2006 The Authors Journal compilation 2006 Blackwell Verlag, Berlin Accepted on 19 July 2006 J Zool Syst Evol Res doi: 10.1111/j.1439-0469.2006.00382.x 1 Division of General Human Genetics, Department of Medical Genetics, Institute of Human Genetics, University of Tübingen, Tübingen, Germany; 2Department of Wildlife Ecology and Management, University of Freiburg, Freiburg, Germany; 3Department of Experimental Ecology (Biology 3), University of Ulm, Ulm, Germany; 4Department of Zoology, Natural History Museum, University of Oslo, Oslo, Norway Female genetic heterogeneity affects the reproduction of great tits (Parus major L., 1758) in low-quality woodlands J. Tomiuk1, M. Stauss1, G. Segelbacher2, J. Fietz3, J. Kömpf1 and L. Bachmann4 Abstract Genetic heterogeneity is considered an important parameter for individual fitness and reproductive success. In 1999 and 2000, we studied the population genetics of great tit (Parus major L., 1758) in southwestern Germany from two different forest types (deciduous and mixedconiferous), which may significantly differ in prey diversity and/or food supply. Adults of 99 families were genotyped at four enzyme and eight microsatellite loci, in order to estimate individual heterozygosity. In the mixed-coniferous forest, a significant positive correlation between the genetic heterogeneity of females and early egg-laying date and clutch size was detected. Early egg-laying date and increased clutch size are conditions that positively affect the number of fledglings. This effect of individual heterozygosity was not observed in the deciduous woodland. Maternal genetic heterogeneity, however, did not correlate with fledgling condition, and individual heterozygosity of fathers had no impact on breeding success in either habitat. The positive effect of female genetic heterogeneity on brood size of great tits in mixed-coniferous forests is attributed to early egg-laying date, i.e. a maternal effect, rather than to a specific mating strategy that optimizes fitness through an increased brood size and the quality of offspring. Key words: Genetic variation – inbreeding avoidance – maternal effects – mating strategy Introduction The fundamental meaning of genetic variability for individuals and populations has been an issue in evolutionary biology at all times (Dobzhansky 1970). Classical population genetic models predict a positive association between genetic heterogeneity and fitness for any set of markers (e.g. Ohta 1971; Charlesworth 1991). Avoidance of inbreeding depression is one of the main arguments put forward in favour of this association. Yet, experimental studies have sometimes revealed contradictory findings (e.g. review by Zouros and Foltz 1987). In the common mussel (Mytilus edulis L., 1758), for example, Koehn and Gaffney (1984) found a positive correlation between heterozygosity and fitness-related characters such as growth rate, whereas Pierce and Mitton (1982) noticed a negative effect of heterozygosity on individual fitness of the tiger salamander Ambystoma tigrinum (Green, 1825). Allozymes and microsatellites are frequently used to assess heterozygosity and the choice of a particular marker system is certainly an issue (David 1998; Thelen and Allendorf 2001). Most microsatellites are considered neutral, although the structure of some particular microsatellites may be under selection (Li et al. 2002). Allozymes, however, are essential components of biochemical pathways. Variation of their activity and substrate specificity may have a substantial impact on the fitness of organisms. Allelic variation at such loci may nevertheless be neutral and merely act as neutral markers of closely linked fitness loci (Nei and Graur 1984). Combining both kinds of markers in ecological studies is therefore considered suitable for the assessment of genetic variation of individuals (Pujolar et al. 2005). In Parus species, a diet consisting of a high proportion of alternative prey types is considered an indicator for suboptimal habitats (Cowie and Hinsley 1987). For example, the diet of great tit (Parus major L., 1758) nestlings is less diverse in J Zool Syst Evol Res (2007) 45(2), 144–150 deciduous forests than in mixed woodlands where the diet of nestlings includes a high proportion of spiders (Gibb and Betts 1963). Some Parus species, e.g. the blue tit (Parus caeruleus L., 1758), are better adapted to deciduous forests where individuals show a better breeding performance than those in lowquality habitats (mixed woodlands dominated by coniferous trees) (Blondel et al. 1987; Cowie and Hinsley 1987; van Balen and Potting 1990; Stauss 2000; Stauss et al. 2005). Stauss (2000) found, during a study period of more than 10 years, that great tit females start laying eggs 3 days earlier in deciduous forests than in mixed-coniferous forests. The density of great tit breeding pairs was significantly higher in deciduous forests (1.73 ± 0.38 pairs ha)1) than in mixed-coniferous forests (1.04 ± 0.21 pairs ha)1). Furthermore, the average hatching success was higher in deciduous habitats (90%) than in mixed-coniferous ones (84%). These findings strongly support the quality assessment of the two habitat types, i.e. high-quality habitat (deciduous forest) and low-quality habitat (mixed-coniferous forest). In 1999 and 2000, in particular, the effect of genetic heterogeneity of breeding great tits on fitness-related brood parameters in mixed-coniferous and deciduous woodlands was focussed. The association between genetic variability of breeding great tit individuals and their reproductive success was analysed. Such correlations have previously been reported for blue tits. In this species, high genetic variability of females was associated with an increased brood size, and paternal genetic heterogeneity was associated with increased fledging success and a higher number of sired recruits (Foerster et al. 2003). It was also found that genetic heterogeneity of great tit females has an impact on their reproduction in mixedconiferous woodlands, an effect that was neither observed in deciduous forests nor for paternal genetic variability. The significant association between female genetic heterogeneity Maternal genetic heterogeneity and reproduction of Parus major and some brood parameters of great tits in mixed-coniferous forests is considered as a maternal effect. Materials and Methods Study area Great tit (P. major L., 1758) populations were studied in three forests near Tübingen, southwestern Germany (4833¢N, 900¢E). A study plot of 35 ha was dominated by 60% coniferous trees, e.g. scots pines (Pinus sylvestris L., 1753) and spruces (Picea abies L., 1753). Two study plots (9 and 16 ha) in the same forest consist of 67% beeches (Fagus sylvatica L., 1753) and 21% oaks (Quercus robur L., 1753). For more detailed information, see Stauss et al. (2005). The data from the two deciduous plots were pooled, because there were no significant differences in any of the estimated parameters (Wilcoxon rank sum test). The data presented here were obtained during a long-term population biological study of great tits and blue tits (P. caeruleus) from 1990 to 2004 (Stauss 2000; Stauss et al. 2005). In the course of the study, 173 nest boxes were installed in the deciduous forest and 236 nest boxes in the mixed woodland. The nest boxes were arranged in a 30 m · 30 m grid. Nests were checked regularly during the breeding seasons. Reproductive parameters such as laying date, clutch size and the number of hatchlings and fledglings were recorded. Adults and fledglings were weighed 14–16 days after hatching, i.e. 1 or 2 days before the nestlings fledged. In 1999, 17 females, 16 males and 17 families from the mixed forest and 28 females, 29 males and 29 families from the deciduous forest were analysed. In 2000, the sample consisted of 22 females, 23 males and 23 families from the mixed forest and 30 females, 29 males and 30 families from the deciduous forests. Roughly, one third of the adult birds monitored in 2000 were already breeding in 1999. Eight identical breeding pairs (five in the coniferous and three in the mixed forest) were noticed in both years. Another three female yearlings were recruits in the mixed woodland in 2000. Genetic variability During the breeding seasons in 1999 and 2000, blood (about 50 ll) was sampled through tapping the Vena ulnaris. Blood was stored in 250 ll EDTA buffer (1 mM, pH 7.4) in plastic vials and frozen until further processing. Approximately, 150 ll diluted blood was used for DNA isolation using the Qiagen DNA Blood Mini Kit (Qiagen, Hilden, Germany). Allelic variation within 99 families was studied. In both years, 96 males and 98 females were successfully genotyped at up to eight microsatellite loci: Pk-12 (GenBank accession no. AF041466), Mcy-4 (Double et al. 1997), Pocc-6 and Pocc-8 (Bensch et al. 1997), Pat-14 and Pat-43 (Galbusera et al. 2000) and Gf-4 and Gf-6 (Petren 1998). The four microsatellite loci, Pk-12, Pat-14, Pat-43 and Pocc-8, were analysed by polyacrylamide gel electrophoresis and silver staining, and the four microsatellites, Mcy-4, Pocc-6, Gf-4 and Gf-6, were scored by fragment-length analysis on an ABI-310 automatic sequencer (Applied Biosystems, Foster City, CA, USA). Approximately, 100 ll diluted blood was used for the electrophoretic