Male-biased sex ratio among unhatched eggs in great tit Parus major, blue tit P. caeruleus and collared flycatcher Ficedula albicollis

An increasing number of studies have demonstrated that brood sex ratios are frequently unequal, but the proximate mechanisms underlying this deviation are largely unknown. In the current study we analysed deviation from expected 1:1 sex ratio among dead embryos from unhatched eggs collected from partially unhatched clutches of three passerine bird species. We showed that male embryos were significantly overrepresented among unhatched eggs of great tit Parus major , blue tit P. caeruleus and collared flycatcher Ficedula albicollis . Moreover, the bias in sex ratio differed among species and tended to differ among study years. We discuss several hypotheses to explain the observed male bias among unhatched eggs. We conclude that sex specific embryo mortality may contribute to explain the observed variation in sex ratios in several species of wild birds and that sexing unhatched eggs is important in studies of sex ratio allocation.     

Diet of red-breasted flycatcher and Siberian tit nestlings in Central Yakutia

Results of comparative analysis of food selectivity patterns for two ecologically close hollow-nesting birds—red-breasted flycatcher Ficedula parva (Muscicapidae) and Siberian tit Parus cinctus (Paridae)—according to the way of catching, the place of foraging and the daily activity in nestling feeding are considered.     

Genetic and environmental variation in immune response of collared flycatcher nestlings

This paper aims at partitioning genetic and environmental contribution to the phenotypic variance in nestling immune function measured with the hypersensitivity test after inoculation with phytohaemagglutinin. A cross-fostering experiment with artificial enlargement of some broods was conducted. Variation in nestling immune response was related to their common origin, which suggests heritable component of cell-mediated immunity. A common rearing environment also explained a significant part of variation. However, deterioration of rearing conditions as simulated by enlargement of brood size did not affect nestling immunocompetence, although it affected nestling body mass. Variation in body mass explained some of the variation in immune response related to rearing environment, which means that growth is more sensitive to the shifts in rearing conditions than the development of immune function. Heritable variation in immune response suggests that there should be potential for selection to operate and the micro evolutionary changes in immunity of flycatcher nestlings are possible.     

Polluted environment and cold weather induce laying gaps in great tit and pied flycatcher

We studied the occurrence of laying gaps in free-living populations of the pied flycatcher, Ficedula hypoleuca, and the great tit, Parus major, in a pollution gradient of a copper smelter in south-west Finland. Laying gaps were 2.8 times more common in F. hypoleuca than in P. major. The probability of laying gaps was highest in the heavily polluted zone and lowest in the unpolluted zone for both bird species. Cold weather at the time of laying increased the number of laying gaps in both species, but in P. major this effect was most pronounced in the heavily polluted environment. In the most heavily polluted environment the laying gaps were more likely to occur near the beginning of the laying sequence in both species. The laying gap probability increased with increasing laying date in P. major but not in F. hypoleuca. We suggest that the increased number of laying gaps in the polluted environment results from limited Ca availability and the interference of heavy metals with Ca metabolism in laying females.     

Costs of incubation and immunocompetence in the collared flycatcher

This paper investigates the costs of incubation in terms of reduced reproductive success and investigates whether incubation competes with immune function for resources. I performed a clutch size manipulation experiment in which two eggs were either removed from or added to the nests of collared flycatchers, Ficedula albicollis, for 1 week during incubation and subsequently returned to their original nests before hatching. To induce immune response, the females were challenged with sheep red blood cells. While the duration of incubation, hatching success and fledgling number did not differ between experimental groups, fledgling condition was significantly lower in broods that had been enlarged during incubation. Neither the females' condition nor their ability to respond to a novel antigen differed between treatments. The relationship between antibody production and female condition was significantly positive, but only among females incubating reduced clutches. I conclude that the costs of incubation in the collared flycatcher are not negligible and are manifested only at the chick-rearing phase.     

Rehabilitating degraded forests in Central Europe into self–sustaining forest ecosystems

There is a need for a consistent forest restoration strategy for the `Black Triangle', Central Europe. In the past 50 years, forests in this area have been heavily affected by industrial pollution. Recently, the amount of pollutants has decreased. This means that effective forest restoration programmes can be started. Forest decline must be seen as an ecological disturbance which cannot be solved by applying technical measures only. An ecosystem approach to forest restoration must be introduced into restoration policy and management. Basic principles and working methods of such an approach are briefly described and proposals are made for forest restoration policy, management and research in the area.     

