Relative High Fitness and Large Genome Size May Lead to the High Diversification of Plastic Foragers

Dylan J Padilla Perez, Martha M. Muñoz, David K Skelly

Explaining variation in diversification of species across the Tree of Life is an important challenge for evolutionary biologists.  Growing evidence suggests that key innovations or historical contingency give rise to high diversification of species, but the genetic mechanisms through which this process may occur remain poorly investigated.  Based on fitness landscapes, a high diversification is predicted to result from local adaptation as species navigate genotype space.  To test this prediction, we conducted a comparative analysis of 997 reptile species that vary in their locomotion while foraging.  The species ranged from those that travel long distances to acquire food (''active foragers'') to those that barely move and acquire food in nearby sites (''sit-and-wait foragers''), or those that adopt a plastic strategy.  We found that active and plastic foragers not only have higher diversification of species but also have higher fitness compared to sit-and-wait foragers.  While traversing across heterogeneous environments, active and plastic foragers could accelerate the pace of evolution by exposing cryptic genetic variation to selection.  This is possible in active and plastic foragers because their larger genomes and nucleotide diversity potentially facilitate variation in gene expression, allowing natural selection to operate effectively to the point where divergence by ecological speciation could occur.  Restricted locomotion among sit-and-wait foragers potentially led to relatively low diversification of species via stochastic processes.  We used emerging genomic data and macroevolutionary observations supported by microevolutionary processes to provide key insights into mechanisms of diversification.