Effects of diet and temperature on monarch butterfly wing morphology and flight ability

Abstract

Background While global change research has greatly expanded in recent years, it remains unclear how environmental change will impact the mobility of many organisms. Flight is an important mode of transportation that affects ecological functions, including mate location, foraging, and migration. However, the effects of increasing temperature and diet quality on flight remain largely unknown. Here, we explore the effects of rearing temperature and larval diet quality on the flight ability of an iconic and ecologically threatened migratory insect, the monarch butterfly, Danaus plexippus. Experimental Design Monarch larvae were reared at two temperatures (25 °C and 28 °C) and on three milkweed species with varying phytochemistry (Asclepias incarnata, Asclepias syriaca, and Asclepias curassavica) in a fully factorial experiment. We tested flight ability using an automated flight mill, which measured cumulative flight distance, duration, and instantaneous velocity. Results Higher rearing temperatures reduced monarch flight ability, and larval diet quality influenced forewing morphology. Dietary milkweed with higher cardenolide concentrations (A. curassavica) induced shorter, wider forewings whereas milkweed with low to intermediate cardenolides (A. incarnata and A. syriaca) induced longer, narrower forewings, which are considered better for gliding flight used during migration. Implications for Insect Conservation Our results provide evidence that projected increases in temperature and the subsequent expansion of tropical milkweed (A. curassavica) into the central breeding range of eastern North American migratory monarchs could reduce migration success. Further research is needed to identify mechanisms explaining the effects of diet and temperature on monarch flight ability and fitness, to ensure that appropriate conservation strategies are employed to preserve migratory populations.

Effect of urbanization and its environmental stressors on the intraspecific variation of flight functional traits in two bumblebee species

“…Trait variation does not only show developmental instability, but it also has ecological implications. Wing size FA impacts the management of lengthy flights (Fernandez et al, 2017, Soule et al, 2020), compared to wing shape which is often associated with flight maneuverability. Thus, size asymmetry could specifically impact flight performance, flight length in time and space, and even affect bumblebee interactions with plants, the provisioning of larvae with food and their pollination rate.…”

“…Flight performance does not only depend on body size, but it is also affected by asymmetries in shape and size between wings (Grilli et al, 2017;Soule et al, 2020).…”

“…Flight performance largely depends on body size, and is also affected by asymmetries in shape and size between wings (Grilli et al, 2017; Soule et al, 2020). Variation in these traits does not only show developmental instability, but also has deep ecological implications.…”

“…Both wing size and shape are important functional traits in pollinators. This is because wing size is believed to be related to flight length and it influences metabolic costs (Fernandez et al, 2017; Soule et al, 2020), while shape is considered as important for flight maneuverability (Kolliker et al, 2003, Grilli et al, 2017). Thus, their asymmetry could reduce flight performance ability and thus could reduce fitness and even impact on species interactions and pollination efficiency.…”

“…Both wing size and shape are important functional traits in pollinators. This is because wing size is believed to be related to flight length and it influences metabolic costs (Fernandez et al, 2017; Soule et al, 2020), while shape is considered important for flight maneuverability (Kölliker et al, 2003, Grilli et al, 2017).…”