Crowding does not affect monarch butterflies' resistance to a protozoan parasite
Alaidrous W, Villa SM, de Roode JC and others. Ecology and evolution, April 2022.
Read the paper Free to read · doi:10.1002/ece3.8791
What this paper is about
Caterpillars crowded together meet more parasites and may also be physiologically stressed, which could cut either way for resistance.
The authors varied larval density in monarchs and measured resistance to OE. Crowding made no difference, with or without food limitation.
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Abstract
Host density is an important factor when it comes to parasite transmission and host resistance. Increased host density can increase contact rate between individuals and thus parasite transmission. Host density can also cause physiological changes in the host, which can affect host resistance. Yet, the direction in which host density affects host resistance remains unresolved. It is also unclear whether food limitation plays a role in this effect. We investigated the effect of larval density in monarch butterflies, Danaus plexippus, on the resistance to their natural protozoan parasite Ophryocystis elektroscirrha under both unlimited and limited food conditions. We exposed monarchs to various density treatments as larvae to mimic high densities observed in sedentary populations. Data on infection and parasite spore load were collected as well as development time, survival, wing size, and melanization. Disease susceptibility under either food condition or across density treatments was similar. However, we found high larval density impacted development time, adult survival, and wing morphology when food was limited. This study aids our understanding of the dynamics of environmental parasite transmission in monarch populations, which can help explain the increased prevalence of parasites in sedentary monarch populations compared to migratory populations.
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title = {Crowding does not affect monarch butterflies' resistance to a protozoan parasite (listing)},
author = {{Milkweed USA}},
year = {2026},
url = {https://milkweedusa.com/research/crowding-does-not-affect-monarch-butterflies-resistance-to-a-2022/},
note = {Accessed DATE}
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