Search results for "Asexual"
showing 6 items of 46 documents
Speciation in monogonont rotifers
1997
Monogonont rotifers are cyclical parthenogens livingin limnic habitats with considerable seasonalvariation and often with island-like features. Theoccurrence of bisexual reproduction in these organismsmakes it feasible to define ’fields for generecombination‘, i.e. biological species. In thispaper, we analyze the structure of the diversity inmonogonont rotifers using several data sets: taxonomicand intraspecific diversity as reported inidentification keys, morphological variation reportedin ecological studies, and allozyme and matingbehavior patterns. Our analysis suggests that siblingspecies may be frequent in rotifers. Monogonontrotifers seem to meet conditions for an activespeciation, wh…
Pythium carbonicum, a new species isolated from a spoil heap in northern France, the ITS region, taxonomy and comparison with related species.
2003
Pythium carbonicum (F-72) sp. nov. was found in soil samples taken on the top of a spoil heap in northern France. The morphology of this new species resembles that of a recently described species: Pythium megacarpum. However, the antheridial and oogonial characteristics of this new species are unique, and the comparison of its ITS region of the nuclear ribosomal DNA indicates that this species is also related to the genus Phytophthora. The fungus does not sporulate, the sporangia germinate directly into mycelium through germ tubes. The oogonia of P. carbonicum are smooth-walled and also papillated, and are provided with monoclinous and diclinous antheridia that wrap around, forming a compli…
Origin and evolution of Artemia reproductive and genetic diversity
2017
El modo de reproducción de una especie determina su diversidad genética y, a su vez, su éxito ecológico y evolutivo (Normarck et al., 2003; Simon et al., 2003; De Meeûs et al, 2007). En una población sexual, la recombinación meiótica permite que nuevas combinaciones de genes se formen y destruyan constantemente. De hecho, las poblaciones sexuales son generalmente más diversas genéticamente en comparación con las poblaciones asexuales. Por el contrario, en un linaje estrictamente asexual, donde se supone que la mutación (con la mayoría de mutantes deletéreos) sea la única fuente de diversidad genética, se espera que la diversidad clonal de la población se reduzca en cada generación. Por esto…
Selection on life-history traits and genetic population divergence in rotifers
2009
A combination of founder effects and local adaptation – the Monopolization hypothesis – has been proposed to reconcile the strong population differentiation of zooplankton dwelling in ponds and lakes and their high dispersal abilities. The role genetic drift plays in genetic differentiation of zooplankton is well documented, but the impact of natural selection has received less attention. Here, we compare differentiation in neutral genetic markers (FST) and in quantitative traits (QST) in six natural populations of the rotifer Brachionus plicatilis to assess the importance of natural selection in explaining genetic differentiation of life-history traits. Five life-history traits were measur…
Mictic patterns of the rotifer Brachionus plicatilis Müller in small ponds
1995
Populations of the rotifer Brachionus plicatilis were monitored in three small ponds in a marsh on the Mediterranean coast. Samples were taken approximately every three weeks from July 1992 to November 1993. Salinity, temperature, conductivity, pH and oxygen concentration were measured in the field. Population density was determined from preserved quantitative samples. Individuals were classified as mictic females, amictic females, non-ovigerous females, and males, differentiating between two morphotypes (‘S’ and ‘L’). From these counts, a level of mixis was calculated. We also determined the proportion of mictic females in natural populations by culturing females isolated from fresh sample…
Data from: Intralocus tactical conflict: genetic correlations between fighters and sneakers of the dung beetle Onthophagus taurus
2015
Males and females differ in their phenotypic optima for many traits, and since the majority of genes are expressed in both sexes, some alleles can be beneficial to one sex but harmful to the other (intralocus sexual conflict; ISC). ISC theory has recently been extended to intrasexual dimorphisms, where certain alleles may have opposite effects on the fitness of males of different morphs that employ alternative reproductive tactics (intralocus tactical conflict; ITC). Here we use a half-sib breeding design to investigate the genetic basis for ISC and ITC in the dung beetle Onthophagus taurus. We found positive heritabilities and intersexual genetic correlations for almost all traits investig…