Certainty of paternity and paternal effort in the collared flycatcher

Models of optimal parental investment predict that variationin certainty of paternity can affect the optimal level of paternalinvestment when a male's expected paternity in different nestingattempts is not fixed throughout his lifetime. Several attemptsto test this prediction experimentally in monogamous birds havefailed to induce a reduction in care by males. This may be becausethe method used, detaining males, is a poor model for what happenswhen a male's certainly of paternity is naturally reduced. Wecaught and detained female collared flycatchers Ficedula albicollisfor 1 h immediately after laying on one or two occasions inan attempt to induce variation in certainty of paternity forthe males they were mated to. By capturing females immediatelyafter laying we hoped to exploit the existence of an "inseminationwindow" since males should be very sensitive to female absenceduring this period. The general effect of the experimental manipulationwas consistent with reduced certainty of paternity: males respondedby reducing their level of paternal care to nestlings, and malesmated to females that had been caught on one morning fed nestlingssignificantly less often and made a smaller share of feedingvisits than males mated to control females. The effects of theexperiment were generally weak, however, and we argue that certaintyof paternity may be fixed well before egg laying, in which caseexperimental manipulations are unlikely to have large effects.It is difficult to predict die effects of natural variationin certainty of paternity on levels of male paternal care becausedifferential allocation by females mated to attractive malesmay act in the opposite direction     

The extended Moran effect and large-scale synchronous fluctuations in the size of great tit and blue tit populations

1. Synchronous fluctuations of geographically separated populations are in general explained by the Moran effect, i.e. a common influence on the local population dynamics of environmental variables that are correlated in space. Empirical support for such a Moran effect has been difficult to provide, mainly due to problems separating out effects of local population dynamics, demographic stochasticity and dispersal that also influence the spatial scaling of population processes. Here we generalize the Moran effect by decomposing the spatial autocorrelation function for fluctuations in the size of great tit Parus major and blue tit Cyanistes caeruleus populations into components due to spatial correlations in the environmental noise, local differences in the strength of density regulation and the effects of demographic stochasticity. 2. Differences between localities in the strength of density dependence and nonlinearity in the density regulation had a small effect on population synchrony, whereas demographic stochasticity reduced the effects of the spatial correlation in environmental noise on the spatial correlations in population size by 21.7% and 23.3% in the great tit and blue tit, respectively. 3. Different environmental variables, such as beech mast and climate, induce a common environmental forcing on the dynamics of central European great and blue tit populations. This generates synchronous fluctuations in the size of populations located several hundred kilometres apart. 4. Although these environmental variables were autocorrelated over large areas, their contribution to the spatial synchrony in the population fluctuations differed, dependent on the spatial scaling of their effects on the local population dynamics. We also demonstrate that this effect can lead to the paradoxical result that a common environmental variable can induce spatial desynchronization of the population fluctuations. 5. This demonstrates that a proper understanding of the ecological consequences of environmental changes, especially those that occur simultaneously over large areas, will require information about the spatial scaling of their effects on local population dynamics.     

Soil phosphorus supply controls P nutrition strategies of beech forest ecosystems in Central Europe

Phosphorus availability may shape plant–microorganism–soil interactions in forest ecosystems. Our aim was to quantify the interactions between soil P availability and P nutrition strategies of European beech (Fagus sylvatica) forests. We assumed that plants and microorganisms of P-rich forests carry over mineral-bound P into the biogeochemical P cycle (acquiring strategy). In contrast, P-poor ecosystems establish tight P cycles to sustain their P demand (recycling strategy). We tested if this conceptual model on supply-controlled P nutrition strategies was consistent with data from five European beech forest ecosystems with different parent materials (geosequence), covering a wide range of total soil P stocks (160–900 g P m^?2; <1 m depth). We analyzed numerous soil chemical and biological properties. Especially P-rich beech ecosystems accumulated P in topsoil horizons in moderately labile forms. Forest floor turnover rates decreased with decreasing total P stocks (from 1/5 to 1/40 per year) while ratios between organic carbon and organic phosphorus (C:P_org) increased from 110 to 984 (A horizons). High proportions of fine-root biomass in forest floors seemed to favor tight P recycling. Phosphorus in fine-root biomass increased relative to microbial P with decreasing P stocks. Concomitantly, phosphodiesterase activity decreased, which might explain increasing proportions of diester-P remaining in the soil organic matter. With decreasing P supply indicator values for P acquisition decreased and those for recycling increased, implying adjustment of plant–microorganism–soil feedbacks to soil P availability. Intense recycling improves the P use efficiency of beech forests.     

