Incongruence between morphology and molecules, i.e., genetic differentiation of lineages that are morphologically identical, or morphological variation among accessions sharing identical genotypes, has been increasingly reported and is most problematic in taxa with reduced morphologies. We here review and discuss these issues for plant taxonomy, taking Salicornia, one of the taxonomically most challenging genera of angiosperms, as a model. We argue in favour of a taxonomic system that remains as much 'workable' as possible for traditional morphology‐based taxonomy, but avoids merging genetically widely divergent lineages despite their morphological similarity. Our revised classification of Eurasian taxa includes four species, ten subspecies and one nothosubspecies. The molecular and morphological characteristics as well as the geographical distribution of each taxon are described. A key to the Eurasian taxa based on morphology and geographical distribution is presented.
The main factor of differentiation at six nuclear microsatellite and seven cpDNA loci in Salicornia from the Mediterranean and Atlantic coasts of France is cytotypic identity, suggesting the presence of a strong reproductive barrier among sympatric cytotypes. Within cytotypes, a substantial proportion of the differentiation between species is due to confounded phylogeographic signal. Conspecific individuals tend to be significantly more related than individuals from different species at the population scale, but mean kinship coefficients among pairs of conspecific and nonconspecific individuals from different populations are not significantly different, suggesting the absence of reproductive isolation among species of the same cytotype. The observed association between morphology and genetic variation within populations would thus result from the selfing mating system (Fis = 0.70) generating substantial linkage within the genome, linkage that would quickly disappear among unrelated individuals from different populations. Salicornia species thus function as a network of inbred populations, strongly challenging taxonomic concepts.
In the northeastern part of Belgium, the Centaurea jacea complex shows extensive morphological variation and is represented by a diploid (2n l 22) and a tetraploid (2n l 44) cytotype. Polysomic inheritance of allozyme markers in the tetraploids, suggesting autopolyploidy, is here demonstrated for the first time. In order to test whether the two cytotypes occupy distinct habitats and possess different gene pools, patterns of allozymic and morphological variation were investigated in relation to ploidy level and site characteristics in 26 populations from the Belgian Ardennes. The two cytotypes showed a parapatric distribution, the diploids occurring at higher elevations (mostly above 500 m) than the tetraploids (mostly below 500 m). Three mixed populations were found near the contact zone of the two cytotypes. Within the mixed populations no triploid plant and no evidence for gene flow between cytotypes were found, despite widely overlapping flowering periods. The two cytotypes can be distinguished on the basis of morphological traits and enzymatic gene pools. The congruence of morphological and allozymic variation with chromosome numbers suggests a secondary contact between the two cytotypes with limited gene flow between them. The origin and persistence of the parapatric distribution are discussed.
JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. . International Association for Plant Taxonomy (IAPT) is collaborating with JSTOR to digitize, preserve and extend access to Taxon. http://www.jstor.org This content downloaded from 62.122.76.60 on Fri, 20 Jun 2014 01:30:24 AM All use subject to JSTOR Terms and Conditions VANNEROM). -Nouvelle Flore de la Belgique, du Grand-Duche de Luxembourg, du Nord de la France et des Regions voisines (Pteridophytes et Spermatophytes). Ed. Patrimoine J. bot. nat. Belgique, I973, XCVII + 821 p., 20 pl. couleurs et I carte h.t., Preface de F. DEMARET. La parution d'une Flore, description analytique des taxons vegetaux d'une region donnee, est toujours un evenement qui retient l'attention des biovegetalistes, des botanistes de terrain surtout. C'est particulierement vrai pour le present ouvrage dont le titre indique le contenu biologique general et circonscrit le territoire floristique concerne: Belgique, G.-D. L., S. des Pays-Bas, districts les plus occidentaux de l'Allemagne et les 9 departements frangais septentrionaux, de celui du Nord a la Somme, la Marne et la Moselle. La carte annexee a l'Introduction divise cet ensemble en une douzaine de districts phytogeographiques aux limites beaucoup plus naturelles. Une des premieres preoccupations des utilisateurs devra done consister a "oublier" les frontieres internationales et administratives.II ne faudrait pas croire qu'il s'agit d'une deuxieme 6dition de la "Flore de la Belgique, du Nord de la France et des Regions voisines" (Liege I967), realisee par une 6quipe d'auteurs sensiblement la meme, excellent ouvrage rapidement epuise, consacre au meme territoire. La refonte de la matiere et l'enrichissement de la documentation font de la Flore de I973 un ouvrage nouveau.Le taxon de base reste l'espece; on ne voit guere comment on pourrait faire autrement. Les cles dichotomiques, outil indispensable au floriste, semblent bien avoir ete l'objet d'un soin tout particulier, a la fois dans le choix des caracteres d'identification et dans celui des mots charges de les traduire. L'usage de ces cles devrait en confirmer la 374 374 TAXON VOLUME 24 TAXON VOLUME 24 This content downloaded from 62.122.76.60 on Fri,
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