Estimativas populacionais de Dendrobates tinctorius (Anura: Dendrobatidae) em três áreas da Guiana Francesa e primeiro relato de quitridiomicose.

A região Neotropical abriga o maior número de espécies de anuros da Terra e é também uma das regiões em que os anfíbios estão mais ameaçados. No entanto, poucos dados estão atualmente disponíveis para avaliar a situação daspopulações de anfíbios neotropicais. Estudamos três populações de Dendrobates tinctorius na Guiana Francesa (Tresor, Favard e Nouragues) usando o modelo de Captura-Marcação-Recaptura (CMR) para a realização de estimativas robustas da densidade da espécie nesses três locais. Além disso, avaliamos a prevalência do fungo patogênico Batrachochytrium dendrobatidis (Bd) em duaspopulações (Favard and Nouragues). O uso do modelo CMR revelou uma densidade de 4,67 indivíduos/100 m² para Tresor, 8,43 indivíduos/100 m² para Favard e 4,28 indivíduos/100 m² para Nouragues, fornecendo estimativas das densidades populacionais de D. tinctorius na Guiana Francesa com as quais estimativas populacionais futuras poderão ser comparadas. Constatamos que 25 ocasiões de encontro podem ser suficientes para estimativas de uma população estável se as capturas forem concentradas no tempo. Bd foi detectado em ambas as áreas (Favard 7/152, Nouragues 3/18). Propomos, portanto, o início de um acompanhamento de longa-duração dessa espécie em vários locais (dentro e fora de áreas protegidas) da Guiana Francesa, combinando estudos de CMR com ocasiões de encontros concentrados em um curto período de tempo e o monitoramento de Bd.The Neotropics shelter the highest number of frog species on Earth and is also one of the regions where anurans aremost threatened. Nonetheless, few data are available to assess the population status of Neotropical anurans. We studied three populations (Tresor, Favard, and Nouragues) of the poison frog, Dendrobates tinctorius, in French Guiana and used Capture-Mark-Recapture (CMR) to make robust estimations of the species’ density at these three sites. In addition, we assessed the prevalence of the pathogen fungal Batrachochytrium dendrobatidis (Bd) in two populations (Favard and Nouragues). Based on the CMR protocol, the densities of frogs was 8.43 individuals/100 m² at Favard, 4.28 individuals/100 m² at Nouragues and from 2.30 to 4.67 individuals/100 m² at Tresor (depending on the CMR model used); these data provide a baseline for population densities of D. tinctorius in French Guiana, against which future population estimates can be compared. We found that 25 encounter events may be sufficient for stable population estimates, if the captures are concentrated in time. Bd was detected at both sites (Favard 7/152; Nouragues 3/18)

Setting temporal baselines for biodiversity : the limits of available monitoring data for capturing the full impact of anthropogenic pressures

Temporal baselines are needed for biodiversity, in order for the change in biodiversity to be measured over time, the targets for biodiversity conservation to be defined and conservation progress to be evaluated. Limited biodiversity information is widely recognized as a major barrier for identifying temporal baselines, although a comprehensive quantitative assessment of this is lacking. Here, we report on the temporal baselines that could be drawn from biodiversity monitoring schemes in Europe and compare those with the rise of important anthropogenic pressures. Most biodiversity monitoring schemes were initiated late in the 20th century, well after anthropogenic pressures had already reached half of their current magnitude. Setting temporal baselines from biodiversity monitoring data would therefore underestimate the full range of impacts of major anthropogenic pressures. In addition, biases among taxa and organization levels provide a truncated picture of biodiversity over time. These limitations need to be explicitly acknowledged when designing management strategies and policies as they seriously constrain our ability to identify relevant conservation targets aimed at restoring or reversing biodiversity losses. We discuss the need for additional research efforts beyond standard biodiversity monitoring to reconstruct the impacts of major anthropogenic pressures and to identify meaningful temporal baselines for biodiversity

Introducing water frogs – Is there a risk for indigenous species in France?

The ecological success of introduced species in their new environments is difficult to predict. Recently, the water frog species Rana ridibunda has raised interest, as different genetic lineages were introduced to various European countries. The aim of the present study was to analyze the potential invasiveness of R. ridibunda and assess the risk of replacement for indigenous water frog species. The investigation of over 700 water frogs from 22 locations in southern France and four locations in Spain shows that the competition with indigenous species is mainly limited to a particular habitat type, characterized by high-oxygen and low-salinity freshwater. The competitive strength of R. ridibunda may be related to a higher growth rate and longevity as compared to the indigenous species R. grafi and R. perezi. Our data suggest that R. ridibunda is a risk to the diversity of indigenous water frog assemblages in France. Future monitoring needs to clarify the distribution of R. ridibunda, its ecological niche, and the risk status for indigenous water frog species

