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Energetic Causes and Consequences of Reproductive Diapause and Migration in Monarch Butterflies (Danaus plexippus L.)
Monarch butterflies (Danaus plexippus L.) undergo an iconic annual, long-distance migration taking them up to 4,000 km from their summer breeding grounds in southern parts of Canada and northern parts of the United States to their overwintering grounds in the mountains of central Mexico. My research leverages the unique life history and physiology of the monarch butterfly to better understand the physiology, development, and energetics of reproductive diapause, which is necessary for monarch butterfly migration and overwintering. While monarchs in North American (NA) are famous for their migration, they have recently dispersed to many locations around the globe where they no longer migrate across most of its range, i.e. Costa Rica (CR). My research leverages this demographic history to better understand what plastic strategies are important for N. American migration. We quantified plasticity across generations in NA monarchs for wing morphology and metabolic traits that are related to long-distance migration and asked whether CR monarch butterflies have lost or decreased plasticity in these traits. We found that the non-migratory CR descendants of the migratory NA population retain some, but not all ancestral seasonal trait plasticity. We reared monarchs under a decreasing photoperiod to induce and understand the developmental and energetic consequences of reproductive diapause. Monarchs reared under a short-day photoperiod enter reproductive diapause and were seasonally plastic in larval metabolism, development time, and adult head mass. Finally, I tested for differences in flight muscle structure and mitochondrial density in these same monarchs to understand whether the structures of the flight muscle and its mitochondria are plastic in response to photoperiod. We find that monarchs reared under short-day do not change their flight muscle structures or number of mitochondria. In summary, seasonal plasticity is lost in a piecemeal fashion in the absence of environmental heterogeneity in monarchs. Additionally, monarchs may rely on changes in the amount of overall flight muscle rather than in mitochondrial physiology to support more efficient long-distance flight.
Evolution and Development|Cellular biology|Entomology
Julick, Cole, "Energetic Causes and Consequences of Reproductive Diapause and Migration in Monarch Butterflies (Danaus plexippus L.)" (2022). ETD collection for University of Nebraska - Lincoln. AAI29322844.