Search

Land use changes are considered a significant cause of amphibian declines worldwide. However, little is known regarding which land uses have more pervasive impacts and which help to supplement the biodiversity conserved in protected areas. In addition, amphibian species respond to a broad array of geographical constraints, which may blur responses to disturbance, depending on the species' natural history.Here, we explored whether functional diversity patterns of amphibian assemblages are linked to human land use while considering spatial autocorrelation and phylogenetic relatedness among species. We surveyed tadpoles along 500 km in coastal wetlands in southern Brazil and quantified four traits related to tadpole habitat use and predator avoidance.Spatial components influenced functional richness to a greater extent than land use. Functional evenness was higher in ponds surrounded by more exotic reforestation, and to a lesser extent an effect of crop area. Functional divergence was also associated with reforestation areas.Our results showed that some land uses (reforestation with exotic species and temporary crops) have more pervasive impacts on tadpole communities. Such changes in amphibian communities occurred even at low levels of landscape change. Our findings highlight that conversion to human land use requires complementary approaches (i.e., tadpole and adult responses) to provide early warning signals about habitat modification effects. [ABSTRACT FROM AUTHOR]

Understanding seasonal patterns of assembly mechanisms are key to comprehending the metacommunity dynamics of organisms inhabiting temporary habitats such as wetland macroinvertebrates. However, tests of the seasonal variation in assembly mechanisms of macroinvertebrates in wetlands with differing hydroperiods are rare, especially in the Neotropical region. We tested for seasonal patterns in the metacommunity assembly mechanisms of macroinvertebrates in small subtropical highland wetlands of southern Brazil with different hydroperiods. We also tested whether patterns varied between macroinvertebrate taxa with different dispersal modes. Macroinvertebrates were sampled in 12 wetlands classified into "short," "medium," and "long" hydroperiods (N = 4 in each category) in three seasons (fall, winter, and spring) over two full hydrological cycles (from 2012 to 2014). We assessed the role of spatial and environmental variables to metacommunity structure using distance‐based redundancy analysis and variation partitioning. Environmental and spatial variables explained macroinvertebrate metacommunity structure, although their relative influence markedly changed among seasons and hydroperiods. Environmental variables were important in fall and winter, whereas spatial variables predominated in spring. Different environmental variables influenced the metacommunity structure in each hydroperiod. Environmental variables influenced active‐dispersing macroinvertebrates, whereas the influence of environmental and spatial variables on passive‐dispersing taxa changed among seasons. We showed that the assembly mechanisms of macroinvertebrate metacommunities show a distinct temporal dynamic among wetlands with different hydroperiods. Our findings contribute to a more complete understanding of the metacommunity structure in temporary ecosystems. [ABSTRACT FROM AUTHOR]

The use of machinery and pesticides in modern agriculture are supposed to negatively affect the viability and diversity of invertebrate egg banks. Studies that evaluate the emergence of invertebrates through analysis of their dormant stages are needed in order to identify the resiliency of food webs in wetlands. In this study, the following hypotheses were tested: (1) richness is lower in conventional rice fields than in organic ones and natural wetlands; (2) richness is lower in older rice fields than younger fields; (3) composition varies among different rice systems and ages; and (4) emergence rate may vary among rice systems and ages over time. Dry sediment samples were collected from six rice fields cultivated under different systems, nine conventional rice fields with different cultivation ages and three natural wetlands. Our study showed that the richness was surprisingly higher in conventional rice fields than wetlands, with cladocerans being more associated with the former and insects more frequent in the latter. Invertebrate richness was similar among rice fields of different ages, but the composition differed between 20-year-old fields and younger fields. Variation in the viable resting stages found across different rice cultivation systems and ages contributes valuable information to wetland restoration initiatives. Many practices used in agriculture negatively affect the invertebrate egg banks. We evaluated the effects of different rice cultivation systems and ages on resting stages of wetland invertebrates in southern Brazil. The richness was higher in conventional rice fields than in wetlands, and the composition was modified by rice system and age. These results improve our understanding of local biodiversity changes due to the expansion of rice fields. [ABSTRACT FROM AUTHOR]