Biomedical subjects

A P Møller

Publications and source records attributed to A P Møller.

At least 19 recordsLinked to original sources

PubMed2007

An analysis of pre- and post-hatching maternal effects mediated by carotenoids in the blue tit.

Maternal effects increase phenotypic plasticity in offspring traits and may therefore facilitate adaptation to environmental variability. Carotenoids have been hypothesized to mediate costs of reproduction in females as well as maternal effects. However, assessing potential transgenerational and population consequences of environmental availability of carotenoids requires a better understanding of mechanisms of maternal effects mediated by these antioxidant pigments. Manipulating dietary availability of carotenoids to egg-laying female blue tits and subsequently cross-fostering nestlings between female treatments allowed us to specifically investigate the relative importance of maternal effects through egg carotenoids and through post-hatching care mediated by antioxidants in females. Nestling body size and mass and plasma antioxidants were not significantly affected by pre- or post-hatching maternal effects mediated by antioxidants, although both types of maternal effects in interaction explained the variation in growth, as measured by wing length. Development of the ability to mount a cell-mediated immune response as well as its temporal dynamics was influenced by both pre- and post-hatching maternal effects, with an advantage to nestlings originating from, or reared by, carotenoid-supplemented females. In addition, nestlings reared by carotenoid-fed females had a lower blood sedimentation rate, indicating that they may have been less infected than nestlings from controls. Finally, prehatching maternal effects in interaction with nestling plasma carotenoid levels affected the development of carotenoid-based plumage. Maternal effects mediated by carotenoids may thus act as a proximate factor in development and phenotypic plasticity in traits associated with nestling fitness, such as immune response and ability to metabolize and use antioxidants, and ultimately participate in the evolution of phenotypic traits.

Animals↗

PubMed2006

Rapidly advancing laying date in a seabird and the changing advantage of early reproduction.

1. Bird ringing schemes have collected immense amounts of data on timing of breeding for over 100 years. These data provide an unexploited source of information on temporal change in breeding date. 2. We investigated changes in breeding date of the Arctic tern Sterna paradisaea Pont. in Denmark during 1929-98, using information on ringing date of young. 3. Mean ringing date advanced by over 18 days during 70 years, while there was no temporal change in variance in date. 4. Advanced mean ringing date was explained by an increase in mean temperature during April and May and an increase in North Atlantic Oscillation (NAO) index for May. 5. Variance in ringing date increased in years with high temperatures in April and high NAO index values in April. 6. There was changing temporal patterns of selection for early breeding as reflected by analyses of the difference in mean ringing date for Arctic tern young that were subsequently recorded as survivors and mean ringing date for all young. The intensity of selection on breeding date changed from favouring late breeding in the 1930s to favouring early breeding during the 1990s. 7. Analyses of bird ringing information for millions of offspring of hundreds of bird species deposited in national ringing schemes may provide unlimited access to long-term time series of reproductive variables.

Animals↗

PubMed2006

A quantitative trait locus for recognition of foreign eggs in the host of a brood parasite.

Avian brood parasites reduce the reproductive output of their hosts and thereby select for defence mechanisms such as ejection of parasitic eggs. Such defence mechanisms simultaneously select for counter-defences in brood parasites, causing a coevolutionary arms race. Although coevolutionary models assume that defences and counter-defences are genetically influenced, this has never been demonstrated for brood parasites. Here, we give strong evidence for genetic differences between ejector and nonejectors, which could allow the study of such host defence at the genetic level, as well as studies of maintenance of genetic variation in defences. Briefly, we found that magpies, that are the main host of the great spotted cuckoo in Europe, have alleles of one microsatellite locus (Ase64) that segregate between accepters and rejecters of experimental parasitic eggs. Furthermore, differences in ejection rate among host populations exploited by the brood parasite covaried significantly with the genetic distance for this locus.

Animals↗

PubMed2006

Sociality, age at first reproduction and senescence: comparative analyses of birds.

Evolutionary theories of senescence suggest that aging evolves as a consequence of early reproduction imposing later viability costs, or as a consequence of weak selection against mutations that act late in life. In addition, highly social species that live in sites that are protected from extrinsic mortality due to predation should senesce at a slower rate than solitary species. Therefore, species that start reproducing late in life should senesce at a slower rate than species that start reproducing early. In addition, social species should senesce more slowly than solitary species. Here I investigate the rate of senescence using an extensive data set on longevity records under natural field conditions to test predictions about the evolution of senescence among 271 species of birds. Longevity records increased with sampling effort and body mass, but once these confounding variables were controlled statistically, there was a strongly positive relationship between relative longevity and relative adult survival rate. Relative longevity after controlling statistically for sampling effort, body mass and adult survival rate, increased with age at first reproduction, but not with degree of breeding sociality. These findings suggest that the evolution of senescence is related to timing of first reproduction, but that the evolution of breeding sociality has played a negligible role in the evolution of senescence.

