There are several hypotheses for explaining the latitudinal gradients in species diversity (link). Of which, the evolutionary rate hypothesis states that warm temperature increases the rate of speciation. I want to know why warm temperature facilitates evolution.
This is not a question, but... some other hypotheses specifically discuss how a factor influences the rate of evolution (e.g., the size hypothesis discusses how large area can promote speciation). I think temperature hypothesis is a better name for the evolutionary rate hypothesis.