Limnetica 36

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Does the effect of aquatic plant types on invertebrate assemblages change across seasons in a subtropical wetland?

Luciana I. Gallardo, Romina P. Carnevali, Eduardo A. Porcel and Alicia S. G. Poi

Habitat complexity is one of the fundamental factors determining the distribution of invertebrate assemblages due to the different architectures and growth forms of aquatic plants, which affect their density, species richness, biomass, and trophic structure. In this paper, we compared the density and richness of macroinvertebrates present in two species of aquatic plants with different architectures (Salvinia biloba and Egeria najas) across seasons. Samples of aquatic plants and associated invertebrates were collected seasonally in a wetland located in Corrientes (Argentina) with a net area of 962 cm2. To characterize the different habitat types, we selected 12 traits of aquatic plants, including fractal complexity. A total of 15 225 invertebrates from 13 major groups were recorded from both habitat types (41 families and 24 genera in S. biloba and 24 families and 22 genera in E. najas). Significant differences in the total density (number of invertebrates per 1000 g plant dry weight) and taxa richness at family level were found between habitat types. Non-metric multidimensional scaling reflected differences in the seasonal patterns of 16 macroinvertebrate genera selected between both habitat types. A Similarity Analysis showed statistically significant differences between the habitat types and seasons. Structurally more complex habitat (S. biloba) supported a greater number of taxa and the highest number of individuals per plant dry weight. The differences in the density and richness of the invertebrate assemblages between S. biloba and E. najas were maintained throughout the seasons. The habitat structuring of aquatic macrophytes is a key factor in macroinvertebrate assemblages, and it is important to keep in mind when comparing wetlands with different aquatic vegetation.