International Journal of Aquaculture, 2024, Vol.14, No.4, 184-194 http://www.aquapublisher.com/index.php/ija 191 deep-sea fish like Coryphaenoides rupestris has revealed how genetic differentiation at functional loci can drive adaptation to different depths, highlighting the role of disruptive selection in promoting intraspecific diversity (Gaither et al., 2018). 7.2 CRISPR and gene editing techniques CRISPR and other gene editing techniques have revolutionized the study of molecular mechanisms underlying diversification. These tools allow for precise manipulation of genetic material, enabling researchers to investigate the functional roles of specific genes in adaptation and speciation. For example, studies on water striders have identified genes involved in both bristle density and leg length, traits essential for water surface locomotion. The genetic correlation between these traits suggests that pleiotropy might facilitate diversification by simultaneously impacting multiple adaptive traits. Such insights are crucial for understanding how genetic changes contribute to the exploitation of new ecological niches and subsequent species diversification. 7.3 Bioinformatics and phylogenetic analysis Bioinformatics and phylogenetic analysis are indispensable in studying the evolutionary relationships and diversification patterns of aquatic organisms. The use of multilocus approaches and coalescent-based phylogeography has proven effective in resolving recent diversification events. For instance, the colonization and diversification of aquatic insects in Macaronesia were elucidated using 59 nuclear loci derived from a draft genome, highlighting the value of combining genomics with phylogenetic reconstruction. Similarly, the phylogenomic analysis of diatoms has provided insights into the transitions between marine and freshwater habitats, revealing the role of gene tree discordance and hemiplasy in adaptation 1. These methodologies enable researchers to construct well-resolved phylogenies and understand the complex evolutionary processes driving diversification in aquatic life forms. 8 Concluding Remarks The diversification of aquatic life forms is driven by a multitude of molecular mechanisms and environmental factors. In deep-sea fish such as Coryphaenoides rupestris, genomic differentiation at functional loci is influenced by depth, suggesting disruptive selection and ecotype differentiation linked to distinct phenotypic requirements at different depths. Freshwater eDNA has proven effective in detecting invasive species, assessing community assemblages, and mapping the distribution of rare taxa. However, there is a notable geographical and taxonomic bias in eDNA research, with under-representation in regions like Africa and South America and among certain taxa such as freshwater arthropods. Climate change, particularly global cooling, has been identified as a significant driver of diversification in marine clades, while global warming influences speciation rates in freshwater clades. Cryptic species are more frequently found in freshwater habitats compared to terrestrial or marine environments, likely due to the greater heterogeneity and fragmentation of freshwater habitats. Diatoms exhibit complex molecular acclimation mechanisms to cope with salinity changes, which are crucial for their survival and diversification in varying aquatic environments. The molecular mechanisms underlying biomineralization in marine invertebrates, such as corals and molluscs, are critical for their adaptation to changing environmental conditions, including ocean acidification and temperature changes. CCMs in aquatic photosynthetic organisms play a vital role in global carbon sequestration and primary productivity, with significant implications for understanding their evolutionary origins and future applications. Advances in sequencing technologies and molecular markers have enhanced our understanding of genetic diversity and population structure in aquatic species, which is essential for effective conservation strategies. The evolutionary history and diversification of aquatic bugs (Nepomorpha) are influenced by climate fluctuations and tectonic reconfigurations, with significant implications for understanding their adaptation and diversification dynamics. Incorporating biological traits at multiple spatial-temporal scales is crucial for forecasting responses of aquatic ecosystems to environmental changes and developing effective conservation strategies. The findings from these studies have profound implications for conservation and biodiversity. Understanding the genomic differentiation and cryptic diversity in aquatic species can help in designing targeted conservation efforts
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