Adenosine deaminase polymorphism in the house sparrow, Passer domesticus

A polymorphism at the adenosine deaminase locus of the house sparrow, Passer domesticus, has been investigated by starch gel electrophoresis. Five alleles have been identified, and most populations seem to be close to the Hardy-Weinberg equilibrium. The allele frequencies differ strikingly across Europe, and in Britian there are significant differences between urban and rural populations. Samples from introduced populations in Australia and New Zealand lack some of the rarer alleles, as predicted from the Founder Effect.     

Sexual variation in heritability and genetic correlations of morphological traits in house sparrow (Passer domesticus)

Estimates of genetic components are important for our understanding of how individual characteristics are transferred between generations. We show that the level of heritability varies between 0.12 and 0.68 in six morphological traits in house sparrows (Passer domesticus L.) in northern Norway. Positive and negative genetic correlations were present among traits, suggesting evolutionary constraints on the evolution of some of these characters. A sexual difference in the amount of heritable genetic variation was found in tarsus length, wing length, bill depth and body condition index, with generally higher heritability in females. In addition, the structure of the genetic variance-covariance matrix for the traits differed between the sexes. Genetic correlations between males and females for the morphological traits were however large and not significantly different from one, indicating that sex-specific responses to selection will be influenced by intersexual differences in selection differentials. Despite this, some traits had heritability above 0.1 in females, even after conditioning on the additive genetic covariance between sexes and the additive genetic variances in males. Moreover, a meta-analysis indicated that higher heritability in females than in males may be common in birds. Thus, this indicates sexual differences in the genetic architecture of birds. Consequently, as in house sparrows, the evolutionary responses to selection will often be larger in females than males. Hence, our results suggest that sex-specific additive genetic variances and covariances, although ignored in most studies, should be included when making predictions of evolutionary changes from standard quantitative genetic models.     

Food supplementation affects extrapair paternity in house sparrows (Passer domesticus)

Extrapair paternity (EPP) is common among birds, but the reasonswhy it varies within and among species are less clear. In particular,few studies have experimentally examined how food availabilityinfluences paternity and sexual behavior. We manipulated foodsupply in a nest-box population of house sparrows, Passer domesticus,a colonial passerine with extensive biparental care. Duringthree successive breeding attempts, we changed food availabilityat nest sites and examined behavior and genetic parentage. DNAfingerprinting revealed that the level of EPP within broodswas five times lower in pairs nesting at sites continuouslysupplied with extra food. With extra food, mates spent longertime together at the nest, but this was mainly due to a changein female behavior; females but not males increased total nestattendance. Moreover, we found that individual males did notchange within-pair copulation frequency across treatments, suggestingthat our experiment did not influence male control over fertilizationsthrough copulation behavior. Instead, our study shows that ecologicalfactors can have a strong influence on the time budgets of malesand females, which consequently affects the occurrence of EPP.     

Genetic relatedness in wintering groups of house sparrows (Passer domesticus)

Social behaviour of group-living animals is often influenced by the relatedness of individuals, thus understanding the genetic structure of groups is important for the interpretation of costs and benefits of social interactions. In this study, we investigated genetic relatedness in feeding aggregations of free-living house sparrows ( Passer domesticus ) during the nonbreeding season. This species is a frequent model system for studies of social behaviour (e.g. aggression, social foraging), but we lack adequate information on the kin structure of sparrow flocks. During two winters, we ringed and observed sparrows at feeding stations, and used resightings to identify stable flock-members and to calculate association indices between birds. We genotyped the birds using seven highly polymorphic microsatellite loci, and estimated pairwise relatedness coefficients and relatedness categories (close kin vs. unrelated) by maximum likelihood method. We found that most birds were unrelated to each other in the flocks (mean ± SE relatedness coefficient: 0.06 ± 0.002), although most individuals had at least a few close relatives in their home flock (14.3 ± 0.6% of flock-mates). Pairwise association between individuals was not significantly related to their genetic relatedness. Furthermore, there was no difference between within-flock vs. between-flock relatedness, and birds had similar proportions of close kin within and outside their home flock. Finally, relatedness among members of different flocks was unrelated to the distance between their flocks. Thus, sparrow flocks were not characterized by association of relatives, nevertheless the presence of some close kin may provide opportunity for kin-biased behaviours to evolve.     

Sex-specific fitness correlates of dispersal in a house sparrow metapopulation

1.  Dispersal affects many important ecological and evolutionary processes. Still, little is known about the fitness of dispersing individuals.
2.  Here, we use data from a long-term study of a house sparrow Passer domesticus metapopulation to compare lifetime reproductive success (LRS) of resident and immigrant individuals, all with known origin.
3.  Lifetime production of recruits by immigrant males was much lower than for resident males, because of shorter life span and lower annual mating success. In contrast, lifetime production of recruits did not differ significantly between immigrant and resident females.
4.  Over their lifetime, dispersers contributed fewer recruits to the local population than residents. This shows that immigrant house sparrows have different, sex specific, demographic effects on the population dynamics than residents.     

