Niche conservatism occurs when populations, species, and clades retain similar ecological characteristics over time. Niche conservatism may help to explain many different ecological and evolutionary patterns. In my talk, I will review recent research from my collaborators and I that explore this idea. First, I will discuss the role that niche conservatism may play in generating patterns of species richness, including differences in species richness between habitats within regions, and differences in species richness between regions at the global scale. Second, I will discuss the relevance of niche conservatism (particularly slow rates of climatic niche evolution) for how species may respond to anthropogenic climate change. Finally, I will discuss our new research focusing on two relatively unexplored aspects of niche conservatism: (1) the evolution of diel activity patterns in vertebrates (i.e. nocturnal vs. diurnal activity), and (2) the distribution and species richness of animal phyla across marine and terrestrial environments, one of earth’s most dramatic but most poorly understood biodiversity patterns.