Multiscale Anthropogenic Impacts on Stream Condition and Fish Assemblages in Amazonian Landscapes.

Land use change and forest degradation are resulting in pervasive changes to tropical ecosystems around the globe. While evidence from terrestrial systems demonstrates the severity of these disturbances for biodiversity conservation and provision of ecosystem services, the consequences for freshwater ecosystems remain poorly understood. This is especially true for the Amazon basin, the world's largest basin in both area and total discharge, and in particular for the complex network of low-order streams that make up the vast majority of its watercourses. These streams connect terrestrial and aquatic ecosystems throughout landscapes and host much, if not the majority, of the freshwater fish fauna of the Amazon basin, which itself is one of the most diverse in the world. Despite the biological significance of these stream networks, the consequences of land use change for the condition of instream habitat and fish fauna remain very poorly studied and understood. This thesis aims to address part of this knowledge gap by investigating the effects of anthropogenic disturbances occurring at multiple spatial scales on stream condition and fish assemblages from human-modified Amazonian forests in the state of Para, Brazil. The thesis starts by asking how instream habitat (composed of both water quality and physical habitat features) responds to landscape-scale anthropogenic disturbances and natural features (Chapter 2). Chapter 3 then investigates changes in fish species richness, abundance and composition following changes in both instream habitat and landscape-scale anthropogenic disturbance. Last, in Chapter 4 I attempt to disentangle the relative importance of those multiscale environmental predictor variables on species-specific disturbance responses, and evaluate the potential effectiveness of the Brazilian legislation in accounting for them. The thesis uses field data on fish assemblages, instream habitat, and natural features of streams as well as data on land use change at multiple scales of the surrounding landscapes from satellite images. A total of 99 low-order streams were surveyed from five river basins in two large regions (Santarem and Paragominas, both with more than 1 million ha) in the eastern Brazilian Amazon agricultural-forest frontier. I sampled a total of 25,526 fish specimens belonging to 143 species, 27 families and seven orders. Streams appeared to be exceptionally heterogeneous in their abiotic and biotic features. For instance beta diversity of fish assemblages between streams accounted for ca. 70% of the total (gamma) diversity in each river basin. Overall these findings underscore the importance of multiple land use changes and disturbances, at multiple spatial scales, in shaping instream habitat, including links between catchment-scale forest cover and water temperature, and the impacts of road crossings on channel morphology. Both landscape and instream habitat variables were isolated as having a marked effect on stream fish, but instream habitat differences were shown to be particularly important in explaining patterns of fish species abundance compared to other landscape factors that are more amenable to management such as the protection of riparian forest strips. However the results of the thesis also highlight the complexity of Amazonian stream systems and the difficulties in disentangling the effects of multiscale environmental predictor variables underpinned by naturally heterogeneous biophysical characteristics-with instream habitat and fish assemblages affected by a broad suite of drivers that often varied across river basins and regions. I use the findings of the thesis to discuss challenges and recommendations for the management and conservation of low-order streams in Amazonian human-modified landscapes. In particular I emphasize the need for catchment-wide collective management approaches that go beyond the protection of riparian forests within individual properties as prioritized by existing Brazilian environmental legislation. Keywords: forest-agriculture frontier, water quality, physical habitat, human-modified tropical forests, ichthyofauna, deforestation, road crossings

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear un derstanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5–7 vast areas of the tropics remain understudied.8–11 In the American tropics, Amazonia stands out as the world’s most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepre sented in biodiversity databases.13–15 To worsen this situation, human-induced modifications16,17 may elim inate pieces of the Amazon’s biodiversity puzzle before we can use them to understand how ecological com munities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple or ganism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region’s vulnerability to environmental change. 15%–18% of the most ne glected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lostinfo:eu-repo/semantics/publishedVersio

A social and ecological assessment of tropical land uses at multiple scales: the Sustainable Amazon Network

