International Journal of Aquaculture, 2024, Vol.14, No.3, 126-138 http://www.aquapublisher.com/index.php/ija 134 instance, the high phylogenetic diversity in freshwater habitats, despite their small area, underscores the importance of both fossil and molecular data in revealing the complex evolutionary history of these ecosystems (Román‐Palacios et al., 2022). The contributions of the fossil record, molecular phylogenetics, and the integration of these data sources are crucial for understanding the origins and maintenance of aquatic biodiversity. These approaches provide complementary insights that enhance our knowledge of the evolutionary and biogeographic processes shaping the diversity of life in aquatic environments. 7 Biogeographic Patterns in Different Aquatic Systems 7.1 Freshwater ecosystems Freshwater ecosystems, despite covering only about 2% of the Earth's surface, exhibit a remarkable level of species richness and phylogenetic diversity. This high biodiversity is largely attributed to the unique evolutionary histories and diversification rates of species inhabiting these environments. Freshwater habitats have been shown to harbor a significant number of species that are derived from terrestrial ancestors, highlighting a complex biogeographic history where terrestrial lineages have repeatedly colonized freshwater systems (Román‐Palacios et al., 2022). The conservation importance of these habitats is underscored by their exceptional biodiversity, which is often overlooked in broader biodiversity studies that tend to focus on terrestrial and marine environments (Román‐Palacios et al., 2022). 7.2 Marine ecosystems Marine ecosystems, which cover approximately 70% of the Earth's surface, display a different pattern of biodiversity compared to freshwater systems. The largest marine biodiversity hotspot is located in the Indo-Australian Archipelago (IAA), driven primarily by taxa associated with tropical coral reefs. This region forms a 'bullseye' of species richness, with a steep gradient extending to the periphery of the Indo-Pacific region (Cowman et al., 2017). The biogeographic patterns in marine ecosystems are shaped by a combination of paleoand neo-endemic species, indicating multiple historical processes that have contributed to the current biodiversity. Time-calibrated molecular phylogenies and ancestral biogeographic estimates have been instrumental in understanding the origins and maintenance of coral reef fish biodiversity, revealing complex patterns of endemism and provinciality (Cowman et al., 2017). 7.3 Transitional and brackish water ecosystems Transitional and brackish water ecosystems, such as estuaries and mangroves, represent unique biogeographic zones where freshwater and marine influences converge. These ecosystems often serve as critical habitats for a variety of species that are adapted to fluctuating salinity levels. The biogeographic patterns in these systems are influenced by the dynamic interactions between freshwater and marine species, leading to unique assemblages that are distinct from those found in purely freshwater or marine environments. The evolutionary histories of species in transitional ecosystems are shaped by their ability to adapt to varying salinity conditions, which can drive speciation and contribute to the overall biodiversity of these habitats. The biogeographic patterns in different aquatic systems are shaped by a combination of historical biogeography, phylogenetic diversity, and ecological factors. Freshwater ecosystems exhibit high species richness derived from terrestrial ancestors, marine ecosystems are characterized by complex patterns of endemism and provinciality, and transitional ecosystems represent unique zones of biodiversity influenced by both freshwater and marine species. Understanding these patterns is crucial for the conservation and management of aquatic biodiversity across different habitats. 8 Conservation Implications 8.1 Phylogenetic diversity and conservation Phylogenetic diversity (PD) is a crucial aspect of biodiversity that reflects the evolutionary history and
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