Evolution of female colours in birds: The role of female cost of reproduction and paternal care.

Female ornamentation is frequently observed in animal species and is sometimes found as more evolutionary labile than male ornamentation. A complex array of factors may explain its presence and variation. Here we assessed the role of female cost of reproduction and paternal care. Both factors have been pinpointed as important by theoretical studies but have not been investigated yet in details at the interspecific level. We worked on 133 species of North temperate Passeriformes bird species for which both the clutch volume - here taken as the proxy of female cost of reproduction - and amount of paternal care are relatively well known. Using spectrometry, we measured the whole-body coloured plumage patches and quantified three metrics corresponding to brightness (i.e. achromatic component), colour chromaticity (i.e. intensity) and colour volume (i.e. diversity). We found a strong association between male and female colour metrics. Controlling for this association, we found additional small but detectable effects of both cost of reproduction and paternal care. First, females of species with more paternal care were slightly brighter. Second, the interaction between the level of paternal care and egg volume was correlated with female colour intensity: females with more paternal care were more chromatic, with this association mostly present when their investment in reproduction was low. Together these results suggest that female cost of reproduction and paternal care are part of the multiple factors explaining variation of female coloration, besides the strong covariation between male and female coloration.

Long-Term Decrease in Coloration: A Consequence of Climate Change?

AbstractClimate change has been shown to affect fitness-related traits in a wide range of taxa; for instance, warming leads to phenological advancements in many plant and animal species. The influence of climate change on social and secondary sexual traits, which are associated with fitness because of their role as quality signals, is, however, unknown. Here, we use more than 5,800 observations collected on two Mediterranean blue tit subspecies (Cyanistes caeruleus caeruleus and Cyanistes caeruleus ogliastrae) to explore whether blue crown and yellow breast patch colorations have changed over the past 15 years. Our data suggest that coloration has become duller and less chromatic in both sexes. In addition, in the Corsican C.c. ogliastrae, but not in the mainland C.c. caeruleus, the decrease is associated with an increase in temperature at molt. Quantitative genetic analyses do not reveal any microevolutionary change in the color traits over the study period, strongly suggesting that the observed change over time was caused by a plastic response to the environmental conditions. Overall, this study suggests that ornamental colorations could become less conspicuous because of warming, revealing climate change effects on sexual and social ornaments and calling for further research on the proximate mechanisms behind these effects.

Are behaviour and stress-related phenotypes in urban birds adaptive?

Urbanisation is a world-wide phenomenon converting natural habitats into new artificial ones. Environmental conditions associated with urbanisation represent great challenges for wildlife. Behaviour and stress tolerance are considered of major importance in the adaptation to novel urban habitats and numerous studies already reported behavioural and stress response phenotypes associated with urbanisation, often suggesting they represented adaptations, while rarely demonstrating it. The main goal of this study was to test the adaptive nature of urban shifts in behavioural and stress-related traits, and by adaptive we mean phenotypic change favouring traits in the same direction as selection. Using 7 years of monitoring of urban and forest great tits, we first tested for differences in exploratory behaviour, aggressiveness and breath rate, between both habitats. Second, we performed habitat-specific analyses of selection on the three former traits using (a) reproductive success and (b) survival estimated via capture-mark-recapture models, as fitness estimates, to determine whether shifts in these behavioural and stress-related traits were aligned with patterns of ongoing selection. We found that urban birds displayed higher exploratory behaviour and aggressiveness, and higher breath rate, compared to forest birds. Selection analyses overall revealed that these shifts were not adaptive and could even be maladaptive. In particular, higher handling aggression and higher breath rate in urban birds was associated with lower fitness. Higher exploration scores were correlated with lower survival in both habitats, but higher reproductive success only in forest males. Overall, differences in patterns of selection between habitats were not consistent with the phenotypic divergence observed. Taken together, these results highlight that phenotypic shifts observed in cities do not necessarily result from new selection pressures and could be maladaptive. We hypothesise that divergences in behavioural traits for urban birds could result from the filtering of individuals settling in cities. We thus encourage urban evolutionary scientists to further explore the adaptive potential of behavioural traits measured in urban habitats (a) by replicating this type of study in multiple cities and species, (b) by implementing studies focusing on immigrant phenotypes and (c) by measuring selection at multiple life stages.

