Simple Sequence Repeat Gene Polymorphisms in Yellow-Rumped Flycatcher With Gender-Specific Associations and Personality Variations

This study explores the genetic and physiological facets of personality variations in the yellow-rumped flycatcher (Ficedula zanthopygia), with a focus on potential sex-specific associations between simple sequence repeat (SSR) polymorphisms, body condition index (BCI) and behavioral traits. During the 2020 breeding seasons at Zuojia Nature Reserve, northeast China, we conducted field investigations using several stress tests to quantify personality as reflected in breathing rates. This metric demonstrated significant reproducibility between life stages, thereby validating its use as a reliable association with individual boldness. We further examined the influence of genetic diversity by genotyping 10 highly polymorphic SSR loci and calculating individual heterozygosity. As a reflection of stronger personalities, we found significant associations between individual heterozygosity and breathing rates in female adults, with greater heterozygosity correlated with lower breathing rates. The opposite pattern was observed in male nestlings, and no significant correlations were observed in male adults or male chicks. In addition, the BCI tended to be negatively correlated with breathing rates in female adults, suggesting that individuals with better body conditions were less fearful. These findings underscore the importance of genetic diversity and body condition in modulating personality traits, particularly in females. Overall, our results highlight the likelihood that the sex of these birds underlies their behavioral variations. Moreover, this study provides insight into the genetic basis of personality in cavity-nesting birds and emphasizes the need for further research to elucidate specific genetic pathways that influence these traits.