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The evolution of polymorphism in the warning coloration of the Amazonian poison frog Adelphobates galactonotus
No full textWhile intraspecific variation in aposematic signals can be selected for by different predatory responses, their evolution is also contingent on other processes shaping genetic variation. We evaluate the relative contributions of selection, geographic isolation, and random genetic drift to the evolution of aposematic color polymorphism in the poison frog Adelphobates galactonotus, distributed throughout eastern Brazilian Amazonia. Dorsal coloration was measured for 111 individuals and genetic data were obtained from 220 individuals at two mitochondrial genes (mtDNA) and 7963 Single Nucleotide Polymorphisms (SNPs). Four color categories were described (brown, blue, yellow, orange) and our models of frog and bird visual systems indicated that each color was distinguishable for these taxa. Using outlier and correlative analyses we found no compelling genetic evidence for color being under divergent selection. A time-calibrated mtDNA tree suggests that the present distribution of dorsal coloration resulted from processes occurring during the Pleistocene. Separate phylogenies based on SNPs and mtDNA resolved the same well supported clades, each containing different colored populations. Ancestral character state analysis provided some evidence for evolutionary transitions in color type. Genetic structure was more strongly associated with geographic features, than color category, suggesting that the distribution of color is explained by localized processes. Evidence for geographic isolation together with estimates of low effective population size implicates drift as playing a key role in color diversification. Our results highlight the relevance of considering the neutral processes involved with the evolution of traits with important fitness consequences. © 2019, The Author(s), under exclusive licence to The Genetics Society
Effects of natural light and depth on rates of photo-oxidation of dissolved organic carbon in a major black-water river, the Rio Negro, Brazil
No full textSystems rich in terrigenous dissolved organic carbon (DOC), like the Rio Negro, can contribute significant amounts of carbon dioxide back to the atmosphere and support important microbial communities. We investigated photo-oxidation in the Rio Negro: (1) the depth to which light causes complete photo-oxidation to CO2 and changes in DOC structure, (2) the daily rate of change of absorbance indices, (3) the relationship between sub-surface rates of photo-oxidation to CO2 and light exposure, (4) the areal rates of photo-oxidation, and (5) the stability of fluorophore signals. Experiments were run in an outdoor pool of Rio Negro water, under natural sunlight during the dry seasons of 2015 and 2018. In 2018, rates of complete photo-oxidation and changes in absorbance indices decayed exponentially, approaching their asymptotes between 9 and 15 cm depth. In 2015, direct absorbance indices ceased changing at 14 cm depth. Fluorescence of humic acid-like moieties continued to decrease, sometimes to 35–43 cm depth. This indicates that partial photo-oxidation of DOC, and thus interaction with the microbial community, occurs to greater depths than previously expected. Areal rates of CO2 production were 28.8 and 39.3 mg C m−2 d−1 (two experiments, October 2018). Sub-surface (1.1 cm) rates were strongly related to light levels, reaching a maximum of 0.68 mg C l−1 d−1 in September. Complete photo-oxidation ceased below 29.6 mW cm−2 d−1 UV radiation, providing a daily baseline for observable production of CO2. Absorbance indices changed by 9 to 14% d−1 at high light levels, except for R254/365 (4.4% d−1). Fluorophore emission ranges were stable between 2014 and 2018, indicating that emissions can be compared across time and space. This study contributes to better estimates and understanding of photo-oxidation in tropical, black-water rivers, which will be useful for carbon modelling. © 2020 Elsevier B.V
Different patterns of nutrient cycling in contiguous phytophysiognomies of Atlantic Forest, Brazil
Get PDFThe present study aimed to evaluate fine aboveground litterfall, deposition of nitrogen and phosphorus from total litterfall and leaf litter decomposition in areas of tall forest (Mata Alta) and low forest on sandy soils (Mussununga) in southeastern Brazil. Fine litterfall was collected monthly for two years (from June/2007 to May/2009) in 10 conical collectors (0.25 m2) in each phytophysiognomy (1 ha plots). The material was subsequently separated into leaves, branches, flowers and fruits, and unidentified material. Leaf decomposition rates were evaluated using 15 litterbags, three of which were collected every 30 days. Higher litterfall occurred in both phytophysiognomies during the rainy season, with leaves predominating. The lowest litterfall, nutrient input, and leaf litter decomposition values appeared to be nutrient conservation strategies, contributing to the ecological functioning of the Mussununga where soil fertility was lower than in the Mata Alta. © 2020 Universidade Federal Rural do Rio de Janeiro (UFRRJ)
Anticancer and Immunomodulatory Activities of a Novel Water-Soluble Derivative of Ellipticine
No full textClimatic and edaphic controls over tropical forest diversity and vegetation carbon storage
