Influence of morphometric and geographic factors on plant community composition of temporary freshwater rockpools in the Maltese Islands

Abstract

We investigated the influence of 6 morphometric and geographic factors on the structure and composition of plant communities in 56 temporary freshwater rockpools from 7 pool landscapes in the Maltese Islands. The factors considered were water depth, sediment depth, surface area, shading, distance from the coast, and elevation above sea level. Coverage data for 30 plant taxa in 3 functional forms (aquatic, amphibious, and terrestrial) were collected during one hydrological cycle. The relationships between pool morphometry, pool location, and community composition were tested using multivariate analyses. The contribution of spatial variables to variation in community composition across pools was examined using principal coordinate analysis of neighbour matrices (PCNM). The results suggested that pool morphometry varied both within and across landscapes, reflected in similar differences in community composition. Moreover, 47.6% of the explained community variation in the whole dataset was contributed exclusively by space predictors, suggesting that pool “location” is an important determinant of community composition. The morphometric property that exerted the highest influence on the dominance of a given plant functional form was the pool surface area, with greater surface areas promoting the presence of amphibious species relative to obligate hydrophytes. Conversely, the presence of specific species was mainly controlled by water depth and sediment depth. The most influential predictors of community composition varied across landscape, suggesting that pool location can be an important determinant of community structure and composition, and pool morphometry would favour certain functional forms and species over others.