Termites became the dominant decomposers of the tropics after two diversification pulses

Insects have the highest species richness among animals, but the extent of their diversity and the timing of their diversification remain unclear. Insect diversification is difficult to infer due to the incompleteness of the fossil record. Phylogenetic trees of extant species reconstructed from an exhaustive sampling can be useful to address major evolutionary questions. Here, we investigated the diversification of termites, which comprise 2,995 described species, using estimates of speciation, extinction, and net diversification rates inferred from molecular phylogenies including 2,800 samples representing 1,377 putative species. Termites originated in the Early Cretaceous ~132 million years ago. Estimated extinction rates were close to zero despite fossil evidence of extinction; therefore, we focused our interpretations on the net diversification rates. Our analyses detected two significant rate shifts. The first shift occurred at the end of the Cretaceous, initially in the Kalotermitidae, then in the Neoisoptera as they started outcompeting Kalotermitidae. The second shift involved multiple lineages of Neoisoptera, especially Termitidae, which diversified as they colonized the world after the global cooling initiated at the Eocene-Oligocene transition. Our results indicate that termites became the dominant insect decomposers of tropical ecosystems as global climate change impacted ecosystems.