Rapid differentiation of plasticity in life history and morphology during invasive range expansion and concurrent local adaptation in the horned beetle Onthophagus taurus

Understanding the interplay between genetic differentiation, ancestral
plasticity, and the evolution of plasticity during adaptation to
environmental variation is critical to predict populations’ responses to
environmental change. However, the role of plasticity in rapid adaptation
in nature remains poorly understood. We here use the invasion of the
horned beetle Onthophagus taurus in the United States during the last half
century to study the contribution of ancestral plasticity and
post-invasion evolution of plastic responses in rapid population
differentiation. We document latitudinal variation in life history and
morphology, including genetic compensation in development time and body
size, likely adaptive responses to seasonal constraints in the North.
However, clinal variation in development time and size was strongly
dependent on rearing temperature, suggesting that population
differentiation in plasticity played a critical role in successful
adaptation on ecological timescales. Clinal variation in wing shape was
independent of ancestral plasticity, but correlated with derived
plasticity, consistent with evolutionary interdependence. In contrast,
clinal variation in tibia shape aligned poorly with thermal plasticity.
Overall, this study suggests that post-invasion evolution of plasticity
contributed to range expansions and concurrent adaptation to novel
climatic conditions.