Name: Diego de Souza Bretas
Type: MSc dissertation
Publication date: 29/11/2021

Namesort descending Role
Leonora Pires Costa Advisor *

Examining board:

Namesort descending Role
Ana Carolina Loss Rodrigues Internal Examiner *
Guilherme Siniciato Terra Garbino External Examiner *
Leonora Pires Costa Advisor *

Summary: Abstract: The water opossum (Chironectes minimus) is one of really few semi-aquatic marsupial species known in the Neotropical region. Morphologically, it is a very peculiar animal, which presents a series of adaptations similar to those found in otters. Its conservation status varies, depending on the spatial scale observed and, due to its lifestyle, it ends up being underrepresented in inventories based on traditional capture techniques. As a consequence, it is poorly understood in terms of its basic ecological aspects. Historically, its geographic distribution is not uniform, generating inconsistencies about its classification. It is well known that it is essential to understand the distribution of any given species as an essential step on the development of efficient strategies for the conservation of biodiversity, both currently and in future environmental scenarios. Modern tools, such as Species Distribution Models, are able to predict the potential distribution of various taxa, based on occurrence records and environmental variables relevant to their persistence. In this context, this study estimated the geographic distribution of current watershed and in different future scenarios, from the elaboration of species distribution models, using MaxEnt 3.4.1 and RStudio software. We used 480 occurrence records and ten bioclimatic variables in the elaboration of both current distribution models and in different future environmental scenarios. Based on the generated models, we can see the expansion of the potential geographic distribution of C. minimus currently known by the IUCN, reinforcing the need for its update. Regarding the geographic distribution of the species in the future, we could observe the contraction of environmentally suitable areas according to the increase on the intensity of global warming effects. Large portions of environmentally suitable areas for its persistence in the equatorial zone are lost, leaving only small isolated patches between South and Central America, in the Guianas region and in the southern and southeastern portion of Brazil. Some regions remained stable in relation to the probability of occurrence of the species, which may represent an indication of greater success in choosing future locations for studies involving C. minimus. The compilation of the new occurrence records in a complete database allowed us to elaborate more accurate distribution models, filling some important gaps in the current geographic distribution of the water opossum. Regarding the type of geographic distribution presented by the species, our results suggest that, although some gaps exist, the species has a continuous distribution. However, in different future scenarios, even in the most optimistic, the distribution is fragmented, which can lead to the interruption of the gene flow between the separated populations and, thus, influence the process of differentiation between subgroups or their local extinction and/or global. All the models created showed that environmental changes resulting from global warming processes are factors that greatly affect the environmental suitability in several areas of the potential distribution of watershed and, consequently, increase its extinction risk. So, with the objective of conservation in the medium to long term, future efforts should focus on reducing habitat loss, restoring natural habitats already identified and expanding and creating new areas of environmental protection encompassing the geographic distribution of the species. We also suggest that future studies should be emphasized in the Guianas, Amazon region and central parts of Brazil. We confirm the use of computational modeling as an efficient tool in predicting the most likely areas for the occurrence of the water opossum, especially in the delineation of paths for future sampling efforts.

Key words: Geographic distribution; models; water opossum; Chironectes minimus

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