PROJECTION MATRIX ANALYSIS OF THE DEMOGRAPHY OF AN INVASIVE, NONNATIVE SHRUB (ARDISIA ELLIPTICA)

Abstract

Despite recent advances in the study of invasive, nonnative species, we still understand very little about the variability of their population dynamics over space and time, and the processes that contribute to their demographic success. The goal of this study was to quantify the population dynamics of the invasive, subtropical shrub, Ardisia elliptica (Myrsinaceae), growing in a disturbed area of Everglades National Park, Florida, USA. We used bootstrap sampling and randomization tests to test hypotheses about spatial and tem- poral variation in population dynamics. Five populations spanning a range of habitats were studied for three years. Significant spatial and temporal variation in fruit production, relative growth, fates of vegetative individuals, and population growth rates were detected; however, spatial variation among populations had an overall stronger effect than temporal variation. Population growth rates were greater than 1 or not different from 1, implying that popu- lations are on average increasing in size. Similar to most other shrubs, prospective analysis showed that stasis of large stage classes had the highest elasticities. However, a retrospective analysis indicated that it was variation in growth to larger stage classes that contributed the most to observed variation in population growth rates. Simulations suggest that his- torically higher population growth rates of A. elliptica were necessary to produce current population sizes in Everglades National Park.