International Journal of Molecular Zoology 2024, Vol.14, No.5, 281-289 http://animalscipublisher.com/index.php/ijmz 284 et al., 2021). These findings underscore the importance of environmental conditions in determining phenotypic variation and heritability in wild bird populations. 4.2 Genetic architecture The genetic architecture of traits, including the number and effect size of contributing loci, significantly impacts heritability. For example, a study on the genomic architecture of clutch size and egg mass in great tits revealed that these traits are influenced by many loci of small effect distributed across the genome, with no single locus having a large impact (Santure et al., 2013). This polygenic nature of traits suggests that heritability is spread across numerous genetic factors, making it complex to predict evolutionary responses. Additionally, the heritability of early-life telomere length in house sparrows was found to be low, indicating a polygenic trait strongly affected by environmental conditions. 4.3 Interaction between genes and environment The interaction between genetic and environmental factors, known as genotype-environment interactions (GxE), can significantly influence heritability. In tree swallows, the relationship between candidate genes and phenological traits such as laying date and incubation duration was found to be affected by environmental variables like breeding density and temperature (Bourret and Garant, 2015). This highlights the complexity of predicting trait evolution, as GxE interactions can modulate the expression of genetic potential under varying environmental conditions. Furthermore, a study on roe deer demonstrated that accounting for environmental similarity among relatives could reduce heritability estimates for certain traits, indicating that genetic variation for habitat selection plays a role in environmental similarity (Gervais et al., 2022). 4.4 Population-specific factors Heritability estimates can vary significantly across different populations due to population-specific factors. For instance, a study on Savannah sparrows breeding in agricultural grasslands found varying heritability estimates for morphological traits, influenced by the specific environmental and genetic context of the population (Cava et al., 2019). Additionally, a meta-analysis of heritability in behavior across different taxa revealed considerable variation among behaviors, with migratory behaviors being the most heritable (Dochtermann et al., 2019). These findings suggest that heritability is not a fixed parameter but can vary depending on the population's genetic makeup and environmental context. 5 Case Study: Heritability of Plumage Coloration in the Zebra Finch 5.1 Background on zebra finches The zebra finch (Taeniopygia guttata) is a small, socially monogamous bird native to Australia. It is widely used as a model organism in various fields of biological research due to its pronounced sexual dimorphism in plumage coloration and vocal behavior (Figure 2). Zebra finches are opportunistic breeders, and their adaptability to different environmental conditions makes them an excellent subject for studying genetic and environmental influences on phenotypic traits (Hauber et al., 2021). The study of Hauber et al. (2021) show a clear similarity between the tutor and tutee zebra finch songs, suggesting effective vocal learning, which is a crucial element of zebra finch social behavior. Additionally, there is a marked difference between the male and female call spectrograms, highlighting sexual dimorphism in vocalization patterns. This supports the idea that vocal learning and sexual differences in calls are both key features of zebra finches, making them valuable model organisms for studying vocal communication and social learning. 5.2 Research approach To investigate the heritability of plumage coloration in zebra finches, researchers have employed various experimental designs. One common approach involves controlled breeding experiments to isolate genetic factors from environmental influences. For instance, a study used a three-generation breeding design to homogenize the genetic background while comparing wild-type and white plumage morphs, which differ significantly in melanization (Krause et al., 2017). Another study sequenced the melanocortin-1 receptor (MC1R) gene in different plumage morphs and controlled for population structure to avoid artefactual associations.
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