Search results for "selection"

Distortion of symmetrical introgression in a hybrid zone: evidence for locus-specific selection and uni-directional range expansion

2006

The fate of species integrity upon natural hybridization depends on the interaction between selection and dispersal. The relative significance of these processes may be studied in the initial phase of contact before selection and gene flow reach equilibrium. Here we study a hybrid zone of two salamander species, Lyciasalamandra antalyana and Lyciasalamandra billae, at the initial phase of hybridization. We quantify the degree and mode of introgression using nuclear and mtDNA markers. The hybrid zone can be characterized as an abrupt transition zone, the central hybrid zone being only c. 400 m, but introgressed genes were traced up to 3 km. Introgression was traced in both sexes but gene flo…

Effect of hairless gene polymorphism on the breeding values of milk production traits in Valle del Belice dairy sheep

2013

The aim of this work was to assess the association between the hairless genotypes and estimated breeding values (EBVs) for milk yield (MY), fat (FAT) and protein (PRT) content in Valle del Belice dairy sheep breed. A data set from 465 randomly chosen unrelated individuals was analyzed. EBV for MY, FAT and PRT contents were estimated by REML analysis of a single trait repeatability animal model. The genotype effect on EBV was assessed by ANOVA and by the Tukey–Kramer multiple comparison test. The PCR-SSCP test showed the presence of CC and CT genotypes in Valle del Belice individuals. Some differences in milk production traits between the genotypes were found. For MY, individuals with CT gen…

2015

Small and isolated populations usually exhibit low levels of genetic variability, and thus, they are expected to have a lower capacity to adapt to changes in environmental conditions, such as exposure to pathogens and parasites. Comparing the genetic variability of selectively neutral versus functional loci allows one to assess the evolutionary history of populations and their future evolutionary potential. The genes of the major histocompatibility complex (MHC) control immune recognition of parasites, and their unusually high diversity is genes which is likely driven by parasite-mediated balancing selection. Here, we examined diversity and differentiation of neutral microsatellite loci and…

Genetic diversity and clonal variation within the main Sicilian olive cultivars based on morphological traits and microsatellite markers

2014

The richness of Olea europaea (L.) genetic resources in Sicily is well documented. In the last 30 years, mostof the local cultivars, landraces and ecotypes have been gathered together in a large ex-situ collection,containing more than 300 genotypes. In this study, 45 putative clones of the main Sicilian olive cultivarswere characterized morphologically using microsatellite markers to unambiguously identify possiblesuperior genotypes. The microsatellites employed were polymorphic (observed heterozygosity = 0.71;polymorphic information content = 0.59), discriminated 52% of the genotypes and enabled the detectionof intra-cultivar polymorphism, derived from both somatic mutations, indicating th…

A genome-wide view of Caenorhabditis elegans base-substitution mutation processes

2009

Knowledge of mutation processes is central to understanding virtually all evolutionary phenomena and the underlying nature of genetic disorders and cancers. However, the limitations of standard molecular mutation detection methods have historically precluded a genome-wide understanding of mutation rates and spectra in the nuclear genomes of multicellular organisms. We applied two high-throughput DNA sequencing technologies to identify and characterize hundreds of spontaneously arising base-substitution mutations in 10 Caenorhabditis elegans mutation-accumulation (MA)-line nuclear genomes. C. elegans mutation rate estimates were similar to previous calculations based on smaller numbers of m…

Unmasking frequency-dependent selection in tri-cultures of Drosophila melanogaster.

1989

Larval-to-adult viability was measured for three strains of Drosophila melanogaster: a wild strain and two eye colour mutant strains (cardinal and sepia) starting from seventy different genotypic compositions. Analyses of a sub-set of the data (not considering all genotypic frequencies) demonstrate frequency-dependence in the three strains. These results suggest that in this experiment, frequency-dependent selection may be masked by other selective forces, only being apparent when specific analyses are carried out.

Relatedness Does not Affect Competitive Behavior of Rival Males or Offspring Growth in Multiply Sired Litters of Bank Voles (Myodes glareolus)

2014

Kin selection operates through the fitness of an organism's relatives. In the polyandry context, kin selection may be observable on the one hand in competition between rival males and, on the other hand, in competition between litter mates. Sperm competition theory predicts that males should invest less into mating when competing for fertilizations against a close relative as compared to an unrelated male. We tested this hypothesis with bank voles (Myodes glareolus) by mating each focal male to two females: one of which had previously mated with a full sibling of the focal male and the other one with a male unrelated to the focal male. However, we found no effect of rival male relatedness o…

On female choice, heterozygosity and the lek paradox

2008

The good-genes and compatible-genes benefits of mate choice.

2009

Genetic benefits from mate choice could be attained by choosing mates with high heritable quality ("good genes") and that are genetically compatible ("compatible genes"). We clarify the conceptual and empirical framework for estimating genetic benefits of mate choice, stressing that benefits must be measured from offspring fitness because there are no unequivocal surrogates for genetic quality of individuals or for compatibility of parents. We detail the relationship between genetic benefits and additive and nonadditive genetic variance in fitness, showing that the benefits have been overestimated in previous verbal treatments. We point out that additive benefits readily arise from nonaddit…

Multiple quantitative trait loci influence intra-specific variation in genital morphology between phylogenetically distinct lines of Drosophila monta…

2011

The evolution of animal genitalia has gained renewed interest because of their potential roles during sexual selection and early stages of species formation. Although central to understanding the evolutionary process, knowledge of the genetic basis of natural variation in genital morphology is limited to a very few species. Using an outbred cross between phylogenetically distinct lines of Drosophila montana, we characterized quantitative trait loci (QTLs) affecting the size and shape of the distiphallus, a prominent part of the male intromittent organ. Our microsatellite-based linkage analysis shows that intra-specific variation in the distiphallus involves several QTLs of largely additive …