Publications (8)15.74 Total impact
- [Show abstract] [Hide abstract] ABSTRACT: The benefits of extrapair mating behaviour for females of socially monogamous bird species are unclear despite substantial research effort. The genetic compatibility hypothesis proposes genetic benefits such that females paired to social mates of low genetic compatibility avoid or diminish negative fitness consequences by mating with a more compatible extrapair mate, resulting in offspring of higher genetic quality. Furthermore, within the context of inbreeding depression observed in natural populations, a high degree of overall genetic similarity between social pair mates may be regarded as a special case of genetic incompatibility. We tested the hypothesis that female extrapair matings represent an adaptive behavioural response to avoid negative consequences of being paired to a genetically similar social pair male in the coal tit, Parus ater, a socially monogamous passerine with high rates of extrapair paternity. In contrast to what was predicted, we found no evidence for a positive association between the genetic similarity of social pair mates (measured as band-sharing coefficients from multilocus DNA fingerprints) and the occurrence of extrapair paternity. Furthermore, the genetic similarity of the cuckolding female with its social mate was not higher when compared pairwise to that of its extrapair mate in 63 uniquely composed triplets. Finally, three parameters of reproductive success were not related to the genetic similarity of social pair mates. We conclude that avoiding the potentially negative fitness consequences of being paired to a genetically similar social pair mate did not select for and thus cannot maintain female extrapair mating behaviour in our study population.
- [Show abstract] [Hide abstract] ABSTRACT: Avian extrapair mating systems provide an interesting model to assess the role of genetic benefits in the evolution of female multiple mating behavior, as potentially confounding nongenetic benefits of extrapair mate choice are seen to be of minor importance. Genetic benefit models of extrapair mating behavior predict that females engage in extrapair copulations with males of higher genetic quality compared to their social mates, thereby improving offspring reproductive value. The most straightforward test of such good genes models of extrapair mating implies pairwise comparisons of maternal half-siblings raised in the same environment, which permits direct assessment of paternal genetic effects on offspring traits. But genetic benefits of mate choice may be difficult to detect. Furthermore, the extent of genetic benefits (in terms of increased offspring viability or fecundity) may depend on the environmental context such that the proposed differences between extrapair offspring (EPO) and within-pair offspring (WPO) only appear under comparatively poor environmental conditions. We tested the hypothesis that genetic benefits of female extrapair mate choice are context dependent by analyzing offspring fitness-related traits in the coal tit (Parus ater) in relation to seasonal variation in environmental conditions. Paternal genetic effects on offspring fitness were context dependent, as shown by a significant interaction effect of differential paternal genetic contribution and offspring hatching date. EPO showed a higher local recruitment probability than their maternal half-siblings if born comparatively late in the season (i.e., when overall performance had significantly declined), while WPO performed better early in the season. The same general pattern of context dependence was evident when using the number of grandchildren born to a cuckolding female via her female WPO or EPO progeny as the respective fitness measure. However, we were unable to demonstrate that cuckolding females obtained a general genetic fitness benefit from extrapair fertilizations in terms of offspring viability or fecundity. Thus, another type of benefit could be responsible for maintaining female extrapair mating preferences in the study population. Our results suggest that more than a single selective pressure may have shaped the evolution of female extrapair mating behavior in socially monogamous passerines.
- [Show abstract] [Hide abstract] ABSTRACT: Despite substantial research effort, the benefits of female extra-pair matings in socially monogamous bird species remain elusive. The good genes hypothesis assumes that females engage in extra-pair copulations with males of superior genetic quality compared to their respective social mate. Therefore, a negative association between the degree of cuckoldry and male survival is predicted, if genetic quality is phenotypically reflected by high viability. Furthermore, genetic sires of extra-pair offspring (EPO) should survive better than the social fathers they cuckolded. We tested these predictions in a nestbox population of the coal tit (Parus ater), a socially monogamous passerine with low breeding dispersal and high rates of extra-pair paternity (EPP). Based on 257 genotyped first broods of two consecutive years, we found no relationship between the incidence of EPP or the proportion of EPO within a given brood and male or female recapture probabilities. Furthermore, recapture rates did not differ between social and genetic fathers of EPO or males that did or did not appear as extra-pair sires in other broods. Our results were not affected by differential (short-range) breeding dispersal with respect to EPP or by other potentially confounding variables. Hence, they are not in accordance with the good genes as viability genes hypothesis.
