DESICCATION FREQUENCY REDUCES SPECIES DIVERSITY AND PREDICTABILITY OF COMMUNITY STRUCTURE IN COASTAL ROCK POOLS

Abstract

Success of aquatic organisms in temporary ponds depends on both survival through the dry period (i.e., resting eggs) and population dynamics through the wet period (i.e., recolonization, dispersal). We hypothesized that pools with high desiccation frequency would contain simpler communities (fewer species), and these communities would have greater compositional constancy (persistence) due to a restricted set of species. To test these hypotheses we examined diversity, species richness, abundance, evenness, community persistence, and community structure (species ranking) over time using 49 erosional rock pools located on the north coast of Jamaica. Diversity, species richness, and abundance decreased with increased frequency of pool desiccation. Pools were classified as temporary or permanent. In temporary pools, despite substantial inter-pool differences, diversity, species richness, evenness, and abundance did not change significantly over time. Contrary to our hypothesis, community persistence (compositional stability) decreased with increased frequency of pool desiccation. Species rank also changed significantly over time in pools that were classified as temporary. However, temporary pools had lower variability in community structure, suggesting the existence of a common type of community: one dominated by weedy species with good dispersal and colonization abilities. A somewhat unexpected conclusion is that high habitat variability (i.e., temporary pools) may lower the variability in some community descriptors. Thus, it appears that the reduction of community variability is achieved at the expense of its richness and diversity.