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)

Weak warning signals can persist in the absence of gene flow

Aposematic organisms couple conspicuous warning signals with a secondary defense to deter predators from attacking. Novel signals of aposematic prey are expected to be selected against due to positive frequency-dependent selection. How, then, can novel phenotypes persist after they arise, and why do so many aposematic species exhibit intrapopulation signal variability? Using a polytypic poison frog (Dendrobates tinctorius), we explored the forces of selection on variable aposematic signals using 2 phenotypically distinct (white, yellow) populations. Contrary to expectations, local phenotype was not always better protected compared to novel phenotypes in either population; in the white population, the novel phenotype evoked greater avoidance in natural predators. Despite having a lower quantity of alkaloids, the skin extracts from yellow frogs provoked higher aversive reactions by birds than white frogs in the laboratory, although both populations differed from controls. Similarly, predators learned to avoid the yellow signal faster than the white signal, and generalized their learned avoidance of yellow but not white. We propose that signals that are easily learned and broadly generalized can protect rare, novel signals, and weak warning signals (i.e., signals with poor efficacy and/or poor defense) can persist when gene flow among populations, as in this case, is limited. This provides a mechanism for the persistence of intrapopulation aposematic variation, a likely precursor to polytypism and driver of speciation

Extending the known distribution of Nicosia’s chameleon, Furcifer nicosiai Jesu, Mattioli & Schimmenti, 1999 (Squamata: Chamaeleonidae)

info:eu-repo/semantics/publishedVersio

Evolutionary patterns of volatile terpene emissions across 202 tropical tree species

International audiencePlant responses to natural enemies include formation of secondary metabolites acting as direct or indirect defenses. Volatile terpenes represent one of the most diverse groups of secondary metabolites. We aimed to explore evolutionary patterns of volatile terpene emission. We measured the composition of damage-induced volatile terpenes from 202 Amazonian tree species, spanning the angiosperm phylogeny. Volatile terpenes were extracted with solid-phase micro extraction and desorbed in a gas chromatography–mass spectrometry for compound identification. The chemical diversity of the terpene blend showed a strong phylogenetic signal as closely related species emitted a similar number of compounds. Closely related species also tended to have compositionally similar blends, although this relationship was weak. Meanwhile, the ability to emit a given compound showed no significant phylogenetic signal for 200 of 286 compounds, indicating a high rate of diversification in terpene synthesis and/or great variability in their expression. Three lineages (Magnoliales, Laurales, and Sapindales) showed exceptionally high rates of terpene diversification. Of the 70 compounds found in >10% of their species, 69 displayed significant correlated evolution with at least one other compound. These results provide insights into the complex evolutionary history of volatile terpenes in angiosperms, while highlighting the need for further research into this important class of compounds

Automatic high-frequency measurements of full soil greenhouse gas fluxes in a tropical forest

Measuring in situ soil fluxes of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) continuously at high frequency requires appropriate technology. We tested the combination of a commercial automated soil CO2 flux chamber system (LI-8100A) with a CH4 and N2O analyzer (Picarro G2308) in a tropical rainforest for 4 months. A chamber closure time of 2 min was sufficient for a reliable estimation of CO2 and CH4 fluxes (100 % and 98.5 % of fluxes were above minimum detectable flux - MDF, respectively). This closure time was generally not suitable for a reliable estimation of the low N2O fluxes in this ecosystem but was sufficient for detecting rare major peak events. A closure time of 25 min was more appropriate for reliable estimation of most N2O fluxes (85.6 % of measured fluxes are above MDF ± 0.002 nmol m−2 s−1). Our study highlights the importance of adjusted closure time for each gas

Different "metabolomic niches" of the highly diverse tree species of the French Guiana rainforests

Tropical rainforests harbor a particularly high plant diversity. We hypothesize that potential causes underlying this high diversity should be linked to distinct overall functionality (defense and growth allocation, anti-stress mechanisms, reproduction) among the different sympatric taxa. In this study we tested the hypothesis of the existence of a metabolomic niche related to a species-specific differential use and allocation of metabolites. We tested this hypothesis by comparing leaf metabolomic profiles of 54 species in two rainforests of French Guiana. Species identity explained most of the variation in the metabolome, with a species-specific metabolomic profile across dry and wet seasons. In addition to this "homeostatic" species-specific metabolomic profile significantly linked to phylogenetic distances, also part of the variance (flexibility) of the metabolomic profile was explained by season within a single species. Our results support the hypothesis of the high diversity in tropical forest being related to a species-specific metabolomic niche and highlight ecometabolomics as a tool to identify this species functional diversity related and consistent with the ecological niche theory

31P-NMR metabolomics revealed species-specific use of phosphorous in trees of a French Guiana rainforest

Productivity of tropical lowland moist forests is often limited by availability and functional allocation of phosphorus (P) that drives competition among tree species and becomes a key factor in determining forestall community diversity. We used non-target³¹P-NMR metabolic profiling to study the foliar P-metabolism of trees of a French Guiana rainforest. The objective was to test the hypotheses that P-use is species-specific, and that species diversity relates to species P-use and concentrations of P-containing compounds, including inorganic phosphates, orthophosphate monoesters and diesters, phosphonates and organic polyphosphates. We found that tree species explained the 59% of variance in ³¹P-NMR metabolite profiling of leaves. A principal component analysis showed that tree species were separated along PC 1 and PC 2 of detected P-containing compounds, which represented a continuum going from high concentrations of metabolites related to non-active P and P-storage, low total P concentrations and high N:P ratios, to high concentrations of P-containing metabolites related to energy and anabolic metabolism, high total P concentrations and low N:P ratios. These results highlight the species-specific use of P and the existence of species-specific P-use niches that are driven by the distinct species-specific position in a continuum in the P-allocation from P-storage compounds to P-containing molecules related to energy and anabolic metabolism

Decay of similarity across tropical forest communities : integrating spatial distance with soil nutrients

Altres ajuts: Acord transformatiu CRUE-CSICUnderstanding the mechanisms that drive the change of biotic assemblages over space and time is the main quest of community ecology. Assessing the relative importance of dispersal and environmental species selection in a range of organismic sizes and motilities has been a fruitful strategy. A consensus for whether spatial and environmental distances operate similarly across spatial scales and taxa, however, has yet to emerge. We used censuses of four major groups of organisms (soil bacteria, fungi, ground insects, and trees) at two observation scales (1-m sampling point vs. 2,500-m plots) in a topographically standardized sampling design replicated in two tropical rainforests with contrasting relationships between spatial distance and nutrient availability. We modeled the decay of assemblage similarity for each taxon set and site to assess the relative contributions of spatial distance and nutrient availability distance. Then, we evaluated the potentially structuring effect of tree composition over all other taxa. The similarity of nutrient content in the litter and topsoil had a stronger and more consistent selective effect than did dispersal limitation, particularly for bacteria, fungi, and trees at the plot level. Ground insects, the only group assessed with the capacity of active dispersal, had the highest species turnover and the flattest nonsignificant distance−decay relationship, suggesting that neither dispersal limitation nor nutrient availability were fundamental drivers of their community assembly at this scale of analysis. Only the fungal communities at one of our study sites were clearly coordinated with tree composition. The spatial distance at the smallest scale was more important than nutrient selection for the bacteria, fungi, and insects. The lower initial similarity and the moderate variation in composition identified by these distance-decay models, however, suggested that the effects of stochastic sampling were important at this smaller spatial scale. Our results highlight the importance of nutrients as one of the main environmental drivers of rainforest communities irrespective of organismic or propagule size and how the overriding effect of the analytical scale influences the interpretation, leading to the perception of greater importance of dispersal limitation and ecological drift over selection associated with environmental niches at decreasing observation scales

Recent Asian origin of chytrid fungi causing global amphibian declines

Globalized infectious diseases are causing species declines worldwide, but their source often remains elusive. We used whole-genome sequencing to solve the spatiotemporal origins of the most devastating panzootic to date, caused by the fungus Batrachochytrium dendrobatidis, a proximate driver of global amphibian declines. We traced the source of B. dendrobatidis to the Korean peninsula, where one lineage, BdASIA-1, exhibits the genetic hallmarks of an ancestral population that seeded the panzootic. We date the emergence of this pathogen to the early 20th century, coinciding with the global expansion of commercial trade in amphibians, and we show that intercontinental transmission is ongoing. Our findings point to East Asia as a geographic hotspot for B. dendrobatidis biodiversity and the original source of these lineages that now parasitize amphibians worldwide

Development and worldwide use of non-lethal, and minimal population-level impact, protocols for the isolation of amphibian chytrid fungi

© The Author(s) 2018.Parasitic chytrid fungi have emerged as a significant threat to amphibian species worldwide, necessitating the development of techniques to isolate these pathogens into culture for research purposes. However, early methods of isolating chytrids from their hosts relied on killing amphibians. We modified a pre-existing protocol for isolating chytrids from infected animals to use toe clips and biopsies from toe webbing rather than euthanizing hosts, and distributed the protocol to researchers as part of the BiodivERsA project RACE; here called the RML protocol. In tandem, we developed a lethal procedure for isolating chytrids from tadpole mouthparts. Reviewing a database of use a decade after their inception, we find that these methods have been applied across 5 continents, 23 countries and in 62 amphibian species. Isolation of chytrids by the non-lethal RML protocol occured in 18% of attempts with 207 fungal isolates and three species of chytrid being recovered. Isolation of chytrids from tadpoles occured in 43% of attempts with 334 fungal isolates of one species (Batrachochytrium dendrobatidis) being recovered. Together, these methods have resulted in a significant reduction and refinement of our use of threatened amphibian species and have improved our ability to work with this group of emerging pathogens.T.W.J.G., M.C.F., D.S.S., A.L., E.C., F.C.C., J.B., A.A.C., C.M., F.S., B.R.S., S.O., were supported through the Biodiversa project RACE: Risk Assessment of Chytridiomycosis to European Amphibian Biodiversity (NERC standard grant NE/K014455/1 and NE/E006701/1; ANR-08-BDVA-002-03). M.C.F., J.S., C.W., P.G. were supported by the Leverhulme Trust (RPG-2014-273), M.C.F., A.C., C.W. were supported by the Morris Animal Foundation. J.V. was supported by the Bolyai János Research Grant of the Hunagrian Academy of Sciences (BO/00597/14). F.G. and D.G. were supported by the Conservation Leadership Programme Future Conservationist Award. C.S.A. was supported by Fondecyt (No. 1181758). M.C.F. and A.C. were supported by. Mohamed bin Zayed Species Conservation Fund Project (152510704). GMR held a doctoral scholarship (SFRH/ BD/69194/2010) from Fundação para a Ciência e a Tecnologia. L.F.T., C.L., L.P.R. K.R.Z., T.Y.J., T.S.J. were supported by São Paulo Research Foundation (FAPESP #2016/25358-3), the National Counsel of Technological and Scientifc Development (CNPq #300896/2016–6) and a Catalyzing New International Collaborations grant from the United States NSF (OISE-1159513). C.S.A. was supported by Fondecyt (No. 1181758). T.M.D. was supported by the Royal Geographical Society and the Royal Zoological Society of Scotland. B.W. was supported by the National Research Foundation of Korea (2015R1D1A1A01057282).Peer Reviewe