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Patterns of parasitism in monarch butterflies during the breeding season in eastern N orth A merica
Author(s) -
FLOCKHART D. T. TYLER,
DABYDEEN ANJULI,
SATTERFIELD DARA A.,
HOBSON KEITH A.,
WASSENAAR LEONARD I.,
NORRIS D. RYAN
Publication year - 2018
Publication title -
ecological entomology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.865
H-Index - 81
eISSN - 1365-2311
pISSN - 0307-6946
DOI - 10.1111/een.12460
Subject(s) - danaus , biology , obligate , culling , range (aeronautics) , ecology , annual cycle , monarch butterfly , host (biology) , seasonal breeder , latitude , parasite hosting , zoology , parasitism , larva , geography , herd , materials science , geodesy , world wide web , computer science , composite material
1. Migratory behaviour can result in reduced prevalence of pathogens in host populations. Two hypotheses have been proposed to explain this relationship: (i) ‘migratory escape’, where migrants benefit from escaping pathogen accumulation in contaminated environments; and (ii) ‘migratory culling’, where the selective removal of infected individuals occurs during migration. 2. In the host–parasite system between the monarch butterfly ( Danaus plexippus L inn.) and its obligate protozoan parasite Ophryocystis elektroscirrha ( OE ), there is evidence to support both hypotheses, particularly during the monarchs' autumn migration. However, these processes can operate simultaneously and could vary throughout the monarchs' annual migratory cycle. Assessing the relative strength for each hypothesis has not previously been done. 3. To evaluate both hypotheses, parasite infection prevalence was examined in monarchs sampled in eastern N orth A merica during A pril– S eptember, and stable isotopes (δ 2 H , δ 13 C ) were used to estimate natal origin and infer migration distance. There was stronger support for the migratory escape hypothesis, wherein infection prevalence increased over the breeding season and was higher at southern latitudes, where the breeding season tends to be longer compared with northern latitudes. Little support was found for the migratory culling hypothesis, as infection prevalence was similar whether monarchs travelled shorter or longer distances. 4. These results suggest that migration allows individuals to escape parasites not only during the autumn, as shown in previous work, but during the monarchs' spring and summer movements when they recolonise the breeding range. These results imply a potential fitness advantage to monarchs that migrate further north to exploit parasite‐free habitats.