Distribution of Barrier Island Plants in Relation to Overwash Disturbance: A Test of Life History Theory

Abstract

We document the relationships between the distributions of species and the pattern of "overwash" disturbance for plant species on Hog Island, a barrier island off the southern part of the Delmarva Peninsula (Virginia, U.S.A.). Overwash disturbance is the mortality of plants due to sand deposition during storms that create high waves that wash over the island. We analyzed the distribution of each of 95 species in relation to the pattern of overwash disturbance. We then used the results to test the hypotheses that, as one moves from areas of low overwash disturbance frequency to areas of high overwash disturbance frequency, (1) the number of annual and biennial plant species increases relative to perennial species and (2) the number of woody plant species decreases relative to herbaceous species. These hypotheses are derived from life history theory which predicts that early maturation and short lifespan are advantageous in highly disturbed environments. There were large differences among the plant species in their tolerances to overwash disturbance. As expected, there were fewer woody plant species than expected at random in areas of high overwash disturbance frequency. However, the hypothesis that annual plant species would be more common than expected at random in frequently disturbed areas was not supported. This result may be explained by advantages of clonal growth and reproduction in perennial plants, in areas of high overwash probability.