Geography0 aSpecies Delimitation Inferring Gaps in Morphology across Geograp a1940 v613 a

Species are commonly delimited on the basis of gaps in patterns of morphological variation, but there seems to be little recent work on methods to objectively assess such gaps. Here, we introduce a statistical approach that uses measurements of continuous morphological characters and geographic variation in those characters to (i) measure the strength of the evidence for the existence of a gap in morphological variation between two hypothesized species and (ii) examine if a gap in morphological variation between two hypothesized species can be explained by an alternative hypothesis of geographic variation within a species. This approach is based on recent developments in analyses of multivariate normal mixtures, estimates of multivariate tolerance regions, and principal coordinates of neighboring matrices. We demonstrate the application of the approach by examining previously proposed hypotheses of species limits in the plant genus Escallonia. We discuss the main features of the method, including potential limitations, in relation to other approaches that use gaps in morphological variation as a criterion for species delimitation. The method we propose can help strengthen the link between the theory and practice of species delimitation by increasing the transparency and consistency of taxonomic decisions based on morphology, thus contributing to integrative approaches for species delimitation that consider morphological and geographic data on an equal footing with other kinds of information. [Geographic variation; morphological variation; normal mixture; operational criteria; species limits; tolerance limit.]

1 aZapata, Felipe1 aJiménez, Iván uhttps://ubsc.myspecies.info/node/12