Metabolic adaptations in a range-expanding arthropod.

Despite an increasing number of studies documenting life-history evolution during range expansions or shifts, we lack a mechanistic understanding of the underlying physiological processes. In this explorative study, we used a metabolomics approach to study physiological changes associated with the recent range expansion of the two-spotted spider mite (Tetranychus urticae). Mite populations were sampled along a latitudinal gradient from range core to edge and reared under benign common garden conditions for two generations. Using gas chromatography-mass spectrometry, we obtained metabolic population profiles, which showed a gradual differentiation along the latitudinal gradient, indicating (epi)genetic changes in the metabolome in association with range expansion. These changes seemed not related with shifts in the mites' energetic metabolism, but rather with differential use of amino acids. Particularly, more dispersive northern populations showed lowered concentrations of several essential and nonessential amino acids, suggesting a potential downregulation of metabolic pathways associated with protein synthesis.