Multivariate selection and intersexual genetic constraints in a wild bird population

Area of Science:

• Evolutionary biology
• Quantitative genetics
• Animal behavior

Background:

• Intralocus sexual conflict (ISC) arises when selection differs between sexes for genetically correlated traits.
• ISC's impact on wild populations is understudied, despite its potential evolutionary significance.
• Sexual dimorphism in morphological traits is common, but its genetic basis and evolutionary drivers require further investigation.

Purpose of the Study:

• To quantify the microevolutionary impacts of intralocus sexual conflict in a wild population of great tits (Parus major).
• To investigate the role of ISC in shaping the evolution of morphological traits.
• To estimate the reduction in a population's rate of adaptation due to sex-specific selection (gender load).

Main Methods:

• Combined intra- and intersex additive genetic (co)variances with sex-specific selection estimates.
• Employed a multivariate framework to analyze morphological traits (wing length, tarsus length, bill depth, bill length).
• Estimated cross-sex genetic correlations and gender load using quantitative genetic principles.

Main Results:

• Large genetic correlations were found between homologous male and female traits.
• Evidence for sex-specific multivariate survival selection suggested a significant role for ISC.
• Estimated gender load at 50% (95% CI: 13–86%), indicating a substantial reduction in the population's rate of adaptation.
• Cross-sex genetic correlation for fitness was near zero (-0.003).

Conclusions:

• Intralocus sexual conflict plays an appreciable role in the microevolutionary dynamics of great tit populations.
• Multivariate quantitative genetics and selection analyses are powerful tools for quantifying ISC impacts in wild populations.
• The study provides novel insights into the evolution of sexual dimorphism and the genetic architecture of fitness in the face of sexual conflict.