Remsburg, A.J. 2007. Aquatic and terrestrial vegetation influence lacustrine dragonfly (order Odonata) assemblages at multiple life stages. PhD Dissertation, University of Wisconsin, Madison.

Understanding how animals respond to habitat structure is a fundamental objective in ecology, but is particularly challenging when the animals require distinct habitats for different life stages. Although the majority of animals have spatially segregated life stages, research on habitat associations has generally been restricted to only one of the life stages. The relative importance of aquatic and terrestrial habitat structure is not well known for the order Odonata (dragonflies and damselflies).

In northern Wisconsin (USA) lakes, housing development contributes to heterogeneity in riparian and littoral vegetation structure. I surveyed odonate larval assemblages at 41 sites across 17 lakes. Based on mixed-effects multiple regressions, model selection identified site-level littoral macrophyte abundance as a key driver of larval odonate species richness, and riparian wetland plant abundance as the best predictor for odonate density. Subsequent field experiments on larval predation and adult site selection helped explain these patterns. Additional surveys of the most abundant family (Gomphidae) at 22 lake sites indicated that local larval densities depend most on recruitment, which I estimated from adult densities during the previous year. Densities of emergent Gomphidae skins (exuviae) were most related to densities of the later-instar (second-year) larvae, further suggesting that larval survivorship and movement are less variable spatially than recruitment from the previous life stage.

Field experiments conducted at two South African lakes demonstrated how riparian tree structures alter adult odonate abundances. Riparian shade reduced the abundance of odonates at these potential breeding sites. Perch structures, added to separate experimental plots, supported locally higher adult abundances, but dragonflies were not sensitive to perch structure density or diversity. Thus shade is the critical habitat component that should be addressed for odonate conservation in South Africa.

Collectively, this research describes the role of habitat structure during multiple life stages. Field experiments demonstrate that generalist predators are sensitive to vegetation structure. The results suggest that riparian habitat selection by animals with complex life cycles can influence aquatic communities.