INFECTION DYNAMICS OF BATRACHOCHYTRIUM DENDROBATIDIS IN TWO FROG SPECIES INHABITING QUITO'S METROPOLITAN GUANGÜILTAGUA PARK, ECUADOR.

Batrachochytrium dendrobatidis (Bd) infection is one of the principal causes of amphibian declines worldwide. The presence of Bd has been determined in Gastrotheca riobambae tadpoles that inhabit ponds in Quito's Metropolitan Guangüiltagua Park, Ecuador. This study sought to determine whether these tadpoles are infected and to determine the presence of chytridiomycosis in another frog species, Pristimantis unistrigatus, which also inhabits the park and has different reproductive biology and distinct behavioral habits. We used end-point and real-time PCR techniques to detect and quantify Bd infection. At 1 yr, samples were taken from the skin of P. unistrigatus using swabs and were also taken from the mouthparts of G. riobambae tadpoles. It was found that the two species were infected with a Bd prevalence of 39% (53/135) in G. riobambae tadpoles and 15% (57/382) in P. unistrigatus frogs. The two types of samples (tissue and swabs) from mouthparts showed differences in the zoospores per microliter loads (x̄=1,376.7±3,450.2 vs. x̄=285.0±652.3). Moreover, a correlation (r2=0.621) was discovered between the monthly mean maximum temperature of the pond with disease prevalence in G. riobambae tadpoles. Infection levels in the P. unistrigatus population varied significantly over time, and distance to the pond was a determinant factor for infection intensity.

Predators like it hot: Thermal mismatch in a predator-prey system across an elevational tropical gradient.

Climate change may have dramatic consequences for communities through both direct effects of peak temperatures upon individual species and through interspecific mismatches in thermal sensitivities of interacting organisms which mediate changes in interspecific interactions (i.e. predation). Despite this, there is a paucity of information on the patterns of spatial physiological sensitivity of interacting species (at both landscape and local scales) which could ultimately influence geographical variation in the effects of climate change on community processes. In order to assess where these impacts may occur, we first need to evaluate the spatial heterogeneity in the degree of mismatch in thermal tolerances between interacting organisms. We quantify the magnitude of interspecific mismatch in maximum (CTmax ) and minimum (CTmin ) thermal tolerances among a predator-prey system of dragonfly and anuran larvae in tropical montane (242-3,631 m) and habitat (ponds and streams) gradients. To compare thermal mismatches between predator and prey, we coined the parameters maximum and minimum predatory tolerance margins (PTMmax and PTMmin ), or difference in CTmax and CTmin of interacting organisms sampled across elevational and habitat gradients. Our analyses revealed that: (a) predators exhibit higher heat tolerances than prey (~4°C), a trend which remained stable across habitats and elevations. In contrast, we found no differences in minimum thermal tolerances between these groups. (b) Maximum and minimum thermal tolerances of both predators and prey decreased with elevation, but only maximum thermal tolerance varied across habitats, with pond species exhibiting higher heat tolerance than stream species. (c) Pond-dwelling organisms from low elevations (0-1,500 m a.s.l.) may be more susceptible to direct effects of warming than their highland counterparts because their maximum thermal tolerances are only slightly higher than their exposed maximum environmental temperatures. The greater relative thermal tolerance of dragonfly naiad predators may further increase the vulnerability of lowland tadpoles to warming due to potentially enhanced indirect effects of higher predation rates by more heat-tolerant dragonfly predators. However, further experimental work is required to establish the individual and population-level consequences of this thermal tolerance mismatch upon biotic interactions such as predator-prey. ​.

El cambio climático puede acarrear consecuencias dramáticas en las comunidades, ya sea mediante los efectos directos de las temperaturas extremas sobre cada especie particular, o por los efectos indirectos en las interacciones entre especies (p.ej. depredación). Sin embargo, no existe actualmente información a escala local o regional sobre los patrones geográficos de la sensibilidad térmica de especies que interaccionan, que en última instancia puede afectar a los procesos de las comunidades. Es por ello que para estimar dónde se van a producir los impactos del calentamiento, necesitamos primero tener un conocimiento de los niveles de desajustes espaciales que puedan presentar las interacciones biológicas. En este estudio hemos cuantificado los desajustes interespecíficos en las tolerancias térmicas extremas al calor (CTmax ) y al frío (CTmin ) en un sistema de depredador-presa, de larvas de libélulas y anfibios, en un gradientes de altitud tropical (242-3,631 m) y entre hábitats (charcas y arroyos). Para comparar los desajustes entre depredador y presa, definimos dos parámetros: margen máximo y mínimo de tolerancia a la depredación (PTMmax y PTMmin ) que se definiría como la diferencia respectiva entre CTmax y CTmin entre los organimos que interaccionan. Nuestros resultados muestran: (1) los depredadores muestran mayor tolerancia al calor que las presas (~4°C), diferencia que se mantiene invariable entre hábitats y altitudes. Por el contrario, no encontramos diferencias en las tolerancias térmicas mínimas entre estos grupos. (2) Las tolerancias térmicas máximas y mínimas, tanto en depredadores como en presas, disminuyen con la elevación pero sólo la tolerancia al calor varía entre hábitats, siendo más resistentes las especies de charcas frente a las de arroyos. (3) Las especies que habitan charcas de baja altitud (0-1,500 m) son más susceptibles a recibir impactos directos del calentamiento que las de alta montaña, ya que sus tolerancias térmicas máximas son sólo ligeramente superiores a las temperaturas extremas que se registran en la actualidad. La mayor tolerancia térmica relativa que presentan las larvas depredadoras de libélulas, puede incrementar la vulnerabilidad al calentamiento de los renacuajos de baja altitud, por los efectos indirectos que pueden infringir sobre ellos las libélulas depredadoras, más tolerantes al calor. Sin embargo, es necesario realizar más investigaciones experimentales, para establecer las consecuencias individuales y poblacionales de este desajuste en las tolerancias térmicas en las interacciones bióticas, como las de depredador-presa. ​.

Post-epizootic microbiome associations across communities of neotropical amphibians.

Microbiome-pathogen interactions are increasingly recognized as an important element of host immunity. While these host-level interactions will have consequences for community disease dynamics, the factors which influence host microbiomes at larger scales are poorly understood. We here describe landscape-scale pathogen-microbiome associations within the context of post-epizootic amphibian chytridiomycosis, a disease caused by the panzootic chytrid fungus Batrachochytrium dendrobatidis. We undertook a survey of Neotropical amphibians across altitudinal gradients in Ecuador ~30 years following the observed amphibian declines and collected skin swab-samples which were metabarcoded using both fungal (ITS-2) and bacterial (r16S) amplicons. The data revealed marked variation in patterns of both B. dendrobatidis infection and microbiome structure that are associated with host life history. Stream breeding amphibians were most likely to be infected with B. dendrobatidis. This increased probability of infection was further associated with increased abundance and diversity of non-Batrachochytrium chytrid fungi in the skin and environmental microbiome. We also show that increased alpha diversity and the relative abundance of fungi are lower in the skin microbiome of adult stream amphibians compared to adult pond-breeding amphibians, an association not seen for bacteria. Finally, stream tadpoles exhibit lower proportions of predicted protective microbial taxa than pond tadpoles, suggesting reduced biotic resistance. