ALBINISM AND PHENOTYPE OF BARN SWALLOWS (HIRUNDO RUSTICA) FROM CHERNOBYL

The effects of mutation on phenotypic expression are supposed to be mainly deleterious because mutations disrupt the expression of genes that function relatively well under current environmental conditions. Thus, mutations are assumed to give rise to deviant phenotypes that are generally selected against. Radioactive contamination in the Chernobyl region of Ukraine is associated with a significant increase by a factor two to 10 in mutation rate in microsatellite markers of the barn swallow, Hirundo rustica. Barn swallows from Chernobyl had a temporally constant, elevated frequency of partial albinism compared to the situation before radioactive contamination and compared to birds from a control area. Albinism disproportionately affected the carotenoid-based plumage of the head, suggesting that carotenoid metabolism is particularly susceptible to the effects of radiation. Individuals with partially albinistic plumage had, on average, lower mean phenotypic values than other birds, and this was particularly the case for males. Furthermore, differences in phenotypic variation, as determined using Levene's test, were significantly larger in partial albinos compared to nonalbinos in males, but not in females, even though the null expectation would be the opposite due to the lower mean phenotypic values of partial albinos. Although small phenotypes were commonly associated with germline mutations, there was no general decrease in overall body size during the period 1991-2000, implying that small individuals were selected against. Because partial albinism is disfavored by natural selection, the effects of mutations are deleterious, giving rise to a balance between mutation and selection.

Studies of the evolution of elaborate ornaments have concentrated on their role in increasing attractiveness to mates. The classic examples of such sexually selected structures are the elongated tails of some bird species. Elongated tails can be divided into three categories: graduated tails, pin tails and streamers. There seems to be little debate about whether graduated and pin tails are ornaments; i.e. costly signals used in mate choice. However, in the case of streamers there is considerable discussion about their function. It has been suggested that tail streamers could be (i) entirely naturally selected, (ii) entirely sexually selected, (iii) partly naturally and partly sexually selected. The prime example of a species with tail streamers is the swallow (Hirundo rustica) in which both sexes have tail streamers. In this paper we discuss the aerodynamic consequences of different types of manipulation of the streamer and/or outer tail feather. We make qualitative predictions about the aerodynamic performance of swallows with manipulated tail streamers; these predictions differ depending on whether streamers have a naturally or sexually selected function. We demonstrate that these hypotheses can only be separated if tail streamers are shortened and changes in aerodynamic performance measured during turning flight.

Anthropogenic stressors, such as radioactive contaminants released from the Chernobyl and Fukushima Daiichi accidents, deteriorate ecological and evolutionary processes, as evidence for damaging effects of radioactive contamination on wildlife is accumulating. Yet little is known about physiological traits of animals inhabiting contaminated areas, and how those are affected by individual quality and phenology. We investigated variation in body temperature of wild barn swallows, Hirundo rustica, exposed to radioactive contamination from the Chernobyl accident in Ukraine and Belarus. We tested whether exposure to variable levels of radioactive contamination modified core body temperature of birds, and whether individual and phenological characteristics modulated radiosensitivity of body temperature. We showed that barn swallow body temperature varied with exposure to environmental radioactive contamination and that individual characteristics and phenology affected radioactive exposure. Increased radiosensitivity and up‐regulation of body temperature were detected in birds of low body condition, high risk of capture, and in animals captured late during the day but early during the season. These results highlight the complex ways that the body temperature of a wild bird is impacted by exposure to increased radioactive contamination in natural habitats. By impacting body temperature, increased radioactive contamination may compromise energetic balance, jeopardize responsiveness to global warming, and increase risk of overheating.

How species are responding to climate change is a key topic in evolutionary ecology. Increasing temperatures are expected to affect phenotypic traits involved in thermoregulation, thus decreasing body size and/or increasing body appendages associated with heat exchange, as predicted by Bergmann's and Allen's rules.Results from long‐term studies of variation in morphology over time have generally provided results supporting these predictions. However, two outstanding questions are frequently raised in studies relating changes in phenotypes to increasing temperatures: (1) whether such changes involve a shift in animal shape through the non‐proportional variation of different body parts; and (2) whether they result from adaptive evolutionary responses.Relying on capture‐recapture histories of almost 9000 breeding individuals from a declining Italian population of an Afro‐Palearctic migratory bird, the barn swallow (Hirundo rustica), we documented a decrease in some body size traits (body mass, keel and wing length) over a 31‐year period (1993–2023), with body mass declining the most (up to 4.0% in males). However, this was not the case for bill and partly tarsus length. Intra‐individual lifelong changes in morphological traits of sexually mature birds showed only a limited contribution to trends over time in phenotypically plastic morphological traits.Viability and fecundity selection analyses revealed that smaller individuals did not enjoy greater success compared to larger ones. For some traits, the opposite was actually the case.The shifts in body size and, partly, shape over time we observed were coherent with predictions deriving from Bergmann's and Allen's rules. Yet, natural selection did not consistently favour smaller individuals. We thus call for caution in interpreting recent decreases in body size as adaptive evolutionary responses to climate warming, as they may rather reflect phenotypically plastic responses to changing climatic/environmental conditions occurring during early ontogenetic stages.

