International Journal of Molecular Ecology and Conservation, 2025, Vol.15, No.1, 19-29 http://ecoevopublisher.com/index.php/ijmec 25 However, in actual evolution, the two are not isolated from each other, but may interact and cooperate with each other. HGT provides "materials" for SV: When an exogenous DNA segment enters the goat genome through HGT, it becomes part of the host genome and undergoes structural variation processes such as replication, deletion, and recombination like other endogenous sequences (Dai et al., 2021). In addition, SV creates conditions for HGT: Certain structural variations can increase the chance of exogenous DNA integration into the genome. Typical examples include large chromosome translocations or breaks that produce double-stranded DNA break ends, which make it easier for viruses or exogenous DNA to insert and integrate (Huang, 2013). HGT and SV also participate in functional innovation together: sometimes the new traits exhibited by goats are not caused by a single mechanism, but the result of the combined action of HGT and SV. From a global perspective, HGT increases the compositional diversity of the genome, while SV increases the permutation and combination diversity of the genome. The combination of the two makes the goat genome highly plastic, capable of producing a wide range of variations for selection in response to environmental changes or ecological invasions. HGT tends to cause jump-like changes, while SV can bring about gradual accumulation (a little change in the number of copies). The two complement each other, making goat evolution both leapfrogging and fine-tuning. 5.2 The impact of HGT and SV synergy on adaptation and evolution The synergy of HGT and SV is not only interesting in terms of specific mechanisms, but also has a profound impact on the adaptive evolutionary pattern and potential of goats at a macro level. Synergy improves the efficiency of goat adaptive evolution. Traditional Darwinian evolution relies on the accumulation of small mutations, while HGT+SV can be regarded as a "warp speed engine": HGT skips the gradual change step and directly provides new features, while SV amplifies the scope of influence of new features in a short period of time. Secondly, synergy enriches the innovation and diversity of evolution. HGT provides genetic elements of different systems, and SV produces new combinations through recombination, which actually gives goats the opportunity to explore phenotypic space that "conventional evolution" cannot reach (Bian et al., 2024). Synergy is reflected in the evolutionary model as intermittent and continuous coexistence (Nakaya and Miyazawa, 2015). When HGT events occur, they often correspond to rapid differentiation or the generation of new branches on the evolutionary tree; in the HGT gap period, SV leads to slow adjustments, and the population optimizes and adapts based on existing traits. From a broader biological evolution perspective, the synergy of HGT and SV highlights the multidimensionality of evolutionary mechanisms. 5.3 The significance and prospects of co-evolution From the perspective of evolutionary biology, the synergy of HGT and SV in goats has far-reaching significance, which is the best interpretation of the diversity and flexibility of life evolution. As a mammal, goats use HGT methods similar to those common in microorganisms, and cooperate with large genome variations to open up a wider path for themselves. For conservation biology and livestock genetics, this synergy means that the value of genetic diversity is more multi-level. To maintain the diversity of the goat gene pool, we should not only pay attention to allele frequencies, but also pay attention to the richness of structural variations and the retention of exogenous sequences. This co-evolutionary model also provides a model for other species. Goats are not the only ones. Many wild or cultivated species also show signs of HGT and SV co-evolution (e.g., the rice genome has HGT from bacteria, accompanied by large fragment duplication; cattle have multiple ERV internalizations and CNVs). The study of HGT and SV co-evolution is still in its infancy, and the future is full of unknowns worth exploring. New sequencing technologies such as metagenomic assembly and long-fragment haplotype typing will help us discover more hidden HGT events and complex SVs. 6 Application Prospects and Future Research Directions 6.1 Application prospects in genetic improvement The understanding of HGT and SV in goat adaptability is not only of academic significance, but also provides new ideas for practical animal husbandry. In terms of goat breed breeding, traditional breeding mainly focuses on
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