Science has a critical role to play in guiding more sustainable development trajectories. Here, we present the Sustainable Amazon Network (Rede Amazonia Sustentavel, RAS): a multidisciplinary research initiative involving more than 30 partner organizations working to assess both social and ecological dimensions of land-use sustainability in eastern Brazilian Amazonia. The research approach adopted by RAS offers three advantages for addressing land-use sustainability problems: (i) the collection of synchronized and co-located ecological and socioeconomic data across broad gradients of past and present human use; (ii) a nested sampling design to aid comparison of ecological and socioeconomic conditions associated with different land uses across local, landscape and regional scales; and (iii) a strong engagement with a wide variety of actors and non-research institutions. Here, we elaborate on these key features, and identify the ways in which RAS can help in highlighting those problems in most urgent need of attention, and in guiding improvements in land-use sustainability in Amazonia and elsewhere in the tropics. We also discuss some of the practical lessons, limitations and realities faced during the development of the RAS initiative so far.Keywords: Social–ecological systems, Tropical forests, Land use, Interdisciplinary research, Sustainability, Trade-off

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5,6,7 vast areas of the tropics remain understudied.8,9,10,11 In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepresented in biodiversity databases.13,14,15 To worsen this situation, human-induced modifications16,17 may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost

Physical habitat simulation for small-sized characid fish species from tropical rivers in Brazil

Physical habitat simulation (PHABSIM) is an important step of the instream flow incremental methodology (IFIM), which is applied to establish environmental flow regimes. This study applied the PHABSIM in two reaches of the Velhas river basin, whose long-term discharges are similar but are under different degrees of impact. Suitability curves were obtained for fish species using traditional methods (Astyanax sp., Piabarchus stramineus, Piabina argentea and Serrapinnus heterodon) and generalized additive models for fish density (Astyanax sp., P. argentea and S. heterodon). The results of habitat use depended on the method for curves generation. Applying the suitability curves by traditional methods, different discharge scenarios were simulated. The flow increasing from a dry scenario to a discharge of 1 year of return promotes a possible habitat increase for all species. However, the same hydrological flow percentiles produce different habitat proportions in different rivers. This work demonstrates that regardless of how suitability curves for the Neotropical species are generated, caution should be taken when applying them. However, the PHABSIM method allows more complex analyses than the traditional approaches based on minimal flow estimations, which is usually applied in South America.</jats:p

Deep barcode divergence in Brazilian freshwater fishes: the case of the Sao Francisco River basin

Background and aims. The application of DNA barcoding as a global standard for fish identification is probing diverse worldwide realms (Nearctic, Australian and the Neotropics) and environments (e. g. marine and freshwater). Comparing the patterns of sequence divergence among conspecific and congeneric taxa between realms can provide valuable information on recent evolutionary histories of lineages as barcode data accumulates. Materials and methods. Herein, we have analyzed over 100 species (around 50%) of the Neotropical fish fauna from the Sao Francisco River, in southeast Brazil. Our aims were to test the performance of DNA barcoding in this biodiversity-rich region, and to compare patterns of genetic divergence with previous studies. Results. The mean Kimura two-parameter distances within species, genera, families, orders, and classes were 0.5, 10.6, 21.0, 22.7, and 24.4%, respectively, with 100% of the species examined successfully differentiated by barcoding. With the exception of Astyanax bimaculatus lacustris, Piabina argentea, and Bryconamericus stramineus, all other species yield a single, cohesive cluster of barcode sequences. The average 'nearest-neighbor distance' was 11.12%, 21-fold higher than the mean within species distance of around 0.54%. In a few instances, deep lineage divergences among conspecifics (up to 10%) and congenerics (up to 22.9%) taxa were revealed. Conclusions. Reflecting possible cases of cryptic speciation and the deeper phylogeographic history of Sao Francisco fish fauna, with some higher clades extending back into the late Cretaceous and Cenozoic (90 mya), when much of the diversification of the Neotropical region apparently took place. In addition, barcodes also highlighted misidentifications and helped to document range extensions for known species.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq