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Author Notes:

Correspondence: Amanda A. Pierce, amanda.pierce@emory.edu

Conceived and designed the experiments: AAP JDR SA RAB.

Performed the experiments: AAP JDR SA RAB.

Analyzed the data: AAP JDR SA RAB.

Wrote the paper: AAP JDR SA RAB.

We thank M. Maudsley, B. Puckett, and S. Sanders for assisting with monarch field capture, and S. Burton and M. Weathers for assistance in parasite load quantification

S. and A. Montgomery, S. Marques, and E. Kilpatrick provided land access and expertise.

R. Murashige assisted with logistical support on O’ahu. F. and K. Starr helped with milkweed locations, local information, and field maps.

We thank the de Roode lab and two anonymous reviewers for constructive comments on previous drafts of the manuscript.

The findings and conclusions in this article are those of the authors and do not represent the views of the U.S. Fish and Wildlife Service.

The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

The authors have declared that no competing interests exist.

Subjects:

Research Funding:

Funding for this project was provided by the National Science Foundation (grant DEB-0643831 to S.A., grant DEB-1019746 to J.D.R.), a Ruth L. Kirschstein National Research Service Award through the National Institutes of Health (NIH) to R.A.B., and the NIH training grant 5T32AI055404-10 (L. Real, PI).

Extreme Heterogeneity in Parasitism Despite Low Population Genetic Structure among Monarch Butterflies Inhabiting the Hawaiian Islands

Journal Title:

PLoS ONE

Volume:

Volume 9, Number 6

Publisher:

, Pages e100061-e100061

Type of Work:

Article | Final Publisher PDF

Abstract:

Host movement and spatial structure can strongly influence the ecology and evolution of infectious diseases, with limited host movement potentially leading to high spatial heterogeneity in infection. Monarch butterflies (Danaus plexippus) are best known for undertaking a spectacular long-distance migration in eastern North America; however, they also form non-migratory populations that breed year-round in milder climates such as Hawaii and other tropical locations. Prior work showed an inverse relationship between monarch migratory propensity and the prevalence of the protozoan parasite, Ophryocystis elektroscirrha. Here, we sampled monarchs from replicate sites within each of four Hawaiian Islands to ask whether these populations show consistently high prevalence of the protozoan parasite as seen for monarchs from several other non-migratory populations. Counter to our predictions, we observed striking spatial heterogeneity in parasite prevalence, with infection rates per site ranging from 4–85%. We next used microsatellite markers to ask whether the observed variation in infection might be explained by limited host movement and spatial sub-structuring among sites. Our results showed that monarchs across the Hawaiian Islands form one admixed population, supporting high gene flow among sites. Moreover, measures of individual-level genetic diversity did not predict host infection status, as might be expected if more inbred hosts harbored higher parasite loads. These results suggest that other factors such as landscape-level environmental variation or colonization-extinction processes might instead cause the extreme heterogeneity in monarch butterfly infection observed here.

Copyright information:

This is an Open Access work distributed under the terms of the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/).
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