Aging↗

PubMed2006

The design of complex sexual traits in male barn swallows: associations between signal attributes.

Variation in the expression of sexually selected traits among individuals is widely investigated on the premise that these traits evolved to signal male quality. Significant repeatabilities of sexual signals and their associations with condition, mating success, survivorship and age may be the signatures of sexual selection. However, little is known about the relationship between these sexual attributes. Here we studied 28 acoustic and visual traits in the barn swallow, Hirundo rustica, that may potentially function in sexual selection. Based on effect sizes calculated at the between-individual level, we assessed the relationship between repeatability, condition-dependence, attractiveness, age-dependence and viability indicator value of sexual traits using sexual signals as the units of analyses. Those traits that showed high within-year repeatability also showed high between-year repeatability, indicating that between-individual variation is consistent within and among seasons. In addition, age-dependence of traits, probably causing between-year variation, was negatively related to between-year repeatability. Condition-dependence was negatively correlated with effect sizes for the extent to which traits predicted viability. Therefore, traits that are positively related to immediate condition are those that are negatively related to survival, which may be the signature of a trade-off between current and future reproductive success ultimately reflecting signal reliability. No other significant relationship was found between trait attributes. We conclude that multiple sexual signals reflect different aspects of male quality in the barn swallow.

Animals↗

PubMed2006

Rapid increase in cuckoo egg matching in a recently parasitized reed warbler population.

Parasitic cuckoos lay eggs that mimic those of their hosts, and such close phenotypic matching may arise from coevolutionary interactions between parasite and host. However, cuckoos may also explicitly choose hosts in a way that increases degree of matching between eggs of cuckoos and parasites, with female preference for specific host phenotypes increasing the degree of matching. We tested for temporal change in degree of matching between eggs of the parasitic European cuckoo (Cuculus canorus) and its reed warbler (Acrocephalus scirpaceus) host during 24 consecutive years in a recently parasitized reed warbler population. Cuckoo-host egg matching in an ultraviolet-brownness component yielding most of the chromatic variance of eggs improved during the study period. Improved matching was not due to changes in cuckoo egg phenotype. Cuckoo eggs matched host eggs for ultraviolet-brownness within nests irrespective of duration of sympatry. Ultraviolet-brownness of cuckoo eggs was similar to that of reed warbler eggs at parasitized nests, but differed from that of reed warbler eggs at unparasitized nests. These findings provide tentative support for the cuckoo preference hypothesis suggesting that cuckoo-host egg matching could partially be due to cuckoo females selecting host nests based on the appearance of their eggs.

Animals↗

PubMed2006

Chernobyl as a population sink for barn swallows: tracking dispersal using stable-isotope profiles.

Stable-isotope profiles of feathers can reveal the location or habitat used by individual birds during the molting period. Heterogeneity in isotope profiles will reflect heterogeneity in molt locations, but also heterogeneity in breeding locations, because spatial heterogeneity in molt locations will be congruent with spatial heterogeneity in breeding locations in species with high connectivity between breeding and molting sites. We used information on the congruence of spatial heterogeneity in molt and breeding location to study population processes in Barn Swallows (Hirundo rustica) from a region. near Chernobyl, Ukraine, that has been radioactively contaminated since 1986; from an uncontaminated control region near Kanev, Ukraine; and from a sample of pre-1986 museum specimens used to investigate patterns prior to the nuclear disaster at Chernobyl, from both regions. Previous studies have revealed severe reductions in Barn Swallow reproductive performance and adult survival in the Chernobyl region, implying that the population is a sink and unable to sustain itself. Female Barn Swallows are known to disperse farther from their natal site than males, implying that female stable-isotope profiles should tend to be more variable than profiles of males. However, if the Barn Swallows breeding at Chernobyl are not self-sustaining, we would expect males there also to originate from a larger area than males from the control region. We found evidence that the sample of adult Barn Swallows from the Chernobyl region was more isotopically heterogeneous than the control sample, as evidenced from a significant correlation between feather sigma13C and sigma15N values in the control region, but not in the Chernobyl region. Furthermore, we found a significant difference in feather sigma15N values between regions and periods (before and after 1986). When we compared the variances in sigma13C values of feathers, we found that variances in both sexes from post-1986 samples from Chernobyl were significantly larger than variances for feather samples from the control region, and than variances for historical samples from both regions. These findings suggest that stable-isotope measurements can provide information about population processes following environmental perturbations.

