Dispersal-fecundity trade-offs in wild insect populations.

Wing reduction is a common feature of upland insect communities. This phenomenon is thought to be primarily driven by selection against flight, which is typically unfavourable in upland environments due to high winds and cold temperatures. In some insect taxa, wing reduction has been directly linked to increased fecundity. However, few studies have directly tested for shifts in fecundity linked to flight musculature. Here, we test for dispersal-fecundity trade-offs in the widespread subalpine stonefly Zelandoperla fenestrata. Our analysis of 450 stoneflies across 81 localities reveals significant dispersal-fecundity trade-offs. Specifically, we identify a positive association between the size of their flight muscles and the length of their wings, and a negative association between wing length and ovarian mass. Furthermore, we found a significant negative relationship between flight musculature and ovary mass. These results represent a rare example of a dispersal-fecundity trade-off in the wild and illustrate that such trade-offs can potentially involve corresponding reductions in both flight musculature and wing development. Our findings suggest that widespread taxa subject to variable environmental conditions may benefit from flexible allocation of energetic resources.