Mobility and lifetime fecundity in new versus old populations of the Glanville fritillary butterXy

Life history theory often assumes a trade-oV between dispersal and reproduction, and such a trade-oV is commonly observed in wing-dimorphic insects. The results are less consistent for wing-monomorphic species, for which it is more diYcult to assess dispersal capacity and rate. Three replicate experiments were carried out in consecutive years on the Glanville fritillary butterXy in a large outdoor population cage to study the relationship between lifetime egg production and mobility. The experimental material included females originating from newly-established and old populations, as previous studies have shown dispersal capacity to depend on population age. There was a consistent and signiWcant interaction between mobility and population age, such that in newly-established populations mobile females had higher fecundity than less mobile females, while in old populations there was no such relationship. As selection favours individuals with the highest fecundity, selection pressure on mobility is likely to be diVerent between the two population types, which may contribute to maintenance of variation in dispersal rate in the metapopulation as a whole. Several other female traits also aVected lifetime fecundity, including lifespan, number of matings and date of eclosion, although these eVects were not consistent across the years. These results highlight the importance of conducting experiments in more than one year before generalizing about patterns in life history variation.