Evolution of flight morphology in a butterfly that has recently expanded its geographic range

Abstract

Individuals colonizing unoccupied habitats typically possess characters associated with increased dispersal and, in insects, colonization success has been related to flight morphology. The speckled wood butterfly, Pararge aegeria, has undergone recent major expansions in its distribution: in the north of its range, P. aegeria has colonized many areas in north and east England, and in the south, it was first recorded on Madeira in 1976. We examined morphological traits associated with flight and reproduction in the northern subspecies tircis, and in the southern subspecies aegeria, from sites colonized about 20 years ago in northern England and on Madeira, respectively. Investment in flight was measured as relative wing area and thorax mass, and investment in reproduction as relative abdomen mass. All measurements were from individuals reared in a common environment and there were significant family effects in most of the variables measured. Compared with individuals from sites continuously occupied in recent history, colonizing individuals were larger (adult live mass). In the subspecies tircis, colonizing individuals also had relatively larger thoraxes and lower wing aspect ratios indicating that evolutionary changes in flight morphology may be related to colonization. However, sex by site interactions in analyses of thorax mass and abdomen mass suggest different selection pressures on flight morphology between the sexes in relation to colonization. Overall, the subspecies aegeria was smaller (adult live mass) and had a relatively larger thorax and wings, and smaller abdomen than subspecies tircis. Evolutionary changes in flight morphology and dispersal rate may be important determinants of range expansion, and may affect responses to future climate change.

Does habitat fragmentation affect temperature-related life-history traits? A laboratory test with a woodland butterfly

“…estimated rate of expansion during the twentieth century without correcting for geometric distribution of potential new areas for colonization). The dispersal range of the average individual is likely to be considerably less than such values of an invasion front (Hill et al 1999). However, in Drosophila there are cases where microclimatic natural selection overrides the importance of migration at even much smaller spatial scale as multiple adaptive differences between D. melanogaster isofemale lines derived from two opposite slopes of a canyon that contrast sharply in physical factors have been shown (Nevo et al 1998).…”

“…Mostly, studies on allocation in flying insects assume thorax mass to be an indicator of flight investment and abdomen mass an indicator of reproductive potential (e.g. Hill et al 1999).…”

Within-patch mobility and flight morphology reflect resource use and dispersal potential in the dryad butterfly Minois dryas

“…Therefore, it is worth to examine whether the dryads living in wet meadows differ in mobility and flight morphology from those inhabiting xerothermic grasslands. It can be expected that the individuals from former group should be more mobile and cover longer distances, which should also be reflected in their morphology since they are the descendants of the most dispersive butterflies and their mobility is likely to possess a substantial genetic component (Hill et al 1999;Merckx et al 2003;Haag et al 2005).…”

Foraging Rates of Larval Dragonfly Colonists Are Positively Related to Habitat Isolation: Results from a Landscape‐Level Experiment

“…Phenotype-dependent dispersal has the potential to modify the impact that dispersers have on the patches they col onize (Duckworth and Badyaev 2007;Benard and Mc Cauley 2008). For example, if fecundity and dispersal ca pacity are inversely related (e.g., Hill et al 1999a), the extent to which dispersers affect the demography of the receiving patch they colonize will be less than predicted based on the mean population fecundity. Similarly, the impact of immigrants as predators or competitors in the community of the receiving patch will depend on traits that may be associated with differences in dispersal be havior.…”