Aquatic and terrestrial drivers of dragonfly (Odonata) assemblages within and among north-temperate lakes

The physical structure of vegetation influences diversity, interactions, movement, and thermoregulation of animals. Vegetation structure might be a good indicator of habitat requirements of generalist predators, such as dragonflies and damselflies (order Odonata), and thereby affect species diversity. Odonates use aquatic and terrestrial habitats during larval and adult life stages, respectively, but the relative importance of vegetation in these habitats is poorly understood. We compared how aquatic and riparian habitat variables affected odonate larvae from 41 sites (each 30 m in shoreline length) on 17 lakes in northern Wisconsin. We used principal components analyses to reduce multiple habitat variables to 2 lakelevel axes (lake size and development, lake wetlands and predators), 2 site-level littoral axes (littoral macrophytes, littoral muckiness), and 2 site-level riparian axes (riparian structural complexity, riparian tall wetland plants). Most (61.6%) of the variance in larval species richness occurred at the site level. Density of the most abundant family, Gomphidae, was positively related to riparian tall wetland plants, whereas species richness was positively correlated with abundance of littoral macrophytes (on the basis of multiple linear regression with an information theoretic approach). Surveys in 18 paired littoral microsites in 9 lakes indicated that larvae from the clasper and sprawler behavioral guilds were most abundant in microsites with submerged macrophytes. However, predation risk, assessed by tethering larvae in patches of submerged macrophytes, did not differ between habitats with and without macrophytes. We tested whether shoreline plants affected recruitment from the adult stage by comparing adult odonate behaviors in response to 2 riparian vegetation treatments. Adult damselfly abundance was higher where we placed potted wetland plants than at manicured lawns without tall vegetation. Our results indicate that odonate larvae might be influenced by vegetation structure in both aquatic and riparian habitats and demonstrate how animals with complex life histories link aquatic and terrestrial communities.