Different Types Of Traits Research Articles

Parasites and health affect multiple sexual signals in male common wall lizards, Podarcis muralis

Multiple advertising sexual traits may either advertise different characteristics of male condition or be redundant to reinforce reliability of signals. Research has focused on multiple visual traits. However, in animals that use different multiple additional sensory systems, such as chemoreception, different types of traits might have evolved to signal similar characteristics of a male quality using different sensory channels. We examined whether ventral coloration and chemicals in femoral gland secretions of male common wall lizards, Podarcis muralis, are affected by their health state (blood-parasite load and cell-mediated immune response). Our results indicated that less parasitized lizards had brighter and more yellowish ventral colorations and also femoral secretions with higher proportions of two esters of octadecenoic acid. In addition, lizards with a greater immune response had more saturated coloration and secretions with higher proportions of octadecenoic acid methyl ester. We suggest that these signals would be reliable because only healthier males seemed able to allocate more carotenoids to coloration and presumably costly chemicals to secretions. The use of multiple sensory channels may provide more opportunities to signal a male quality under different circumstances, but also may reinforce the reliability of the signal when both types of traits may be perceived simultaneously.

Patterns and Power of Phenotypic Selection in Nature

Phenotypic selection occurs when individuals with certain characteristics produce more surviving offspring than individuals with other characteristics. Although selection is regarded as the chief engine of evolutionary change, scientists have only recently begun to measure its action in the wild. These studies raise numerous questions: How strong is selection, and do different types of traits experience different patterns of selection? Is selection on traits that affect mating success as strong as selection on traits that affect survival? Does selection tend to favor larger body size, and, if so, what are its consequences? We explore these questions and discuss the pitfalls and future prospects of measuring selection in natural populations.

Effects of misspecification of allele frequencies on the power of Haseman‐Elston sib‐pair linkage method for quantitative traits

It is well known that the Haseman-Elston (H-E) sib-pair linkage method does not assume that the genetic model underlying the trait phenotype is known without error, although this assumption is made for marker loci. However, misspecification of allele frequencies at the marker locus decreases power when some or all parental genotypes are unknown. In this study, the power of the H-E sib-pair method was compared for different types of traits when some or all parental data were missing and allele frequencies at the marker loci were misspecified. Data were generated for a quantitative trait and marker loci in nuclear families using G.A.S.P. (V3.3). Three types of traits were simulated with two equifrequent alleles with a random environmental effect (10%, 30%, and 50%). The simulated data were analyzed using (i) one of the parent's marker data, and (ii) no parental marker data, with both correct and incorrect marker allele frequencies. This test is found to be robust in most of the situations considered except for a slight decrease in power when sample size is small and when the marker locus is not very polymorphic. © 2001 Wiley-Liss, Inc.

Effects of misspecification of allele frequencies on the power of Haseman-Elston sib-pair linkage method for quantitative traits

It is well known that the Haseman-Elston (H-E) sib-pair linkage method does not assume that the genetic model underlying the trait phenotype is known without error, although this assumption is made for marker loci. However, misspecification of allele frequencies at the marker locus decreases power when some or all parental genotypes are unknown. In this study, the power of the H-E sib-pair method was compared for different types of traits when some or all parental data were missing and allele frequencies at the marker loci were misspecified. Data were generated for a quantitative trait and marker loci in nuclear families using G.A.S.P. (V3.3). Three types of traits were simulated with two equifrequent alleles with a random environmental effect (10%, 30%, and 50%). The simulated data were analyzed using (i) one of the parent's marker data, and (ii) no parental marker data, with both correct and incorrect marker allele frequencies. This test is found to be robust in most of the situations considered except for a slight decrease in power when sample size is small and when the marker locus is not very polymorphic.

Genetic architecture of fitness and nonfitness traits: empirical patterns and development of ideas.

Comparative studies of the genetic architecture of different types of traits were initially prompted by the expectation that traits under strong directional selection (fitness traits) should have lower levels of genetic variability than those mainly under weak stabilizing selection (nonfitness traits). Hence, early comparative studies revealing lower heritabilities of fitness than nonfitness traits were first framed in terms of giving empirical support for this prediction, but subsequent treatments have effectively reversed this view. Fitness traits seem to have higher levels of additive genetic variance than nonfitness traits - an observation that has been explained in terms of the larger number loci influencing fitness as compared to nonfitness traits. This hypothesis about the larger functional architecture of fitness than nonfitness traits is supported by their higher mutational variability, which is hard to reconcile without evoking capture of mutational variability over many loci. The lower heritabilities of fitness than nonfitness traits, despite the higher additive genetic variance of the former, occur because of their higher residual variances. Recent comparative studies of dominance contributions for different types of traits, together with theoretical predictions and a large body of indirect evidence, suggest an important role of dominance variance in determining levels of residual variance for fitness-traits. The role of epistasis should not be discounted either, since a large number of loci increases the potential for epistatic interactions, and epistasis is strongly implicated in hybrid breakdown.

Assessment of Genetic Variation in Avena sterilis using Morphologicall Traits, Isozymes, and RFLPs

Genetic patterns revealed by proximity coefficients may be affected by choice of traits, method of scoring, any subsequent transformations of scores, and choice of proximity coefficient. Our objective was to compare restriction fragment length polymorphism (RFLP), isozyme polymorphism, and variation in qualitative and quantitative morphological traits in a geographically stratified set of 177 accessions of a hexaploid wild oat, Avena sterilis L. Jaccard similarity coefficients (SJ) and Russell and Rao similarity coefficients (SRR) were calculated for all pairs of genotypes from restriction fragments and, separately, from isozymes. Standard taxonomic (DSZ), Mahalanobis, and Goodman distances were calculated from 26 morphological trait scores. Clustering of mean DSZ values or mean SJ(RFLP) values between pairs of countries produced similar dendrograms while SRR(isozymes) values resulted in different subgroups. Rankings of within‐country diversity were similar for different types of traits but were unrelated to geographic proximity of provenances of the accessions. Proximity coefficients based on the same type of trait (either RFLP, isozyme, or morphology) were highly correlated (Mantel statistic) (0.6‐0.9),while correlations for proximities based on different types of traits were ≤0.35. Isozyme‐ and RFLP‐based proximities were poorly correlated, and both were poor predictors of morphological relationships with the highest correlation being −0.35 between SJ(RFLP) and DSZ. while broad patterns of variation revealed by different types of traits were similar in this sample of A. sterilis, differences in pairwise estimates of relationship were sufficiently great to question the exclusive use of one type of trait for sampling and management of plant germplasm collections.

Experimental differentiation of meaning change and averaging explanations for context effects

The effects of contexts on correlations between evaluations of traits were examined to provide a differentiation of meaning change and averaging explanations for context effects in evaluative impression formation. Two different types of traits (ambiguous and nonambiguous) were evaluated under two different instructional conditions (P, or person description, and W, or random words). Both types of traits manifested shifts in mean levels of evaluation in Condition P, but not in W, with little evidence for differentml efiects across types of traits. Correlational analyses revealed differences between ambiguous and nonambiguous traits. Ambiguous traits manifested large shifts in the magnitude of intratrait correlations across contexts in Condition P, indicating that meaning change had occurred. There was little evidence for such effects among nonambiguous traits. It was concluded that meaning change is a highly restricted effect and does not represent a serious challenge to averaging explanations for context effects on component ratings in impression formation.