Numerous species have adapted to humans, especially invasive species associated with humans in towns and cities. Short flight distances of populations adapted to urban environments reflect changes in ...behavior and physiology, reflecting phenotypic plasticity or evolution. Here, I tested the hypothesis that the decrease in flight distance to a potential predator (an approaching human) reflected adaptation to urbanization, using a data set of flight distances of 44 common species of European birds in different stages of adaptation to urban environments. Urban populations had consistently shorter flight distances than rural populations of the same species. Variation in relative flight distance of urban populations was predicted by the number of generations since urbanization, as expected by a gradual process of adaptation. Furthermore, species with relatively large populations in urban environments would be an indication of local adaptation to urban environments. Relative flight distance of urban population was shorter for species with large populations in urban compared to rural habitats. Species that had adapted to urban environments as shown by short flight distances were less susceptible to predation by the European sparrowhawk Accipiter nisus than species with relatively long flight distances in urban populations. These findings provide evidence consistent with the hypothesis that recent changes in the tameness of urban birds, as reflected by their relatively short flight distances, is an adaptation to the novel urban environment.
Numerous species have adapted to the proximity of humans, and this feature is no clearer than among species that have invaded towns and cities. The characteristics of species that have successfully ...managed to expand their range into urban areas remain largely unexplored, although they are of general interest in a world that is increasingly urbanised. I hypothesised that widely distributed species with high dispersal abilities, species with a high rate of innovation, a high level of risk-taking, and a fast life history would have a selective advantage in habitats influenced by humans. Consistent with this hypothesis, in a comparative analysis of 39 independent evolutionary events of urbanisation of birds in the Western Palearctic (thus taking the fact that closely related species that have become urbanised are caused by common phylogenetic descent rather than convergent evolution), bird species that adapted to urban habitats were characterised by large breeding ranges, high propensity for dispersal, high rates of feeding innovation (novel ways of acquiring food), short flight distances when approached by a human, and a life history characterised by high annual fecundity and high adult survival rate. Urban species may be disproportionately resistant to parasitism and predation because they had disproportionately strong immune responses, as reflected by the size of the bursa of Fabricius, and a history of weak predation-mediated natural selection, as reflected by the force required to remove feathers from the rump. Urban species had high overall ecological success as indicated by large range size and population size and high population density. This suggests that a suite of ecological features providing them with general ecological success characterises species of birds that have successfully invaded urban environments.
Farmers in most western countries have increased use of fertilizer and pesticides with impact on wild animals and plants, including the abundance of insects and their predators.
I used 1,375 surveys ...of insects killed on car windscreens as a measure of insect abundance during 1997–2017 at two transects in Denmark. I cross‐validated this method against three other methods for sampling insect abundance, and I investigated the effects of this measure of insect abundance on the abundance of breeding insectivorous birds.
The abundance of flying insects was quantified using a windscreen resulting in reductions of 80% and 97% at two transects of 1.2 km and 25 km, respectively, according to general additive mixed model. Insect abundance increased with time of day, temperature, and June date, but decreased with wind resulting in a reduction by 54%. The abundance of insects killed on a car windscreen was strongly positively correlated with the abundance of insects caught in sweep nets and on sticky plates in the same study areas and at the same time as when insects were sampled using windscreens. The decline in abundance of insects on windscreens predicted the rate at which barn swallows Hirundo rustica fed their nestlings, even when controlling statistically for time of day, weather, and age and number of nestlings. The abundance of breeding pairs of three species of aerially insectivorous birds was positively correlated with the abundance of insects killed on windscreens at the same time in the same study area. This suggests a link between two trophic levels as affected by the temporal reduction in the abundance of flying insects.
These findings are consistent with recent dramatic declines in insect abundance in Europe and North America with consequences for the rate of food provisioning of barn swallow offspring, the abundance of aerially insectivorous birds and bottom‐up trophic cascades.
I used 1,375 surveys of insects killed on car windscreens as a measure of insect abundance during 1997–2017 in a study site in Denmark, and I investigated the effects of this measure of insect abundance for insectivorous birds. Abundance of flying insects decreased by 80% and 97% at two transects. The decline in abundance of insects on windscreens predicted the feeding rate of nestling barn swallows Hirundo rustica, even when controlling for time of day, weather, and age and number of nestlings.
