Limits...
Female house sparrows "count on" male genes: experimental evidence for MHC-dependent mate preference in birds.

Griggio M, Biard C, Penn DJ, Hoi H - BMC Evol. Biol. (2011)

Bottom Line: Another potential indirect benefit from mating preferences is genetic compatibility, which does not require extravagant or viability indicator traits.Overall, we found no evidence that females preferred males with high individual MHC diversity.Yet, when we considered individual MHC allelic diversity of the females, we found that females with a low number of alleles were most attracted to males carrying a high number of MHC alleles, which might reflect a mating-up preference by allele counting.

View Article: PubMed Central - HTML - PubMed

Affiliation: Konrad Lorenz Institute for Ethology, Austrian Academy of Sciences, Austria. m.griggio@klivv.oeaw.ac.at

ABSTRACT

Background: Females can potentially assess the quality of potential mates using their secondary sexual traits, and obtain "good genes" that increase offspring fitness. Another potential indirect benefit from mating preferences is genetic compatibility, which does not require extravagant or viability indicator traits. Several studies with mammals and fish indicate that the genes of the major histocompatibility complex (MHC) influence olfactory cues and mating preferences, and such preferences confer genetic benefits to offspring. We investigated whether individual MHC diversity (class I) influences mating preferences in house sparrows (Passer domesticus).

Results: Overall, we found no evidence that females preferred males with high individual MHC diversity. Yet, when we considered individual MHC allelic diversity of the females, we found that females with a low number of alleles were most attracted to males carrying a high number of MHC alleles, which might reflect a mating-up preference by allele counting.

Conclusions: This is the first experimental evidence for MHC-dependent mating preferences in an avian species to our knowledge. Our findings raise questions about the underlying mechanisms through which birds discriminate individual MHC diversity among conspecifics, and they suggest a novel mechanism through which mating preferences might promote the evolution of MHC polymorphisms and generate positive selection for duplicated MHC loci.

Show MeSH
Schematic overview of the experimental apparatus. Solid black lines: opaque divisors. Dashed lines: perches. Solid grey line: metal web. Dashed grey lines: part of the perches considered as choice location (choice area).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3044665&req=5

Figure 3: Schematic overview of the experimental apparatus. Solid black lines: opaque divisors. Dashed lines: perches. Solid grey line: metal web. Dashed grey lines: part of the perches considered as choice location (choice area).

Mentions: In April and May we conducted a female mate preference test using an indoor four-choice apparatus (2 m × 2 m × 0.5 m, Figure 3). The apparatus consisted of four choice chambers, separated by opaque dividers, at the four sides of the central choice chamber. An opaque divider was also set up in the middle of the central chamber to avoid visual interaction between the four stimulus individuals (see Figure 3). The central divider also prevented the females from simultaneously observing two or more stimulus. In one corner of the four dividers, an opening (14 × 14 cm) covered by a metal web allowed the female to observe the stimulus in the side chamber. During the experiment the females could see the stimulus through these holes but they could not physically interact. A perch was positioned in front of each of the four chambers. Perches had a line traced, which corresponded to the limit from which a female could observe the stimulus in the nearby compartment (choice area; Figure 3). When the focal female was not present in one of the four perches in front of the opening (choice time), that time was considered "no-choice time". In accordance with the objectives of the study, females had a choice between three males either with low (1-2 alleles), medium (3 alleles) or high (4-6 alleles) number of MHC-I alleles (HM, MM and HM groups respectively). To control for potential position effects, chambers were randomly assigned to the stimulus individuals. As a control, the fourth chamber contained a female (control group, CF group, n = 39) to test whether focal females were sexually motivated and did not show a bias among the compartments [57]. Stimulus individuals were tested to three experimental groups of focal females: females with low (LF), medium (MF) and high (HF) diversity (number) of MHC class I alleles (18 different females per group, with groups defined as above for males). We ensured that the stimulus males did not differ in body size (wing and tarsus length and body mass) or black breast patch (badge of status; for more details see [44]) (ANOVA test: all F 2,155 < 2.23 P > 0.12). The experiment consisted of 54 mate-preference trials, each with a different focal female as the subject. All birds were unfamiliar with each other because they came from different visually separated aviaries. At the beginning of a trial, test female and stimulus individuals were placed in their experimental chambers and allowed at least 30 min to acclimate before the trial began. After that period, the opaque separators, that covered the mesh windows, were removed and the position of the female was recorded every 1 s for 1 h (all trials were video recorded and then analyzed by students, blind with respect to the MHC genotype of the individuals). We measured the time spent by a female on the part of the perch in front of a male's compartment, and preference was expressed as the proportion of time in front of each male over the total time in the choice area (e.g. [58-61]). Outcomes from all female preference experiments were analysed with a generalized linear model (GLM) in which female preference was the dependent variable (see also [61]). To test the effect of the interaction between female group and stimulus group on female mate preference we used a GLM post hoc test (Tukey honestly significant difference test; see also [57]). Statistical analyses were performed with SPSS 17.0. All the results are presented as mean ± SE. All tests are two-tailed. Analyses were checked to ensure that they met the assumptions of parametric statistics.


