Aim: The Amazon rainforest has approximately 23% of its sampled area dedicated to bats, making it one of the least sampled and most diverse regions for bats in Brazil. The lack of sampling results in a lack of knowledge regarding the accurate geographical distribution of bat species. This lack is referred to as the Wallacean shortfall, which should be addressed with primary data obtained from in situ collections. However, the use of Species Distribution Models (SDMs) can help alleviate this gap. Location: The states of Pará and Acre are located in the Brazilian Amazon. Methods: So, our objective is to decrease the Wallacean shortfall concerning Amazonian bat species. To achieve this, we provide (i) a list of bat species sampled in the states of Pará and Acre in the last five years (2017 to 2022); (ii) the potential distribution of species considered as new occurrences for the region; and (iii) the potential distribution of species classified as Data Deficient (DD) and Near Threatened (NT) according to the IUCN classification. Results: With 96 nights of collection and 129,600 m 2h of mist netting, we obtained 75 bat species, with an estimated total of 94.78 species. Additionally, 21 species were considered as range extensions. Main conclusions: The Brazilian Amazon region has a vast geographic expanse and few established research centers, resulting in a limited sampling of bats and other biological groups. Furthermore, we draw attention to the significant number of bat species with expanded geographical distributions, with 21 out of the 75 sampled species. This should be a reminder that primary biogeographic data is still necessary for the neotropical region.
Also investigate how the potential distribution of this species changes with the addition of new records over the decades (decade effect). Assuming that (1: hypothesis of the effect of the decade) the addition of new occurrence records over time increases the potential size of the species distribution; and (2: Wallacean distance hypothesis) over the years, the new points added are increasingly distant from the research centers. Considering the geographic knowledge gap of Histiotu velatus, our objective is to report a new record of this species and estimate its potential distribution in South America through ENMs. For this, we compiled records of occurrence of species, selected from 1900 to 2015. We used 19 bioclimatic variables available in the WorldCLim database to estimate the potential distribution of the species and we used three modeling algorithms: Maximum Entropy (MXT) Random Forest (RDF) and Support Vector Machine (SVM). We selected the main bat research centers in Brazil, using the Lattes platform for the Wallacean distance hypothesis, using the Euclidean distance calculation. To test the hypothesis of the decade effect, we used beta regression analysis, taking conservative and non-conservative approaches. The results showed that the predicted area expanded and retracted over the decades, with an improvement in the accuracy of the models with the addition of new data. Most of the records are located in the southeastern region of Brazil, but the algorithms predicted areas in countries where there were no records. Only the conservatism approach has had a positive relationship over the decades. The distance from new points does not increase over the years of research centers.