International Journal of Molecular Ecology and Conservation, 2025, Vol.15, No.1, 19-29 http://ecoevopublisher.com/index.php/ijmec 24 translocation/inversion changing the upstream and downstream environment of genes, and insertion elements bringing new enhancers, etc.) (Zhang et al., 2024). Figure 2 Convergent evolution through molecular parallelism of SV-genes involved in the domestication, genetic selection, climatic selection, and artificial selection of sheep and goats (Adopted from Yang et al., 2024) Image caption: The genes presented in the modules “Domestication”, “Genetic selection”, “Climatic selection”, and “Artificial selection” are the common candidate genes (i.e., orthologous genes) with important functions identified in the domestication, improvement, environment, and agronomic trait associated analyses of sheep and goats, respectively (Adopted from Yang et al., 2024) It is worth emphasizing that compared with small variations such as SNPs, SVs can often affect multiple genes or entire pathways at one time, and thus contribute more directly and significantly to complex adaptation (Peng et al., 2024b). For example, a large inversion may simultaneously change the expression coordination of several heat-resistant genes; a large deletion may knock out negative regulatory factors and enhance the activity of disease resistance pathways. These are effects that are difficult to achieve with single point mutations. Therefore, structural variation provides a "macro-genetic lever" for goats to adapt to changing environments. With the in-depth study of the function of goat SV, we can have a more comprehensive understanding of how these "big" variations support the ecological adaptation of goats at the molecular level in the future. 4.3 Discussion on the mechanism of action of structural variation in goat adaptability Structural variation plays a role in goat environmental adaptation through various mechanisms: changing dosage, changing expression time and space, or directly causing activity changes. These mechanisms of action are often more drastic and complex than single-point mutations, and therefore have a more significant impact on adaptive traits (Di Gerlando et al., 2020). Studies on plants and humans in recent years have also shown that the contribution of SVs to complex trait variation is much higher than the proportion of bases they occupy in the genome (Zhang et al., 2024). For omnivorous species such as goats that are distributed in multiple environments, structural variation undoubtedly provides a strong genetic "ammunition", enabling them to quickly adjust themselves according to different ecological pressures and achieve dynamic matching of genome and phenotype. In the future, by deeply correlating the SVs of goats with trait data, it is expected that a complete "genome structural variation-environmental factors-adaptive phenotype" network map will be drawn, providing a valuable example for adaptive evolution research. 5 The Synergistic Effect of HGT and SV and Their Evolutionary Significance 5.1 The interactive effect of horizontal gene transfer and structural variation Horizontal gene transfer and structural variation are two completely different genomic variation processes, one involving the acquisition of exogenous genes and the other involving the rearrangement of endogenous genomes.
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