The relative contribution of local environmental factors and genetic components to the expression of dispersal traits in populations is a key question for understanding population responses to environmental change.
We reared populations from different positions along two independent range expansions gradients, one introduced population and one native expanding population. We compared these to native populations across the US of the Soapberry Bug (Jadera haematoloma) by simultaneous rearing in a common environment. We examined variation in several components of the dispersal phenotype - e.g. wing length, and amount and state of flight muscle, and compared predictions following from the evolution of dispersal literature and previous studies with observed patterns.

Results/Conclusions

Overall the results points toward local site-level factors dominating spatial assortment or evolutionary process in the expression of the dispersal phenotype. Results also show a fecundity-dispersal trade-off going beyond the fact of whether individuals are short or long-winged, also depending on the amount of flight muscle bugs with the same wing length are maintaining.

This study could serve to nuance the debate and interpretations of patterns of variation in dispersal traits during invasions and range expansions.