Get PDFTropical rainforests harbor exceptionally high biodiversity and store large amounts of carbon in vegetation biomass. However, regional variation in plant species richness and vegetation carbon stock can be substantial, and may be related to the heterogeneity of topoedaphic properties. Therefore, aboveground vegetation carbon storage typically differs between geographic forest regions in association with the locally dominant plant functional group. A better understanding of the underlying factors controlling tropical forest diversity and vegetation carbon storage could be critical for predicting tropical carbon sink strength in response to projected climate change. Based on regionally replicated 1-ha forest inventory plots established in a region of high geomorphological heterogeneity we investigated how climatic and edaphic factors affect tropical forest diversity and vegetation carbon storage. Plant species richness (of all living stems >10 cm in diameter) ranged from 69 to 127 ha-1 and vegetation carbon storage ranged from 114 to 200 t ha-1. While plant species richness was controlled by climate and soil water availability, vegetation carbon storage was strongly related to wood density and soil phosphorus availability. Results suggest that local heterogeneity in resource availability and plant functional composition should be considered to improve projections of tropical forest ecosystem functioning under future scenarios
Effects of Forest Fragmentation on Feather Corticosterone Levels in an Amazonian Avian Community
Get PDFEffects of Phylloicus case removal on consumption of leaf litter from two Neotropical biomes (Amazon rainforest and Cerrado savanna)
No full textPhylloicus (Trichoptera, Calamoceratidae) is a stream invertebrate widely distributed across Neotropical biomes, which larvae use allochthonous leaf litter as food resource and to build a case that offers protection against predation. Seasonal changes in leaf litter accumulation on the streambed may affect Phylloicus larvae due to variations in availability of food and case-building material; however, it is unclear how these two processes influence each other. We assessed how case removal affected leaf litter consumption by Phylloicus larvae from two Neotropical biomes (Amazon rainforest and Cerrado savanna), which were experimentally offered leaf litter of Goupia glabra and Maprounea guianensis (common riparian species from the rainforest and savanna biomes, respectively). Our treatments included (i) direct effect of case removal, where larvae had their case removed during the experiment; (ii) time-lag effect, where the case was removed and larvae were allowed to rebuild the case before starting the experiment; and (iii) control, where cases were not removed. Leaf litter consumption by Phylloicus was 9.16 ± 7.47 mg/mg on average, being higher in the savanna than in the rainforest experiment (possibly in relation to a higher difference between the rainforest stream temperature and the experimental temperature, which may have inhibited larval activity), and higher on M. guianensis than on G. glabra (most likely due to the higher leaf litter quality of the former species). Consumption was higher in the time-lag effect treatment than in the direct effect and control treatments, which could be explained by an increase in the larval energetic demand for case building. © 2020, The Japanese Society of Limnology
Lysine demand and essential aminoacids estimate for tambaqui, Colossoma macropomum (Cuvier, 1818)
No full textPurine levels and purinergic signaling in plasma and spleen of Brycon amazonicus exposed to acute heat thermal stress: An attempt to regulate the immune response
No full textEffect of Structural Variation of Dead Trunks on Passalid (Coleoptera: Passalidae) Assemblages in Central Amazonian Campinaranas
No full textThe present study investigated the occurrence of passalids in dead trunks with structural variations. Trunks were found in areas of white sand forests, locally known as Campinarana, in the state of Amazonas, Brazil. The collections were extended from May to December 2009. The mean diameter of the trunks and their stage of decomposition were classified, and the species of Passalidae were classified according to the location of their galleries. We used multiple generalized models to investigate the relationship between abundance and permutational multivariate analysis of variance (PERMANOVA) to investigate the relationships between predictors and passalid composition. A total of 361 passalids belonging to 13 species were collected from 11 tree species, of which Aldina heterophylla represented the highest proportion of logs (55%). Only the diameter of the trunk was related to the abundance of species, with trunks of larger diameters presented more individuals. The passalid composition was correlated with the diameter and decomposition of the trunks of all species of trees and only with the diameter of the trunks of A. heterophylla. Most of the species collected in Campinaranas construct their galleries in two or more regions of the trunk. The region that supported a greater number of colonies was the sapwood, followed by the inner bark and the soil-stem interface. The general habit of passalids found may be advantageous, probably to compensate for the low dispersion and isolation in areas with low availability of resources, such as Campinaranas forests in the Amazon. © 2020, Sociedade Entomológica do Brasil