Species composition and temporal variation of odonate assemblages in the subtropical-pampasic ecotone, Buenos Aires, Argentina

Odonata assemblages present in the ecotone between subtropical forest and pampasic grassland in Punta Lara were characterized and compared. Four pools, one in the forest, 2 in grassland (one within a protected area) and one at the limit of both environments, were sampled during July 1996-June 1998. For each sampling station species richness and diversity were calculated, and were compared through 2 similarity coefficients (Jaccard and Winer). The highest species richness and diversity were registered in the forest, and the lowest in the protected grassland. Cluster analysis showed different schemes according to the similarity coefficient considered; a greater similarity between the forest and intermediate pools (Jaccard coefficient), or a greater similarity between grassland areas (Winer coefficient). Some biogeographical implications are discussed.