Meeting Abstract
Roadsides are a unique anthropogenic habitat. Nitrogen and sodium accumulate due to deposition from exhaust and road salt application, respectively; both nutrients could potentially attract animals, especially herbivores, to roadsides. However, roadside environments may also be toxic, either from very high levels of salt, or from heavy metal accumulation (zinc, cadmium, nickel) from tire and brake pad wear. To what extent might insect pollinators be able to behaviorally adjust or adapt to such conditions along roadsides? This talk will review several ongoing projects relevant to this question. First, surveys of roadside soils, plants and insects are testing how nutrient and heavy metal content varies with traffic volume and urbanization. Second, behavioral experiments are testing whether female butterflies are attracted to or repelled from host plants containing high levels of sodium. Finally, a series of rearing experiments are testing patterns of standing genetic variation in the ability of several species of butterflies to cope with high sodium concentrations in their larval diet. Additional rearing experiments consider responses to heavy metal exposure. To date, results suggest ample variation in performance on a range of salt diets across sibling families, suggesting potential for adaptation to high sodium along roadsides. In addition, exposure to low levels of some heavy metals has little, to sometimes positive (hormetic), responses on performance. Upcoming experiments will consider how nitrogen, sodium, and metals may interact to affect performance of both butterflies and bumblebees. Overall, roadsides serve as an intriguing case study in understanding how animals may adapt to novel, patchy environments that are thought to be ecological traps.