Tree-ring patterns and climate response of Mediterranean fir populations in Central Greece

Central Greece is the distribution common area of the endemic fir species Abies cephalonica and Abies borisii-regis. Forests fires and fir decline are some of the problems both species encountered during the past decades, with these problems being exacerbated lately by climate change. The present research investigates tree-ring patterns and climate responses of three fir populations along a latitudinal gradient in Central Greece. All three populations were homogeneous in their dendrometric, silvicultural and site characteristics but were phenotypically different. The analysis of tree-ring widths site chronologies revealed that 59% of their variability interprets common tree-ring patterns whereas another 25% interprets their differences as they appear from a south to north direction. This variability in tree-ring widths is proportional to the variability observed for precipitation, temperature and drought from a south to north direction in this region. The tree-ring to climate relationships revealed that the main climatic factor affecting fir tree-ring width is late spring and summer precipitation to which is positively correlated. Also, tree-ring widths were positively affected by the temperatures of the October and April before the growing season. However, June drought adversely affected tree-ring widths of the northern site while it positively affected them at the beginning of the spring season, especially for the southern site and in September for the northern sites. All dendrochronological statistics, tree-ring patterns and climate-growth relationships show a south to north trend following the climatic and phenotypic (species) variation observed to the same direction for fir populations in Central Greece.     

Variation in personality and behavioural plasticity across four populations of the great tit Parus major

1. Interest in the evolutionary origin and maintenance of individual behavioural variation and behavioural plasticity has increased in recent years. 2. Consistent individual behavioural differences imply limited behavioural plasticity, but the proximate causes and wider consequences of this potential constraint remain poorly understood. To date, few attempts have been made to explore whether individual variation in behavioural plasticity exists, either within or between populations. 3. We assayed 'exploration behaviour' among wild-caught individual great tits Parus major when exposed to a novel environment room in four populations across Europe. We quantified levels of individual variation within and between populations in average behaviour, and in behavioural plasticity with respect to (i) repeated exposure to the room (test sequence), (ii) the time of year in which the assays were conducted and (iii) the interval between successive tests, all of which indicate habituation to novelty and are therefore of functional significance. 4. Consistent individual differences ('I') in behaviour were present in all populations; repeatability (range: 0.34-0.42) did not vary between populations. Exploration behaviour was also plastic, increasing with test sequence - but less so when the interval between subsequent tests was relatively large - and time of year; populations differed in the magnitude of plasticity with respect to time of year and test interval. Finally, the between-individual variance in exploration behaviour increased significantly from first to repeat tests in all populations. Individuals with high initial scores showed greater increases in exploration score than individuals with low initial scores; individual by environment interaction ('I × E') with respect to test sequence did not vary between populations. 5. Our findings imply that individual variation in both average level of behaviour and behavioural plasticity may generally characterize wild great tit populations and may largely be shaped by mechanisms acting within populations. Experimental approaches are now needed to confirm that individual differences in behavioural plasticity (habituation) - not other hidden biological factors - caused the observed patterns of I × E. Establishing the evolutionary causes and consequences of this variation in habituation to novelty constitutes an exciting future challenge.     

Divergent patterns of age-dependence in ornamental and reproductive traits in the collared flycatcher

Sexual ornaments are predicted to honestly signal individual condition. We might therefore expect ornament expression to show a senescent decline, in parallel with late-life deterioration of other characters. Conversely, life-history theory predicts the reduced residual reproductive value of older individuals will favor increased investment in sexually attractive traits. Using a 25-year dataset of more than 5000 records of breeding collared flycatchers (Ficedula albicollis) of known age, we quantify cross-sectional patterns of age-dependence in ornamental plumage traits and report long-term declines in expression that mask highly significant positive age-dependency. We partition this population-level age-dependency into its between- and within-individual components and show expression of ornamental white plumage patches exhibits within-individual increases with age in both sexes, consistent with life-history theory. For males, ornament expression also covaries with life span, such that, within a cohort, ornamentation indicates survival. Finally, we compared longitudinal age-dependency of reproductive traits and ornamental traits in both sexes, to assess whether these two trait types exhibit similar age-dependency. These analyses revealed contrasting patterns: reproductive traits showed within-individual declines in late-life females consistent with senescence; ornamental traits showed the opposite pattern in both males and females. Hence, our results for both sexes suggest that age-dependent ornament expression is consistent with life-history models of optimal signaling and, unlike reproductive traits, proof against senescence.     