Recent rapid climatic changes are associated with dramatic changes in phenology of plants and animals, with optimal timing of reproduction advancing considerably in the northern hemisphere. However, ...some species may not have advanced their timing of breeding sufficiently to continue reproducing optimally relative to the occurrence of peak food availability, thus becoming mismatched compared with their food sources. The degree of mismatch may differ among species, and species with greater mismatch may be characterized by declining populations. Here we relate changes in spring migration timing by 100 European bird species since 1960, considered as an index of the phenological response of bird species to recent climate change, to their population trends. Species that declined in the period 1990-2000 did not advance their spring migration, whereas those with stable or increasing populations advanced their migration considerably. On the other hand, population trends during 1970-1990 were predicted by breeding habitat type, northernmost breeding latitude, and winter range (with species of agricultural habitat, breeding at northern latitudes, and wintering in Africa showing an unfavorable conservation status), but not by change in migration timing. The association between population trend in 1990-2000 and change in migration phenology was not confounded by any of the previously identified predictors of population trends in birds, or by similarity in phenotype among taxa due to common descent. Our findings imply that ecological factors affecting population trends can change over time and suggest that ongoing climatic changes will increasingly threaten vulnerable migratory bird species, augmenting their extinction risk.
The main objective of this long‐term study (1978–2016) was to find the underlying factors behind the declining trends of eider Somateria mollissima in the Baltic/Wadden Sea.
Specifically, we aimed at ...quantifying the bottom‐up effect of nutrients, through mussel stocks, on reproduction and abundance of eider, and the top‐down effects caused by white‐tailed eagle Haliaeetus albicilla predation.
Bottom‐up effects increase marine primary productivity with subsequent effects on food availability for a major mussel predator. Top‐down effects may also regulate eider populations because during incubation female eiders are vulnerable to predation by eagles.
Our structural equation modelling explained a large percentage of the variance in eider abundance. We conclude that the Baltic/Wadden Sea eider population was regulated directly by white‐tailed sea eagle predation on incubating females and indirectly by the amount of nutrients in seawater affecting both mussel stocks and the breeding success of eiders, reflecting density dependence.
These findings may explain the decreasing trend in the Baltic/Wadden Sea eider population during the last decades as an additive effect of top‐down and bottom‐up factors, and likely as an interaction between them.
In this study, the authors demonstrate that both top‐down and bottom‐up effects must be considered when evaluating the population dynamics of eiders in the Baltic sea and that both effects are playing a role in the conservation of such species. These findings are of interest to a broad audience, beyond conservationists and ecologists.
Humans profoundly impact landscapes, ecosystems, and animal behavior. In many cases, animals living near humans become tolerant of them and reduce antipredator responses. Yet, we still lack an ...understanding of the underlying evolutionary dynamics behind these shifts in traits that affect animal survival. Here, we used a phylogenetic meta-analysis to determine how the mean and variability in antipredator responses change as a function of the number of generations spent in contact with humans under 3 different contexts: urbanization, captivity, and domestication. We found that any contact with humans leads to a rapid reduction in mean antipredator responses as expected. Notably, the variance among individuals over time observed a short-term increase followed by a gradual decrease, significant for domesticated animals. This implies that intense human contact immediately releases animals from predation pressure and then imposes strong anthropogenic selection on traits. In addition, our results reveal that the loss of antipredator traits due to urbanization is similar to that of domestication but occurs 3 times more slowly. Furthermore, the rapid disappearance of antipredator traits was associated with 2 main life-history traits: foraging guild and whether the species was solitary or gregarious (i.e., group-living). For domesticated animals, this decrease in antipredator behavior was stronger for herbivores than for omnivores or carnivores and for solitary than for gregarious species. By contrast, the decrease in antipredator traits was stronger for gregarious, urbanized species, although this result is based mostly on birds. Our study offers 2 major insights on evolution in the Anthropocene: (1) changes in traits occur rapidly even under unintentional human “interventions” (i.e., urbanization) and (2) there are similarities between the selection pressures exerted by domestication and by urbanization. In all, such changes could affect animal survival in a predator-rich world, but through understanding evolutionary dynamics, we can better predict when and how exposure to humans modify these fitness-related traits.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Recent studies revealed that the call of the common cuckoo Cuculus canorus has more inter-individual than intra-individual variation and that the number of syllables depends on environmental ...conditions, but also the presence of male and female conspecifics. However, still very little is known about how song varies at a global scale, especially considering the wide distribution of this species across most of Europe and Asia. Xeno-canto.org is a vocalization repository for birdsong. We used xeno-canto.org as a data source for investigating the variables that affect the number of syllables in cuckoo calls at a large spatial scale. At a very broad geographical scale, the number of syllables in cuckoo calls predicted bird species richness. Additionally, female calls were associated with shorter males calls, and there was a positive correlation between the interaction between female calls and the number of host races parasitized by the cuckoo. These findings confirm that intraspecific and interspecific interactions significantly affect the number of syllables in cuckoo calls, and both environmental variables and biotic interactions should be considered in future studies of vocalizations in cuckoos. Last but not least, we demonstrated that a citizen science project is a useful source for ecological studies at large spatial scales.
