ENVIRONMENTAL FACTORS ASSOCIATED WITH DRAGONFLY ASSEMBLAGES AT EL YUNQUE NATIONAL FOREST

The environment plays a major role in determining biotic communities found in ecosystems. Abiotic factors help shape species dynamics and can affect species survival if drastically changed. Temporal changes in environmental factors result in life history adaptations for species such as aquatic insects. Odonata are model organisms to study these relationships because they are in both terrestrial and aquatic habitats. The objective of this investigation is to evaluate temporal changes of dragonfly assemblages at El Yunque rainforest and associate them with environmental variables. For larvae collection, we established a 100m transect in streams Prieta and Gatos. Each month, five 5m segments are randomly chosen for sampling using aquarium fish nets in pools and riffles for 15 min per segment. Larvae are sorted from benthic material and preserved in ethanol. We also measured temperature and canopy cover at each segment. Results indicate that larvae were more abundant in Prieta than in Gatos stream, even when both streams are of similar size. Analysis of size distribution resulted in a similar pattern for both streams, with small larvae being more abundant than medium and large ones. We also did not find evidence of cohort development, as small and large larvae were present in the same months. Environmental variables evidenced post-hurricane conditions for both streams, with open canopy and warm temperatures. Although this is an ongoing project, we found evidence for the occurrence of multiple dragonfly generations per year in these streams