Home  About us  Contact
 

Clonal Organisms (clonal + organism)

Distribution by Scientific Domains
Life Sciences100%

Selected Abstracts

Major histocompatibility complex variability in the clonal Amazon molly, Poecilia formosa: is copy number less important than genotype?

MOLECULAR ECOLOGY, Issue 6 2009
K. P. LAMPERT
Abstract The evolution of sex is still a major unsolved puzzle in biology. One of the most promising theoretical models to answer this question is the Red Queen hypothesis. The Red Queen hypothesis proposes a fast adaptation of pathogens to common genotypes and therefore a negative frequency-dependent selection against common genotypes. Clonal organisms should be especially endangered when co-occurring with closely related sexual species. In this context, major histocompatibility (MHC) genes have been discussed to be auspicious candidates that could provide the genetic basis on which selection for immune competence could act. In this study, we investigated MHC variability in a clonal teleost fish: the Amazon molly, Poecilia formosa. The Amazon molly is an ideal candidate to test the Red Queen hypothesis as it is a clonal species but co-occurs with a closely related sexual species and should therefore be especially susceptible to pathogen infection. We found that allele numbers did in general not differ between sexual and clonal ,species' but that genotypic variability is reduced in the clonally reproducing fish, especially in the polyploids. We conclude that in clonal organisms, genotype frequency might be more important for immune competence than MHC allele number. Amazon mollies and their co-occurring parental species clearly fulfil a prerequisite of the Red Queen hypothesis and should therefore provide an ideal system to experimentally test this basic principle probably underlying the evolution of sex. [source]

Genetic Exchange Within and Between Assemblages of Giardia duodenalis

THE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 6 2009
ERICA LASEK-NESSELQUIST
ABSTRACT. Meiotic sex evolved early in the history of eukaryotes. Giardia duodenalis (syn. Giardia lamblia, Giardia intestinalis), a parasitic protist belonging to an early diverging lineage of eukaryotes, shows no cytological or physiological evidence of meiotic or sexual processes. Recent molecular analyses challenge the idea that G. duodenalis is a strictly clonal organism by providing evidence of recombination between homologous chromosomes within one subgroup (Assemblage A) of this species as well as genetic transfer from one subgroup to another (Assemblage A,B). Because recombination is not well documented and because it is not known whether the observed inter-assemblage transfer represents true reciprocal genetic exchange or a non-sexual process, we analyzed genic sequences from all major subgroups (Assemblages A,G) of this species. For all assemblages, we detected molecular signatures consistent with meiotic sex or genetic exchange, including low levels of heterozygosity, as indicated by allelic sequence divergence within isolates, and intra- and inter-assemblage recombination. The identification of recombination between assemblages suggests a shared gene pool and calls into question whether it is appropriate to divide the genetically distinct assemblages of G. duodenalis into a species complex. [source]

Major histocompatibility complex variability in the clonal Amazon molly, Poecilia formosa: is copy number less important than genotype?

MOLECULAR ECOLOGY, Issue 6 2009
K. P. LAMPERT
Abstract The evolution of sex is still a major unsolved puzzle in biology. One of the most promising theoretical models to answer this question is the Red Queen hypothesis. The Red Queen hypothesis proposes a fast adaptation of pathogens to common genotypes and therefore a negative frequency-dependent selection against common genotypes. Clonal organisms should be especially endangered when co-occurring with closely related sexual species. In this context, major histocompatibility (MHC) genes have been discussed to be auspicious candidates that could provide the genetic basis on which selection for immune competence could act. In this study, we investigated MHC variability in a clonal teleost fish: the Amazon molly, Poecilia formosa. The Amazon molly is an ideal candidate to test the Red Queen hypothesis as it is a clonal species but co-occurs with a closely related sexual species and should therefore be especially susceptible to pathogen infection. We found that allele numbers did in general not differ between sexual and clonal ,species' but that genotypic variability is reduced in the clonally reproducing fish, especially in the polyploids. We conclude that in clonal organisms, genotype frequency might be more important for immune competence than MHC allele number. Amazon mollies and their co-occurring parental species clearly fulfil a prerequisite of the Red Queen hypothesis and should therefore provide an ideal system to experimentally test this basic principle probably underlying the evolution of sex. [source]

clonality V.0.4: a randomization-based program to test for heterozygosity-genet size relationships in clonal organisms

MOLECULAR ECOLOGY RESOURCES, Issue 5 2008
FRANCK PRUGNOLLE
Abstract clonality V.0.4 is a program for testing heterozygosity-genet size relationships in clonal organisms using a randomization procedure. The software has been developed under the Borland Delphi developing environment and a Windows-executable version is freely downloadable from http://gemi.mpl.ird.fr/SiteSGASS/Prugnolle/ClonalityPage.html. The program compares the observed FIS of the population with the FIS expected if genets (multilocus genotypes present in multiple copies within the population) were chosen randomly from the set of different multilocus genotypes. The randomization procedure is performed with the same number of genets and the same number of repetitions per genet as what is observed in the original data set. [source]