Epigenetics and the city: Non-parallel DNA methylation modifications across pairs of urban-forest Great tit populations.

Identifying the molecular mechanisms involved in rapid adaptation to novel environments and determining their predictability are central questions in evolutionary biology and pressing issues due to rapid global changes. Complementary to genetic responses to selection, faster epigenetic variations such as modifications of DNA methylation may play a substantial role in rapid adaptation. In the context of rampant urbanization, joint examinations of genomic and epigenomic mechanisms are still lacking. Here, we investigated genomic (SNP) and epigenomic (CpG methylation) responses to urban life in a passerine bird, the Great tit (Parus major). To test whether urban evolution is predictable (i.e. parallel) or involves mostly nonparallel molecular processes among cities, we analysed both SNP and CpG methylation variations across three distinct pairs of city and forest Great tit populations in Europe. Our analyses reveal a polygenic response to urban life, with both many genes putatively under weak divergent selection and multiple differentially methylated regions (DMRs) between forest and city great tits. DMRs mainly overlapped transcription start sites and promotor regions, suggesting their importance in modulating gene expression. Both genomic and epigenomic outliers were found in genomic regions enriched for genes with biological functions related to the nervous system, immunity, or behavioural, hormonal and stress responses. Interestingly, comparisons across the three pairs of city-forest populations suggested little parallelism in both genetic and epigenetic responses. Our results confirm, at both the genetic and epigenetic levels, hypotheses of polygenic and largely nonparallel mechanisms of rapid adaptation in novel environments such as urbanized areas.

Graft utilization after normothermic regional perfusion in controlled donation after circulatory death-a single-center perspective from France.

Normothermic regional perfusion (NRP) in controlled donation after circulatory death (cDCD) is a promising procurement strategy. However, a detailed analysis of graft utilization rates is lacking. This retrospective study included all cDCD donors proposed to a single center for NRP procurement of at least one abdominal organ from 2015 to 2020. Utilization rates were defined as the proportion of transplanted grafts from proposed donors in which withdrawal of life sustaining therapies (WLST) was initiated. In total, 125 cDCD donors underwent WLST with transplantation of at least one graft from 109 (87%) donors. In a total of 14 (11%) procedures NRP failure led to graft discard. Utilization rates for kidney and liver grafts were 83% and 59%, respectively. In 44% of the discarded livers, the reason was poor graft quality based on functional donor warm ischemia >45 min, macroscopic aspect, high-transaminases release, or pathological biopsy. In this study, abdominal NRP in cDCD lead to transplantation of at least one graft in the majority of cases. While the utilization rate for kidneys was high, nearly half of the liver grafts were discarded. Cannulation training, novel graft viability markers, and ex-vivo liver graft perfusion may allow to increase graft utilization.

Examining the link between relaxed predation and bird coloration on islands.

Insular ecosystems share analogous ecological conditions, leading to patterns of convergent evolution that are collectively termed as the 'island syndrome'. In birds, part of this syndrome is a tendency for a duller plumage, possibly as a result of relaxed sexual selection. Despite this global pattern, some insular species display a more colourful plumage than their mainland relatives, but why this occurs has remained unexplained. Here, we examine the hypothesis that these cases of increased plumage coloration on islands could arise through a relaxation of predation pressure. We used comparative analyses to investigate whether average insular richness of raptors of suitable mass influences the plumage colourfulness and brightness across 110 pairs of insular endemic species and their closest mainland relatives. As predicted, we find a likely negative relationship between insular coloration and insular predation while controlling for mainland predation and coloration, suggesting that species were more likely to become more colourful as the number of insular predators decreased. By contrast, plumage brightness was not influenced by predation pressure. Relaxation from predation, together with drift, might thus be a key mechanism of species phenotypic responses to insularity.

oXiris® Use in Septic Shock: Experience of Two French Centres.