analyses of three esterase isozymes (EST-1, EST-2, EST-3, E.C. 3.1.1.1) and phosphoglucoisomerase (PGI, E.C. 5.3.1.9), as described in Stauss et al. (2003) and Driesel et al. (2004). Statistical analysis The genetic heterogeneity of individuals was estimated as the observed relative proportion of heterozygous loci per individual. Standardization of reproductive parameters The brood parameters egg-laying date, hatching date, number of fledglings, total brood mass and body mass of fledglings differed significantly between the breeding seasons 1999 and 2000 (Fig. 1, p < 0.027; see also Table S1). For eliminating year effects (not relevant in this study), the data set per year was standardized to the 145 mean ¼ 0 and the standard deviation ¼ 1. After standardization, the observed values of all parameters were close to a normal distribution (Shapiro–Wilks test: 0.020 £ p £ 0.710, UNIVARIATE procedure; SAS 2003). The standardized brood parameters were tested for normality (Shapiro–Wilks test, UNIVARIATE procedure; SAS 2003) and homogeneity of variances between habitats and years (Levene’s test, t-test procedure; SAS 2003). Analyses of variance [general linear models (GLM) procedure and GENMOD procedure for binomially distributed dependent variables; SAS 2003] and regression models [REG procedure and non-linear regression analysis (NLIN) procedure; SAS 2003] were applied to parameters such as egg-laying date, clutch size, hatching date, number of hatchlings, number of fledglings, the mean body mass of fledglings and the total fledging mass, in order to study the impact of habitat quality and parental heterozygosity on the reproductive success of breeding pairs. Pearson’s correlation coefficients were calculated for male and female heterozygosity and brood parameters (CORR procedure; SAS 2003). For these analyses, individual genetic heterogeneity values were logarithmically transformed. For all tests, a significance level of 5% was accepted. Results Individual genetic heterogeneity within and between groups The average degree of individual heterozygosity (relative proportion of heterozygous loci per individual) was determined for adult great tit males and females separately for both habitat types and years (Fig. 2). The observed heterozygosity values did not differ significantly between sexes (p ¼ 0.726). In a subsequent analysis using the GLM procedure (SAS 2003), no significant differences between years in both habitat types (Hfemale: p > 0.573; Hmale: p > 0.559) and between habitat types in both years (Hfemale: p > 0.074; Hmale: p > 0.540) could be detected. Furthermore, the population genetic analyses showed fairly homogeneous genetic structures (allele and genotype frequencies) across habitat types within years (Blank et al. unpublished data). Correlation of brood parameters Most brood parameters are closely correlated to each other in both habitat types (see Table S2). Yet, correlation analyses points to some differences depending on the habitat type. There was a significant correlation between egg laying and clutch size in the mixed-coniferous habitat (p ¼ 0.008) but not in the deciduous habitat (p ¼ 0.064). In the deciduous but not in the mixed-coniferous woodland, early egg-laying date and hatching results in fledglings with high individual body mass (p < 0.001). Egg-laying date is the starting point of the measurements of breeding success. Its overall importance for reproduction was therefore studied in more detail. Egg-laying date and reproductive success Egg-laying date is known to have a major effect on brood parameters (e.g. Verhulst and Tinbergen 1991; Nilsson 1999; Hansson et al. 2000; Wardrop and Ydenberg 2003). Using the framework of generalized linear models in the analysis of variance (GLM procedure; SAS 2003), it was tested whether the time of egg laying had significant effects on clutch size and hatching date. Subsequently, significant effects of clutch size on the number of hatchlings were tested, afterwards significant effects of the number of hatchlings on the number of fledglings were tested, and finally significant effects of the number of fledglings on the total and mean body mass of fledglings were 2006 The Authors J Zool Syst Evol Res (2007) 45(2), 144–150 Journal compilation 2006 Blackwell Verlag, Berlin 146 Tomiuk, Stauss, Segelbacher, Fietz, Kömpf and Bachmann Fig. 1. Brood parameters of great tits in the mixed-coniferous and deciduous woodlands in the breeding seasons of 1999 and 2000. Boxes and solid lines in boxes represent mean ± SD, the broken lines indicate the median and the whiskers show the range of variation. The sample sizes are given within the boxes 