Floodplains comprise a complex mosaic of seasonally-flooded forests, lakes and channels that support productive fisheries. These habitats and their fish populations are increasingly threatened by a ...variety of human pressures, including floodplain deforestation. However, the effects of multiple human pressures on these floodplain fisheries have not been studied in the Amazon River. Here, we investigated the combined effects of forest cover, river water level, fishing effort and distance from nearest urban center on the catch of the most exploited fish taxa. Our study integrated fisheries, hydrological, geographical, and satellite land cover change data for 21 floodplain lake systems over a ten-year period. We found that an ANCOVA model explained 91% of the variation in catch (p < 0.001) and, as usual, fishing effort was the most influential variable. Floodplain forest exerted a positive effect on fish catch, implying that a loss of 1 km2 of floodplain forest induces up to 9% decreasing in fish catches. In addition, high river water level and distance from urban centers also had a positive effect on fish catches; even though, low river water levels did not present such effect. These results provide support to previous findings regarding the effects of habitat, hydrological, and human variables on floodplain fish catch. More importantly, these results provide the first ever quantitative evidence of the effect of floodplain deforestation on fish catch. Our findings point out the need to develop an ecosystemical approach to manage floodplain fisheries in the Amazon and elsewhere in the world.
Aim
The central and western Amazonia underwent several landscape changes during the Quaternary. Whereas the Riverine Barrier Hypothesis is traditionally used to explain the influence of rivers on ...speciation, processes such as river rearrangements have been overlooked to explain the geographic distribution and evolutionary history of Amazonia biota. Here, we tested how river rearrangements influenced the evolutionary history of uakari monkeys, genus Cacajao, a primate genus primarily associated with seasonally flooded forests in central and western Amazonia.
Location
Central and Western Amazonia.
Taxon
The genus Cacajao, including the black uakaris (C. melanocephalus, C. ayresi, C. hosomi); and the bald‐headed uakaris (C. calvus, C. amuna, C. rubicundus, C. ucayalii, C. novaesi).
Methods
We performed a continuous phylogeographic analysis using 77 cytochrome b sequences to identify the origin and dispersal of Cacajao lineages. We used genome‐wide SNP variation (ddRADseq) to investigate population structure, gene flow and demographic history in Cacajao populations and used digital elevation models to identify landscape and riverscape characteristics that may have influenced the geographic distribution of Cacajao.
Results
Our continuous phylogeographic reconstruction pointed out that the ancestral Cacajao lineage occupied the flooded forests of the Solimões River, in central Amazonia, at ~1.7 Mya and descendant lineages dispersed throughout central and western Amazonia more recently. We identified gene flow in both black and bald‐headed uakari populations, even across rivers considered barriers (e.g. the Negro River). Landscape analysis showed that river rearrangements influenced the geographic distribution and population structure in Cacajao. Historical demographic analyses suggest varied scenarios of population size changes among Cacajao monkeys consistent with periods of intense dynamism in flooded habitats and the formation of non‐flooded upland forests.
Main Conclusion
Our results support that the river rearrangements have shaped the geographic distribution and divergence of recently diverged Cacajao lineages. Landscape and riverscape changes, along with retractions of the flooded forests, isolated some Cacajao populations in floodplain areas. Our study also suggests that these events led to the recent changes in demographic histories in species with a restricted geographic distribution.
Understanding the interactive relationships between organisms is key to understanding community structure and planning appropriate conservation measures. Even more so for plant-plant interactions, ...which are poorly understood. We studied the vascular epiphyte community and its interactions with the tree community (phorophytes) in Amazonian black-water floodplain forests (igapó), analyzing 58 floristic inventory plots located along a 517 km stretch of the Brazilian Negro River, in the Central Amazon. The vascular epiphytes and trees were identified and quantified, and the physical attributes of the bark were measured, as well as the diameter at breast height (DBH) of the tree species. A total of 2746 trees ≥ 10 cm DBH were inventoried, of which 969 were phorophytes (35.29%), hosting 4692 individuals of epiphytic species, belonging to 17 families 50 genera, and 106 species.
Pouteria elegans
was the most abundant phorophyte, however,
Aldina latifolia
showed proportionally higher richness and abundance of epiphytes.
