Abstract Detail

Ecology

Wright, Gabrielle [1], Gorchov, David [2].

Frequency of white-tailed deer browse on an invasive shrub, Lonicera maackii, is inversely related to this invasive shrub’s abundance: evidence it serves as a unique food resource.

The preference for invasive plant species by native generalist herbivores depends on the plant species. We explored how preference by white-tailed deer for one invasive species depends on site conditions and community composition. In some southwest Ohio forest stands, the non-native shrub, Lonicera maackii (Caprifoliaceae, Amur honeysuckle) is very abundant and a major component of deer diets. We tested three hypotheses for this high browse rate: (1) deer prefer L. maackii versus other woody plants, (2) L. maackii is not a preferred, but consumed where alternative foods were depleted (due to high deer browse pressure), and (3) L. maackii is a unique (relatively non-substitutable) food resource for deer. This third hypothesis was motivated by the extended leaf phenology of L. maackii and earlier research showing that deer consumption of L. maackii twigs is high in early spring, when its leafed-out twigs provide a higher protein food source than the still leafless twigs of native woody plants.
We assessed preference for L. maackii and co-occurring woody plants across eight sites in southwest Ohio by counting first-year twigs of each woody species that were browsed by deer and unbrowsed in summer 2016, and calculating an electivity index for each of these species. Species were classified as more or less preferred than L. maackii based on electivity values. Neither the proportion of L. maackii twigs browsed, nor its electivity, was correlated with characteristics of the stand or landscape (land cover composition). Lonicera maackii electivity was negative at most sites, refuting the hypothesis that it is preferred. The hypothesis that deer consume L. maackii when more preferred foods are depleted was not supported, as there was no negative relationship among sites between L. maackii browse and the density of twigs of more preferred species. A negative relationship between the proportion of L. maackii twigs browsed and L. maackii density among sites supported the third hypothesis, that this invasive shrub is a unique food resource for deer.
The greater proportional deer browse on L. maackii where this shrub was less abundant, combined with the previous finding that leafy L. maackii twigs provide a high protein food in early spring before native woody plant leaf expansion, indicates this shrub provides a valuable food resource in early spring. We infer that deer seek out even sparse L. maackii in early spring, but this short-term browse is of negligible impact in stands where this shrub is abundant.

1 - Miami University, Department of Biology, 700 East High Street, Oxford, OH, 45056, United States
2 - Miami University, Department Of Biology, Pearson Hall, Oxford, OH, 45056, United States

Keywords:
invasive plants
herbivory
Ohio
phenology.

Presentation Type: Oral Paper
Session: 7, Ecology Section - Community Interactions and Responses
Location: 106/Mayo Civic Center
Date: Monday, July 23rd, 2018
Time: 9:30 AM
Number: 7005
Abstract ID:553
Candidate for Awards:None