Considering herbivory, reproduction, and gender when monitoring plants: A case study of Jack-in-the-pulpit (Arisaema triphyllum [L.] Schott)

Arisaema triphyllum (L.) Schott, Jack-in-the-pulpit, a sequential hermaphro dite, can switch between male and female sex expression through time. Older , larger individuals are more likely to become female, but damage to leaves or storage tissue may prevent future sexual reproduction. Therefore repeat ed herbivory could indirectly alter sex ratios within populations. In a fie ld study in hardwood forests in New Jersey, we observed lower than expected flower and fruit production by A. triphyllum in a large sample. The energy reserves of the corms within the study populations may have been depleted by chronic herbivory from white-tailed deer (Odocoileus virginianus Zimmerm an), decreasing the likelihood of flower and fruit production. We found tha t 27.2% of the 3331 monitored A. triphyllum individuals were eaten by white -tailed deer in 1996. Although herbivory by deer declined in 1997 and 1998, long-term effects of repeated overgrazing by deer may result in irreversib le losses of plants that fail to reproduce. Therefore, monitoring based onl y on counting stems may lead to misleading estimates for population-persist ence of gender-modifying plants. Similarly, a count of flowers in a predomi nantly male-biased population is a misleading indicator of reproductive pot ential.