Codonanthopsis crassifolia
was the epiphyte that colonized most of the phorophytes and showed the highest Epiphytic Importance Value (EIV). The average values for thickness, saturated weight, water retention capacity, and diameter were significantly higher in the tree species that housed vascular epiphytes. In addition, the vascular epiphyte richness (
R
2
m = 0.32;
R
2
c = 0.41) and abundance (
R
2
m = 0.36;
R
2
c = 0.90) were strongly influenced by larger diameters of phorophytes and their saturated bark weight. Our results confirm the importance of phorophyte size (DBH) for epiphyte colonization, present the most complete epiphyte list of Amazonian black-water floodplain forests and provide evidence that physical attributes of tree bark drive the structure of vascular epiphyte-phorophyte interactions.
On the Mekong River, north of Stung Treng town in northeastern Cambodia, and below the border with Laos, lies an area of riverine seasonally flooded forest designated as an internationally ...significant Ramsar wetland site because of its exceptional biodiversity and importance to livelihoods. This article reports on the cumulative and cascading impacts of numerous upstream hydropower dams in China and Laos on this vital ecosystem due to the release of water during the dry season, which prevents the flooded forest from undergoing its critically important drying out period. In particular, we investigate the damage being wrought on these flooded forests and on the various species dependent on them. Different species have been variously affected, but some have been largely destroyed. Others are being increasingly impacted. This habitat loss is negatively affecting fisheries, especially for a number of Pangasiidae catfish and Cyprinid carps, which is having an adverse effect on local livelihoods. New dams upriver, and continued high dry-season water from existing dams, are likely to lead eventually to the increased degradation and possibly the eradication of the flooded forests along the mainstream Mekong River, unless measures are taken to address the problem.
The Altillanura is a unique ecosystem within the Colombian Llanos, characterized by well-drained savannas and extensive riparian forests. The Altillanura harbors a rich assemblage of species, largely ...understudied and currently under threat by large-scale and unplanned agribusiness. Moreover, the number of public protected areas in the Colombian Llanos, particularly in the Altillanura, is insufficient to conserve the threatened habitats and species. Therefore, conservation efforts by private reserves are crucial for the protection of the region’s biodiversity. Here we present the first species list of the Tomogrande, a private nature reserve and scientific research field station in the municipality of Santa Rosalía, Vichada, Colombia. After ten years of ongoing research, we have recorded 299 species of plants, 189 species of birds, and 47 species of mammals. Compared to other private nature reserves in Vichada and the Tuparro National Park, the largest protected area in the region, Tomogrande makes a substantial contribution to the conservation of all three taxonomic groups. We advocate that better landscape planning and sustainable practices should become mandatory in the Altillanura to protect its biodiversity and the livelihoods of all stakeholders that inhabit this region.
Aim
To investigate the geographic patterns and ecological correlates in the geographic distribution of the most common tree dispersal modes in Amazonia (endozoochory, synzoochory, anemochory and ...hydrochory). We examined if the proportional abundance of these dispersal modes could be explained by the availability of dispersal agents (disperser‐availability hypothesis) and/or the availability of resources for constructing zoochorous fruits (resource‐availability hypothesis).
Time period
Tree‐inventory plots established between 1934 and 2019.
Major taxa studied
Trees with a diameter at breast height (DBH) ≥ 9.55 cm.
Location
Amazonia, here defined as the lowland rain forests of the Amazon River basin and the Guiana Shield.
Methods
We assigned dispersal modes to a total of 5433 species and morphospecies within 1877 tree‐inventory plots across terra‐firme, seasonally flooded, and permanently flooded forests. We investigated geographic patterns in the proportional abundance of dispersal modes. We performed an abundance‐weighted mean pairwise distance (MPD) test and fit generalized linear models (GLMs) to explain the geographic distribution of dispersal modes.
Results
Anemochory was significantly, positively associated with mean annual wind speed, and hydrochory was significantly higher in flooded forests. Dispersal modes did not consistently show significant associations with the availability of resources for constructing zoochorous fruits. A lower dissimilarity in dispersal modes, resulting from a higher dominance of endozoochory, occurred in terra‐firme forests (excluding podzols) compared to flooded forests.
Main conclusions
The disperser‐availability hypothesis was well supported for abiotic dispersal modes (anemochory and hydrochory). The availability of resources for constructing zoochorous fruits seems an unlikely explanation for the distribution of dispersal modes in Amazonia. The association between frugivores and the proportional abundance of zoochory requires further research, as tree recruitment not only depends on dispersal vectors but also on conditions that favour or limit seedling recruitment across forest types.
Islands and analogous insular habitats are found in several ecological contexts. With the exception of oceanic islands, however, the contribution of these insular habitats to regional biodiversity ...remains poorly investigated, especially in tropical regions. We investigated the understory spider assemblages in an Amazonian river archipelago to evaluate the contribution of fluvial islands to regional spider diversity.
