Intraspecific trait variation significantly influences ecological dynamics, a concept often overlooked in traditional ecological models that focus on trait means and population density. This review synthesizes recent theories to identify six mechanisms by which trait variation alters ecological interactions. These mechanisms include direct effects of trait variation and indirect effects arising from genetic variation's role in trait evolution. Mechanism 1: Jensen's Inequality highlights how nonlinear ecological interactions can be affected by trait variation, altering average interaction strengths. Mechanism 2: Increased degree refers to how trait variation can increase the number and strength of interspecific interactions, affecting network topology and dynamics. Mechanism 3: Portfolio effect describes how trait variation can reduce population density fluctuations by creating negative covariances among phenotypes. Mechanism 4: Phenotypic subsidy involves reproduction by one phenotype increasing the abundance of another, altering interactions with other species. Mechanism 5: Adaptive eco-evolutionary dynamics show how heritable trait variation enables evolutionary responses to ecological interactions, influencing population dynamics. Mechanism 6: Trait sampling emphasizes how stochastic sampling of individual variation in small populations can alter trait means and variances, affecting population dynamics. These mechanisms demonstrate that intraspecific trait variation can have substantial ecological effects, influencing community dynamics, species coexistence, and ecosystem stability. Understanding these mechanisms is crucial for developing accurate ecological models that account for trait variation, which is essential for predicting population dynamics and conservation strategies. The review underscores the need for further research to explore the ecological implications of trait variation and to integrate these insights into ecological models.Intraspecific trait variation significantly influences ecological dynamics, a concept often overlooked in traditional ecological models that focus on trait means and population density. This review synthesizes recent theories to identify six mechanisms by which trait variation alters ecological interactions. These mechanisms include direct effects of trait variation and indirect effects arising from genetic variation's role in trait evolution. Mechanism 1: Jensen's Inequality highlights how nonlinear ecological interactions can be affected by trait variation, altering average interaction strengths. Mechanism 2: Increased degree refers to how trait variation can increase the number and strength of interspecific interactions, affecting network topology and dynamics. Mechanism 3: Portfolio effect describes how trait variation can reduce population density fluctuations by creating negative covariances among phenotypes. Mechanism 4: Phenotypic subsidy involves reproduction by one phenotype increasing the abundance of another, altering interactions with other species. Mechanism 5: Adaptive eco-evolutionary dynamics show how heritable trait variation enables evolutionary responses to ecological interactions, influencing population dynamics. Mechanism 6: Trait sampling emphasizes how stochastic sampling of individual variation in small populations can alter trait means and variances, affecting population dynamics. These mechanisms demonstrate that intraspecific trait variation can have substantial ecological effects, influencing community dynamics, species coexistence, and ecosystem stability. Understanding these mechanisms is crucial for developing accurate ecological models that account for trait variation, which is essential for predicting population dynamics and conservation strategies. The review underscores the need for further research to explore the ecological implications of trait variation and to integrate these insights into ecological models.