Grassland disturbance increases monarch butterfly oviposition and decreases arthropod predator abundance

Journal Article · Sat Mar 09 00:00:00 EST 2019 · Biological Conservation

DOI:https://doi.org/10.1016/j.biocon.2019.03.007· OSTI ID:1546976

Haan, Nathan L. ^[1]; Landis, Douglas A. ^[1]

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1. Michigan State Univ., East Lansing, MI (United States). Dept. of Entomology and Great Lakes Bioenergy Research Center

Many species of conservation concern depend on disturbance to create or maintain suitable habitat. We evaluated effects of disturbance on the eastern migratory monarch butterfly (Danaus plexippus L.), which has declined markedly in recent decades, primarily attributed to the loss of milkweed host plants from annual crop fields in the US Midwest. Currently, remaining milkweeds in this region primarily occur in perennial grasslands, where disturbance is infrequent, predatory arthropods are abundant, and seasonal patterns of plant phenology differ from crop fields. In a two-year study in Michigan, USA, we applied three treatments to 23 patches of common milkweed (Asclepias syriaca L.); one-third of each patch was left undisturbed, while the remaining thirds were mowed in either mid-June or mid-July, respectively, and allowed to regenerate. We subsequently measured effects on monarch oviposition, predator abundance, survival of sentinel eggs and larvae, and tested how milkweed phenology and aphid colonization—both of which are reset by disturbance—structure predation risk for immature monarchs. Monarchs laid more eggs on regenerating versus undisturbed stems under both mowing regimes. Predators were strongly suppressed by mowing treatments, requiring 2–4 weeks to recolonize milkweed after disturbance, and were more abundant on flowering or aphid-infested stems. We found no significant differences in monarch egg/larval survival, although it tended to be higher in mowed plots. Overall, monarchs laid more eggs on regenerating stems where their offspring may also experience enemy-free space. Future work should focus on testing grassland disturbance as a management tool to improve productivity of existing monarch breeding habitat.

• Research Organization: Univ. of Wisconsin, Madison, WI (United States). Great Lakes Bioenergy Research Center
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER)
• Grant/Contract Number: SC0018409
• OSTI ID: 1546976
• Alternate ID(s): OSTI ID: 1547639
• Journal Information: Biological Conservation, Vol. 233, Issue C; ISSN 0006-3207
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
Butterfly conservation
Disturbance
Grasslands
Monarch butterfly
Predation