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

Abstract

Does the effect of aquatic plant types on invertebrate assemblages change across seasons in a subtropical wetland?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 cm 2 . 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.

Disentangling vegetation structure effect on invertebrate communities in contrasting growth periods in subtropical protected wetlands of Argentina

“…E. najas, which has the highest complexity of vegetation structure, supports a greater number of individuals per plant dry weight, that is, two times higher than those found on P. azurea, particularly during the growth sampling date. Gallardo et al (2017) also found that the invertebrate community associated with E. najas has higher abundance and taxa richness than those associated with the free-floating (FF) Salvinia biloba Raddi in periurban subtropical wetlands. Also, values of invertebrate abundance on P. azurea found in this study are broadly in line with those recorded by Poi et al (2017b) in the same macrophyte species and study area.…”

“…Also, the data suggest that these invertebrate communities can display substantial differences in the taxonomic composition even when they have similar abundance values in the two contrasting sampling dates, growth and decline. Previous studies were focused mainly on abundance of invertebrates, and with the exception of the study of Gallardo et al (2017) in periurban wetlands, all of them assess the effect of the vegetation structure or plant growth periods separately (Balla & Davis 1995, Bechara 1996, Poi de Neiff & Neiff 2006, Thomaz et al 2008, Dibble & Thomaz 2009, Fontanarrosa et al 2013, Franceschini et al 2020b. Our study provides evidence that considering the effect of microhabitat structure in contrasting sampling dates of macrophyte growth periods as well as integrating both abundance and composition might contribute to a better understanding of the structure and variation of invertebrate communities in subtropical wetlands.…”

Field-Scale Floating Treatment Wetlands: Quantifying Ecosystem Service Provision from Monoculture vs. Polyculture Macrophyte Communities

“…While there is debate in the literature about the importance of macrophyte species richness for indicators including number of invertebrate taxa, abundance, and diversity, most studies demonstrate that increases in macrophyte diversity and/or structural diversity have significant impacts on at least one of these metrics [13][14][15]30]. It is possible that plant rooting structure for each community type was not sufficiently different to drive differences in invertebrate communities, despite polycultures having a visually denser root network (often due to the higher density of Mentha aquatica) compared to the Phragmitesdominated monocultures.…”