International Journal of Molecular Evolution and Biodiversity 2024, Vol.14, No.1, 26-33 http://ecoevopublisher.com/index.php/ijmeb 28 Comparative genomics: By comparing the genomes of different species, researchers can identify genes that are selectively constrained in evolution. This can be achieved by analyzing the conservation of homologous genes in different species, where genes with higher conservation are often subject to strong selective constraints. Comparing protein structures: Researchers can also analyze the structure of proteins to determine which parts of the protein are selectively constrained. If the functional parts of a protein are strongly selectively constrained, the structure of these parts will remain highly conserved across different species. 2.3 The role of selective constraints in ecological niches Selective constraints play a crucial role in ecological niches, affecting biodiversity, population dynamics, and species adaptability (Yan et al., 2021). Niche is the sum of the roles and resource utilization of species in an ecosystem, while selective constraints determine how species adapt and respond to environmental changes. In ecological niches, positive selective constraints help populations adapt to new environmental conditions, thereby promoting species diversity. For example, in new habitats, species may experience positive selective constraints to adapt to new resource utilization strategies. This constraint drives resource allocation and niche differentiation, leading to the formation of new niches. Negative selective constraints hinder the spread of maladaptive features or genes, helping to maintain the adaptability of organisms. It can maintain biodiversity because harmful features are less likely to spread within populations. However, excessive negative selective constraints may lead to species having overly conservative ecological niches, limiting their adaptability. Neutral selectivity constraints and weak selectivity constraints are usually related to randomness and genetic drift in evolution. Their role in different ecological niches is relatively small, but they can influence the evolutionary path of species over a long period of time. Selective constraints play an important role in the formation and maintenance of ecological niches, and different types of selective constraints shape the ecological niche and adaptability of species. Further research on the role of selective constraints can help to better understand the maintenance of biodiversity and the stability of ecosystems. 3 Differences in Selective Constraints in Three Ecological Niches Selective constraints in niches are an important field of ecological and evolutionary biology research, and the study of the differential patterns of selective constraints in different niches provides an opportunity to gain a deeper understanding of the mechanisms of niche differentiation and biological adaptation. Niche characteristics shape the performance of selective constraints in different niches, promoting species diversity and ecosystem stability. 3.1 Research on the differential patterns of selective constraints in different ecological niches Biocommunities in different ecological niches face different environmental pressures and resource availability, which leads to differences in selective constraint patterns in different ecological niches (Li and Han, 2022). Research has shown that the nature and degree of selective constraints are influenced by factors such as the characteristics of biological communities, resource distribution, and competitive relationships. Taking herbivores as an example, different herbivorous species face different selective constraints in different ecological niches such as grasslands and forests. In grasslands, herbivorous animals face more intense competition, resulting in stronger selective constraints that encourage them to develop higher herbivorous efficiency and faster response abilities. In forests, resources are relatively abundant and selective constraints are weak, resulting in some forest herbivorous animals being more diverse in size and life history strategies. In the ecological niche of the African savannah, wild zebras and wildebeests are two typical herbivores. They face selective constraints due to limited vegetation and intense food competition. Wild zebras adapt to grassland ecological niches with their agile running and quick reaction ability, in order to timely avoid predators and obtain food (Figure 1). In contrast, wildebeests have developed higher herbivorous efficiency to more effectively utilize
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