Female house sparrows "count on" male genes: experimental evidence for MHC-dependent mate preference in birds.

Griggio M, Biard C, Penn DJ, Hoi H - BMC Evol. Biol. (2011)

Schematic overview of the experimental apparatus. Solid black lines: opaque divisors. Dashed lines: perches. Solid grey line: metal web. Dashed grey lines: part of the perches considered as choice location (choice area).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3044665&req=5

Figure 3: Schematic overview of the experimental apparatus. Solid black lines: opaque divisors. Dashed lines: perches. Solid grey line: metal web. Dashed grey lines: part of the perches considered as choice location (choice area).
Mentions: In April and May we conducted a female mate preference test using an indoor four-choice apparatus (2 m × 2 m × 0.5 m, Figure 3). The apparatus consisted of four choice chambers, separated by opaque dividers, at the four sides of the central choice chamber. An opaque divider was also set up in the middle of the central chamber to avoid visual interaction between the four stimulus individuals (see Figure 3). The central divider also prevented the females from simultaneously observing two or more stimulus. In one corner of the four dividers, an opening (14 × 14 cm) covered by a metal web allowed the female to observe the stimulus in the side chamber. During the experiment the females could see the stimulus through these holes but they could not physically interact. A perch was positioned in front of each of the four chambers. Perches had a line traced, which corresponded to the limit from which a female could observe the stimulus in the nearby compartment (choice area; Figure 3). When the focal female was not present in one of the four perches in front of the opening (choice time), that time was considered "no-choice time". In accordance with the objectives of the study, females had a choice between three males either with low (1-2 alleles), medium (3 alleles) or high (4-6 alleles) number of MHC-I alleles (HM, MM and HM groups respectively). To control for potential position effects, chambers were randomly assigned to the stimulus individuals. As a control, the fourth chamber contained a female (control group, CF group, n = 39) to test whether focal females were sexually motivated and did not show a bias among the compartments [57]. Stimulus individuals were tested to three experimental groups of focal females: females with low (LF), medium (MF) and high (HF) diversity (number) of MHC class I alleles (18 different females per group, with groups defined as above for males). We ensured that the stimulus males did not differ in body size (wing and tarsus length and body mass) or black breast patch (badge of status; for more details see [44]) (ANOVA test: all F 2,155 < 2.23 P > 0.12). The experiment consisted of 54 mate-preference trials, each with a different focal female as the subject. All birds were unfamiliar with each other because they came from different visually separated aviaries. At the beginning of a trial, test female and stimulus individuals were placed in their experimental chambers and allowed at least 30 min to acclimate before the trial began. After that period, the opaque separators, that covered the mesh windows, were removed and the position of the female was recorded every 1 s for 1 h (all trials were video recorded and then analyzed by students, blind with respect to the MHC genotype of the individuals). We measured the time spent by a female on the part of the perch in front of a male's compartment, and preference was expressed as the proportion of time in front of each male over the total time in the choice area (e.g. [58-61]). Outcomes from all female preference experiments were analysed with a generalized linear model (GLM) in which female preference was the dependent variable (see also [61]). To test the effect of the interaction between female group and stimulus group on female mate preference we used a GLM post hoc test (Tukey honestly significant difference test; see also [57]). Statistical analyses were performed with SPSS 17.0. All the results are presented as mean ± SE. All tests are two-tailed. Analyses were checked to ensure that they met the assumptions of parametric statistics.

Bottom Line: Another potential indirect benefit from mating preferences is genetic compatibility, which does not require extravagant or viability indicator traits.Overall, we found no evidence that females preferred males with high individual MHC diversity.Yet, when we considered individual MHC allelic diversity of the females, we found that females with a low number of alleles were most attracted to males carrying a high number of MHC alleles, which might reflect a mating-up preference by allele counting.

View Article: PubMed Central - HTML - PubMed

Affiliation: Konrad Lorenz Institute for Ethology, Austrian Academy of Sciences, Austria. m.griggio@klivv.oeaw.ac.at

ABSTRACT

Background: Females can potentially assess the quality of potential mates using their secondary sexual traits, and obtain "good genes" that increase offspring fitness. Another potential indirect benefit from mating preferences is genetic compatibility, which does not require extravagant or viability indicator traits. Several studies with mammals and fish indicate that the genes of the major histocompatibility complex (MHC) influence olfactory cues and mating preferences, and such preferences confer genetic benefits to offspring. We investigated whether individual MHC diversity (class I) influences mating preferences in house sparrows (Passer domesticus).

Results: Overall, we found no evidence that females preferred males with high individual MHC diversity. Yet, when we considered individual MHC allelic diversity of the females, we found that females with a low number of alleles were most attracted to males carrying a high number of MHC alleles, which might reflect a mating-up preference by allele counting.

Conclusions: This is the first experimental evidence for MHC-dependent mating preferences in an avian species to our knowledge. Our findings raise questions about the underlying mechanisms through which birds discriminate individual MHC diversity among conspecifics, and they suggest a novel mechanism through which mating preferences might promote the evolution of MHC polymorphisms and generate positive selection for duplicated MHC loci.

Show MeSH