森林生态系统发展和植物种群变化的热力学过程

随着生态学的发展,人们对自然生态系统的认识逐渐从对自然现象的记录、描述,发展为对机制的系统认识。热力学定律为人们提供了认识系统发展规律的理论基础,但在生态系统中的应用还处于起步阶段。基于前人关于生态系统可用能的研究。探讨了森林生态系统和植物种群变化的热力学过程。在生态系统水平上,把可用能耗散分为了植物耗散和环境耗散两个部分,并探讨了这两个过程之间的关系。第一次明确地提出蒸散是植物耗散的主要部分。在植物种群水平上,“可用能储存”与“可用能耗散”是决定植物竞争力的关键因子,在同一区域相同条件下,拥有更大可用能耗散能力的物种应当被优先选择。因此,群落中的优势物种应当比同层次的伴生种具有相对高的生长速度和更强的蒸腾能力。研究试图在热力学理论体系与实际生态系统的生理生态过程之间建立了纽带和桥梁,为开展森林生态系统的健康评估、深刻认识植物与环境的关系、以及评价物种竞争能力提供新的理论视野。     

Replicated analysis of the genetic architecture of quantitative traits in two wild great tit populations

Currently, there is much debate on the genetic architecture of quantitative traits in wild populations. Is trait variation influenced by many genes of small effect or by a few genes of major effect? Where is additive genetic variation located in the genome? Do the same loci cause similar phenotypic variation in different populations? Great tits (Parus major) have been studied extensively in long‐term studies across Europe and consequently are considered an ecological ‘model organism’. Recently, genomic resources have been developed for the great tit, including a custom SNP chip and genetic linkage map. In this study, we used a suite of approaches to investigate the genetic architecture of eight quantitative traits in two long‐term study populations of great tits—one in the Netherlands and the other in the United Kingdom. Overall, we found little evidence for the presence of genes of large effects in either population. Instead, traits appeared to be influenced by many genes of small effect, with conservative estimates of the number of contributing loci ranging from 31 to 310. Despite concordance between population‐specific heritabilities, we found no evidence for the presence of loci having similar effects in both populations. While population‐specific genetic architectures are possible, an undetected shared architecture cannot be rejected because of limited power to map loci of small and moderate effects. This study is one of few examples of genetic architecture analysis in replicated wild populations and highlights some of the challenges and limitations researchers will face when attempting similar molecular quantitative genetic studies in free‐living populations.     

Indicators of physiological stress and the elaboration of sexual traits in the collared flycatcher

Stress may have consequences for the evolution of condition-dependentsexual traits. For example, stress may be related to sexualtraits through immune function, and sexual traits can reflecthow individuals bear the costs of stress-mediated immunosuppression.However, male traits may be directly associated with stress,and such traits would then indicate stress tolerance. Here,we present initial results for the relationship between physiologicalstress estimated by the levels of heat shock proteins (HSP60and HSP70) and heterophil/lymphocyte ratio and the elaborationof sexual traits, such as forehead and wing patch size and songfeatures in the collared flycatcher Ficedula albicollis. Malesproducing longer and more versatile songs had significantlyhigher levels of HSP70, but other traits were unrelated to stress.In general, effect sizes for the relationship between stressand sexual traits had broad confidence intervals and variedbetween being small and medium effects. Immunoglobulin levels,leukocyte abundance, haemoparasite prevalence, male age, anddate and time effects did not affect the relationship betweenstress and sexual traits. These preliminary results, servinga basis for further experimental studies indicate that the relationshipbetween sexual traits and stress does not seem to be strong,but stress may partially constrain the expression of some sexualtraits.     

Natural selection and inheritance of breeding time and clutch size in the collared flycatcher

Many characteristics of organisms in free-living populations appear to be under directional selection, possess additive genetic variance, and yet show no evolutionary response to selection. Avian breeding time and clutch size are often-cited examples of such characters. We report analyses of inheritance of, and selection on, these traits in a long-term study of a wild population of the collared flycatcher Ficedula albicollis. We used mixed model analysis with REML estimation ("animal models") to make full use of the information in complex multigenerational pedigrees. Heritability of laying date, but not clutch size, was lower than that estimated previously using parent-offspring regressions, although for both traits there was evidence of substantial additive genetic variance (h2 = 0.19 and 0.29, respectively). Laying date and clutch size were negatively genetically correlated (rA = -0.41 +/- 0.09), implying that selection on one of the traits would cause a correlated response in the other, but there was little evidence to suggest that evolution of either trait would be constrained by correlations with other phenotypic characters. Analysis of selection on these traits in females revealed consistent strong directional fecundity selection for earlier breeding at the level of the phenotype (beta = -0.28 +/- 0.03), but little evidence for stabilising selection on breeding time. We found no evidence that clutch size was independently under selection. Analysis of fecundity selection on breeding values for laying date, estimated from an animal model, indicated that selection acts directly on additive genetic variance underlying breeding time (beta = -0.20 +/- 0.04), but not on clutch size (beta = 0.03 +/- 0.05). In contrast, selection on laying date via adult female survival fluctuated in sign between years, and was opposite in sign for selection on phenotypes (negative) and breeding values (positive). Our data thus suggest that any evolutionary response to selection on laying date is partially constrained by underlying life-history trade-offs, and illustrate the difficulties in using purely phenotypic measures and incomplete fitness estimates to assess evolution of life-history trade-offs. We discuss some of the difficulties associated with understanding the evolution of laying date and clutch size in natural populations.     

