Semester

Summer

Date of Graduation

2014

Document Type

Thesis

Degree Type

MS

College

Eberly College of Arts and Sciences

Department

Biology

Committee Chair

James B. McGraw

Committee Co-Chair

Petra Bohall Wood

Committee Member

Stephen DiFazio

Abstract

American ginseng (Panax quinquefolius L.) is a long-lived forest herb found throughout Appalachia, well-known for its reputation as a medicinal plant species. Harvest of ginseng for the international medicinal plant trade has been a significant contributor to population decline of the species. As a declining species with life-history traits similar to many other herbaceous perennials and both cultural and economic value, American ginseng has become a focal species for many demographic and conservation based studies. Seed dispersal is a critical component of ginseng demography lacking empirical evidence for potential dispersal mechanisms. To date, gravity is considered to be the primary mechanism of dispersal, but the production of red, fleshy berries during the late fall suggest animal dispersal. Based on berry morphology, timing of ripening, and field-based observations, songbird and small mammal species were determined to be two likely candidates for ginseng dispersal. In Chapter 2, I investigated the frequency and type of songbird species interacting with ginseng berries using infrared, motion-activated wildlife cameras in the field and observed songbird digestive behavior in captivity. Thrushes were found to most frequently remove berries in the field and regurgitate viable seeds, on average, 16 minutes after ingestion. In Chapter 3, small mammal interactions were investigated using infrared, motion-activated wildlife cameras and cafeteria-style feeding boxes in the field. In addition, the impacts of high tree mast years, an environmental event linked to small mammal population dynamics, on seedling recruitment was investigated using historical mast indices and long-term ginseng population data. Small mammals more frequently interacted with ginseng berries in camera images compared to thrushes and mice were observed to predate ginseng seeds during feeding trials. The impacts of high tree mast years were found to differ between sites, but recruitment was found to decrease with increasing mast production at four sites. Overall, thrushes were found to be the primary animal disperser of American ginseng while small mammals are most often seed predators. As the primary animal disperser, thrushes provide the first documented opportunity for intermediate and long distance dispersal events. Dispersal events over such distances are becoming increasingly more important for ginseng to persist in the presence of intense harvest, deer browse, and climate change; three significant factors contributing to declining ginseng populations. Additionally, small mammal predation of ginseng seeds could further contribute to population declines.

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