International Journal of Molecular Evolution and Biodiversity 2024, Vol.14, No.1, 26-33 http://ecoevopublisher.com/index.php/ijmeb 27 1 The Concept of Ecological Niche 1.1 Defining niche and its role in ecology Niche is a key concept used to describe the functional roles and resource utilization strategies of species in their living environment. In short, niches represent how a species interacts with its surrounding environment to acquire the necessary resources for survival, including food, habitat, and ways of survival (Zhang et al., 2018). Each species occupies a different ecological niche in the ecosystem, and this diversity helps maintain the stability and biodiversity of the ecosystem. The concept of ecological niche plays a crucial role in ecology. It helps us understand why different species can coexist in the same environment without competing with each other. Each species avoids excessive competition and achieves resource allocation and collaborative survival through its unique ecological niche (Feng et al., 2019). In addition, niches also contribute to the stability of ecosystems, as species in different niches depend on each other, forming complex food webs and ecological chains, maintaining ecosystem balance. 1.2 The importance of niche diversity and niche differentiation Niche diversity refers to the richness of different niches in an ecosystem (Sánchez-Lanzas et al., 2020). The presence of more species with different ecological niches in an ecosystem typically indicates higher diversity in the ecosystem. The increase in niche diversity helps to improve the stability of ecosystems, as it reduces competition pressure between species. In diverse ecological niches, different species can find their own unique resource utilization strategies, thereby reducing the intensity of resource competition and competition. Niche differentiation refers to the differentiation of ecological niches between different species to avoid direct competition. During the long-term evolution process, species gradually adjust their resource utilization strategies to occupy different ecological niches, which is called niche differentiation (Dent and Estrada-Villegas, 2021). Niche differentiation is an important factor in biodiversity in ecosystems, providing opportunities for collaborative survival among different species while maintaining the functionality and stability of the ecosystem. 2 Basic Concepts of Selective Constraints 2.1 Definition and types of selective constraints Selective constraint is one of the key concepts in the process of biological evolution, which describes the limitations or tendencies on certain characteristics or genes of organisms. Selective constraints refer to the influence of natural selection on specific traits or genes (Massip et al., 2019). Selective constraints can be divided into forward selective constraints, reverse selective constraints, neutral selective constraints, and weak selective constraints. Positive selective constraints promote the rapid diffusion of a trait or gene within a species, as they provide significant adaptive advantages. This constraint typically involves adaptive characteristics, such as resistance or reproductive success traits under certain environmental conditions. Negative selectivity constraint is the selection of unfavorable effects on a certain trait or gene, which usually leads to its reduction in the species. This constraint typically involves harmful mutations or maladaptive features. Neutral selective constraints occur without significant adaptive advantages or adverse effects. In this case, the evolution of traits or genes is influenced by random factors, such as genetic drift. Weak selectivity constraints involve a relatively small impact of selection on traits or genes, with relatively weak adaptive advantages. In this case, there may be some variation in traits or genes within the species, but there is no clear selection trend. 2.2 How to measure and analyze selective constraints In order to understand and analyze selective constraints, biologists use various methods to measure and study different types of selective constraints. One of the most common methods is to compare gene sequences and protein structures (Bai et al., 2020) to look for signs of selective constraints.
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