Data from: Digging their own macroevolutionary grave: Fossoriality as an evolutionary dead-end in snakes

The tree of life is highly asymmetrical in its clade wise species richness and this has often been attributed to variation in diversification rates either across time or lineages. Variations across lineages are usually associated with traits that increase lineage diversification. Certain traits can also hinder diversification by increasing extinction and such traits are called evolutionary dead-ends. Ecological specialization has usually been considered as an evolutionary dead-end. However, recent analyses of specializations along single axes have provided mixed support for this model. Here, we test if fossoriality, a trait that forces specialization at multiple axes, acts as an evolutionary dead-end in squamates (lizards and snakes) using recently developed phylogenetic comparative methods. We show that fossoriality is an evolutionary dead-end in snakes but not in lizards. Fossorial snakes exhibit reduced speciation and increased extinction compared to non-fossorial snakes. Our analysis also indicates that transition rates from fossoriality to non-fossoriality in snakes are significantly lower than transition rates from non-fossoriality to fossoriality. Overall our results suggest that broad scale ecological interactions that lead to specialization at multiple axes limit diversification.