Degree Type

Dissertation

Date of Award

2018

Degree Name

Doctor of Philosophy

Department

Ecology, Evolution, and Organismal Biology

Major

Ecology and Evolutionary Biology

First Advisor

Diane Debinski

Second Advisor

John Pleasants

Abstract

The population of monarch butterflies east of the Rocky Mountains has experienced a significant decline over the past twenty years. In order to increase monarch numbers in the breeding range, habitat restoration that includes planting milkweeds is essential. Milkweeds in the genus Asclepias and Cynanchum are the only host plants for larval monarch butterflies in North America, but larval performance, survival, and oviposition preference across milkweed species native to the Midwest, especially those with overlapping ranges, is not well documented. We examined early instar survival, survival and development from first instar to adult, oviposition inclination, and oviposition preference on nine milkweed species native to Iowa. The milkweeds included Asclepias exaltata (poke milkweed), A. hirtella (tall green milkweed), A. incarnata (swamp milkweed), A. speciosa (showy milkweed), A. sullivantii (prairie milkweed), A. syriaca (common milkweed), A. tuberosa (butterfly milkweed), A. verticillata (whorled milkweed), and Cynanchum laeve (honey vine milkweed). We report: (1.) early instars that fed on C. laeve plants were an instar behind larvae that fed on any other species, while larvae that fed on A. verticillata weighed more than larvae that fed on any other species, but that larvae early in development can survive on all nine milkweeds tested, (2.) fewer larvae that fed on A. hirtella and A. sullivantii reached adulthood compared to larvae that fed on the other milkweed species in greenhouse experiments, but larval duration (days), pupal duration (days), pupal mass, pupal length, and adult wet mass were not significantly different although survival probability varied from 30% to 75% among the nine milkweed species, (3.) A. incarnata had the greatest egg counts of all species when female monarchs were presented with either a single milkweed species or multiple milkweed species in laboratory experiments, but females laid more total eggs when exposed to multiple milkweeds than when compared to a single milkweed species, and (4) A. incarnata and A. syriaca were preferred for oviposition in the field during the breeding seasons of 2015-2017, although eggs were observed on all nine milkweed species. This research highlights the utility of multiple native milkweed species as host plants for monarch butterflies, but that preferences for some species exist among the milkweed species tested. These preferences should inform further research about milkweed use as pollinator conservation efforts continue.

DOI

https://doi.org/10.31274/etd-180810-6068

Copyright Owner

Victoria Marie Pocius

Language

en

File Format

application/pdf

File Size

157 pages

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