Genomic distribution and estimation of nucleotide diversity in natural populations: perspectives from the collared flycatcher (Ficedula albicollis) genome

Properly estimating genetic diversity in populations of nonmodel species requires a basic understanding of how diversity is distributed across the genome and among individuals. To this end, we analysed whole‐genome resequencing data from 20 collared flycatchers (genome size ≈1.1 Gb; 10.13 million single nucleotide polymorphisms detected). Genomewide nucleotide diversity was almost identical among individuals (mean = 0.00394, range = 0.00384–0.00401), but diversity levels varied extensively across the genome (95% confidence interval for 200‐kb windows = 0.0013–0.0053). Diversity was related to selective constraint such that in comparison with intergenic DNA, diversity at fourfold degenerate sites was reduced to 85%, 3′ UTRs to 82%, 5′ UTRs to 70% and nondegenerate sites to 12%. There was a strong positive correlation between diversity and chromosome size, probably driven by a higher density of targets for selection on smaller chromosomes increasing the diversity‐reducing effect of linked selection. Simulations exploring the ability of sequence data from a small number of genetic markers to capture the observed diversity clearly demonstrated that diversity estimation from finite sampling of such data is bound to be associated with large confidence intervals. Nevertheless, we show that precision in diversity estimation in large outbred population benefits from increasing the number of loci rather than the number of individuals. Simulations mimicking RAD sequencing showed that this approach gives accurate estimates of genomewide diversity. Based on the patterns of observed diversity and the performed simulations, we provide broad recommendations for how genetic diversity should be estimated in natural populations.     

Long-term dynamics of Collembolan populations in forest and meadow ecosystems

The population dynamics of soil-dwelling springtails in a spruce forest (Piceetum oxalidosum) and a dry meadow with young planted spruce trees was analyzed based on an eight-year sampling in Moscow Region. Fluctuations of population densities of the most species are less than 10 fold. The seasonal dynamics (the number and position of peaks) is more constant in surface-dwelling species than in hemi-and euedaphic ones. The occurrence of the density peaks in specific seasons is merely a tendency. Two types of the size structure of populations are revealed: the “left-sided” type with prevalence of small immature individuals and the “symmetrical” one with prevalence of medium-sized individuals. Synchronization of reproduction in the species studied is possible only under the effect of external climatic factors. The seasonal density dynamics of most abundant species is related to the temperature and, to a lesser extent, precipitation. The mean density of some species in the following year can be predicted based on the mean temperature and/or sum of precipitation in the current year. In the forest, the density-dependent regulation of springtail abundance is probable. The springtail populations do not respond to overgrowing of the meadow with spruce trees at least at the beginning of this process.     

Hybridization cost of delayed maturation of secondary sexual traits in the collared flycatcher

In many species, individuals do not attain their full adult coloration until one or several years after reaching sexual maturity, and this signaling of juvenile status is thought to enable young individuals to avoid aggression from older, dominant conspecifics. We propose that hybridization may be one of several costs and benefits associated with such delayed maturation. We tested this idea in a hybrid zone of collared (Ficedula albicollis) and pied (F. hypoleuca) flycatchers on the Baltic islands of Oland and Gotland. One-year-old (subadult) male collared flycatchers differed from older birds in many plumage traits, and approached male pied flycatchers in phenotype. On both islands, subadult male collared flycatchers hybridized at a higher rate than adults. Mate-choice experiments in aviaries suggest that this difference is at least partly due to female pied flycatchers having a preference for subadults when constrained to choose a heterospecific mate. Because novel morphologies are often derived from changes in ontology, juvenile forms may resemble adults of closely related taxa. When such juveniles are reproductively mature, their phenotypic similarity to the adults of closely related species may increase their risk of hybridization.