Prolonged high secretion of glucocorticoids normally reflects a state of chronic stress, which has been associated with an increase in disease susceptibility and reduction in Darwinian fitness. Here, ...we hypothesize that an increase in oxidative stress accounts for the detrimental effects of prolonged high secretion of glucocorticoids. We performed a meta-analysis on studies where physiological stress was induced by administration of glucocorticoids to evaluate the magnitude of their effects on oxidative stress. Glucocorticoids have a significant effect on oxidative stress (Pearson
r
= 0.552), although this effect depends on the duration of treatment, and is larger in long-term experiments. Importantly, there was a significant effect on tissue, with brain and heart being the most and the least susceptible to GC-induced oxidative stress, respectively. Furthermore, effect size was larger (1) in studies using both sexes compared to males only, (2) when corticosterone rather than dexamethasone was administered and (3) in juveniles than in adults. These effects were not confounded by species, biochemical biomarker, or whether wild or laboratory animals were studied. In conclusion, our meta-analysis suggests that GC-induced oxidative stress could be a further mechanism underlying increases in disease susceptibility and decreases in Darwinian fitness observed under chronic stress.
Are Organisms Adapting to Ionizing Radiation at Chernobyl? Møller, Anders Pape; Mousseau, Timothy Alexander
Trends in ecology & evolution (Amsterdam),
April 2016, 2016-Apr, 2016-04-00, 20160401, Letnik:
31, Številka:
4
Journal Article
Recenzirano
Numerous organisms have shown an ability to survive and reproduce under low-dose ionizing radiation arising from natural background radiation or from nuclear accidents. In a literature review, we ...found a total of 17 supposed cases of adaptation, mostly based on common garden experiments with organisms only deriving from typically two or three sampling locations. We only found one experimental study showing evidence of improved resistance to radiation. Finally, we examined studies for the presence of hormesis (i.e., superior fitness at low levels of radiation compared with controls and high levels of radiation), but found no evidence to support its existence. We conclude that rigorous experiments based on extensive sampling from multiple sites are required.
In total,17 studies have suggested that they have demonstrated adaptation to ionizing radiation from Chernobyl, while in fact only two of these fulfill the criteria for evolutionary adaptation.
Lack of evidence of adaptation mainly derived from the lack of replication and of rigorous experimental design.
There was no evidence of hormesis, with organisms at low levels of radiation performing better than at typical background radiation in uncontaminated areas.
Large animals have longer flight distances when approached by a potential predator than small animals, and predators therefore have longer flight distances than their prey. The ubiquitous presence of ...humans in urban areas selects for differential invasion by animals with short flight distances, and adaptation to urban environments results in further reductions in flight distance. Because prey are better able to cope with the proximity of humans than predators due to differences in flight distance, urban areas may act as refuges. Predators on average have a flight distance that is 8 times larger than that of their prey. In urban areas, humans were present within a distance of 54 m (the mean flight distance of raptor species) 16% of the time and 4% of the time within a distance of 7 m (the mean flight distance of prey species). In contrast, humans were present 1.2% of the time within a distance of 54 m but only 0.1% of the time within a distance of 7 m in rural habitats. Therefore, prey gained a 10-fold increase in predator refuge in urban compared with rural habitats. The reduction in flight distance between the ancestral rural and the current urban habitats decreased with the difference in flight distance between raptors and that of prey. The difference in flight distance between predators and that of prey increased with increasing preference of prey by sparrowhawks Accipiter nisus relative to their abundance, providing evidence of a selective advantage for prey. These results suggest that birds that are prey of raptors enjoy a selective advantage from association with humans.
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