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Background: Environmental pollution in general, and radioactive contamination in particular, may deeply affect host-parasite relationships and their consequences for the evolution of organisms. The nuclear accident that occurred more than 30 years ago in Chernobyl resulted in significant changes in diversity and richness of microbial communities that could influence characteristics of animal-bacteria interactions, including host immune responses and competitive interference by bacteria. Given the high mortality rate of birds breeding in radioactively contaminated zones, those with stronger defences against infections should experience significant fitness advantages., Methodology/principal Findings: Here we characterized antimicrobial capacity of barn swallows (Hirundo rustica) from different Ukrainian populations (subject to a gradient of ionizing radiation) against 12 bacterial species. We also quantified constitutive innate immunity, which is the non-specific first barrier of protection of hosts against microbial parasites. We found a positive association between specific antimicrobial capacity of individual hosts and radiation levels in breeding habitats even after controlling for other confounding variables such as sex and age. However, no significant relationship was found between immunocompetence (non-specific response) and background radiation., Conclusions/significance: These results suggest that radiation selects for broad antimicrobial spectra of barn swallows, although not for all bacterial strains. We discuss these results in the framework of host-parasite evolution under extreme environmental conditions.

Host defences against cuckoo parasitism and cuckoo trickeries to overcome them are a classic example of antagonistic coevolution. Recently it has been reported that this relationship may turn to be mutualistic in the case of the carrion crow (Corvus corone) and its brood parasite, the great spotted cuckoo (Clamator glandarius), given that experimentally and naturally parasitized nests were depredated at a lower rate than non-parasitized nests. This result was interpreted as a consequence of the antipredatory properties of a fetid cloacal secretion produced by cuckoo nestlings, which presumably deters predators from parasitized host nests. This potential defensive mechanism would therefore explain the detected higher fledgling success of parasitized nests during breeding seasons with high predation risk. Here, in a different study population, we explored the expected benefits in terms of reduced nest predation in naturally and experimentally parasitized nests of two different host species, carrion crows and magpies (Pica pica). During the incubation phase non-parasitized nests were depredated more frequently than parasitized nests. However, during the nestling phase, parasitized nests were not depredated at a lower rate than non-parasitized nests, neither in magpie nor in carrion crow nests, and experimental translocation of great spotted cuckoo hatchlings did not reveal causal effects between parasitism state and predation rate of host nests. Therefore, our results do not fit expectations and, thus, do not support the fascinating possibility that great spotted cuckoo nestlings could have an antipredatory effect for host nestlings, at least in our study area. We also discuss different possibilities that may conciliate these with previous results, but also several alternative explanations, including the lack of generalizability of the previously documented mutualistic association.

Rationale: The Spanish guideline for COPD (GesEPOC) recommends COPD treatment according to four clinical phenotypes: non-exacerbator phenotype with either chronic bronchitis or emphysema (NE), asthma-COPD overlap syndrome (ACOS), frequent exacerbator phenotype with emphysema (FEE) or frequent exacerbator phenotype with chronic bronchitis (FECB). However, little is known on the distribution and outcomes of the four suggested phenotypes., Objective: We aimed to determine the distribution of these COPD phenotypes, and their relation with one-year clinical outcomes., Methods: We followed a cohort of well-characterized patients with COPD up to one-year. Baseline characteristics, health status (CAT), BODE index, rate of exacerbations and mortality up to one year of follow-up were compared between the four phenotypes., Results: Overall, 831 stable COPD patients were evaluated. They were distributed as NE, 550 (66.2%); ACOS, 125 (15.0%); FEE, 38 (4.6%); and FECB, 99 (11.9%); additionally 19 (2.3%) COPD patients with frequent exacerbations did not fulfill the criteria for neither FEE nor FECB. At baseline, there were significant differences in symptoms, FEV1 and BODE index (all p<0.05). The FECB phenotype had the highest CAT score (17.1±8.2, p<0.05 compared to the other phenotypes). Frequent exacerbator groups (FEE and FECB) were receiving more pharmacological treatment at baseline, and also experienced more exacerbations the year after (all p<0.05) with no differences in one-year mortality. Most of NE (93%) and half of exacerbators were stable after one year., Conclusions: There is an uneven distribution of COPD phenotypes in stable COPD patients, with significant differences in demographics, patient-centered outcomes and health care resources use., Competing Interests: The study was funded by an unrestricted grant from Astra-Zeneca. Several authors of the manuscript (BGC, JLLC, JJS) disclose potential competing interest with different pharmaceutical companies in the form of travel grants and honoraria for speaking or participation at meetings. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