New polymorphic microsatellite loci in the house sparrow, Passer domesticus

We developed 13 new polymorphic microsatellite loci in the house sparrow (Passer domesticus), which exhibited from 2 to 15 alleles. Observed and expected heterozygosities ranged from 0.17 to 0.77 and from 0.35 to 0.85, respectively. We detected no linkage disequilibrium between loci. Allele frequencies supported Hardy-Weinberg equilibrium for 8 loci out of 13 after Bonferroni correction. Combined with loci previously isolated in the house sparrow, these new microsatellite markers provide valuable tools to study population genetics of this species.     

Diversifying selection on MHC class I in the house sparrow (Passer domesticus)

Genes of the major histocompatibility complex (MHC) are the most polymorphic loci known in vertebrates. Two main hypotheses have been put forward to explain the maintenance of MHC diversity: pathogen-mediated selection and MHC-based mate choice. Host–parasite interactions can maintain MHC diversity via frequency-dependent selection, heterozygote advantage, and diversifying selection (spatially and/or temporally heterogeneous selection). In this study, we wished to investigate the nature of selection acting on the MHC class I across spatially structured populations of house sparrows ( Passer domesticus ) in France. To infer the nature of the selection, we compared patterns of population differentiation based on two types of molecular markers: MHC class I and microsatellites. This allowed us to test whether the observed differentiation at MHC genes merely reflects demographic and/or stochastic processes. At the global scale, diversifying selection seems to be the main factor maintaining MHC diversity in the house sparrow. We found that (i) overall population differentiation at MHC was stronger than for microsatellites, (ii) MHC marker showed significant isolation by distance. In addition, the slope of the regression of F _ST on geographical distance was significantly steeper for MHC than for microsatellites due to a stronger pairwise differentiation between populations located at large geographical distances. These results are in agreement with the hypothesis that spatially heterogeneous selective pressures maintain different MHC alleles at local scales, possibly resulting in local adaptation.     

Natural and sexual selection on a plumage signal of status and on morphology in house sparrows,Passer domesticus

Temporal patterns of natural and sexual selection on male badge size and body traits were studied in a population of house sparrows, Passer domesticus. Badge size was a heritable trait as revealed by a significant father-son regression. Survival during autumn dispersal and winter was not related to badge size or body traits in yearling male house sparrows. Badges that signal dominance status were affected positively by directional selection for mating. Adult male house sparrows suffered an opposing selection pressure on badge size during autumn. Contrary to males, female house sparrows did not experience significant directional or stabilizing selection on any body trait. Directional sexual selection on male badge size due to female choice moves male sparrows away from their survival optimum. Opposing directional natural selection on badge size due to autumn mortality caused by predation maintains a stable badge size.     

Causes and consequences of adaptive seasonal sex ratio variation in house sparrows

1. Here we examine how sex ratio variation in house sparrow broods interacts with other demographic traits and parental characteristics to improve the understanding of adaptive significance and demographic effects on variation in sex ratio. 2. The sex ratio in complete broods did not deviate significantly from parity (54.9% males). 3. There was sex-specific seasonal variation in the probability of recruitment. Male nestlings that hatched late in the breeding season had larger probability of surviving than early hatched males. 4. An adaptive adjustment of sex ratio should favour production of an excess of males late in the breeding season. Accordingly, the proportion of male offspring increased throughout the breeding season. 5. A significant nonlinear relationship was present between sex ratio and age of the female. However, there was no relationship between parental phenotype and standardized hatch day that could explain the observed seasonal change in sex ratio. 6. The sex-specific number of offspring recruited by a pair to subsequent generations was closely related to the brood sex ratio. 7. These results indicate an adaptive adjustment of sex ratio to seasonal variation in environmental conditions that affects the offspring fitness of the two sexes differently. Our results also suggest that such a sex ratio variation can strongly influence the demography and structural composition of small passerine populations.     

Antagonistic effects of a Mhc class I allele on malaria-infected house sparrows

Genes of the Major Histocompatibility Complex ( Mhc ) play a fundamental role during the immune response because MHC molecules expressed on cell surface allow the recognition and presentation of antigenic peptides to T-lymphocytes. Although Mhc alleles have been found to correlate with pathogen resistance in several host-parasite systems, several studies have also reported associations between Mhc alleles and an accrued infection risk or an accelerated disease progression. The existence of these susceptibility alleles is puzzling, as the cost generated by the infection should rapidly eliminate them from the population. Here, we show that susceptibility alleles may be maintained in a population of house sparrows ( Passer domesticus ) if they have antagonistic effects on different malaria parasites. We found that one Mhc class I allele was associated with a 2.5-fold increase in the risk to be infected with a Plasmodium strain, but with a 6.4-fold reduction in the risk to harbour a Haemoproteus strain. We suggest that this antagonistic effect might arise because Mhc genes can alter the competitive interactions between malaria parasites within the host.     

