Document: CHR-3-42-40

Reproductive compensation by wild carrot, Daucus carota: The interaction of plant competition and mammalian herbivory.

SACCHI, C.F.* ¹ and J.L.DOOLEY ²

Kutztown University, Kutztown, PA, 19530, USA ¹
Muskingum College, New Concord, OH, 43762, USA ²

Abstract:
Over two growing seasons we tested the hypothesis that there is a continuum of reproductive response by plants exposed to herbivory based on the competitive environment where plants grow, from negative responses to herbivory in competitive environments to overcompensatory responses in low competition environments. We experimentally studied the reproductive response of wild carrot, Daucus carota, to grazing by white tailed deer, Odocoileus virginiana, under conditions of ambient and reduced interspecific plant competition. In a fully crossed experimental design, wild carrot plants growing in an abandoned agricultural field were assigned to a reduced competition or a competition-present treatment and plants were either clipped to simulate deer herbivory or were left unclipped; plants were protected from subsequent herbivory using mesh cages. Over two summers that differed in the abundance and distribution of natural precipitation, wild carrot plants that were clipped exhibited a compensatory reproductive response and produced mature umbels that were comparable in size to those on intact, unclipped plants regardless of competitive environment in which they grew. Clipped plants produced a similar number of umbels compared with unclipped plants. Competition effects were not apparent, with plants in the low and high competition environments producing similar sizes and numbers of umbels. We conclude that for wild carrot, under the environmental conditions influencing the population we studied, there was no evidence for a continuum of response to grazing by deer. Further, plants grazed by deer exhibited reproductive compensation but suffered neither apparent reproductive loss nor evidence for reproductive overcompensation.

Keywords: herbivore impact, overcompensation

This abstract is being presented at: 4:00 PM in session:
Oral Session #17: Mammalian Herbivory.