Seed dispersal by feral horses on Assateague Barrier Island, Maryland.
Braunskill, Kesha*,1, Vulinec, Kevina1, 1 Delaware State University, Dover, DE
ABSTRACT- Assateague Island National Seashore, Maryland, USA, is a barrier island of dynamic sand dunes, stabilized by native grasses. Conservation of the grass community remains an important part of the Seashores management plan. Feral horses (Equus caballus) are among other potential large herbivorous seed dispersers, such as sika (Cervus nippon) and white-tailed (Odocoileus virginianus) deer, and have inhabited the Island since the 1600s. Managing the horse population is important because of the negative effects grazing has on plant structure, inflorescence, and ultimately dune morphology. The role of feral horses in the dispersal and predation of seeds of both native and exotic plant species has not been investigated on Assateague Island. The objective of our study is to examine seed dispersal and viability of native grasses and exotic plants by feral horses on the Island. Fecal samples were collected from horses and planted in the Delaware State University greenhouse. We compared germination period of seeds that have passed through horse digestive tracts with those that have not. Our data show that the horses are dispersing viable seeds. However, the horses are inhibiting the germination of some plant species found on the Island including: Tapered rosette grass (Dichanthelium acuminatum), and the exotic species Salt sandspurry (Spergularia marina). Inhibited germination of native and exotic species could hinder their persistence. In addition, horses pass viable seeds of Smooth cordgrass (Spartina alterniflora) and Saltmeadow cordgrass (Spartina patens), which are essential dune building grasses, and the native grass, Saltgrass (Distichlis spicata) found in the bayside marshes on the Island. Horses are considered an introduced species in the barrier island ecosystem; thus, seed dispersal by this species may be an additional management concern.
Key words: seed dispersal, Equus caballus, barrier island
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