Higher investment in flight morphology does not trade off with fecundity estimates in a poleward range-expanding damselfly

1. Evolutionary increases in dispersal-related traits are frequently documented during range expansions. Investment in flight-related traits is energetically costly and a trade-off with fecundity may be expected during range expansion. 2. However, in contrast to wing-dimorphic species, this trade-off is not general in wing-monomorphic species. In the absence of a dispersal--fecundity trade-off, an increased investment in clutch size at the expansion front is expected possibly at a cost of reduced offspring size. 3. The study evaluated investment in female flight morphology and fecundity-related traits (clutch size, hatchling size) and potential trade-offs among these traits in replicated populations of the poleward range-expanding damselfly Coenagrion scitulum. 4. Females at the expansion front had a higher relative thorax length, indicating an increased investment in flight; this can be explained by spatial sorting of dispersal ability or in situ natural selection at the expansion front. Edge females produced larger hatchlings, however, this pattern was totally driven by the population-specific thermal larval regimes and could not be attributed to the range expansion per se. By contrast, clutch sizes did not differ between core and edge populations. There was no signal of a dispersal-fecundity trade-off either for a trade-off between clutch size and hatchling size. 5. These results indicate that evolution of a higher dispersal ability at the expansion front of C. scitulum does not trade off with investment in fecundity, hence a dispersal-fecundity trade-off is unlikely to slow down range expansion of this species