BACKGROUND: Sepsis is a dysregulated host response to an infection and can result in organ dysfunctions and death. Extracorporeal blood purification techniques aim to improve the prognosis of these patients by modulating the unbalanced immune response. This study reports our experience with the use of the oXiris® membrane for septic shock patients requiring continuous renal replacement therapy (CRRT). SUMMARY: Thirty-one patients were diagnosed with septic shock and underwent CRRT with the oXiris® membrane between 2014 and 2019. We compared the observed hospital mortality with that predicted by the Simplified Acute Physiology Score II (SAPS II). Change in the Sequential Organ Failure Assessment (SOFA) score and of the main clinical and biological parameters over time were analyzed. Hospital mortality was lower than predicted for the most severe patients (60 vs. 91% for the [74-87] SAPS II quartile and 70 vs. 98% for the [87-163] SAPS II quartile, p < 0.02). There was no significant improvement in the SOFA score from 0h to 48 h. An 88% relative decrease in norepinephrine infusion was observed (median at 0 h was 1.69 [0.52-2.45] µg/kg/min; at 48 h it was 0.20 [0.09-1.14] µg/kg/min, p = 0.002). Lactataemia and pH were significantly improved over time. Patients with intra-abdominal sepsis as well as those with Gram-negative bacilli (GNB) infections seemed to benefit the most from the therapy. Key Messages: CRRT with the oXiris® haemofilter resulted in higher observed survival than predicted by a severity score (SAPS II) for the most severe patients. Haemodynamic status and lactataemia appeared to improve, especially in intra-abdominal sepsis and GNB infections.

Urban versus forest ecotypes are not explained by divergent reproductive selection.

Increasing urbanization offers a unique opportunity to study adaptive responses to rapid environmental change. Numerous studies have demonstrated phenotypic divergence between urban and rural organisms. However, comparing the direction and magnitude of natural selection between these environments has rarely been attempted. Using seven years of monitoring of great tits (Parus major) breeding in nest-boxes across the city of Montpellier and in a nearby oak forest, we find phenotypic divergence in four morphological and two life-history traits between urban and forest birds. We then measure reproductive selection on these traits, and compare selection between the habitats. Urban birds had significantly smaller morphological features than their rural counterparts, with a shorter tarsus, lower body mass, and smaller wing and tail lengths relative to their overall body size. While urban female tarsus length was under stabilizing selection, and forest males show positive selection for tarsus length and negative selection for body mass, selection gradients were significantly divergent between habitats only for body mass. Urban great tits also had earlier laying dates and smaller clutches. Surprisingly, we found selection for earlier laying date in the forest but not in the city. Conversely, we detected no linear selection on clutch size in the forest, but positive selection on clutch size in the urban habitat. Overall, these results do not support the hypothesis that contemporary reproductive selection explains differences in morphology and life history between urban- and forest-breeding great tits. We discuss how further experimental approaches will help confirm whether the observed divergence is maladaptive while identifying the environmental drivers behind it.

Great tits and the city: Distribution of genomic diversity and gene-environment associations along an urbanization gradient.

Urbanization is a growing concern challenging the evolutionary potential of wild populations by reducing genetic diversity and imposing new selection regimes affecting many key fitness traits. However, genomic footprints of urbanization have received little attention so far. Using RAD sequencing, we investigated the genomewide effects of urbanization on neutral and adaptive genomic diversity in 140 adult great tits Parus major collected in locations with contrasted urbanization levels (from a natural forest to highly urbanized areas of a city; Montpellier, France). Heterozygosity was slightly lower in the more urbanized sites compared to the more rural ones. Low but significant effect of urbanization on genetic differentiation was found, at the site level but not at the nest level, indicative of the geographic scale of urbanization impact and of the potential for local adaptation despite gene flow. Gene-environment association tests identified numerous SNPs with small association scores to urbanization, distributed across the genome, from which a subset of 97 SNPs explained up to 81% of the variance in urbanization, overall suggesting a polygenic response to selection in the urban environment. These findings open stimulating perspectives for broader applications of high-resolution genomic tools on other cities and larger sample sizes to investigate the consistency of the effects of urbanization on the spatial distribution of genetic diversity and the polygenic nature of gene-urbanization association.

Nest design in a changing world: great tit Parus major nests from a Mediterranean city environment as a case study.

