Responses of stream fish assemblages to timing and extent of deforestation in Western Amazon

Author(s)

Gabriel Lourenço Brejão

• Document type: Doctoral Thesis
• Press: São José do Rio Preto. 2018-08-23.
• Institution: Universidade Estadual Paulista (Unesp). Instituto de Biociências Letras e Ciências Exatas. São José do Rio Preto
• Defense date: 2018-05-04
• Advisor: Lilian Casatti; David Joseph Hoeinghaus; Silvio Frosini de Barros Ferraz

Abstract

The streams of the Neotropical region harbor a small-sized fish fauna, frequently with limited geographical distribution and, generally, highly dependent on riparian vegetation for feeding, shelter, and reproduction. The watershed native vegetation removal is one among several modifications, which effects on aquatic environments are not entirely understood yet. The knowledge of deforestation history along with current landscape structure enhances the power of analysis to evaluate ecological deforestation effects. Moreover, distinct ways of deforestation process might affect the fish community composition and functioning. The Machado river, in Rondônia, an important tributary of Amazon basin, exhibit high diversity and endemism and presents a recent history of high deforestation and land use intensification, which can cause profound changes in aquatic environments. Thus, the general aim of this Thesis is to comprehend how deforestation process influences the ichthyofauna. To reach this aim, we analyzed the relation between fish species abundance to environmental gradients of time and extent of deforestation, to detect which species were strongly affected – positively or negatively – by deforestation (Chapter 1). Knowing the fish species responses, we determined how fish assemblage composition and structure was related to deforestation time and intensity (Chapter 2). We end the study by presenting how the environmental components influenced the taxonomic and functional turnover rates, considering the process age – recent or old deforestation (Chapter 3). In Summary, we found that (1.) Stream fish populations present distinct responses to deforestation time and extent, regarding their taxonomic and functional structures, most negative threshold responses occurred at low levels of deforestation and soon after impact, so even in minimal change is expected to affect biodiversity ! negatively. Delayed positive threshold responses to extreme deforestation by a few species do not offset the loss of sensitive taxa and likely contribute to biotic homogenization; (2.) The sensitive fish richness and abundance lost occurred synchronically to the habitat structure loss, but there was a time-lag response for habitat homogenization indicators, and tolerant fish richness and abundance increase followed this time-lag; and (3.) Species/functional traits turnover was different than expected by chance, indicating that deterministic processes are structuring this stream fish community. Although we found a high species turnover, functional traits turnover was lower than the expected by the species turnover. It means that taxonomically dissimilar, but functionally similar, suggesting that the species turnover is occurring mainly among functionally equivalents species. In conclusion, by adding the temporal layer to analyze the initial stage of land use changes in this portion of Amazon, was possible to verify the extreme sensitivity of fish assemblages to deforestation. And there is possible to consider stream fish as a flag group to be included on conservation plannings, aiming to reduce the effects of biodiversity loss on a regional scale. (AU)

• FAPESP's process: 12/21916-0 - Relationships among the deforestation process and the fish diversity patterns at Western Amazon streams
• Grantee: Gabriel Lourenço Brejão
• Support Opportunities: Scholarships in Brazil - Doctorate