Irrigated rice fields in southern Brazil remain without surface water for 2 years during the fallow phase. The present study tested the hypothesis that the hydrologic regime adopted in rice fields of southern Brazil does not compromise the viability of resting stages of aquatic invertebrates. Dry sediment samples were collected from 9 rice fields with different durations of the fallow phase: 20 days, 1 year, and 2 years after the harvesting period. A total of 2,853 invertebrates distributed across 40 taxa emerged after rewetting dry sediments over the experiment duration (58 days). The dominant invertebrates were microcrustaceans represented by 1,041 individuals and 17 species. Invertebrate richness and density on rice fields fallowed (i.e., dried) for 1 year were greater than that for rice fields drained 20 days and 2 years. Aquatic invertebrate composition varied between rice fields fallowed for 20 days compared to those that remained dry for 1 or 2 years. The existence of viable resting stages in dry rice sediments over all stages of the fallow phase should help guide wetland restoration initiatives in southern Brazil.

Wetlands (e.g. ponds, meadows) can be found in many landscapes, playing an important role in maintaining regional biodiversity and supporting heterogeneous communities. Spiders are diversified predators that are highly influenced by changes in plant community structure, heterogeneous habitats sustain high spider diversity and abundance. We investigated the characteristics of spider biodiversity in ponds with different habitat structures, by examining patterns across habitats of ponds with different vegetation levels. Sampling took place in four occasions over a year. We compared spider abundance, species richness and composition among ponds including distinct vegetation variables, related to life form, type of leaves, coverage and height. Overall 1174 individuals (194 adults) of 11 families and 37 morphospecies were sampled. We found mostly expected differences in the manner that communities were structured between different habitats. Thus, higher variability of abundance was explained for higher habitat structure of ponds. We also found differences in species composition between ponds with low emergent vegetation and higher habitat structures. Additionaly, spiders were consistently structured more by turnover than nestedness components, with a greater beta diversity of web‐builders. Our results suggest varying levels of habitat structures and species substitution shape pond spider communities, depending on habitat heterogeneity and spider guild. Those findings demonstrate the clear role of spatial habitat structure, with more spider species preferring to build webs or actively hunt at vegetated environments on ponds.

Exotic pine invasion influences native wetland assemblages by changing environmental conditions such as hydrological regime and physicochemical characteristics. The expansion of cultivated pine has been a concern in southern Brazil and its impacts on aquatic biodiversity are poorly known. We tested the hypotheses that: (1) pine invasion decreases aquatic macroinvertebrate richness and abundance, modifying composition and macroinvertebrate functional feeding groups in ponds; and (2) β-diversity between natural and pine ponds is determined mainly by species nestedness. Five ponds in native grassland and five in a pine-planted matrix were sampled seven times from 2007 to 2009. The pine ponds had reduced macroinvertebrate richness and abundance, and different taxa and functional feeding groups. Comparing ponds in natural and cultivated pine areas, β-diversity as determined by nestedness did not differ from the value resulting from the turnover. Reduction of surface in ponds in pine areas may be one of the main causes for the lower macroinvertebrate richness and abundance because many taxa do not have adaptations to tolerate or escape the dry phase. Our results suggest that pine invasion has a negative impact on macroinvertebrate structure in southern Brazil coastal ponds.

Exotic pine invasion affects native wetland communities in the Southern Hemisphere by changing the hydrological regimen and physicochemical characteristics. Studies evaluating the emergence of aquatic invertebrates from dormant stages are vital to identify the resilience of aquatic communities in ponds invaded by exotic pine species. In the present study, we tested the hypotheses that: (1) pine invasion decreases the richness of drought-resistant aquatic invertebrates in ponds; (2) pine invasion modifies the invertebrate composition in ponds; and (3) these differences in species composition (β diversity) are associated primarily with species turnover. Dry sediment samples were collected from three natural ponds in native grassland and three ponds in a pine invasion matrix in southern Brazil. In all, 7205 invertebrates, primarily represented by cladocerans (18 species), were sampled after rewetting dry sediments. Pine invasion decreased the richness of aquatic invertebrates because the natural ponds had almost 60% more species and a higher number of estimated species than the pine ponds. The composition differed between natural and pine ponds, and this difference in species composition (β diversity) was associated primarily with the replacement of some species by others. The presence of pine appears to alter colonisation and survival rates of aquatic invertebrates that aestivate in dry sediments in southern Brazil wetlands.

The main goals of this study were: (1) test how beta diversity of aquatic macroinvertebrates varies among samples from different spatial scales in permanent and intermittent wetlands; and (2) test how beta diversity of aquatic macroinvertebrates varies among different wetland habitat types. Four collections were carried out over 1 year in 16 freshwater coastal wetlands in southern Brazil. The habitat types identified were: 1) hydrophytes, represented by submersed and floating plants; 2) reed-like emergent plants; and 3) leafy emergent plants. Additive partitioning of diversity was used to decompose the total variation in macroinvertebrate composition (regional diversity) into alpha (fine spatial scale) and beta components (intermediate and broad spatial scales). A total of 51,290 macroinvertebrates distributed among 63 families were collected. Additive partitioning of diversity showed similar patterns for both permanent and intermittent wetlands. In general, alpha diversity component was much lower than beta components. The beta diversity was greater among wetlands than among distinct habitats within wetlands. We found a strong evidence of scale dependence on diversity partitioning of macroinvertebrate communities, with beta diversity at broad spatial scale making a large contribution to total diversity in coastal wetlands of southern Brazil.