The paper by Chase and Myers explores the interplay between deterministic and stochastic processes in shaping community structure and biodiversity. deterministic theories emphasize niche-based processes such as environmental filtering, biotic interactions, and interspecific trade-offs, while stochastic theories focus on chance colonization, random extinction, and ecological drift. The authors develop a framework to disentangle the relative importance of these processes in generating site-to-site variation in species composition (β-diversity) along ecological gradients and among biogeographic regions with different regional species pools. They use null-model approaches to account for local and regional factors that create stochastic turnover, providing insights into how ecological niches influence biodiversity patterns. The framework highlights the importance of considering both deterministic and stochastic processes across scales to understand community assembly and biodiversity dynamics.The paper by Chase and Myers explores the interplay between deterministic and stochastic processes in shaping community structure and biodiversity. deterministic theories emphasize niche-based processes such as environmental filtering, biotic interactions, and interspecific trade-offs, while stochastic theories focus on chance colonization, random extinction, and ecological drift. The authors develop a framework to disentangle the relative importance of these processes in generating site-to-site variation in species composition (β-diversity) along ecological gradients and among biogeographic regions with different regional species pools. They use null-model approaches to account for local and regional factors that create stochastic turnover, providing insights into how ecological niches influence biodiversity patterns. The framework highlights the importance of considering both deterministic and stochastic processes across scales to understand community assembly and biodiversity dynamics.