Investigations of urbanization effects on birds have focused mainly on breeding traits expressed after the nest-building stage (e.g. first-egg date, clutch size, breeding success, and offspring characteristics). Urban studies largely ignored how and why the aspects of nest building might be associated with the degree of urbanization. As urban environments are expected to present novel environmental changes relative to rural environments, it is important to evaluate how nest-building behavior is impacted by vegetation modifications associated with urbanization. To examine nest design in a Mediterranean city environment, we allowed urban great tits (Parus major) to breed in nest boxes in areas that differed in local vegetation cover. We found that different measures of nest size or mass were not associated with vegetation cover. In particular, nests located adjacent to streets with lower vegetation cover were not smaller or lighter than nests in parks with higher vegetation cover. Nests adjacent to streets contained more pine needles than nests in parks. In addition, in nests adjacent to streets, nests from boxes attached to pine trees contained more pine needles than nests from boxes attached to other trees. We suggest that urban-related alterations in vegetation cover do not directly impose physical limits on nest size in species that are opportunistic in the selection of nesting material. However, nest composition as reflected in the use of pine needles was clearly affected by habitat type and the planted tree species present, which implies that rapid habitat change impacts nest composition. We do not exclude that urbanization might impact other aspects of nest building behaviour not covered in our study (e.g. costs of searching for nest material), and that the strengths of the associations between urbanization and nest structures might differ among study populations or species.

Disentangling drivers of reproductive performance in urban great tits: a food supplementation experiment.

Worldwide urban expansion induces degradation of the natural environment, resulting in new constraints in terms of breeding sites, anthropogenic disturbances as well as food resources. The alteration of resource abundance and type may induce non-adaptive investments in reproduction from urban dwellers. Food availability and quality have been identified as potential drivers of the decline in passerine body mass and fledging success in urbanized landscapes, particularly if birds misinterpret cues of food abundance used to adjust their reproductive investment. In a previous study, we demonstrated in urban great tits, Parus major, that highly preferred larger cavities have larger clutches with lower breeding success, leading to a maladaptive breeding investment. Previous studies also showed that urban great tits are smaller or thinner than rural ones, both at nestling and adult stages. Here, we present the results of a food-supplementation experiment to examine whether food resources mediate this maladaptive breeding investment and constrain the reproductive performance of this urban bird population. We predicted higher performance in food-supplemented broods, especially in larger cavities, and stronger effects of the supplementation in more artificialized territories. Surprisingly, we found that food-supplemented nestlings and their parents had lower body mass and condition, especially in areas with more pedestrians. Supplementation was also associated with lower nestling survival until fledging in places that presented lower levels of naturalness, independently of cavity size. This work highlights a lack of knowledge on avian feeding behaviour in cities, a key element for understanding how breeding performance is affected by human presence and habitat naturalness.

Assortative mating by colored ornaments in blue tits: space and time matter.

Assortative mating is a potential outcome of sexual selection, and estimating its level is important to better understand local adaptation and underlying trait evolution. However, assortative mating studies frequently base their conclusions on small numbers of individuals sampled over short periods of time and limited spatial scales even though spatiotemporal variation is common. Here, we characterized assortative mating patterns over 10 years in four populations of the blue tit (Cyanistes caeruleus), a passerine bird. We focused on two plumage ornaments-the blue crown and the yellow breast patch. Based on data for 1,657 pairs of birds, we found large interannual variation: assortative mating varied from positive to negative. To determine whether there was nonetheless a general trend in the data, we ran a within-study meta-analysis. It revealed that assortative mating was moderately positive for both ornaments. It also showed that mating patterns differed among populations and especially between two neighboring populations that displayed phenotypic divergence. Our results therefore underscore that long-term studies are needed to draw broad conclusions about mating patterns in natural populations. They also call for studying the potential role of assortative mating in local adaptation and evolution of ornaments in both sexes.

Peripheral venous catheter insertion simulation training: A randomized controlled trial comparing performance after instructor-led teaching versus peer-assisted learning.

INTRODUCTION: Peripheral venous catheter insertion is a procedural skill that every medical student should master. Training is often limited to a small number of students and is poorly evaluated. The objective of this study was to evaluate the performance of peer-assisted learning in comparison to instructor-led teaching for peripheral venous catheter insertion training. METHODS: Students were randomized to the control group attending a traditional instructor-led training session (slideshow and demonstration by an anesthetist instructor, followed by training on a procedural simulator) or to the test group attending a peer-assisted training session (slideshow and demonstration video-recorded by the same instructor, followed by training on a procedural simulator). The primary endpoint was the performance of peripheral venous catheter insertion, assessed on procedural simulator one week later by blinded experts using a standardized 20-item grid. Students self-evaluated their confidence levels using a numeric 10-point scale. RESULTS: Eighty-six students were included, 73 of whom attended the assessment session. The median performance score was 12/20 [8-15] in the instructor-led teaching group versus 13/20 [11-15] in the peer-assisted learning group (P=0.430). Confidence levels improved significantly after the assessment session and were significantly higher in the peer-assisted learning group (7.6/10 [7.0-8.0] versus 7.0/10 [5.0-8.0], P=0.026). CONCLUSION: Peer-assisted learning is effective for peripheral venous catheter insertion training and can be as effective as instructor-led teaching. Given the large number of students to train, this finding is important for optimizing the cost-effectiveness of peripheral venous catheter insertion training.