2006 The Authors J Zool Syst Evol Res (2007) 45(2), 144–150 Journal compilation 2006 Blackwell Verlag, Berlin Maternal genetic heterogeneity and reproduction of Parus major 147 Table 1. Analyses of variance and covariance (GLM procedure; SAS 2003). The effects of habitat type and egg-laying date as covariates on clutch size, hatching date and fledging success, of clutch size on the number hatchlings, of the number of hatchlings on the number of fledglings and of the number of fledglings on the total and mean body mass of fledglings were estimated Source Fig. 2. Genetic heterogeneity of female and male great tits in deciduous and mixed-coniferous forests in 1999 and 2000. Boxes and solid lines in boxes represent mean ± SD, the broken line indicates the median and the whiskers show the range of variation. The sample sizes are given within boxes tested. As can be seen from Table 1, there is a dominant effect of the egg-laying date on clutch size (p ¼ 0.026) and hatching date (p < 0.001). The other downstream brood parameters were mainly affected by the respective preceding brood parameters. Table 1 shows that the habitat-specific effect of female genetic heterogeneity on the number of offspring and their quality is mediated through early egg-laying date. Paternal heterozygosity and reproductive success Correlation of individual heterozygosity of fathers and breeding success was detected in neither habitat type. Female heterozygosity and reproductive success The analyses of variance (GLM procedure; SAS 2003) revealed a significant effect of female heterozygosity, egg-laying date and habitat on clutch size (Table 1). Therefore, the female heterozygosity was correlated with egg-laying date and clutch size for both habitats separately (Pearson’s correlation coefficient, CORR procedure; SAS 2003). As can be seen from Fig. 3, egg-laying date is significantly correlated with female heterozygosity in the mixed-coniferous habitat (F1,35 ¼ 11.42, p ¼ 0.002). Consistently, clutch size is also significantly correlated with female genetic heterogeneity (F1,35 ¼ 6.49, p ¼ 0.015). In the deciduous forest, neither egg-laying date nor clutch size was significantly correlated to female heterozygosity (see also Table S3). Female heterozygosity and egg-laying date The correlation of female heterozygosity, egg-laying date and habitat type was now analysed in more detail. A linear correlation of female heterozygosity on egg-laying date did not strongly fit the data (model: F3,89 ¼ 2.78, p ¼ 0.045, GLM procedure; SAS 2003). The dependency of egg-laying date on female heterozygosity could be much better explained by a model assuming an increasing negative effect of female homozygosity on egg-laying date in the mixed-coniferous habitat and random effects in the deciduous habitat (Fig. 3). To achieve this, heterozygosity values of the females in the mixed-coniferous habitat were logarithmically transformed and an NLIN procedure (SAS 2003) was applied to the data df Clutch size Model 4 Error 88 Habitat 1 Egg-laying date 1 1 Hfemale 1 Hfemale (habitat) Hatching date (days after 1 April) Model 4 Error 88 Habitat 1 Egg-laying date 1 1 Hfemale 1 Hfemale (habitat) Number of hatchlings Model 4 Error 88 Habitat 1 Clutch size 1 1 Hfemale 1 Hfemale (habitat) Number of fledglings Model 4 Error 86 Habitat 1 Number of hatchlings 1 1 Hfemale 1 Hfemale (habitat) Total brood mass (g) Model 4 Error 86 Habitat 1 Number of fledglings 1 1 Hfemale 1 Hfemale (habitat) Mean body mass of fledglings (g) Model 4 Error 86 Habitat 1 Number of fledglings 1 1 Hfemale 1 Hfemale (habitat) Fledging success (fledglings per egg) Model 6 Error 84 Year 1 Habitat 1 Year · habitat 1 Egg-laying date 1 1 Hfemale 1 Hfemale (habitat) MS F 2.96 0.875 5.986 4.515 0.007 5.245 3.38 0.013 6.82 5.16 0.01 6.00 0.011 0.026 0.929 0.016 19.446 0.113 0.423 70.806 0.394 0.374 171.94 <0.001 3.74 626.06 3.48 3.30 0.056 <0.001 0.065 0.073 16.675 0.273 1.082 55.716 0.223 0.943 61.00 <0.001 3.96 203.81 0.82 3.45 0.050 <0.001 0.368 0.067 11.288 0.485 0.047 40.051 0.556 0.008 23.30 <0.001 0.10 82.66 1.15 0.02 0.756 <0.001 0.287 0.900 19.476 0.106 0.046 75.185 0.111 0.032 184.04 <0.001 0.44 710.47 1.05 0.31 0.511 <0.001 0.308 0.581 0.933 0.983 2.438 0.991 0.383 1.723 0.95 0.440 2.48 1.01 0.39 1.75 0.119 0.318 0.534 0.189 4.26 <0001 10.06 1.50 5.40 4.05 0.58 1.04 0.002 0.225 0.023 0.047 0.450 0.311 0.078 0.018 0.185 0.028 0.099 0.074 0.011 0.019 p df, degree of freedom; MS, mean squares (type III); F, F-value; p, type I error. Significant effects are given in bold. (model: F2,91 ¼ 5.10, p ¼ 0.017; coniferous forest: slope ¼ )1.383 ± 0.483, intercept ¼ )1.125 ± 0.369; deciduous