Investigating the relationship between an ornamental plant and an introduced pollinator: Stachys byzantina (lamb's ear) and Anthidium manicatum (European wool-carder bee)

Anthidium manicatum (European wool-carder bee) is an exotic invasive species that first appeared in North America in the early 1960s. Since then its range has expanded to cover much of the continental United States. This species could have a potentially devastating impact on the local ecosystem. Males are notoriously aggressive to heterospecifics, and females strip nearby plants of their valuable trichomes for nesting material. This project explores the impact of female A. manicatum on their preferred trichome source, Stachys byzantina (lamb’s ear). Trichomes fill several functional roles for plants, but most importantly they help deter herbivory. The removal of trichomes by A. manicatum is known as “carding”, and results in a section of the leaf or stem being stripped bare of trichomes. Three main findings were established in this study: (1) incidences of carding occur near each other on lamb’s ear plants. This suggests that something is attracting A. manicatum to the same leaf or area of a plant to gather nesting material; (2) the volatile organic compounds (VOCs) given off by S. byzantina change after removal of trichomes via mechanical carding. This was established using gas chromatography and flame ionization detection and we propose that this change in VOCs is responsible for attracting further incidents of carding by A. manicatum; (3) herbivores (earwig nymphs) are found at significantly higher rates on carded areas of leaves than on non-carded areas of S. byzantina leaves (p<0.001, Chi-square test) indicating a significant risk to the plant following trichome removal.