树麻雀代谢率和器官重量在季节驯化中表型的可塑性变化

动物能量代谢的生理生态特征与物种的分布和丰富度密切相关,基础代谢率(BMR)是内温动物能量预算的重要组成部分。北温带的小型鸟类,通过增加产热来适应低温环境。增加BMR的基础之一是中心器官(代谢机器)发生明显的变化。本研究中我们测定了树麻雀(Passermontanus)的BMR、体重和各器官的重量,分析了麻雀各器官的季节性变化及与BMR的关系。方差分析表明:麻雀的BMR存在明显的季节性变化,在冬季和秋季较高。麻雀内部器官的变化同样有明显的季节性,冬季和秋季麻雀的肝脏、心脏、肌胃、小肠、直肠和整体消化道的重量,都有明显的增加。相关分析表明:麻雀的BMR与肝脏、心脏和消化道等内部器官存在明显的相关性。我们的结果验证了“中心限制假说”,即麻雀体内存在着与BMR相关的“代谢机器”,中心器官是提高麻雀BMR的基础之一。     

Enzyme polymorphisms in the House Sparrow, Passer domesticus

Methods are described for the visualization of 20 enzymes from the house sparrow, Passer domesticus, in starch gels and by iso-electric focussing. Many of the methods are applicable to other avian species. Two samples of sparrows from the east midlands of England have been analysed. The patterns that are manifest in the gels can be ascribed to between 33 and 35 loci, of which the same nine are polymorphic in both samples. The level of heterozygosity in these birds is about 15%, which at first sight is higher than an introduced population in Australia. However, this difference disappears when homologous loci are compared.     

Individual-learning ability predicts social-foraging strategy in house sparrows

Social foragers can use either a ‘producer’ strategy, which involves searching for food, or a ‘scrounger’ strategy, which involves joining others'' food discoveries. While producers rely on personal information and past experience, we may ask whether the tendency to forage as a producer is related to being a better learner. To answer this question, we hand-raised house sparrow (Passer domesticus) nestlings that upon independence were given an individual-learning task that required them to associate colour signal and food presence. Following the testing phase, all fledglings were released into a shared aviary, and their social-foraging tendencies were measured. We found a significant positive correlation between individual''s performance in the individual-learning task and subsequent tendency to use searching (producing) behaviour. Individual-learning score was negatively correlated with initial fear of the test apparatus and with body weight. However, the correlation between individual learning and searching remained significant after controlling for these variables. Since it was measured before the birds entered a social group, individual-learning ability could not be the outcome of being a producer. However, the two traits may be initially associated, or individual learning could facilitate producing behaviour. To our knowledge, this is the first evidence that associates individual-learning abilities with social-foraging strategies in animal groups.     

Environmental selection is a main driver of divergence in house sparrows (Passer domesticus) in Romania and Bulgaria

Both neutral and adaptive evolutionary processes can cause population divergence, but their relative contributions remain unclear. We investigated the roles of these processes in population divergence in house sparrows (Passer domesticus) from Romania and Bulgaria, regions characterized by high landscape heterogeneity compared to Western Europe. We asked whether morphological divergence, complemented with genetic data in this human commensal species, was best explained by environmental variation, geographic distance, or landscape resistance—the effort it takes for an individual to disperse from one location to the other—caused by either natural or anthropogenic barriers. Using generalized dissimilarity modeling, a matrix regression technique that fits biotic beta diversity to both environmental predictors and geographic distance, we found that a small set of climate and vegetation variables explained up to ~30% of the observed divergence, whereas geographic and resistance distances played much lesser roles. Our results are consistent with signals of selection on morphological traits and of isolation by adaptation in genetic markers, suggesting that selection by natural environmental conditions shapes population divergence in house sparrows. Our study thus contributes to a growing body of evidence that adaptive evolution may be a major driver of diversification.     

Age-related patterns of reproductive success in house sparrows Passer domesticus

A common life history pattern in many organisms is that reproductive success increases with age. We report a similar pattern in house sparrows Passer domesticus , older individuals performed better than yearlings for most measures of reproductive success. Older males and females began breeding earlier in a given season and fledged more young than their yearling counterparts. Individual males also fledged more young in their second breeding season than they did in their first, but individual females did not show consistent improvement in reproductive success from year one to two. A path analysis indicated that age in both sexes acted primarily through the timing of breeding; earlier nesters laid more eggs and hence fledged more young but did not have more nesting attempts. We tested whether the increased reproductive success with age arose from high quality individuals surviving to be older (selection hypothesis). In contrast to the main prediction of this hypothesis that reproductive success and survival should be positively related, we found that survival from one year of age to two years of age was negatively related to reproductive success in the first year for males and females combined. Additionally, individuals that survived to breed as two-year-olds did not differ in total young fledged in their first year from those that did not survive to their second season of breeding. Our results indicate that fledgling production increases with age due to improvements in timing of breeding, particularly in females, and not because of the loss of poor breeders or increased output. Mechanisms producing age-related differences in timing of breeding warrant further study.