Landscape- and local- level variables affect monarchs in Midwest grasslands

Landscape Ecology
By: , and 

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Abstract

Context

It is estimated that over one billion milkweed stems need to be restored to sustain the eastern North American migratory population of monarch butterflies; where and in what context the stems should be placed on the landscape is key to addressing habitat deficits.

Objectives

We assessed how the amount of appropriate habitat surrounding a particular patch of monarch habitat affects monarch presence and reproduction. To ensure that habitat restoration efforts are targeted towards areas that maximize monarch population growth, it is important to understand the effects of landscape heterogeneity on monarch occurrence in habitat patches (i.e. grasslands with milkweeds) across the landscape.

Methods

Over two summers (2018–2019), we surveyed monarch adults, larvae, and eggs at sixty grassland sites in Wisconsin that varied in patch size and landscape context (proportion grassland, forest edge density, and road density). We also estimated milkweed density and floral richness to characterize local patch quality.

Results

Adult monarch abundance was highest at patches with the lowest proportion of surrounding grassland and lowest road density, and was heavily influenced by patch quality variables. Egg and larva density in a patch increased with milkweed density and floral richness within a patch. Patch size was unrelated to monarch abundance.

Conclusions

These results suggest that optimal sites for monarch habitat restoration are within landscapes which contain little habitat and that high milkweed density and floral richness and abundance should be conservation goals.

Study Area

Publication type Article
Publication Subtype Journal Article
Title Landscape- and local- level variables affect monarchs in Midwest grasslands
Series title Landscape Ecology
DOI 10.1007/s10980-021-01341-4
Volume 37
Year Published 2022
Language English
Publisher Springer
Contributing office(s) Upper Midwest Environmental Sciences Center
Description 16 p.
First page 93
Last page 108
Country United States
State Wisconsin
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