The elongated tail of the male barn swallow (Hirundo rustica) is regarded as one of the classic examples of a male trait exaggerated by female choice. However, recently a hypothesis has been proposed suggesting that the streamers, or elongated outer tail feathers, may aid aerodynamic performance through the Norberg mechanism, providing lift at slow speeds and high angles of attack when the tail is fully spread. The possibility exists that the tail streamer has evolved under natural selection, sexual selection, or a combination of both selection pressures. We tested these three hypotheses by reducing the streamer length of free-flying swallows and measuring their aerodynamic performance, using stereo-video. Measurements of flight performance were made from the digitized three-dimensional flight paths. Five flight variables best described the individual variation in flight performance. Four of these five parameters—mean velocity, mean curvature, maximum agility, and mean rate change of curvature in the XY plane—had significant second-order polynomial relationships with tail streamer manipulation. The first and second principal components (from principal components analysis of the flight variables) also showed similar relationships with streamer manipulation. The combination of a curvilinear relationship between flight performance and streamer length and an aerodynamic optimum between 0 and 20 mm reduction is only predicted if both natural and sexual selection have been acting on streamer morphology. Our data therefore suggest that sexual selection has extended streamer length by around 10 mm beyond its aerodynamic optimum. We suggest that both natural and sexual selection have been important in shaping tail morphology in the barn swallow, and the relative importance of both selection pressures is discussed. Key words: barn swallows, flight performance, Hirundo rustica, maneuverability, natural selection, Norberg mechanism, sexual selection. [Behav Ecol 11: 228–238 (2000)]

The severe nuclear accident at Chernobyl in 1986 resulted in the worst reported accidental exposure of radioactive material to free-living organisms. Short-term effects on human populations inhabiting polluted areas include increased incidence of thyroid cancer, infant leukaemia, and congenital malformations in newborns. Two recent studies have reported, although with some controversy, that germline mutation rates were increased in humans and voles living close to Chernobyl, but little is known about the viability of the organisms affected. Here we report an increased frequency of partial albinism, a morphological aberration associated with a loss of fitness, among barn swallows, Hirundo rustica, breeding close to Chernobyl. Heritability estimates indicate that mutations causing albinism were at least partly of germline origin. Furthermore, evidence for an increased germline mutation rate was obtained from segregation analysis at two hypervariable microsatellite loci, indicating that mutation events in barn swallows from Chernobyl were two- to tenfold higher than in birds from control areas in Ukraine and Italy.

Decision letter: Limited role of generation time changes in driving the evolution of the mutation spectrum in humans

Editor's evaluation: Limited role of generation time changes in driving the evolution of the mutation spectrum in humans

Author response: Limited role of generation time changes in driving the evolution of the mutation spectrum in humans

Fires enhance flammability in<i>Ulex parviflorus</i>

DNA damage in barn swallows ( Hirundo rustica) from the Chernobyl region detected by use of the comet assay

Individual variation in microsatellite mutation rate in barn swallows

At the end of 36 years after the Chernobyl disaster, about 5 million people still live in the radioactively contaminated territories of Russia, Ukraine, and Belarus, and the density of radioactive contamination by Cesium-137 and Strontium-90 will remain radiologically significant for decades. We assessed cervical and endometrial cancer primary incidence (new cases) in the female population from the Bryansk region living in conditions of chemical, radioactive, and combined environmental contamination for 2000–2020. We found a significant increase in the long-term trend in the primary incidence of cervical and endometrial cancer in all the studied groups, regardless of the environmental conditions of residence (p < 0.00001). We did not find statistically significant differences in the incidence of cervical and endometrial cancer in women, regardless of the level of chemical, radioactive, and combined environmental contamination. However, women living in environmentally unfavorable areas (in total, in the territories of chemical, radioactive, and combined contamination) are statistically significantly more likely to develop endometrial cancer in terms of relative risk compared to environmentally safe (control) areas (RR 1.17 (1.08–1.27)). No such pattern was found for cervix cancer. It should be noted, since environmentally safe (control) areas have a certain level of contamination (albeit low), RR is underestimated.

The effects of radiation on sperm swimming behavior depend on plasma oxidative status in the barn swallow ( Hirundo rustica)

Impaired swimming behaviour and morphology of sperm from barn swallows Hirundo rustica in Chernobyl