Parallel evolution of behavior, physiology, and life history associated with altitudinal shifts in forest type in Heliconius butterflies.

Parallel evolution of morphological traits is widely reported, providing evidence for the role of local conditions in driving adaptive divergence. Comparatively, fewer studies have tested for parallelism in behavior, and it is less clear to what extent heritable behavioral shifts contribute to adaptive divergence. We exploit repeated incipient speciation across altitudinal gradients to explore behavior and physiology in Heliconius butterflies adapted to high-elevation. We performed common garden experiments with H. chestertonii, a high-altitude specialist from the Colombian Cordillera Occidental, and H. erato venus, a low-elevation proxy for the ancestral population, and compared our results to existing data for an equivalent Ecuadorian taxa-pair. Using broad-scale climatic data, we show that both pairs diverge across similar ecological gradients, confirmed using localized data loggers in the ranges of H. chestertonii and H. e. venus. We further show that H. chestertonii and H. e. venus have divergent activity patterns, attributable to different responses to microclimate, and life histories. Finally, we provide evidence for parallelism in these traits with H. himera and H. e. cyrbia. We propose that this is a result of selection associated with independent colonizations of high-altitude forests, emphasizing the importance of heritable behavioral and physiological adaptations during population divergence and speciation.
(© The Author(s) 2023. Published by Oxford University Press on behalf of The Society for the Study of Evolution (SSE).)