Monarch–parasite interactions in managed and roadside prairies

Abstract

Roadsides cover an extensive area within the United States, are actively managed, and have been considered potential areas of habitat for several taxa. For monarch butterflies (Danaus plexippus), roadsides may act as important habitat along their migration route by providing nectar and host plant resources, which is especially important considering the loss and fragmentation of monarch habitat throughout their breeding range. However, the interactions between monarchs and their parasites may be altered in these areas by management regimes. Monarchs are infected by Ophryocystis elektroscirrha (OE), an obligate, spore-forming protist of monarchs and queens, and Lespesia archippivora, a generalist tachinid fly parasitoid. Roadsides could increase parasitism by concentrating monarchs in certain areas or decrease parasitism by modifying habitat (e.g., the roadside management practice of mowing could reduce the availability of OE spores by removing the above ground portion of host plants and generating re-growth), including the distribution and abundance of host plants. In this study, we compared the proportion of infected monarchs between roadside prairies and managed prairies to evaluate the potential of roadside prairies as habitat for monarch butterflies. Our results suggest that the proportion of infected monarchs does not differ between roadside prairies and managed prairies. Thus, roadsides may provide habitat for monarchs that is similar in quality (at least in terms of parasitism rates) to managed prairies. The role of roadsides as habitat for monarchs should be considered when developing roadside management strategies.