Revisiting the evolution of wing dimorphisms in the genomics era

Dispersal strategies are critical life history traits influencing bio-geographical, ecological, and evolutionary patterns and processes, including range expansion and contractions, abiotic and biotic interactions, and rates of speciation. Yet, dispersal strategies are challenging to study because they are complex suites of morphological, physiological, and behavioral traits. Thus, our understanding of how and why dispersal strategies evolve remains incomplete. Wing dimorphisms have evolved repeatedly within nearly every major insect order and are characterized by the co-occurrence of fully winged dispersing and short- or wingless non-dispersing morphs within species or populations, making them ideal model systems for studying the evolution of alternative dispersal strategies. Forty years ago, Derek Roff proposed that wing dimorphisms are a threshold trait that evolves as an intermediate step on the trajectory toward complete loss of flight, driven by the high physiological and life history costs of dispersal. Here, we synthesize recent mechanistic studies of wing-morph determination along with new phylogenetic reconstructions of wing dimorphism in the well-developed model Gryllus field crickets to update and refine our evolutionary hypotheses and identify critical areas for future inquiry.