Different aspects of human activities can cause environmental change that endanger species persistence, alter species distributions, and lead to changes in antagonistic and mutualistic interactions, whereas deforestation and flooding of riparian forest results in landscapes consisting of patchily distributed riparian forest fragments in a matrix of pastures, plantations, and urban areas. Therefore, we assessed the richness, abundance, and trophic interactions of trap-nesting Hymenoptera and their parasites at four patches of restored riparian forest and at one reference natural fragment, of different sizes and ages, located at the Volta Grande Reservoir, in Minas Gerais and São Paulo states to answer the following questions: (1) Does the richness and abundance of cavity-nesting bees and wasps differ in riparian forest fragments according to the seasonal periods? (2) Does the composition of cavity-nesting bees and wasps vary among restoration and reference sites and between climate seasons (wet and dry)? (3) How do the degrees of specialization of the parasites vary among the patches of forest? We recorded 12 species of wasps, eight of bees, and nine species of parasites. Areas with longer time since restoration (reference site) showed higher species richness. However, the abundance was higher in most recent areas. The composition of bee and wasp assembly has not significantly changed between the climate seasons, although it is different between sampling areas. The richness and abundance were higher in warmer and rainy periods. The rate of bee and wasp mortality was high. The degree of specialization of parasites varies among sampling units, and the network of host-parasite interaction has a modular configuration with generalists and specialists. We concluded that the restored areas with more complex habitat could provide better conditions for the reestablishment of ecological interactions among these insects, the local flora, and other invertebrates, which together contribute to the success of the restored environments.

No abstract

The deforestation has led to local loss of species and important ecosystem services performed by them, causing ecological and economic losses. It is proposed that the reforestation of such areas aims to reduce those impacts. However, particularly in the tropics, little is known about the real success of different types of reforestation in the recovery of the species, and especially of the population parameters. Here we evaluated whether different types of reforestations affect Trypoxylon (Trypargilum) lactitarse Saussure (Hymenoptera: Crabronidae) in terms of abundance, percentage of emergence, proportion of males, fluctuating asymmetry, and foraging capacity. We compared primary forest (control) data to data collected in five different habitats: pasture, secondary forest, and tree plantations of Teak, Ficus, and a mixture of native species. The abundance of T. lactitarse was higher in tree plantations than in pasture. However, among the analyzed parameters, Teak plantation presented lower emergence percentage and the majority of individuals born were males. The emerged females in this habitat showed higher asymmetry and lower foraging capacity. Ficus showed lower individual abundance and mixed plantation showed lower emergence percentage, with both plantation types showing higher male emergence. On the other hand, in secondary forest, the analyzed parameters did not differ in relation to the primary forest, being the habitat more efficient in relation to those with tree planting. The changes in population parameters of T. lactitarse in different reforestations and particularly on Teak monocultures were probably attributed to indirect effects, such as low food availability and inadequate environmental conditions.

No abstract