Filogeografia e modelagem de nicho ecológico de Aegla Leach 1820 (Crustacea, Anomura): um olhar sobre o passado e projeções para o futuro

Abstract

Endemic to southern South America, the family Aeglidae Dana, 1852 comprises only one current genus, Aegla Leach 1820, which has 89 described species. The eglids are distributed in Brazil, Argentina, Bolivia, Chile, Paraguay and Uruguay, in all the main hydrographic basins, being the only anomurans that exclusively inhabit freshwater environments, occurring mainly in rivers and streams. They play an important role in the trophic web and nutrient cycling, constituting an important component freshwater ecosystems’ fauna. However, eglids are the most threatened freshwater decapods in South America, with 70% of the species threatened with extinction, mainly attributed to the high rate of endemism in association with the degradation of aquatic ecosystems. In addition to habitat degradation, another important threat to eglids is climate change, which remains poorly studied for the group. This study investigated the processes related to the diversification and distribution of eglids in the past and the present, as well as the potential effects of future climate changes on the distribution of the genus and the species Aegla platensis and Aegla obstipa, which have wide and restricted distributions, respectively, aiming to contribute to the conservation of freshwater fauna. In chapter I, we evaluate the effects of future climate changes, generating ecological niche models for the present and for the years 2040, 2060, 2080, and 2100, for the genus Aegla, covering its entire area of distribution, and for the species A. platensis and A. obstipa. We also evaluated the efficiency of the environmental Protection Areas (PAs) to preserve the eglids, overlapping polygons from these areas on the generated models and quantifying the coverage of environmental suitability areas. The models indicated a decrease in the areas of potential distribution for Aegla, the disappearance of these areas in 2040 and 2060 for A. obstipa, and changes in reach for A. platensis, suggesting potential negative effects of climate change on the distribution of eglids, which are more severe for species with restricted distribution. The PAs showed low conservation effectiveness for the group, both in the present and in the future projections. This result highlights the importance of considering different taxa and the impacts of future climate change on the distribution of species for PA planning to improve the conservation of freshwater biodiversity. Chapter II investigated the biogeographic history of A. platensis integrating phylogeographic methods using mitochondrial markers and ecological niche modeling for past periods (Pleistocene: Last Interglacial and Last Glacial Maximum and Medium Holocene) and the present. The Pleistocene’s climatic oscillations showed signifiant influence in the diversification of A. platensis, which may be related to changes in aridity and humidity. The Last Interglacial’s mild and humid climate created favorable conditions for the diversification and colonization of new areas, in contrast to the cold and dry climate of the Last Glacial Maximum, which created adverse conditions for the species. Also, several events of dispersion and vicariance contributed to the current distribution of A. platensis. Since the Wolbachia bacterium infects many groups of arthropods, interfering in the mitochondrial DNA polymorphism and confusing the evolutionary inferences based on this marker, in chapter III, we investigated whether the eglids are hosts for Wolbachia. We obtained evidence against bacterium’s presence in the genus Aegla, an important finding that justifies the use of mitochondrial DNA in phylogeographic analyses. This dissertation’s data emphasize the urgent need to take measures for the conservation of eglids and freshwater fauna in general.