Espécies especialistas, generalistas e raras de Odonata (Insecta), em igarapés da Floresta Nacional de Carajás, Amazônia

Abstract

Aquatic ecosystems are constantly affected by various anthropogenic activities. The deforestation of riparian vegetation in streams for the cultivation of short- or long-cycle monocultures, pastures, urbanization, mining, among others, alters the environment. These changes directly impact aquatic insect communities, such as those of the order Odonata, which exhibit high sensitivity to environmental changes, especially the suborder Zygoptera, which has a higher number of specialist species in preserved areas compared to the suborder Anisoptera. Our objective was to assess the occurrence of generalist, specialist, and rare Odonata species in streams inside and outside the Carajás National Forest (FLONA). The collection was conducted in 21 streams located in the region inside and outside FLONA Carajás, in October 2022 and September 2023. In each stream, a 100-meter section was defined and subdivided into 20 segments of 5 meters each. Specimens were captured using entomological nets (sweep nets) between 10:00 AM and 2:00 PM. The specimens were stored in the field in parchment paper envelopes until they arrived at the laboratory. After identification, they were added to the collection of the Ecology Laboratory (LABECO) at the Federal University of Pará – UFPA, Altamira Campus. The Habitat Integrity Index (HII) was applied in all streams to assess the level of physical integrity of these environments. To evaluate species occurrence, we performed two data analyses: the Multinomial Species Classification Test (CLAM) and simple linear regression, using the R environment. We collected 605 specimens, belonging to eight families, 30 genera, and 71 species. Our study found that only species from the suborder Zygoptera were classified as specialists in environments both inside and outside the forest, as well as generalists in habitat use. The habitat integrity index negatively influenced the richness of rare species. Species from the suborder Zygoptera are usually more present in environments with higher integrity due to their eco-physiology. Rare species may be at greater risk of extinction due to their low abundance. Therefore, the removal of vegetation tends to harm species with specialist behavior in more intact areas, in addition to having a negative effect on species classified as rare.