Anders Pape Møller

The T‐cell mediated response to a challenge of the immune system with phytohemagglutinin (PHA) is a common measure used in ecological studies of host‐parasite interactions or parasite‐mediated selection. We investigated the temporal dynamics of this response in house sparrows Passer domesticus in order to determine factors that contribute to temporal and individual variation in PHA response. After an initial significant increase in response from injection to six hours post‐injection, there was no further significant change in mean response after 12, 24, 36, 48 and 72 hours. Responses at night were consistently stronger than during daytime. Individuals may benefit from producing both a strong and a quick immune response to parasite attacks, although this may be impossible because of the observed positive relationship between maximum response and latency to maximum response. House sparrows with Haemoproteus infections had lower PHA responses and smaller maximum responses than individuals without infections. Individuals in prime body condition had stronger PHA responses than individuals in poor condition. House sparrows with large diurnal fluctuations in body mass had a weaker maximum response than individuals with small fluctuations. Since individuals with Haemoproteus infections have large fluctuations in body mass, this result suggests that infected individuals with large fluctuations in mass are unable to mount a strong immune response.

Radioactivity may have both phenotypic and genetic effects through its disruption of physiological processes and mutations. I studied the size and asymmetry of secondary sexual and ordinary morphological characters of stag beetles (Lucanus cervus) in two areas in the Ukraine: near Chernobyl, where levels of radiation are high, and in a control area with low background radiation. Developmental instability of morphological characters was estimated from the degree of fluctuating asymmetry using the restricted maximum likelihood parameter estimation (REML) method to partition measurement error from asymmetry. The degree of asymmetry estimated from unsigned differences in size of right and left secondary sexual character was similar to estimates based on the REML method. Beetles from the contaminated area had a significantly elevated level of fluctuating asymmetry in the secondary sexual character compared with animals from the control area. Male stag beetles found with a female had significantly lower asymmetry than males found alone. While mated males did not differ in asymmetry between areas, unmated males from Chernobyl were much more asymmetric than unmated males from the control area. These findings provide evidence for radiation disrupting developmental homeostasis, and thereby affecting the mating status of free‐living beetles.

Condition-dependent expression of secondary sexual characters and measures of immune function in a cohort of similarly aged male blue peafowl Pavo cristatus was used to test whether different sexual signals provide information about different aspects of phenotypic quality. A measure of cell-mediated immunity and the heterophil—lymphocyte ratio demonstrated condition dependence, but a measure of humoral immunity was not condition dependent. Only train length demonstrated condition-dependent expression, while the number and the size of ocelli in the train did not show significant condition dependence. Although residual train length (after controlling for the number and the size of ocelli in the train) reliably reflected the magnitude of two condition-dependent measures of immunocompetence (positively with cell-mediated immunity and negatively with humoral immunity), residual size of ocelli was negatively related to cell-mediated immunity. Different features of the complex train were related in different ways to measures of immunocompetence.

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.

Females may choose mates based on the expression of secondary sexual characters that signal direct, material fitness benefits or indirect, genetic fitness benefits. Genetic benefits are acquired in the generation subsequent to that in which mate choice is performed, and the maintenance of genetic variation in viability has been considered a theoretical problem. Consequently, the magnitude of indirect benefits has traditionally been considered to be small. Direct fitness benefits can be maintained without consideration of mechanisms sustaining genetic variability, and they have thus been equated with the default benefits acquired by choosy females. There is, however, still debate as to whether or not males should honestly advertise direct benefits such as their willingness to invest in parental care. We use meta-analysis to estimate the magnitude of direct fitness benefits in terms of fertility, fecundity and two measures of paternal care (feeding rate in birds, hatching rate in male guarding ectotherms) based on an extensive literature survey. The mean coefficients of determination weighted by sample size were 6.3%, 2.3%, 1.3% and 23.6%, respectively. This compares to a mean weighted coefficient of determination of 1.5% for genetic viability benefits in studies of sexual selection. Thus, for several fitness components, direct benefits are only slightly more important than indirect ones arising from female choice. Hatching rate in male guarding ectotherms was by far the most important direct fitness component, explaining almost a quarter of the variance. Our analysis also shows that male sexual advertisements do not always reliably signal direct fitness benefits.

Buchanan and Evans (2000) have recently suggested that the length of the tail streamer of the barn swallow Hirundo rustica is influenced to a large extent by natural selection, although sexual selection also plays a role. This conclusion was reached from analyses of video films of the flight of males and females after reducing the length of their tails by a variable amount ranging from 0 to 20 mm. Evans (1998) has previously made a similar experiment with a 20 mm manipulation. The optimum phenotype was subsequently derived from analyses of the flight parameters, while taking a number of other factors such as sex, farm, morphology, and date into account. Here we suggest that although it is likely that in fact streamer evolution was due to both natural and sexual selection, there is little direct evidence to support the reported conclusions. Although natural selection obviously plays a role in determining the selective landscape affecting tail length (e.g., Møller, 1989; Møller et al., 1995; Saino and Møller, 1996; Saino et al., 1997), it is far from clear that the cost is mainly measured in terms of foraging ability. Other factors like parasitism and disease have already been shown to be important (Saino and Møller, 1996; Saino et al., 1997). The reasons why the paper by Buchanan and Evans (2000) does not resolve whether tail length is mainly influenced by natural or sexual selection are as follows. (1) Buchanan and Evans did not standardize the conditions under which the measurements were made. (2) They provide no direct evidence for any of their aerodynamic parameters having a fitness consequence. (3) The birds were filmed at variable intervals since the experimental manipulation. (4) The context in which the flight behavior was recorded does not represent the relevant selective pressure.