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Open AccessArticle

Exposure to Non-Native Tropical Milkweed Promotes Reproductive Development in Migratory Monarch Butterflies

by 1,2,3,* and 1,2
1
Odum School of Ecology, University of Georgia, Athens, GA 30602, USA
2
Center for the Ecology of Infectious Disease, University of Georgia, Athens, GA 30602, USA
3
Department of Biology, Emory University, Atlanta, GA 30322, USA
*
Author to whom correspondence should be addressed.
Insects 2019, 10(8), 253; https://doi.org/10.3390/insects10080253
Received: 22 May 2019 / Revised: 22 July 2019 / Accepted: 12 August 2019 / Published: 16 August 2019
(This article belongs to the Special Issue Impact of Introduced Plants on Insects)
Background: North American monarchs (Danaus plexippus) are well-known for their long-distance migrations; however, some monarchs within the migratory range have adopted a resident lifestyle and breed year-round at sites where tropical milkweed (Asclepias curassavica) is planted in the southern coastal United States. An important question is whether exposure to exotic milkweed alters monarch migratory physiology, particularly the ability to enter and remain in the hormonally-induced state of reproductive diapause, whereby adults delay reproductive maturity. Cued by cooler temperatures and shorter photoperiods, diapause is a component of the monarch’s migratory syndrome that includes directional flight behavior, lipid accumulation, and the exceptional longevity of the migratory generation. Methods: Here, we experimentally test how exposure to tropical milkweed during the larval and adult stages influences monarch reproductive status during fall migration. Caterpillars reared under fall-like conditions were fed tropical versus native milkweed diets, and wild adult migrants were placed in outdoor flight cages with tropical milkweed, native milkweed, or no milkweed. Results: We found that monarchs exposed to tropical milkweed as larvae were more likely to be reproductively active (exhibit mating behavior in males and develop mature eggs in females) compared to monarchs exposed to native milkweed. Among wild-caught fall migrants, females exposed to tropical milkweed showed greater egg development than females exposed to native or no milkweed, although a similar response was not observed for males. Conclusions: Our study provides evidence that exposure to tropical milkweed can increase monarch reproductive activity, which could promote continued residency at year-round breeding sites and decrease monarch migratory propensity. View Full-Text
Keywords: Asclepias curassavica; Danaus plexippus; garden; reproductive diapause; physiology; migration; sedentary Asclepias curassavica; Danaus plexippus; garden; reproductive diapause; physiology; migration; sedentary
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MDPI and ACS Style

Majewska, A.A.; Altizer, S. Exposure to Non-Native Tropical Milkweed Promotes Reproductive Development in Migratory Monarch Butterflies. Insects 2019, 10, 253. https://doi.org/10.3390/insects10080253

AMA Style

Majewska AA, Altizer S. Exposure to Non-Native Tropical Milkweed Promotes Reproductive Development in Migratory Monarch Butterflies. Insects. 2019; 10(8):253. https://doi.org/10.3390/insects10080253

Chicago/Turabian Style

Majewska, Ania A.; Altizer, Sonia. 2019. "Exposure to Non-Native Tropical Milkweed Promotes Reproductive Development in Migratory Monarch Butterflies" Insects 10, no. 8: 253. https://doi.org/10.3390/insects10080253

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