Extreme heat reduces fitness of monarchs and their parasites

Maya Sarkar, a student at the University of Minnesota, worked with Isabella Ragonese, Dr. Sonia Altizer and Dr. Richard Hall.

Abstract: It is important to understand the consequences of a warming climate, especially in organisms that are more sensitive to temperature changes and where the outcome of warming may not be intuitive. This project used the Monarch-OE system to study how temperature may affect host-parasite interactions. The monarch butterfly (Danaus plexippus) is an iconic North American migratory species and the specialist protozoan parasite OE (Ophryocystis elektroscirrha) is present in all monarch populations. It has been shown that monarch development proceeds faster with increasing temperatures and that increased temperature exposure lowers OE spore infectivity over time. However, the effect of temperature on the host and parasite during active infection is not known. This project examined how temperature affects the monarch-OE system, focusing on the interaction between monarch immune function and parasite replication. Monarchs were inoculated with strains of OE parasite and placed in different temperature treatments. Three lineages (B,F, and D) of migratory monarch were used to test genetic effects, while 2 spore lines (E3 and E10) were used to study virulence effects within 5 different temperature treatments (18, 22, 26, 30, and 34°C). The results of this study provide novel insight to how extreme temperatures affect the fitness of a host and its parasite.