Aging↗

PubMed2006

An analysis of continent-wide patterns of sexual selection in a passerine bird.

Patterns of selection are widely believed to differ geographically, causing adaptation to local environmental conditions. However, few studies have investigated patterns of phenotypic selection across large spatial scales. We quantified the intensity of selection on morphology in a monogamous passerine bird, the barn swallow Hirundo rustica, using 6495 adults from 22 populations distributed across Europe and North Africa. According to the classical Darwin-Fisher mechanism of sexual selection in monogamous species, two important components of fitness due to sexual selection are the advantages that the most attractive males acquire by starting to breed early and their high annual fecundity. We estimated directional selection differentials on tail length (a secondary sexual character) and directional selection gradients after controlling for correlated selection on wing length and tarsus length with respect to these two fitness components. Phenotype and fitness components differed significantly among populations for which estimates were available for more than a single year. Likewise, selection differentials and selection gradients differed significantly among populations for tail length, but not for the other two characters. Sexual selection differentials differed significantly from zero across populations for tail length, particularly in males. Controlling statistically for the effects of age reduced the intensity of selection by 60 to 81%, although corrected and uncorrected estimates were strongly positively correlated. Selection differentials and gradients for tail length were positively correlated between the sexes among populations for selection acting on breeding date, but not for fecundity selection. The intensity of selection with respect to breeding date and fecundity were significantly correlated for tail length across populations. Sexual size dimorphism in tail length was significantly correlated with selection differentials with respect to breeding date for tail length in male barn swallows across populations. These findings suggest that patterns of sexual selection are consistent across large geographical scales, but also that they vary among populations. In addition, geographical patterns of phenotypic selection predict current patterns of phenotypic variation among populations, suggesting that consistent patterns of selection have been present for considerable amounts of time.

Age Factors↗

PubMed2005

Antioxidants, radiation and mutation as revealed by sperm abnormality in barn swallows from Chernobyl.

Reduced levels of antioxidants such as carotenoids and vitamins A and E can increase DNA damage caused by free radicals. Exposure to radiation has been proposed to reduce levels of antioxidants that are used for DNA repair and this reduction may be responsible for increased levels of mutation in radioactively contaminated areas. We test this hypothesis using field measures of antioxidants in blood, liver and eggs of the barn swallow Hirundo rustica while relating these to levels of mutation as reflected by the frequency of abnormal sperm. Antioxidant levels in blood, liver and eggs were reduced in Chernobyl, Ukraine, compared with an uncontaminated control area, and levels of antioxidants correlated negatively with levels of background radiation. The frequency of abnormal sperm was almost an order of magnitude higher in Chernobyl than in the control area and was negatively related to antioxidant levels in blood and liver. This is consistent with the hypothesis of a direct link between radiation and individual levels of antioxidants, suggesting that levels of mutation differ among individuals owing to individual differences in the abundance of antioxidants.

Animals↗

PubMed2005

Testosterone, testes size, and mating success in birds: a comparative study.

Reproductive behaviors of vertebrates are often underpinned by temporal patterns of hormone secretion. We investigated interspecific patterns of circulating testosterone in male birds to test the hypothesis that testosterone plays a crucial role in sexual selection as determined by degree of polygyny and extra-pair paternity. We predicted that the evolution of increased levels of polygyny and extra-pair paternity would have resulted in the evolution of increased levels of testosterone to allow males more efficiently to compete for mates. This hypothesis was tested in comparative analyses of 116 species of birds using Generalized Least Squares Models. We assessed the importance of latitudinal distribution, because this can confound the relationship between testosterone and mating success. There were weak positive phylogenetic correlations between measures of testosterone and estimates of mating success at the social level, but this association appeared to be confounded by latitudinal distribution, a significant correlate of testosterone titers. However, we found a significantly positive relationship between peak and residual peak testosterone (which is the peak testosterone level that is controlled for the baseline level) and extra-pair paternity independent of latitude. These results suggest that selection pressures arising from social and sexual mating differently affected testosterone levels with the former being mediated by factors associated with latitudinal distribution. An analysis of residual testes size revealed a positive association between peak and residual testosterone and testes size relative to body size. In a path analysis, we show that relative testis size primarily evolved in association with intense sperm competition and thus high sperm production, and these mechanisms had a secondary impact on blood testosterone levels at a phylogenetic scale. Our results suggest that sperm competition has played an important role in the evolution of reproductive mechanisms in birds.