forest: mean ¼ 0.130 ± 0.126 for standardized values). The fledging success was also tested in terms of the number of fledglings per egg (Dhondt et al. 1990) as a response to habitat type, egg-laying date and hatching date, and in terms of female heterozygosity with generalized linear models where 2006 The Authors J Zool Syst Evol Res (2007) 45(2), 144–150 Journal compilation 2006 Blackwell Verlag, Berlin 148 Fig. 3. Association between female genetic heterogeneity and egglaying date in the low-quality habitat (mixed coniferous; a) and highquality habitat (deciduous; b). A non-linear model explained the data more adequately than a linear model. The female genetic heterogeneity values in the low-quality habitat were therefore logarithmically transformed (mixed-coniferous forest: r ¼ )0.496, F1,35 ¼ 11.42, p ¼ 0.002; deciduous forest: r ¼ )0.095, F1,54 ¼ 0.21, p ¼ 0.648) the dependent variable is binomially distributed (GENMOD procedure; SAS 2003). The analysis of the reduced model revealed again significant temporal effects (egg-laying and -hatching dates) on fledging success (v2 > 4.19, df ¼ 1, p < 0.047) but no effect of the genetic heterogeneity of females (Table 1; see also Table S3). Discussion In the present study, a habitat-specific effect of maternal genetic heterogeneity on reproduction rate of great tits in mixed-coniferous forests was found. The major fitness parameters in birds is the number of fledglings, but also their body mass, as it is closely correlated with fledgling survival to the next breeding season (Lindén et al. 1992; Slagsvold et al. 1995). In evolutionary terms, it would thus be reasonable if selection would operate on these brood parameters in order to optimize fitness. Yet, some reproductive characters are closely correlated to each other (see Table S2) and this may cause counteracting effects on fitness. The egglaying date and the correlated clutch size may also be affected by environmental conditions that are not primarily determined by the habitat type (e.g. temperature), whereas habitat Tomiuk, Stauss, Segelbacher, Fietz, Kömpf and Bachmann structure may have larger impact on the survival of nestlings after their hatching. It is, for example, very likely that the number of fledglings and their individual body mass are determined by parental feeding abilities according to the resources provided by the habitat (see Slagsvold and Lifjeld 1990; Stauss et al. 2005). It is thus interesting that egg-laying date and clutch size, two parameters that may subsequently affect the number and the individual body mass of fledglings, correlate with female genetic heterogeneity of great tits in the low-quality habitat, whereas the number and the individual body mass of fledglings are not directly depending on the genetic heterogeneity of females (Table 1). Under suboptimal ecological conditions, high genetic heterogeneity of great tit females may indirectly result in a higher number of offspring that may result in large broods with a low quality of fledglings. The lacking association between paternal genetic heterogeneity and reproductive success of great tits may indicate that the feeding effort of males for their brood is less crucial. Summarizing the association between female genetic heterogeneity and brood size is therefore attributed to a maternal effect rather than to a specific improvement of offspring fitness through an evolutionary strategy that evolved to increase nestling quality. Foerster et al. (2003) noted that individual heterozygosity affects survival of 1-year-old females to the next season. The observed correlation between female genetic heterogeneity and egg-laying date in the lowquality habitat is consistent with the results of Foerster et al. (2003) and may also indicate an increased survival of genetically heterogeneous females from one breeding season to the next. The fact that seven of eight female recruits have an individual genetic heterogeneity above the population mean supports this conclusion. Although the evaluation of habitat quality may be a matter of debate and may bias the results (there may be patches of high quality in the low-quality habitat and vice versa and environmental effects may be obscured and not detectable by statistical methods), this study illustrates that environmental pressure on P. major differs between mixed forests and deciduous woodlands. This is in accordance with the results obtained by Mänd et al. (2005) and Sanz (2001), suggesting that great and blue tits prefer deciduous forests to coniferous forests. In this study, it was found that the relatedness of breeding pairs and the expected genetic heterogeneity of their