Digest: Ecological opportunity, competition, and diversity dependence in macroevolution *

The realization that adaptation can happen over observable time has accelerated our understanding of how competition can drive evolution. However, the extent to which competition influences macroevolutionary patterns remains a contentious issue. Classically, the relationship between competition and biodiversity dynamics was examined through the fossil record. More recently, reconstructed molecular phylogenies have provided an additional tool for modeling how species interactions may influence rates of species diversification and trait evolution. However, disentangling the processes of speciation from extinction using only information on extant lineages remains a major challenge (Marshall 2017). Progress in understanding the factors that influence rates of speciation and extinction is therefore integral to our understanding of how biological diversity is distributed and maintained at both regional and global scales (Rosenzweig 1995). Early in their existence, clades often undergo an initial burst of diversification. One explanation for this pattern is the hypothesis of “ecological opportunity,” where a species or clade presented with access to unexploited ecological resources rapidly expands in species abundance and ecological diversity (Schluter 2000). For example, colonization of the remote Hawaiian archipelago led to repeated diversification across a suite of plant and animal taxa, just as the colonization of landlocked African Rift Lakes was followed by the explosive diversification of freshwater cichlid fishes (Stroud and Losos 2016). After this initial burst of diversification, whether early in a clade’s existence or after encountering an ecological opportunity,