Analysis of Variance↗

PubMed2005

Coevolutionary arms races: increased host immune defense promotes specialization by avian fleas.

We investigated the relationship between host defense and specialization by parasites in comparative analyses of bird fleas and T-cell mediated immune response of their avian hosts, showing that fleas with few main host species exploited hosts with weak or strong immune defenses, whereas flea species that parasitized a large number of host species only exploited hosts with weak immune responses. Hosts with strong immune responses were exploited by a larger number of flea species than hosts with weak responses. A path analysis model with an effect of T-cell response on the number of host species, or a model with host coloniality directly affecting host T-cell response, which in turn affected the number of host species used by fleas, best explained the data. Therefore, parasite specialization may have evolved in response to strong host defenses.

Animals↗

PubMed2005

Covariation between brain size and immunity in birds: implications for brain size evolution.

Parasitism can negatively affect learning and cognition, setting the scene for coevolution between brain and immunity. Greater susceptibility to parasitism by males may impair their cognitive ability, and relatively greater male investment in immunity could compensate for greater susceptibility to parasites, in particular when males have a relatively large brain. We analysed covariation between relative size of immune defence organs and brain in juvenile and adult birds. The relative size of the bursa of Fabricius and the spleen in adults covaried positively with relative brain size across bird species. The relative size of these two immune defence organs covaried with sex differences in relative size of the brain, indicating that the relationship between immune defence and brain size was stronger for males. In contrast, liver and heart size or sexual size dimorphism in size did not covary with immune defence. Thus, species in which males have relatively large brains also have relatively large immune defence organs.

Adaptation, Physiological↗

PubMed2005

Rapid evolutionary change in a secondary sexual character linked to climatic change.

The ability of organisms to respond evolutionarily to rapid climatic change is poorly known. Secondary sexual characters show the potential for rapid evolutionary change, as evidenced by strong divergence among species and high evolvability. Here we show that the length of the outermost tail feathers of males of the socially monogamous barn swallow Hirundo rustica, feathers that provide a mating advantage to males, has increased by more than 1 standard deviation during the period from 1984 to 2003. Barn swallows from the Danish population studied here migrate through the Iberian Peninsula to South Africa in fall, and return along the same route in spring. Environmental conditions on the spring staging grounds in Algeria, as indexed by the Normalized Difference Vegetation Index, predicted tail length and change in tail length across generations. However, conditions in the winter quarters and at the breeding grounds did not predict change in tail length. Environmental conditions in Algeria in spring showed a temporal deterioration during the study period, associated with a reduction in annual survival rate of male barn swallows. Phenotypic plasticity in tail length of males, estimated as the increase in tail length from the age of 1 to 2 years, decreased during the course of the study. Estimates of directional selection differentials for male tail length with respect to mating success, breeding date, fecundity, survival and total selection showed temporal variation, with the intensity of breeding date selection, survival selection and total selection declining during the study. Response to selection as estimated from the product of heritability and total selection was very similar to the observed temporal change in tail length. These findings provide evidence of rapid micro-evolutionary change in a secondary sexual character during a very short time period, which is associated with a rapid change in environmental conditions.

Algeria↗

PubMed2004

Geographic variation in the G matrices of wild populations of the barn swallow.

In this paper, we present an analysis of genetic variation in three wild populations of the barn swallow, Hirundo rustica. We estimated the P, E, and G matrices for six linear morphological measurements and tested for variation among populations using the Flury hierarchical method and the jackknife followed by MANOVA method. Because of nonpositive-definite matrices, we had to employ 'bending' to analyse the G and E matrices with the Flury method. Both statistical methods agree in finding that the P and G matrices are significantly different but comparison between the analysis of the P matrices and pairwise analyses of the P, E, and G matrices suggests caution in interpreting the Flury results concerning differences in matrix structure. The significant variation among the populations in the G matrices appears to be due in large measure to the most geographically distant population.

Animals↗

PubMed2004

Genetic variation in infestation with a directly transmitted ectoparasite.

