Search results for "selection"
showing 10 items of 1940 documents
To quiver or to shiver: increased melanization benefits thermoregulation, but reduces warning signal efficacy in the wood tiger moth
2013
Melanin production is often considered costly, yet beneficial for thermoregulation. Studies of variation in melanization and the opposing selective forces that underlie its variability contribute greatly to understanding natural selection. We investigated whether melanization benefits are traded off with predation risk to promote observed local and geographical variation in the warning signal of adult male wood tiger moths ( Parasemia plantaginis ). Warning signal variation is predicted to reduce survival in aposematic species. However, in P. plantaginis , male hindwings are either yellow or white in Europe, and show continuous variation in melanized markings that cover 20 to 90 per cent o…
Colour polymorphism torn apart by opposing positive frequency-dependent selection, yet maintained in space.
2015
Summary Polymorphic warning signals in aposematic species are enigmatic because predator learning and discrimination should select for the most common coloration, resulting in positive frequency‐dependent survival selection. Here, we investigated whether differential mating success could create sufficiently strong negative frequency‐dependent selection for rare morphs to explain polymorphic (white and yellow) warning coloration in male wood tiger moths (Parasemia plantaginis). We conducted an experiment in semi‐natural conditions where we estimated mating success for both white and yellow male moths under three different morph frequencies. Contrary to expectations, mating success was positi…
Transforming RNA-Seq Data to Improve the Performance of Prognostic Gene Signatures
2014
Gene expression measurements have successfully been used for building prognostic signatures, i.e for identifying a short list of important genes that can predict patient outcome. Mostly microarray measurements have been considered, and there is little advice available for building multivariable risk prediction models from RNA-Seq data. We specifically consider penalized regression techniques, such as the lasso and componentwise boosting, which can simultaneously consider all measurements and provide both, multivariable regression models for prediction and automated variable selection. However, they might be affected by the typical skewness, mean-variance-dependency or extreme values of RNA-…
Heritability Estimates of Differences in Arbitrary Embryonic Mortality Traits in Turkeys
1971
Abstract INTRODUCTION SPECIFIC embryonic abnormalities in Broad Breasted Bronze turkeys which contributed to low hatchability were classified into eight groups which are referred to as traits in this paper. References to these traits or similar abnormalities in chickens and turkeys are shown in Table 1. The objective of this study was to determine the differences in the rates, relative to unhatched fertile eggs, at which these specific traits could be changed by artificial selection which was accompanied by inbreeding. Rapid changes would indicate the traits more responsive to selection. MATERIALS AND METHODS Four different strains of Broad Breasted Bronze turkeys were introduced as eggs to…
Quantitative measure of sexual selection with respect to the operational sex ratio: a comparison of selection indices
2006
Despite numerous indices proposed to predict the evolution of mating systems, a unified measure of sexual selection has remained elusive. Three previous studies have compared indices of sexual selection under laboratory conditions. Here, we use a genetic study to compare the most widely used measures of sexual selection in natural populations. We explored the mating and reproductive successes of male and female bank voles,Clethrionomys glareolus, across manipulated operational sex ratios (OSRs) by genotyping all adult and pup bank voles on 13 islands using six microsatellite loci. We used Bateman's principles (IsandIand Bateman gradients) and selection coefficients (s′ andβ′) to evaluate, f…
Restrictive mating by females on black grouse leks
2007
In bird species with pair bonds, extra-pair matings could allow females to choose genetically superior males. This is not needed in lekking species because female choice is not constrained by pairing opportunities. However, polyandry has been reported in most lekking species studied so far. Using 12 microsatellite loci, we determined the paternity of 135 broods of black grouse sampled between 2001 and 2005 (970 hatchlings and 811 adult birds genotyped). The paternity assignments were combined to lek observations to investigate the mating behaviour of black grouse females. About 10% of the matings seemed to take place with males displaying solitarily. Forty per cent of the copulations betwee…
Limited indirect fitness benefits of male group membership in a lekking species
2014
In group living species, individuals may gain the indirect fitness benefits characterizing kin selection when groups contain close relatives. However, tests of kin selection have primarily focused on cooperatively breeding and eusocial species, whereas its importance in other forms of group living remains to be fully understood. Lekking is a form of grouping where males display on small aggregated territories, which females then visit to mate. As females prefer larger aggregations, territorial males might gain indirect fitness benefits if their presence increases the fitness of close relatives. Previous studies have tested specific predictions of kin selection models using measures such as …
The genetic architecture of sexually selected traits in two natural populations of Drosophila montana
2015
The work was supported by the National Environment Research Council (grant NE/E015255/1 to MGR and RKB) and the Academy of Finland (project 132619 to AH). We investigated the genetic architecture of courtship song and cuticular hydrocarbon traits in two phygenetically distinct populations of Drosophila montana. To study natural variation in these two important traits, we analysed within-population crosses among individuals sampled from the wild. Hence, the genetic variation analysed should represent that available for natural and sexual selection to act upon. In contrast to previous between-population crosses in this species, no major quantitative trait loci (QTLs) were detected, perhaps be…
Signatures of selection in the genome of Swedish warmblood horses selected for sport performance
2019
Abstract Background A growing demand for improved physical skills and mental attitude in modern sport horses has led to strong selection for performance in many warmblood studbooks. The aim of this study was to detect genomic regions with low diversity, and therefore potentially under selection, in Swedish Warmblood horses (SWB) by analysing high-density SNP data. To investigate if such signatures could be the result of selection for equestrian sport performance, we compared our SWB SNP data with those from Exmoor ponies, a horse breed not selected for sport performance traits. Results The genomic scan for homozygous regions identified long runs of homozygosity (ROH) shared by more than 85%…
Comprehensive geriatric assessment decreases prevalence of orthostatic hypotension in older persons
2013
Background: Orthostatic hypotension (OH) is associated with significant morbidity and mortality among older people. We have studied whether its prevalence can be reduced by a Comprehensive Geriatric Assessment (CGA). Study design and setting: 1000 randomly-selected persons aged ≥75 years were divided into intervention ( n = 500) and control groups ( n = 500). We focused on those subjects in whom an orthostatic blood pressure test had been performed at least once during the study period (2004–2007) ( n = 365 and 332 for intervention and control groups, respectively). A CGA, including evaluation of the adequacy of the medication, was performed annually in the intervention group but not in th…