Abstract
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.
Highlights
During range expansions or range shifts, species’ life histories can evolve on ecological timescales (Phillips et al 2010)
This study aimed to test (1) whether the metabolome of T. urticae evolved during its recent range expansion; that is, whether a gradual change in the mite’s intermediary metabolism is present from range core to range edge, showing in the appearance of progressively distinct metabolic phenotypes; (2) whether this metabolic differentiation could be associated with the up- or downregulation of certain metabolic pathways, for instance enhanced glycolytic activities or lipid metabolism; and (3) whether this evolutionary change in the species’ metabotype is associated with the life-history differentiation that has occurred during its range expansion
Of the 18 different metabolites, 11 amino acids could be shown to play an important role in the aminoacyl-tRNA biosynthesis and four in the valine, leucine, and isoleucine biosynthesis
Summary
During range expansions or range shifts, species’ life histories can evolve on ecological timescales (Phillips et al 2010). Changing environmental conditions force species to locally adapt, and spatial assortment of dispersive phenotypes leads to increased dispersiveness at the expanding/ shifting range edge (Shine et al 2011). These evolutionary processes of local adaptation and spatial selection affect key life-history traits such as fecundity, development and dispersal (reviewed in Chuang and Peterson 2016). We expect range-edge populations to exhibit physiological adaptations that underlie these observed trait evolutions Such adaptations should be especially significant in energy-producing pathways, and more in glycolysis (Eanes 2011). Life-history differentiation is expected to be associated with changes in the metabolome (i.e., the set of circulating metabolites within an organism, Oliver et al 1998), as was, for example, found for aging in Caenorhabditis elegans (Fuchs et al 2010) and reproduction in the malaria mosquito Anopheles gambiae (Fuchs et al 2014)
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