Genetic variation in levels of parasitism of hosts is an underlying assumption of studies of coevolution, but few such estimates are available from the field. We studied genetic variation in the abundance of the chewing louse Hirundoecus malleus on its barn swallow host Hirundo rustica. These parasites are directly transmitted and a test of genetic variation of parasite abundance would thus provide a particularly strong test. The prevalence and the abundance of the chewing lice did not differ significantly between adult male and female hosts. The resemblance in parasite intensity of H. malleus of offspring and their parents was positive and highly significant, and an analysis of extra-pair paternity in the host allowed partitioning of this resemblance between genetic and common environment effects. There was no significant resemblance in parasite intensity between extra-pair offspring and their foster parents, although the resemblance remained for within-pair offspring. This provides evidence for the abundance of directly transmitted parasites having an additive genetic component. We found no evidence of common environment effects as parents did not resemble each other with respect to lice abundance.

Animals↗

PubMed2004

Parasitism, host immune defence and dispersal.

Host-parasite interactions have been hypothesized to affect the evolution of dispersal by providing a possibility for hosts to escape debilitating parasites, and by influencing the level of local adaptation. We used a comparative approach to investigate the relationship between a component of host immune function (which reflects the evolutionary history of parasite-induced natural selection) and dispersal in birds. We used a sample of 46 species of birds for which we had obtained field estimates of T-cell response for nestlings, mainly from our own field studies in Denmark and Spain. Bird species with longer natal, but not with longer breeding dispersal distances had a stronger mean T-cell-mediated immune response in nestlings than species with short dispersal distances. That was also the case when controlling for the potentially confounding effect of migration from breeding to wintering area, which is known from previous studies to be positively associated with dispersal distance. These relationships held even when controlling for similarity among species because of common ancestry. Avian hosts with a larger number of different breeding habitats had weaker mean T-cell-mediated immune responses than habitat specialists. This relationship held even when controlling for similarity among species because of common ancestry. Therefore, T-cell-mediated immunity is an important predictor of evolutionary changes in dispersal ability among common European birds.

Animal Migration↗

PubMed2003

Sexual selection, germline mutation rate and sperm competition.

BACKGROUND: An important component of sexual selection arises because females obtain viability benefits for their offspring from their mate choice. Females choosing extra-pair fertilization generally favor males with exaggerated secondary sexual characters, and extra-pair paternity increases the variance in male reproductive success. Furthermore, females are assumed to benefit from 'good genes' from extra-pair sires. How additive genetic variance in such viability genes is maintained despite strong directional selection remains an evolutionary enigma. We propose that sexual selection is associated with elevated mutation rates, changing the balance between mutation and selection, thereby increasing variance in fitness and hence the benefits to be obtained from good genes sexual selection. Two hypotheses may account for such elevated mutation: (1) Increased sperm production associated with sperm competition may increase mutation rate. (2) Mutator alleles increase mutation rates that are revealed by the expression of condition-dependent secondary sexual characters used by choosy females during their mate choice. M Petrie has independently developed the idea that mutator alleles may account for the maintenance of genetic variation in viability despite strong directional selection. RESULTS: A comparative study of birds revealed a positive correlation between mutation rate at minisatellite loci and extra-pair paternity, but not between mutation rate and relative testes mass which is a measure of relative sperm production. Minisatellite mutation rates were not related to longevity, suggesting a meiotic rather than a mitotic origin of mutations. CONCLUSION: We found evidence of increased mutation rate in species with more intense sexual selection. Increased mutation was not associated with increased sperm production, and we suggest that species with intense sexual selection may maintain elevated mutation rates because sexual selection continuously benefits viability alleles expressed in condition-dependent characters. Sexual selection may increase mutational input, which in turn feeds back on sexual selection because of increased variance in viability traits.

Animals↗

PubMed2003

Maternal antibodies but not carotenoids in barn swallow eggs covary with embryo sex.

Mothers influence their offspring phenotype by varying egg quality. Such maternal effects may be mediated by transmission of antibodies and antioxidants. Mothers should adjust allocation of maternal substances depending on embryonic sex because of differences in reproductive value, potentially dependent on paternal genetic effects as reflected by secondary sexual characters. We manipulated sexual attractiveness of male barn swallows (Hirundo rustica) and investigated maternal investment in eggs in relation to offspring sex. Mothers allocated more antibodies against a pathogen to eggs with a daughter than a son. However, concentration of antioxidants was independent of embryonic sex. Sex-dependent allocation was independent of paternal attractiveness. Thus, mothers adjusted allocation of substances to offspring in a complex manner, that may be part of a strategy of favouritism of daughters, which have larger mortality than sons. Such effects may have important consequences for secondary and tertiary sex ratios, but also for ontogeny of adult phenotype.

Animals↗