Interspecific variation in the relationship between clutch size, laying date and intensity of urbanization in four species of hole-nesting birds.

The increase in size of human populations in urban and agricultural areas has resulted in considerable habitat conversion globally. Such anthropogenic areas have specific environmental characteristics, which influence the physiology, life history, and population dynamics of plants and animals. For example, the date of bud burst is advanced in urban compared to nearby natural areas. In some birds, breeding success is determined by synchrony between timing of breeding and peak food abundance. Pertinently, caterpillars are an important food source for the nestlings of many bird species, and their abundance is influenced by environmental factors such as temperature and date of bud burst. Higher temperatures and advanced date of bud burst in urban areas could advance peak caterpillar abundance and thus affect breeding phenology of birds. In order to test whether laying date advance and clutch sizes decrease with the intensity of urbanization, we analyzed the timing of breeding and clutch size in relation to intensity of urbanization as a measure of human impact in 199 nest box plots across Europe, North Africa, and the Middle East (i.e., the Western Palearctic) for four species of hole-nesters: blue tits (Cyanistes caeruleus), great tits (Parus major), collared flycatchers (Ficedula albicollis), and pied flycatchers (Ficedula hypoleuca). Meanwhile, we estimated the intensity of urbanization as the density of buildings surrounding study plots measured on orthophotographs. For the four study species, the intensity of urbanization was not correlated with laying date. Clutch size in blue and great tits does not seem affected by the intensity of urbanization, while in collared and pied flycatchers it decreased with increasing intensity of urbanization. This is the first large-scale study showing a species-specific major correlation between intensity of urbanization and the ecology of breeding. The underlying mechanisms for the relationships between life history and urbanization remain to be determined. We propose that effects of food abundance or quality, temperature, noise, pollution, or disturbance by humans may on their own or in combination affect laying date and/or clutch size.

Worldwide patterns of bird colouration on islands.

Island environments share distinctive characteristics that offer unique opportunities to investigate parallel evolution. Previous research has produced evidence of an island syndrome for morphological traits, life-history strategies and ecological niches, but little is known about the response to insularity of other important traits such as animal signals. Here, we tested whether birds' plumage colouration is part of the island syndrome. We analysed with spectrophotometry the colouration of 116 species endemic to islands and their 116 closest mainland relatives. We found a pattern of reduced brightness and colour intensity for both sexes on islands. In addition, we found a decrease in the number of colour patches on islands that, in males, was associated with a decrease in the number of same-family sympatric species. These results demonstrate a worldwide pattern of parallel colour changes on islands and suggest that a relaxation of selection on species recognition may be one of the mechanisms involved.

Variation in clutch size in relation to nest size in birds.

Nests are structures built to support and protect eggs and/or offspring from predators, parasites, and adverse weather conditions. Nests are mainly constructed prior to egg laying, meaning that parent birds must make decisions about nest site choice and nest building behavior before the start of egg-laying. Parent birds should be selected to choose nest sites and to build optimally sized nests, yet our current understanding of clutch size-nest size relationships is limited to small-scale studies performed over short time periods. Here, we quantified the relationship between clutch size and nest size, using an exhaustive database of 116 slope estimates based on 17,472 nests of 21 species of hole and non-hole-nesting birds. There was a significant, positive relationship between clutch size and the base area of the nest box or the nest, and this relationship did not differ significantly between open nesting and hole-nesting species. The slope of the relationship showed significant intraspecific and interspecific heterogeneity among four species of secondary hole-nesting species, but also among all 116 slope estimates. The estimated relationship between clutch size and nest box base area in study sites with more than a single size of nest box was not significantly different from the relationship using studies with only a single size of nest box. The slope of the relationship between clutch size and nest base area in different species of birds was significantly negatively related to minimum base area, and less so to maximum base area in a given study. These findings are consistent with the hypothesis that bird species have a general reaction norm reflecting the relationship between nest size and clutch size. Further, they suggest that scientists may influence the clutch size decisions of hole-nesting birds through the provisioning of nest boxes of varying sizes.

