Species richness and ß-diversity of aquatic macrophytes in the Upper Paraná River floodplain

Abstract

In this paper, we estimated the aquatic macrophyte species richness in the Upper Parana River floodplain using non-parametric estimators. Fifty species were recorded in intensive surveys of several floodplain habitats. Based on a random sample of 20 lagoons, 6 connected to the Parana River, 6 to one tributary and 8 to another, all estimators gave values very similar to the "true" number of species recorded in inten sive surveys. The comparison among the lagoons connected with these rivers showed that the species richness was different, after controlling for sampling effort. Corre spondence analysis and Mantel 's test showed that the beta diversity was significantly higher among the groups of lagoons than within groups of lagoons connected with the same river. The high connectivity among the lagoons of the same river can account for such results. Within the groups of lagoons, the highest species turnover (beta diversity) was found for Parana River lagoons, which are predominantly temporary and more variable. This result is in accordance with a general ecological prediction, which stres ses that beta diversity should increase with environmental variability.

Phytoplankton diversity in the Upper Paraná River floodplain during two years of drought (2000 and 2001)

“…The lowest mean values of water temperature and depth in the three subsystems were observed during August (2000 and2001). In general, the environments connected to the Paraná River presented high mean values of electric conductivity, Zeu and NO 3 , whereas high mean concentrations of TN, TP and SRP were registered in the Baía and Ivinhema subsystems.…”

“…Biotopes associated with the Paraná River presented the highest mean values of beta diversity and the highest values of coefficient of variation of abiotic variables. Studies on aquatic macrophytes in this system also revealed high values of beta diversity for the Paraná subsystem, which coincided with high environmental variability (Bini et al, 2001;Thomaz et al, 2004c).…”

“…Sampling was from the subsurface of the pelagic zone in each environment during the rainy period, when normally the potamophase occurs (February 2000 and2001) and during the dry period, when the limnophase occurs (August 2000 and2001). The limnologi-…”

Influência da heterogeneidade ambiental sobre os atributos da comunidade de Chironomidae em lagoas de inundação neotropicais

“…Estas plantas, quando em densidades moderadas, podem aumentar a heterogeneidade das zonas litorâneas, proporcionando hábitat e apoio para muitas comunidades aquáticas (Junk, 1970;wetzeL, 1983). Nestas condições, os bancos de macrófitas exercem papel fundamental na ciclagem de nutrientes e na formação de detritos nos ambientes aquáticos (petRucio & esteves, 2000;Bini et al, 2001) e servem ainda como local de oviposição dos adultos (waRd, 1992;tRivinho-stRixino & stRixino, 1995) e abrigo para os primeiros estágios de muitas larvas de Chironomidae. Quando há macrófitas submersas, além das emersas, o ambiente torna-se mais heterogêneo, como verificado na lagoa Osmar.…”

Caloric density of aquatic macrophytes in different environments of the Baía river subsystem, upper Paraná river floodplain, Brazil

“…Tropical and subtropical floodplains possess an abundance of aquatic macrophytes of different species and ecological groups (Bini, 1996;Bini et al, 2001). The presence of these plants generally represents high primary production, biomass (Esteves, 1998;Pedralli, 2000), nutrient cycling and stock capacity for the ecosystem (Henry-Silva et al, 2001).…”