Inheritance and genetic diversity of some enzymes in the sexual and diploid pool of the agamic complex of Maximae (Panicum maximum Jacq., P. infestum Anders. and P. trichocladum K. Schum.)

La tribu des #Maximae (#Panicum maximum Jacq., #P. infestum Anders., #P. trichocladum K. Shum. ) comprend deux pools sympatriques avec différents modes de reproduction et de niveaux de ploidie : un pool tétraploïde et apomictique d'une part, et un pool plus petit, pool diploïde et sexué d'autre part. Chez ce dernier, la sexualité autorise ces croisements et rend ainsi possible la mise en évidence de la structure (monomérique ou dimérique) de 9 systèmes enzymatiques et de leur déterminisme génétique (16 loci). Des distorsions de ségrégation ont été observées dans les systèmes malate déshydrogenase et estérase. La diversité du pool diploïde est importante en accord avec son mode de reproduction (allogamie et anémophile). Cette diversité est divisée en 3 groupes correspondant à l'origine géographique des populations. Cette organisation est très proche de celle observée à partir de caractères morphologiques. (Résumé d'auteur

Super-Genotype: Global Monoclonality Defies the Odds of Nature

The ability to respond to natural selection under novel conditions is critical for the establishment and persistence of introduced alien species and their ability to become invasive. Here we correlated neutral and quantitative genetic diversity of the weed Pennisetum setaceum Forsk. Chiov. (Poaceae) with differing global (North American and African) patterns of invasiveness and compared this diversity to native range populations. Numerous molecular markers indicate complete monoclonality within and among all of these areas (FST = 0.0) and is supported by extreme low quantitative trait variance (QST = 0.00065–0.00952). The results support the general-purpose-genotype hypothesis that can tolerate all environmental variation. However, a single global genotype and widespread invasiveness under numerous environmental conditions suggests a super-genotype. The super-genotype described here likely evolved high levels of plasticity in response to fluctuating environmental conditions during the Early to Mid Holocene. During the Late Holocene, when environmental conditions were predominantly constant but extremely inclement, strong selection resulted in only a few surviving genotypes

Genetic structure of a population sample of apomictic dandelions

In Northern Europe, dandelion populations consist solely of triploid or higher polyploid apomicts. Without a regular sexual cycle or lateral gene transmission, a clonal structure is expected for Taraxacum apomicts, although this was not found by compatibility analysis. In this study, we investigate whether this observation could be suported by performing independent tests based on data from hypervariable microsatellite markers as well as more conservative data based on allozymes and matrilinear cpDNA markers. In addition, population genetic methods were used to test departure from panmictic expectations, which is expected for clonal populations. Results indicated that many data sets, again, did not agree with expectations from clonal evolution because only small groups of genotypes exhibit no marker incompatibility. Population genetic analysis revealed that virtually all genotypes, but not individuals, agreed with random segregation and genotypic equilibria. Exceptions were genotypes with rare allozyme alleles or nearly identical microsatellite genotypes. Consequently, a population sample of apomictic dandelions essentially harbours genotypes that resulted from segregation and/or recombination and only a few genotypes that may have differentiated by somatic mutations [KEYWORDS: Taraxacum, apomixis, AFLPs, character incompatibility]