- [Show abstract] [Hide abstract] ABSTRACT: In the majority of socially monogamous bird species, extra-pair paternity (EPP) has been shown to be common, while its frequency varies considerably among as well as within species. Our knowledge of factors affecting this variation, however, still remains comparatively poor. A thorough analysis of EPP patterns on an individual level may lead to a better understanding of the general diversity in EPP. Here, we analyse intra- and inter-annual as well as individual variation in the occurrence of EPP in first and second broods of coal tits (Parus ater) in three successive years. Based on a sample of 483 broods with 3559 offspring genotyped, we show that EPP was extraordinarily frequent in the study population, surpassing the values observed in other species of the genus Parus by far. On the population level, the rates of EPP were found to be remarkably similar between years, while there was pronounced intra-annual variation such that EPP rates increased significantly from first to second broods. Considering consecutive broods of individual females and males, the general occurrence of EPP was 'inconsistent' (i.e. EPP often affected only one of two broods), but the proportion of extra-pair young (EPY) per brood showed significant repeatability for both sexes in case of mate retention. When mate change occurred, repeatability collapsed, indicating that pair identity was more important in determining the repeatability of EPP than female or male identity alone. This was further supported by the fact that, besides female and male age, also their interaction (reflecting pair age combination) significantly predicted the proportion of EPY, though not in all breeding periods surveyed. Hence, the identity of the breeding pair (reflecting possible interactions of male and female characteristics) should be explicitly considered and accounted for in future studies investigating patterns of EPP on an individual level. Finally, we show that, depending on the boundary conditions, in principle, all coal tits experience EPP: When analysing three or more broods of the same individual, there were no completely 'faithful' females and also nearly no males, which were not cuckolded at least once.
- [Show abstract] [Hide abstract] ABSTRACT: In order to assess the potentially harmful consequences of blood sampling in nestling coal tits (Parus ater), we analysed fledging success, fledgling local recruitment and recruit natal dispersal for nestlings originating from 27 blood-sampled broods and nestlings from 39 control broods. No adverse effects of blood sampling were detectable.
- [Show abstract] [Hide abstract] ABSTRACT: Differential survival of males and females affects the structure and dynamics of avian populations, but studying sex-specific survival rates is difficult. This is especially true for offspring if the period between hatching and first breeding is considered. Under certain conditions, however, the determination of of offspring sex ratio, recruitment and dispersal may help in the investigation of sex-specific survival rates to the age of first breeding. Applying a molecular technique we sexed a large sample of Coal Tit (Parus ater) nestlings from a nest box population in a coniferous forest near Lingen/Emsland (Lower Saxony, Germany). The study covered a period of two years and included first and second broods. We found that the sex ratio did not deviate from unity. Through capturing breeding adults in the second year, we were able to examine local recruitment rates and natal dispersal distances of male and female offspring. The sexes differed significantly neither in recruitment probability, which was generally high, nor in dispersal distance, which was generally low. Our results indicate that there is no difference in the survival rate of male and female Coal Tits during their first year of life. The relevance of our findings are discussed with regard to the characteristics of the study population.
- [Show abstract] [Hide abstract] ABSTRACT: Whether female birds choose extra-pair mating partners to obtain genetic fitness benefits is intensely debated. The most straightforward and crucial test of 'good genes' models of female extra-pair mating is the comparison of naturally 'cross-fostered' maternal half-siblings sharing the same rearing environment as any systematic differences in performance between the two categories of offspring phenotype can be attributed to differential paternal genetic contribution. We analysed local recruitment and first-year reproductive performance of maternal half-siblings in the coal tit (Parus ater), a passerine bird with high levels of extra-pair paternity. We provide a highly comprehensive measure of the long-term fitness consequences of female extra-pair matings based on a large sample of 736 within-pair offspring (WPO) and 368 extra-pair offspring (EPO) from 91 first and 55 second broods, from which 132 breeders recruited into the study population. In contrast to predictions derived from 'good genes' models, we found no differences in local recruitment and seven parameters of first-year reproductive performance when comparing WPO and EPO. These results question the universal validity of findings in other bird species supporting 'good genes' models, particularly as they are based on the best approximation to female fitness obtained so far.
Technische Universität Braunschweig
Brunswyck, Lower Saxony, Germany
- Zoological Institute
University of Bonn
Bonn, North Rhine-Westphalia, Germany
- Institute of Evolutionary Biology and Ecology