Biology subjects

Magnusson, W. E.

Publications and source records attributed to Magnusson, W. E..

4 recordsLinked to original sources

bioRxiv2021

The Maximum Entropy Formalism of statistical mechanics in a biological application: a quantitative analysis of tropical forest ecology

In a time of rapid global change, the question of what determines patterns in species abundance distribution remains a priority for understanding the complex dynamics of ecosystems. The constrained maximization of information entropy provides a framework for the understanding of such complex systems dynamics by a quantitative analysis of important constraints via predictions using least biased probability distributions. We apply it to over two thousand hectares of Amazonian tree inventories across seven forest types and thirteen functional traits, representing major global axes of plant strategies. Results show that constraints formed by regional relative abundances of genera explain eight times more of local relative abundances than constraints based on directional selection for specific functional traits, although the latter does show clear signals of environmental dependency. These results provide a quantitative insight by inference from large-scale data using cross-disciplinary methods, furthering our understanding of ecological dynamics.

ecology↗

bioRxiv2021

eDNA in a bottleneck: obstacles to fish metabarcoding studies in megadiverse freshwater systems

The current capacity of environmental DNA (eDNA) to provide accurate insights into the biodiversity of megadiverse regions (e.g., the Neotropics) requires further evaluation to ensure its reliability for long-term monitoring. In this study, we first evaluated the taxonomic resolution capabilities of a short fragment from the 12S rRNA gene widely used in fish eDNA metabarcoding studies, and then compared eDNA metabarcoding data from water samples with traditional sampling using nets. For the taxonomic discriminatory power analysis, we used a specifically curated reference dataset consisting of 373 sequences from 264 neotropical fish species (including 47 newly generated sequences) to perform a genetic distance-based analysis of the amplicons targeted by the MiFish primer set. We obtained an optimum delimitation threshold value of 0.5% due to lowest cumulative errors. The barcoding gap analysis revealed only a 50.38% success rate in species recovery (133/264), highlighting a poor taxonomic resolution from the targeted amplicon. To evaluate the empirical performance of this amplicon for biomonitoring, we assessed fish biodiversity using eDNA metabarcoding from water samples collected from the Amazon (Adolpho Ducke Forest Reserve and two additional locations outside the Reserve). From a total of 84 identified Molecular Operational Taxonomic Units (MOTUs), only four could be assigned to species level using a fixed threshold. Measures of -diversity analyses within the Reserve showed similar patterns in each site between the number of MOTUs (eDNA dataset) and species (netting data) found. However, {beta}-diversity revealed contrasting patterns between the methods. We therefore suggest that a new approach is needed, underpinned by sound taxonomic knowledge, and a more thorough evaluation of better molecular identification procedures such as multi-marker metabarcoding approaches and tailor-made (i.e., order-specific) taxonomic delimitation thresholds.

ecology↗

bioRxiv2019

Assessing the potential of environmental DNA metabarcoding for monitoring Neotropical mammals: a case study in the Amazon and Atlantic Forest, Brazil

The application of environmental DNA (eDNA) metabarcoding as a biomonitoring tool has greatly increased in the last decade. However, most studies have focused on aquatic macro-organisms in temperate areas (e.g., fishes). We apply eDNA metabarcoding to detect the mammalian community in two high-biodiversity regions of Brazil, the Amazon and Atlantic Forest. We identified critically endangered and endangered mammalian species in the Atlantic Forest and Amazon respectively and found congruence with species identified via camera trapping in the Atlantic Forest. In light of our results, we highlight the potential and challenges of eDNA monitoring for mammals in these high biodiverse areas.

ecology↗

bioRxiv2019

Butterfly assemblages from Amazonian flooded forests are not more species-poor than from unflooded forests

The Amazonian flooded and upland forests harbour distinct assemblages of most taxonomic groups. These differences can be mainly attributed to flooding, which may affect directly or indirectly the persistence of species. Here, we compare the density, richness and composition of butterfly assemblages in vaorzea and terra firme forests, and evaluate whether terrain elevation and flooding can be used to predict the assemblage structure. We found that the total abundance and number of species per plot is higher in vaorzea than in terra firme forests. Vaorzea assemblages showed a higher dominance of abundant species than terra firme assemblages, in which low-flying Haeterini butterflies had higher abundance. After standardizing species richness by sample size and/or coverage, species richness estimates for vaorzea and terra firme forests were similar. There was strong turnover in species composition across vaorzea and terra firme forests associated with terrain elevation, most likely due to differences in the duration of flooding. Despite a smaller total area, less defined vegetation strata, more frequent disturbances and the younger geological age of floodplain forests, Nymphalid butterfly assemblages are not more species poor there than in unflooded forests.

ecology↗