Investigating how dispersal propensity and ability are shaped by species and individual traits in aquatic insects

Background/Question/Methods

Dispersal links populations and communities, thereby playing a central role in many evolutionary and ecological processes.  Additionally, as the climate changes, species persistence may depend on their ability to disperse through an increasingly human-altered landscape to reach suitable environments.  In actively dispersing organisms, realized dispersal arises from the combination of dispersal ability and dispersal propensity.  Following the dispersal of dragonfly species to experimental habitats, I examined the relationship between dispersal behavior and other species traits, including body size, flight morphology, and habitat distribution.  I will also discuss a set of studies I conducted on phenotype dependent dispersal which use a combination of mark-resight approaches, translocations, and the creation of experimental habitats to study dispersal behavior.  Even within highly dispersive species, there is significant variation in both the propensity to disperse and how far individuals travel.  Examining the relationship between dispersal behavior and individual traits (e.g. body size, foraging rates) can provide insights into how these traits shape dispersal behavior and the development of functional connections between populations and communities linked by the movement of these individuals.

Results/Conclusions

Interspecific comparisons indicated that species’ habitat distributions and flight morphology was predictive of dispersal behavior while body size was not.  Habitat generalists were more dispersive than habitat specialists and within the genus Libellula relatively larger thoraces and wings were associated with greater levels of dispersal.  However, within species, body size can be an important determinate of dispersal propensity and dispersal ability through different landscape conditions.  Among territorial male dragonflies where the ability to hold territory is positively related to body size, small males were more likely to disperse to new habitats.  This effect likely acts through dispersal propensity with small males dispersing to seek out sites with lower competition for females.  Body size can also affect dispersal ability and this can interact with landscape structure.  In male dragonflies translocated to terrestrial sites that contain barriers to flight, body size was positively related to return rate to the capture pond.  These results suggest that body size is positively related to the ability to disperse through or around habitat barriers.  These intraspecific comparisons suggest that body size can have opposing effects on dispersal propensity and ability and observed dispersal outcomes reflect individual level responses to the social and environmental conditions encountered.