Microbiome function predicts amphibian chytridiomycosis disease dynamics

[Background] The fungal pathogenBatrachochytrium dendrobatidis (Bd) threatens amphibian biodiversity and ecosystem stability worldwide. Amphibian skin microbial community structure has been linked to the clinical outcome of Bd infections, yet its overall functional importance is poorly understood. [Methods] Microbiome taxonomic and functional profiles were assessed using high-throughput bacterial 16S rRNA and fungal ITS2 gene sequencing, bacterial shotgun metagenomics and skin mucosal metabolomics. We sampled 56 wild midwife toads (Alytes obstetricans) from montane populations exhibiting Bd epizootic or enzootic disease dynamics. In addition, to assess whether disease-specific microbiome profiles were linked to microbe-mediated protection or Bd-induced perturbation, we performed a laboratory Bd challenge experiment whereby 40 young adult A. obstetricans were exposed to Bd or a control sham infection. We measured temporal changes in the microbiome as well as functional profiles of Bd-exposed and control animals at peak infection. [Results] Microbiome community structure and function differed in wild populations based on infection history and in experimental control versus Bd-exposed animals. Bd exposure in the laboratory resulted in dynamic changes in microbiome community structure and functional differences, with infection clearance in all but one infected animal. Sphingobacterium, Stenotrophomonas and an unclassified Commamonadaceae were associated with wild epizootic dynamics and also had reduced abundance in laboratory Bd-exposed animals that cleared infection, indicating a negative association with Bd resistance. This was further supported by microbe-metabolite integration which identified functionally relevant taxa driving disease outcome, of which Sphingobacterium and Bd were most influential in wild epizootic dynamics. The strong correlation between microbial taxonomic community composition and skin metabolome in the laboratory and field is inconsistent with microbial functional redundancy, indicating that differences in microbial taxonomy drive functional variation. Shotgun metagenomic analyses support these findings, with similar disease-associated patterns in beta diversity. Analysis of differentially abundant bacterial genes and pathways indicated that bacterial environmental sensing and Bd resource competition are likely to be important in driving infection outcomes. [Conclusions] Bd infection drives altered microbiome taxonomic and functional profiles across laboratory and field environments. Our application of multi-omics analyses in experimental and field settings robustly predicts Bd disease dynamics and identifies novel candidate biomarkers of infection. [MediaObject not available: see fulltext.]K.A.B. was funded by a CASE studentship from NERC, NERC Biomolecular Analysis Facility grant (NBAF939) and an E.P. Abraham Junior Research Fellowship from St Hilda’s College, University of Oxford. M.C.F and T.W.J.G. were funded by NERC award NE/E006701/1 and the Biodiversa project RACE: Risk Assessment of Chytridiomycosis to European Amphibian Biodiversity. T.W.J.G was also funded by Research England and NERC NE/S000062/1. D.S.S. and A.L. received funding through the project People, Pollution, and Pathogens financed through the call “Mountains as Sentinels of Change” by the Belmont-Forum (ANR-15-MASC-0001 - P3, DFG-SCHM3059/6-1, NERC-1633948, NSFC-41661144004). D.S.S. holds the AXA Chair for Functional Mountain Ecology funded by the AXA Research Fund through the project GloMEc and M.C.F. is a fellow in the CIFAR ‘Fungal Kingdoms’ Program

People, pollution and pathogens – Global change impacts in mountain freshwater ecosystems

Mountain catchments provide for the livelihood of more than half of humankind, and have become a key destination for tourist and recreation activities globally. Mountain ecosystems are generally considered to be less complex and less species diverse due to the harsh environmental conditions. As such, they are also more sensitive to the various impacts of the Anthropocene. For this reason,mountain regions may serve as sentinels of change and provide ideal ecosystems for studying climate and global change impacts on biodiversity. We here review different facets of anthropogenic impacts on mountain freshwater ecosystems. We put particular focus on micropollutants and their distribution and redistribution due to hydrological extremes, their direct influence on water quality and their indirect influence on ecosystem health via changes of freshwater species and their interactions. We show that those changes may drive pathogen establishment in new environments with harmful consequences for freshwater species, but also for the human population. Based on the reviewed literature, we recommend reconstructing the recent past of anthropogenic impact through sediment analyses, to focus efforts on small, but highly productive waterbodies, and to collect data on the occurrence and variability of microorganisms, biofilms, plankton species and key species, such as amphibians due to their bioindicator value for ecosystem health and water quality. The newly gained knowledge can then be used to develop a comprehensive framework of indicators to robustly inform policy and decision making on current and future risks for ecosystem health and human well-being