brood (given the parental genotypes) had no significant effect on the reproductive success of great tits in low-quality habitat. Thus, the results do not support the hypothesis that individuals select mating partners that signal suitable genotypes for high genetic heterogeneity of broods. Nevertheless, it is believed that inbreeding avoidance is the easiest and most efficient mating strategy in order to optimize offspring fitness through increasing their average genetic heterogeneity. Of course, mating strategies may also increase heterozygosity, given that females choose optimal mates. Yet, such a scenario is only possible under strict assumptions, because advantageous genetic-wide heterogeneity is difficult to maintain over generations. Acknowledgements We thank Jutta Calgéer, Kristin Calgéer and Jochen Blank for their assistance in the field. This work was supported by a grant from the 2006 The Authors J Zool Syst Evol Res (2007) 45(2), 144–150 Journal compilation 2006 Blackwell Verlag, Berlin Maternal genetic heterogeneity and reproduction of Parus major German Research Foundation No. DFG to 151/2-1. GS was supported by a grant from the Max Planck Institute for Ornithology, JT was supported by a grant from the German Academic Exchange Service DAAD 13/PPP-N1, and LB was supported by a grant from the Research Council of Norway (ÔNational Centre for BiosystematicsÕ, 146515/420). We are grateful to T. Schenck and P. Galbusera for providing technical assistance. Zusammenfassung Der Reproduktionserfolg von Kohlmeisenweibchen (Parus major L., 1758) wird in Wäldern mit geringer Ressourcenqualität von ihrer genetischen Heterogenität mitbestimmt Individuelle Fitness und reproduktiver Erfolg werden oftmals in einem engen Zusammenhang mit genetischer Heterogenität gesehen. In den Jahren 1999 and 2000 untersuchten wir Kohlmeisenpopulationen (Parus major L., 1758) in süddeutschen Laub- und Nadelmischwäldern. Beide Waldformen können sich bzgl. der Futterdiversität und Futterverfügbarkeit stark unterscheiden. Die Alttiere von 99 Familien wurden für vier Enzym- und acht Mikrosatellitenloci genotypisiert, um die individuelle Heterozygotie abzuschätzen. Im Nadelmischwald fand sich eine signifikante positive Korrelation zwischen der individuellen Heterozygotie der Weibchen und Legedatum sowie Gelegegröße. Ein frühes Legedatum und ein größeres Gelege haben einen positiven Effekt auf die Anzahl von Jungtieren. Ein solcher Effekt konnte im Laubwald allerdings nicht beobachtet werden. Weiterhin bestand kein Zusammenhang zwischen maternaler genetischen Heterogenität und der Masse der Jungtiere, ebenso hatte die väterliche genetische Heterogenität in beiden Waldformen keinen signifikanten Einfluß auf den Bruterfolg. 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AuthorsÕ addresses: Jürgen Tomiuk, Michael Stauss and Jost Kömpf, Division of General Human Genetics, Department of Medical Genetics, Institute of Human Genetics, University of Tübingen, Wilhelmstrasse 27, D-72074 Tübingen, Germany. E-mail: juergen. tomiuk@uni-tuebingen.de, jost.koempf@uni-tuebingen.de, m-stauss@ gmx.de; Gernot Segelbacher, Department of Wildlife Ecology and 2006 The Authors J Zool Syst Evol Res (2007) 45(2), 144–150 Journal compilation 2006 Blackwell Verlag, Berlin 150 Management, University of Freiburg, Tennenbacher Strasse 4, D-79085 Freiburg, Germany. E-mail: gernot.segelbacher@wildlife. uni-freiburg.de; Joanna Fietz, Department of Experimental Ecology (Biology 3), University of Ulm, Albert-Einstein-Allee 11, D-89069 Ulm, Germany. E-mail: joanna.fietz@t-online.de; Lutz Bachmann, Department of Zoology, Natural History Museum, University of Oslo, P.O. Box 1172 Blindern, N-0318 Oslo, Norway. E-mail: lutz. bachmann@nhm.uio.no Supplementary Material The following supplementary material is available for this article online: Table S1. The mean values, standard deviations and the sample sizes of the brood parameters are listed Tomiuk, Stauss, Segelbacher, Fietz, Kömpf and Bachmann Table S2. The pairwise correlation analyses between brood parameters (egg-laying date, clutch size, hatching date, number of hatchlings, number of fledglings, total brood mass and mean body mass of fledglings are given Table S3. Pearson’s correlation coefficients of female genetic heterogeneity and three standardized brood parameters (egglaying date, clutch size and fledging success) of great tits in the mixed-coniferous and deciduous forests are listed This material is available as part of the online article from http://www.blackwell-synergy.com 2006 The Authors J Zool Syst Evol Res (2007) 45(2), 144–150 Journal compilation 2006 Blackwell Verlag, Berlin