Global cooling & the rise of modern grasslands: Revealing cause & effect of environmental change on insect diversification dynamics

Abstract

Utilising geo-historical environmental data to disentangle cause and effect in complex natural systems is a major goal in our quest to better understand how climate change has shaped life on Earth. Global temperature is known to drive biotic change over macro-evolutionary time-scales but the mechanisms by which it acts are often unclear. Here, we model speciation rates for Orthoptera within a phylogenetic framework and use this to demonstrate that global cooling is strongly correlated with increased speciation rates. Transfer Entropy analyses reveal the presence of one or more additional processes that are required to explain the information transfer from global temperature to Orthoptera speciation. We identify the rise of C4 grasslands as one such mechanism operating from the Miocene onwards. We therefore demonstrate the value of the geological record in increasing our understanding of climate change on macro-evolutionary and macro-ecological processes.