Abstract

Adaptation to local environments enables species to thrive in diverse and challenging habitats. Steep elevational gradients provide a compelling natural adaptation laboratory, because abiotic conditions change progressively over short geographical differences. Given that elevation can strongly reshape physiology and behavior of insects, neuromodulatory systems offer a promising lens through which to examine elevation-specific adaptation. We challenged the hypothesis that adaptation to elevation involves octopaminergic signaling in honey bees (Apis mellifera), an important pollinator species occupying different elevations along East African mountains. We collected foragers from two distinct elevations at Mount Kenya (1,150 m and 1,900 m above sea level) and analyzed elevation-dependent changes in octopaminergic signaling. Tissue-specific analysis revealed a striking upregulation of all three octopamine β receptor genes in the thoracic flight muscles and elevated octopamine brain concentrations at high elevation. Expression differences in the brain and fat body were rather modest. We subjected CRISPR/Cas9-mediated octopamine β2 receptor knockouts to cold stress to study the function of octopaminergic signaling in thermoregulation. Loss of AmOARβ2 reduced both the slope and amplitude of heating phases, indicating altered thermogenic dynamics. Together, these results identify the octopaminergic system as a central neuromodulatory regulator of thermogenic performance across elevations in honey bees. More broadly, our study highlights how modulation of conserved aminergic signaling pathways can shape physiological resilience to environmental gradients, pointing to a general mechanism by which insects adapt to changing thermal landscapes. ### Competing Interest Statement The authors have declared no competing interest. Deutsche Forschungsgemeinschaft, https://ror.org/018mejw64, SCHE 1573/14-1 Deutsche Forschungsgemeinschaft, HA 5499/11-1 Volkswagenstiftung, Momentum grant