The study of associations between symbiotic bacterial communities of hosts and those of surrounding environments would help to understand how bacterial assemblages are acquired, and how they are transmitted from one to another location (i.e. symbiotic bacteria acquisition by hosts). Hoopoes (Upupa epops) smear their eggshells with uropygial secretion (oily secretion produced in their uropygial gland) that harbors antibiotic producing bacteria. Trying to elucidate a possible role of nest material and cloaca microbiota in determining the bacterial community of the uropygial gland and the eggshells of hoopoes, we characterized bacterial communities of nest material, cloaca, uropygial gland and eggshells by the ARISA fingerprinting. Further, by adding material with scarce bacteria and antimicrobial properties, we manipulated the bacterial community of nest material and thus tested experimentally its effects on the microbiomes of the uropygial secretion and of the eggshells. The experiment did not influence the microbiome of the uropygial secretion of females, but affected the community established on eggshells. This is the first experimental evidence indicating that nest material influences the bacterial community of the eggshells and, therefore, probability of embryo infection. Some of the bacterial strains detected in the secretion were also in the bacterial communities of the nest material and of cloaca, but their occurrence within nests was not associated, which suggests that bacterial environments of nest material and cloaca are not sources of symbiotic bacteria for the gland. These results do not support a role of nest environments of hoopoes as reservoirs of symbiotic bacteria. We discuss possible scenarios explaining bacterial acquisition by hoopoes that should be further explored.

Selective pressures imposed by pathogenic microorganisms to embryos have selected in hosts for a battery of antimicrobial lines of defenses that includes physical and chemical barriers. Due to the antimicrobial properties of volatile compounds of green plants and of chemicals of feather degrading bacteria, the use of aromatic plants and feathers for nest building has been suggested as one of these barriers. However, experimental evidence suggesting such effects is scarce in the literature. During two consecutive years, we explored experimentally the effects of these nest materials on loads of different groups of bacteria (mesophilic bacteria, Enterobacteriaceae, Staphylococcus and Enterococcus) of eggshells in nests of spotless starlings (Sturnus unicolor) at the beginning and at the end of the incubation period. This was also explored in artificial nests without incubation activity. We also experimentally increased bacterial density of eggs in natural and artificial nests and explored the effects of nest lining treatments on eggshell bacterial load. Support for the hypothetical antimicrobial function of nest materials was mainly detected for the year and location with larger average values of eggshell bacterial density. The beneficial effects of feathers and plants were more easily detected in artificial nests with no incubation activity, suggesting an active role of incubation against bacterial colonization of eggshells. Pigmented and unpigmented feathers reduced eggshell bacterial load in starling nests and artificial nest boxes. Results from artificial nests allowed us to discuss and discard alternative scenarios explaining the detected association, particularly those related to the possible sexual role of feathers and aromatic plants in starling nests. All these results considered together confirm the antimicrobial functionality mainly of feathers but also of plants used as nest materials, and highlight the importance of temporally and geographically environmental variation associated with risk of bacterial proliferation determining the strength of such effects. Because of costs associated to nest building, birds should adjust nest building effort to expected bacterial environments during incubation, a prediction that should be further explored.

Molecular methods have revealed that symbiotic systems involving bacteria are mostly based on whole bacterial communities. Bacterial diversity in hoopoe uropygial gland secretion is known to be mainly composed of certain strains of enterococci, but this conclusion is based solely on culture-dependent techniques. This study, by using culture-independent techniques (based on the 16S rDNA and the ribosomal intergenic spacer region) shows that the bacterial community in the uropygial gland secretion is more complex than previously thought and its composition is affected by the living conditions of the bird. Besides the known enterococci, the uropygial gland hosts other facultative anaerobic species and several obligated anaerobic species (mostly clostridia). The bacterial assemblage of this community was largely invariable among study individuals, although differences were detected between captive and wild female hoopoes, with some strains showing significantly higher prevalence in wild birds. These results alter previous views on the hoopoe-bacteria symbiosis and open a new window to further explore this system, delving into the possible sources of symbiotic bacteria (e.g. nest environments, digestive tract, winter quarters) or the possible functions of different bacterial groups in different contexts of parasitism or predation of their hoopoe host.

Background: Climate change potentially has important effects on distribution, abundance, transmission and virulence of parasites in wild populations of animals., Methodology/principal Finding: Here we analyzed paired information on 89 parasite populations for 24 species of bird hosts some years ago and again in 2010 with an average interval of 10 years. The parasite taxa included protozoa, feather parasites, diptera, ticks, mites and fleas. We investigated whether change in abundance and prevalence of parasites was related to change in body condition, reproduction and population size of hosts. We conducted analyses based on the entire dataset, but also on a restricted dataset with intervals between study years being 5-15 years. Parasite abundance increased over time when restricting the analyses to datasets with an interval of 5-15 years, with no significant effect of changes in temperature at the time of breeding among study sites. Changes in host body condition and clutch size were related to change in temperature between first and second study year. In addition, changes in clutch size, brood size and body condition of hosts were correlated with change in abundance of parasites. Finally, changes in population size of hosts were not significantly related to changes in abundance of parasites or their prevalence., Conclusions/significance: Climate change is associated with a general increase in parasite abundance. Variation in laying date depended on locality and was associated with latitude while body condition of hosts was associated with a change in temperature. Because clutch size, brood size and body condition were associated with change in parasitism, these results suggest that parasites, perhaps mediated through the indirect effects of temperature, may affect fecundity and condition of their hosts. The conclusions were particularly in accordance with predictions when the restricted dataset with intervals of 5-15 years was used, suggesting that short intervals may bias findings.

Symbiotic microorganisms may be directly transferred from parents to offspring or acquired from a particular environment that animals may be able to select. If benefits for hosts vary among microbial strains, natural selection may favour hosts holding the most beneficial one. Enterococci symbionts living in the hoopoe (Upupa epops) uropygial gland are able to synthesise bacteriocins (antimicrobial peptides that inhibit the growth of competitor bacteria). We explored variability in genetic profile (through RAPD-PCR analyses) and antimicrobial properties (by performing antagonistic tests against ten bacterial indicator strains) of the different isolates obtained from the uropygial glands of hoopoe females and nestlings. We found that the genetic profile of bacterial isolates was related to antimicrobial activity, as well as to individual host identity and the nest from which samples were obtained. This association suggest that variation in the inhibitory capacity of Enterococci symbionts should be under selection.

Background: Nestlings of altricial birds capture parents' attention through conspicuous visual displays, including exposure of their gape coloration which informs parents about their level of need, competitive ability or health; information that parents use for deciding food allocation among their offspring. Thus, because nestlings compete with nest mates for parental care, nestling conspicuousness is expected to increase with level of sibling competition along bird phylogeny., Methodology/principal Findings: We test this prediction by jointly using information of brood reduction, clutch size and duration of nestling period as proxies for intensity of sibling competition, and visual models that assess detectability of nestlings by adult birds. As predicted, we found a positive association between nestling conspicuousness and intensity of brood reduction, while clutch size and duration of nestling period did not enter in the best models. Level of brood reduction was positively related with the achromatic component of nestling conspicuousness and body mass was negatively related with the chromatic component., Conclusions: These associations are in agreement with the hypothesis that sibling competition for parental attention has driven the evolution of visual nestling conspicuousness in a context of parent-offspring communication in altricial birds.