International Journal of Aquaculture, 2025, Vol.15, No.5, 240-247 http://www.aquapublisher.com/index.php/ija 244 5.3 Functional correlation between phenotypic variation and mtDNA polymorphism mtDNA variation is now widely believed to be functionally significant, permitting variation in metabolic rate, behavior, and other phenotypic traits within and among populations. Environmental heterogeneity and negative frequency-dependent selection can potentially preserve mtDNA polymorphism, mediating genetic diversity with ecological and phenotypic diversity. This suggests tilapia mtDNA variation can be accountable for adaptive phenotypic variation relevant to ecological success (Dowling and Wolff, 2023). 5.4 An integrated model of “mitochondrial variation-function-ecology” in tilapia adaptation One integration framework proposes that ecological stresses drive mitochondrial genetic variation, which affects mitochondrial function and organismal phenotype. This interactive dynamic process-selection pressure acting across biological scales (organism, tissue, cell, mitochondrion)-evokes adaptation to environment stresses. Mitochondrial-nuclear environments mediate such influences, rendering an integrated mitochondrial genetics-based model of tilapia adaptation applicable (Koch et al., 2021; Dowling and Wolff, 2023; Li et al., 2024). 6 Theoretical and Practical Significance of Mitochondrial Research in Tilapias 6.1 Advancing molecular evolution and phylogenetic theory in fishes Mitochondrial DNA (mtDNA) research has contributed considerably to enhancing the understanding of molecular evolution and phylogenetic relationships in fishes. By examining the D-loop and cytochrome b regions, researchers have been capable of resolving molecular divergence patterns, population structure, and evolutionary history among tilapia species. They provide baseline information for phylogeny reconstruction, tracing maternal lineages, and the processes of genetic adaptation and differentiation in fish populations (Aminisarteshnizi et al., 2024). 6.2 Providing molecular evidence for germplasm conservation and breeding of tilapias Mitochondrial markers are excellent markers employed in assessing genetic diversity, population structure, and integrity of lineage, all of which are critical to germplasm conservation and selective breeding programs. mtDNA can be applied for identification of private haplotypes, detection of introgression, and tracing of genetic variation at and among populations. This molecular evidence supports the development of improved breeding schemes, conservation of unique genetic resources, and management of hybridization risks in farmed and wild tilapia populations (Ekerette et al., 2018; Bian et al., 2019; Chu et al., 2021; Wu et al., 2021). 6.3 Application potential of mtDNA in species identification, market regulation, and resource management Technical uses of mtDNA analysis are also evident in the identification of species, especially in processed items where morphological features are difficult to determine. DNA barcoding using mtDNA markers such as COI is an effective method to identify species in the marketplace, guarantee food safety, and prevent mislabeling. Second, mtDNA data are accessible to resource management and possess the capacity to track stock origin, ensuring genetic diversity, as well as guiding regulatory decision-making towards sustainable fishery and aquaculture management (Wu et al., 2021; Chu et al., 2021; Nascimento et al., 2022). 7 Limitations and Future Research Directions 7.1 Limitations of mtDNA data and the need for nuclear genome integration Mitochondrial DNA (mtDNA) is widely used in phylogenetic and population genetic studies owing to its high mutation rate and maternal inheritance. Nevertheless, its uniparental inheritance, lack of recombination, and low effective population size could limit it to completely distinct evolutionary relationships and population structure. In addition, the presence of nuclear mitochondrial DNA segments (NUMTs) might make the analysis difficult with resulting misplacement of phylogenetic signals. The integration of nuclear DNA markers with mtDNA enhances the resolution and precision of phylogenetic and phylogeographic hypotheses and allows for improved understanding of evolutionary processes and reduces the prospect of drawing false conclusions based on mtDNA alone (Dong et al., 2021).
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