Biology subjects

Guimaraes, M.

Publications and source records attributed to Guimaraes, M..

5 recordsLinked to original sources

bioRxiv2025

When and where to find the tiny creatures: environmental predictors of the abundance of a miniaturized frog species from Northeast Brazil

Amphibians are the most vulnerable terrestrial vertebrates to environmental changes, primarily due to their permeable skin and dependence on water for reproduction. In miniaturized frogs, sensitivity to changes in ecological factors related to humidity may be particularly critical due to their high surface-to-volume ratio, which makes them more susceptible to desiccation. To test this hypothesis, we evaluated the influence of environmental variables on the abundance of calling males of Adelophryne nordestina, a small miniaturized frog with direct development inhabiting the Atlantic Forest leaf litter in northeastern Brazil. We surveyed calling males of A. nordestina over nine months across four transects, each containing 25 survey points, totaling 100 study sites. We employed a Negative Binomial N-Mixture Model to estimate the abundance of calling males and assessed the effect of environmental parameters. Our results indicate that estimated mean detection probability was 0.03, and mean abundance among sites was 85.90. Precipitation, temperature, leaf litter depth, and canopy cover significantly influenced the number of calling males in the study area. We suggest that, as a terrestrial, miniaturized, and direct-developing species, changes in environmental parameters affecting microhabitat humidity impact its reproductive activity. Our findings contribute to the understanding of miniaturized frog ecology and the potential impacts of environmental disturbances on this group.

ecology↗

bioRxiv2024

Insights into the representativeness of biodiversity assessment in large reservoir through eDNA metabarcoding

Monitoring biodiversity on a large scale, such as in hydropower reservoirs, poses scientific challenges. Conventional methods such as passive fishing gear are prone to various biases, while the utilization of environmental DNA (eDNA) metabarcoding has been restricted. Most eDNA studies have primarily focused on replicating results from traditional methods, which themselves have limitations regarding representativeness and bias. In our study, we employed eDNA metabarcoding with three markers (12SrRNA, COI, and 16SrRNA) to evaluate the biodiversity of an 800 km{superscript 2} reservoir. We utilized hydrodynamic modeling to determine water flow velocity and the water renewal ratio throughout the study area. Additionally, we conducted statistical comparisons - rarefaction curves and multivariate methods - among samples as an alternative approach to assess biodiversity representation. The eDNA identified taxa previously documented in the reservoir by traditional monitoring methods, as well as revealed 29 - nine fishes and 20 non-fish - previously unreported species. These results highlight the robustness of eDNA as a biodiversity monitoring technique. Our findings also indicated that by randomly sampling 30% of the original number of samples, we could effectively capture the same biodiversity. This approach enabled us to comprehend the reservoirs biodiversity profile and propose a straightforward, cost-effective monitoring protocol for the future based on eDNA.

molecular biology↗

bioRxiv2023

STRANDS OF CONNECTION: LIVESTOCK GRAZING, VEGETATION DENSITY, AND ORB-WEAVER SPIDER PERSISTENCE

Studies on the effects of grazing disturbances in grasslands have shown mixed results for spider diversity, mainly regarding their guilds. While ungrazing, low, and moderate grazing potentially enhance diversity of orb-weavers, heavy grazing seems to reduce specie[s] richness. On the population level, studies of orb-weavers are scarce, and the effects of grazing are unknow. In this way, we investigated the effects of different levels of grazing on population persistence of orb-weaver spiders, hypothesizing that low to intermediate disturbances benefit populations. We predict that high grazing, due to the removal of vegetation structure, will negatively affect occupancy and abundance of orb-weavers. For that, we experimentally controlled grazing pressure and obtained population occurrence and counts of two orb-weaver spider species, Argiope argentata and Alpaida quadrilorata. We found that A. argentata was directly affected by grazing, as it relies on higher vegetation for web-building. In contrast, A. quadrilorata, which occurs in cattle-resistant rosette plants, showed no effects of grazing. Implications for insect conservation: Our study emphasizes the need for balanced grazing practices and habitat conservation to protect orb-weaver spiders and other arthropods, as well as, species-specific effects for species from the same guild, underscoring their ecological significance in maintaining ecosystem stability.

ecology↗

bioRxiv2021

Environmental DNA from a small sample of reservoir water can tell volumes about its biodiversity.

We evaluated the potential of metabarcoding in assessing the environmental DNA (eDNA) biodiversity profile in the water column of an hydroelectric power plant reservoir in southeast Brazil. Samples were obtained in three technical replicates at 1 km from the dam at 1, 13 and 25 m depths. For each minibarcodes -- COI, 12S and 16S -- 1.5 million paired-reads (150 base pairs) were sequenced. A total of 44 unique taxa were found. COI identified most of the taxa (34 taxa; 77.2 %) followed by 16S (14; 31.8 %) and 12S (10; 22.7 %). All minibarcodes identified fishes (13 taxa), however, COI detected other aquatic macro-invertebrates (18), algae (3) and amoebas (2). Richness was the same across the three depths (35 taxa), although, beta diversity suggested slightly divergent profiles. In just one location we identified 15 taxa never reported previously, 50% of the fish species identified in the last year of fishery monitoring and 13% of the species in biodiversity surveys performed from 2012 to 2021. Clustering into Amplicon Sequence Variants (ASV) showed that 12S and 16S are able to detect predominant haplotypes of fishes, suggesting they are suitable to study population genetics of this group. In this study we reviewed the species occurring within the Tres Irmaos reservoir according to previous conventional surveys and demonstrated that eDNA metabarcoding can be applied to monitor its biodiversity.

molecular biology↗

bioRxiv2019

Full-annual demography and seasonal cycles in a resident vertebrate

Demography is usually studied at a single point in time within a year when species, mostly long-distance migrants, are more active and easier to find. However, this provides only a low-resolution glimpse into demographic temporal patterns, compromising a complete understanding of species population dynamics over full annual cycles. The full annual cycle is often influenced by environmental seasonality, which induces a cyclic behavior in many species. However, cycles have rarely been explicitly included in models for demographic parameters, and most information on full annual cycle demography is restricted to migratory species. Here we used a high-resolution capture-recapture study of a resident tropical lizard to assess the full intra-annual demography and within-year periodicity in survival, temporary emigration and recapture probabilities. We found important variation over the annual cycle and up to 92% of the total monthly variation explained by cycles. Fine-scale demographic studies and assessments on the importance of cycles within parameters are fundamental to understand population persistence over time.

ecology↗