Padrões de diversidade taxonômica, funcional e filogenética na estruturação das assembleias de peixes em três estuários tropicais

Abstract

Estuaries are important coastal ecosystems attractive for fish to use during their life cycle as nursery, feeding grounds, protection and/or reproduction areas. The species distribution pattern in these ecosystems is influenced by the environmental heterogeneity and spatial connectivity. These two conditions have been the focus of several metacommunity studies to understand how environmental processes and dispersal determine patterns. How species respond to environmental conditions depends on their set of functional traits which are reflections of the species evolutionary history. In this context, the main objective of the thesis is to evaluate how metacommunities patterns and taxonomic, functional and phylogenetic diversities of fish assemblages are structured in tropical estuaries with different degrees of anthropogenic pressure. The work results aim to explain how distinct spatial scales interact to drive the species distribution and occurrence locally. Additionally, this work aimed to investigate hydrological condition influences in functional diversity in Mamanguape river estuary over 7 years. Sampling surveys were conducted in three estuaries located along Paraíba coast: the Mamanguape, Paraíba and Gramame river estuaries in 2019. Database from 2011 to 2019 was used to study interannual variation on functional diversity of estuarine fishes in Mamanguape river estuary. These results evidenced hat environmental conditions contributed in different ways spatio-temporally for species distribution. In summary, the difference in organic matter concentration and vegetation cover resulted in the landscape-scale Clementsian structure, salinity, NOx and fine sand resulted in the Q-nested structure for Mamanguape and Paraíba estuaries and Q-Clementsian structure in Gramame estuary, respectively. It is worth highlighting that environmental conditions had a greater influence on species identity spatially, resulting in a higher beta taxonomic diversity proportion, but lower beta functional and phylogenetic diversity. This result indicated that functional redundancy was higher along the estuary due to environmental filtering. However, the similarity in the contribution of alpha and beta taxonomic diversity in the Gramame estuary suggests that spatial connectivity is the limiting factor for the transit of marine species. The higher degree of phylogenetic signal of the fish assemblages in this estuary suggests that phylogenetically close species share the same functional space, and the likely lower distant phylogenetic species frequencies were also due to the restricted connectivity of this estuary. Temporally, environmental conditions were determinants of functional diversity and functional traits, with increasing salinity inducing increased functional divergence and estuarine dependent marine species. Because salinity favored the occurrence of marine species that increased niche differentiation in the estuary. Overall, these results support the hypothesis of marinization of the Mamanguape estuary. In this perspective, we provide knowledge which can be used for decision-making for establishing conservation areas and management of natural resources based on the conservation of ecological processes for fish assemblages that ensure the maintenance of the functioning of estuarine ecosystems.