“You: on the earth’s surface. so young. so dynamic. full of life and suggesting a world of possibility. Me: subterranean. really old. fossilized, almost. intriguing but slightly inscrutable. We brushed past each other in Rabosky and Matute (2013). I thought there was something there, but in the blink of a p-value you were gone.”
One of the perennial questions in evolutionary biology is “What factors determine how many species are on earth?” Researchers take numerous approaches to get at this very big question. One is to look for correlations between attributes of organisms, the environments they inhabit, or geologic history and rates of species diversification. This the study of macroevolution, and it is based on the idea that the discovery of these correlations on large scales (often using datasets with hundreds to thousands of species with deep histories spanning tens of millions of years) would be a powerful indicator of the factors governing species richness. Another approach is to study speciation on a small scale, to examine sets of closely related populations currently in the process of diverging. The thought is that if we can observe the forces driving divergence in contemporary populations, we can use those observations to develop a more general understanding.