We collected spiders on 30 islands ranging from 1 to 1527 ha and at 23 sites in mainland habitats represented by continuous igapó flooded forests and terra firme forests. Spiders were collected by shaking the vegetation over a white sheet during a standardised time of 30 min.
From 1404 adult individuals, we identified 290 spider species or morphospecies, with 150 species being recorded on the fluvial islands, 122 in the igapó flooded forests and 103 in the terra firme forests. Spider assemblages of fluvial islands exhibit lower alpha diversity and equitability compared with mainland habitats. The species composition of fluvial islands was significantly distinct from that of mainland habitats, even when compared with neighbouring igapó flooded forests. Several families and species of spider were significantly associated with a particular habitat, including 8 families and 10 species identified as indicators of fluvial islands.
Fluvial islands effectively contribute to regional diversity since their spider fauna is not a mere impoverished subset of species from mainland habitats. Events that alter the flood pulse in Amazonian rivers (e.g., construction of hydroelectric dams) could threaten the unique biological assemblages of the floodplain habitats, especially the fluvial islands.
Islands are conspicuous features of the Amazon riverine landscapes, but their spider fauna was not yet investigated.
Amazonian fluvial islands contribute to regional spider diversity since their species composition was significantly distinct from that of mainland habitats.
Anthropogenic disturbance that alter the flood pulse in the Amazonian rivers could threaten the biologically distinctive spider assemblages of fluvial islands.
Flooded forest is one of the most important fish habitats in Neotropical rivers, and one that is increasingly subjected to negative impacts from logging, agriculture, and other human activities. The ...purpose of our study was to test quantitatively whether fish richness and abundance in Amazonian floodplain lakes are associated with the area of flooded forest. We sampled fish and several other variables in 35 Amazonian floodplain lakes during the high-water season. Our results highlighted that fish richness and abundance were directly related to flooded forest, inversely related to distance from the river, and influenced by dissolved oxygen concentration <1 mg l⁻¹. The same result applied to fish richness and abundance landed by fisheries. Other variables such as depth and area of open water habitat were also related but the results were less consistent and apparently reliant on sampling methodology. Our results suggest that conservation of the flooded forest is critical for the maintenance of fish assemblages in the Amazon, and that removal of flooded forest will reduce fish richness, fish abundance, and fisheries yield.
Approximately 500 native edible fruits are known from Brazil with nearly 50% of these occurring in the Amazon. Pollen morphology of Brazilian plant species is poorly known yet it is important for ...scientific research. The aim of this study is to document the pollen morphology of 30 native edible fruit species belonging to 13 families. Following acetolysis the pollen was examined by light microscopy. Pollen grains ranged from small to very large. Prolate spheroidal and subprolate shapes predominated in most species, and most pollen grains had outline triangular to subtriangular. Polyads, tetrads and monads were observed, and the aperture arrangement varied from inarperturate to colpate and colporate, with the majority being 3-colporate and having a reticulate sexine. The species documented will contribute to pollen flora of Brazil and the information used in melissopalynollogical studies.
O presente estudo objetivou avaliar a dinâmica de populações arbóreas em fragmentos florestais em São Sebastião da Bela Vista, MG. Para isso, todos os indivíduos arbóreos com diâmetro na altura do ...peito (DAP) maior do que 5 cm, presentes nas unidades amostrais, foram medidos (DAP e altura) e identificados no ano de 2005 e monitorados nos anos 2007 e 2009 (remedição e verificação de mortalidade), quando também foram medidos os indivíduos que alcançaram o diâmetro mínimo de inclusão por ocasião de um eventual recrutamento. Foram calculadas as taxas de dinâmica anual (mortalidade, recrutamento, rotatividade e mudanças líquidas) para todas as populações. Foi observada instabilidade da dinâmica, indicada pela redução constante da abundância e pelo maior número de espécies com balanço negativo de número de indivíduos (período 2005 a 2007 = 13 e 2007 a 2009 = 17) do que balanço positivo (2005 a 2007 = 9 e 2007 a 2009 = 14). As mudanças de riqueza foram insignificantes, com o ganho de duas espécies e o desaparecimento de uma. O estudo demonstrou que, apesar de não apresentar mudanças qualitativas (composição florística), a área demonstrou instabilidade estrutural, com mais populações com maior taxa de mortalidade que de recrutamento.
PDF