Ephemeroptera (Insecta) em riachos de uma paisagem cárstica do cerrado: diversidade, escala e relações com áreas florestais

Abstract

Studies with species inventories are important and provide information in several areas of the biology of the group under study, such as spatial distribution, biogeography, population and community ecology. The generated data can be considered a baseline of ecological and biodiversity information and allow a possible future application, helping in decisionmaking and conservation strategies. The order Ephemeroptera is one of the most important groups of aquatic entomofauna found in the most diverse types of aquatic ecosystems, associated with aquatic plants and sediment, where they actively participate in nutrient cycling and energy flow. An important factor in the distribution and availability of food for aquatic insects is the association between the aquatic environment and vegetation cover. The vegetation surrounding the rivers contributes to the functioning of the system, productivity, availability of resources and source of nutrients and organic matter. Understanding the relationship between species and their environment, as well as identifying the spatial scale at which species respond to landscape structure or the effect of scale, is a major challenge. This information can be important to assist decision makers in the management, maintenance and restoration of biodiversity and its habitats. This thesis is divided into two complementary chapters, the first being an exploratory survey of Ephemeroptera (Insecta) species in karst streams of the Brazilian Cerrado, where we present the distribution, new records and a list containing 35 species, 23 genera and six families of Ephemeroptera, found in the Bodoquena Plateau, adding important information about the knowledge of the insect fauna of karst streams. Camelobaetidius huarpe and Cloeodes vaimaca (Baetidae), Lumahyphes guacra (Leptohyphidae) and Ulmeritoides spinulipenis (Leptophlebiidae) are recorded for the first time in Brazil, while another 26 represent new records for Mato Grosso do Sul. In the second chapter, we tested the potential effect of scale change and operational definition on the percentage of forest cover, on trophic groups of the Ephemeroptera community (Insecta) from karst streams in the Brazilian Cerrado. We hypothesized that there would be a relationship between the richness and abundance of trophic groups in the Ephemeroptera community with the change in scale and operational definition in the percentage of forest cover, so that: i) the shredders would present a positive relationship with the increase in forest cover and a stronger effect in smaller buffers, considering that the species use the plant material available by the riparian vegetation; ii) the collectors would have a diffuse relationship and indifferent effect in relation to the size of the buffers, as they do not depend directly on the input of material from the riparian vegetation, as the species can consume the particulate matter produced by local shredders, as well as dissolved in the water and originating from from upstream areas; and iii) scrapers a negative relationship with the increase in forest cover and a stronger effect in larger buffers, considering that the species use matter from autotrophic production, which depends on the entry of light into the aquatic environment. Our results demonstrate that there is no ideal scale definition to work with for richness or species and a single definition of the buffer size can lead to misinterpretations. From a practical point of view, we believe that the best way is to include the procedure of testing for different metrics and classifications and not assume a priori scales. Although our data show that different functional groups may respond differently to landscape metrics, this strengthens the idea that the functional particularities of biota respond to different environmental conditions of the landscape. These results have implications for sample planning and conservation, as they demonstrate the need to test the scales to be worked on and also the need to describe the operational definition of forest used in each analysis, in order to avoid errors in interpretations and results. errors, as well as in the comparison of results in future works.