Biogeography is the study of where organisms live and why. The abundance and distribution of different species throughout the planet is a function of historical events, quality of habitat, movement and transport of organisms, weather and climate, etc. Biogeographers rely on data and information from many different disciplines, including biology, agronomy, geography, geology, evolution, climatology, paleontology, anthropology, etc., depending on what their research focus is.
In caves, microbial ecologists study the biogeography of the microorganisms to see what influences their distribution, abundance, survivability, habitat selection, and genetic similarities or differences. In habitats like these, sometimes species variation can occur over very small distances and over short periods of time, presumably in response to a number of environmental factors, like flow, etc.