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Life history and metabolism covary, but the mechanisms and individual
traits responsible for these linkages remain unresolved. Dispersal
capability is a critical component of life history that is constrained by
metabolic capacities for energy production. Conflicting relationships
between metabolism and life histories may be explained by accounting for
variation in dispersal and maximal metabolic rates. We used female
wing-polymorphic sand field crickets, Gryllus firmus, selected either for
long wings (LW) and flight-capability or short wings (SW) and high early
lifetime fecundity to test the hypothesis that selection on dispersal
capability drives the evolution of metabolic capacities. While resting
metabolic rates were similar, long-winged crickets reached higher maximal
metabolic rates than short-winged crickets, resulting in improved running
performance. We further provided insight into the mechanisms responsible
for covariation between life history and metabolism by comparing
mitochondrial content of tissues involved in powering locomotion and
assessing function of mitochondria isolated from long- and short-winged
crickets. Our results demonstrated that larger metabolic capacities in
long-winged crickets were underpinned by increases in mitochondrial
content of dorsoventral flight muscle and enhanced bioenergetic capacities
of mitochondria within the fat body, a tissue responsible for fuel storage
and mobilization. Thus, selection on flight-capability remodels metabolism
in a trait and tissue-specific manner to enlarge metabolic capacities
necessary for dispersal.
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