PARENT SESSION
Poster Session 3: Aquatic Ecology
Monday, August 8, 5:00 PM - 6:30 PM, Exhibit Hall 210 D, Level 2, Palais des congrès de Montréal
The spatial distribution and relative abundance of larval dragonflies found in the freshwater marshes of the Florida Everglades.
Urgelles, Raul1, Dorn, Nathan1, Trexler, Joel1, 1 Florida International University, Miami, FL, USA
ABSTRACT- Aquatic macroinvertebrates are essential tools for characterizing habitat quality since they are sensitive indicators of environmental stressors, such as altered hydrology and nutrient enrichment. Long-term monitoring of aquatic macroinvertebrates such as dragonflies (order Odonata, suborder Anisoptera) can be used to assess the progress of restoration initiatives, such as the one being conducted in the Florida Everglades. We present the first comprehensive spatial and temporal survey of dragonfly communities for Everglades freshwater marshes and use statistical methods to analyze the relationship between these assemblages and environmental variables. From 1997 to 2004, we collected and identified the naiads of 15 species of dragonfly from 20 sites (each composed of replicate ha plots) across broad spatial scales, encompassing wet and dry season dynamics. In a preliminary analysis of two years of data, 2002 and 2003, we identified 13 dragonfly species and described their distributions and relative abundance based on their spatial extent (# of sites at which they were collected) and density (annual average # individuals/m2). Two species, Celithemis eponina and Libellula needhami, dominated the assemblage at most sites and showed considerable inter-annual dynamics. C. eponina annual average densities increased in 18 out of 20 sites from 2002 to 2003, while L. needhami decreased in density in 15 out of 20 sites. Since 2003 was a wetter year throughout the ecosystem than 2002, these shifts in dominance may indicate a greater ability by C. eponina to tolerate conditions associated with lengthening hydroperiod. At a site highly stressed with anthropogenic nutrient-enrichment, the normally dominant C. eponina, was completely absent, and Pachydiplax longipennis, a species that is at low densities or absent from all other sites, dominated the assemblage with extremely high densities. We are currently analyzing the remaining years and looking at longer-term responses of dragonfly assemblages to dry-down and re-wetting conditions.&stilde;
Key words: Anisoptera, Everglades, habitat quality, hydroperiod