The intensity threshold of colour vision in a passerine bird, the blue tit (Cyanistes caeruleus).

Many vertebrates use colour vision for vital behaviour but their visual performance in dim light is largely unknown. The light intensity threshold of colour vision is known only for humans, horses and two parrot species. Here, we first explore this threshold in a passerine bird, the blue tit (Cyanistes caeruleus). Using classic conditioning of colour cues to food rewards in three individuals, we find a threshold ranging from 0.05 to 0.2 cd m(-2). Results are comparable to the two previously tested bird species. For tits, nest light conditions probably exceed that threshold, at least after sunrise. These results shed new light on the lively debate questioning the visual performance of cavity nesters and the evolutionary significance of egg and chick coloration. Although this needs further investigation, it is possible that blue tits exploit both colour and brightness cues when viewing their eggs, chicks or conspecifics in their nests.

Assessing multivariate constraints to evolution across ten long-term avian studies.

BACKGROUND: In a rapidly changing world, it is of fundamental importance to understand processes constraining or facilitating adaptation through microevolution. As different traits of an organism covary, genetic correlations are expected to affect evolutionary trajectories. However, only limited empirical data are available. METHODOLOGY/PRINCIPAL FINDINGS: We investigate the extent to which multivariate constraints affect the rate of adaptation, focusing on four morphological traits often shown to harbour large amounts of genetic variance and considered to be subject to limited evolutionary constraints. Our data set includes unique long-term data for seven bird species and a total of 10 populations. We estimate population-specific matrices of genetic correlations and multivariate selection coefficients to predict evolutionary responses to selection. Using Bayesian methods that facilitate the propagation of errors in estimates, we compare (1) the rate of adaptation based on predicted response to selection when including genetic correlations with predictions from models where these genetic correlations were set to zero and (2) the multivariate evolvability in the direction of current selection to the average evolvability in random directions of the phenotypic space. We show that genetic correlations on average decrease the predicted rate of adaptation by 28%. Multivariate evolvability in the direction of current selection was systematically lower than average evolvability in random directions of space. These significant reductions in the rate of adaptation and reduced evolvability were due to a general nonalignment of selection and genetic variance, notably orthogonality of directional selection with the size axis along which most (60%) of the genetic variance is found. CONCLUSIONS: These results suggest that genetic correlations can impose significant constraints on the evolution of avian morphology in wild populations. This could have important impacts on evolutionary dynamics and hence population persistence in the face of rapid environmental change.

Females tend to prefer genetically similar mates in an island population of house sparrows.

BACKGROUND: It is often proposed that females should select genetically dissimilar mates to maximize offspring genetic diversity and avoid inbreeding. Several recent studies have provided mixed evidence, however, and in some instances females seem to prefer genetically similar males. A preference for genetically similar mates can be adaptive if outbreeding depression is more harmful than inbreeding depression or if females gain inclusive fitness benefits by mating with close kin. Here, we investigated genetic compatibility and mating patterns in an insular population of house sparrow (Passer domesticus), over a three-year period, using 12 microsatellite markers and one major histocompability complex (MHC) class I gene. Given the small population size and the distance from the mainland, we expected a reduced gene flow in this insular population and we predicted that females would show mating preferences for genetically dissimilar mates. RESULTS: Contrary to our expectation, we found that offspring were less genetically diverse (multi-locus heterozygosity) than expected under a random mating, suggesting that females tended to mate with genetically similar males. We found high levels of extra-pair paternity, and offspring sired by extra-pair males had a better fledging success than those sired by the social male. Again, unexpectedly, females tended to be more closely related to extra-pair mates than to their social mates. Our results did not depend on the type of genetic marker used, since microsatellites and MHC genes provided similar results, and we found only little evidence for MHC-dependent mating patterns. CONCLUSIONS: These results are in agreement with the idea that mating with genetically similar mates can either avoid the disruption of co-adapted genes or confer a benefit in terms of kin selection.