Lorna M. Moreno1, Elvia Meléndez- Ackerman2, Christopher Cheleuitte2, Brenda Castro3, Josue Sanchez3, Alexandra M. López3, Nicole Rivera3, and Laura Yunes3. (1) University of Puerto Rico, (2) Institute for Tropical Ecosystem Studies, (3) University of Puerto Rico, Río Piedras Campus
Background/Question/Methods Invasive species are an important driver of biodiversity loss and community changes worldwide. The African grass, Megathyrsus maximus, introduced in Mona Island in the early 1900's, has established extensive stand on that reserve but there is still no information about its effect on its natural communities. Soil organisms play important ecosystem functions and their diversity and distribution may be influenced by plant community composition. In this study we are testing for differences in arthropod diversity and composition between grass invaded areas and natural communities in Mona Island. We specifically tested if the presence of M. maximus was related to differences in species composition and abundance of plants and soil fauna. To that effect, we set pitfall traps in two invaded sites and two non- invaded sites for five continuous days. Collected specimens were classified to order and morphospecies and all morphs were counted and photographed. Results/Conclusions In terms of species composition, cluster analyses showed that all but two sites grouped in relation to their plant community type (with grass or without) but soil fauna was highly heterogeneous and did not clustered as expected by plant community type. A nested ANOVA showed a consistent tendency for non-invaded sites to have higher counts of plants but this for soil fauna this tendency was strong only for one of the areas. Our results suggest that the effect of this exotic grass on this dry forest ecosystem is likely to be related to effects on ecosystem productivity rather than species composition.
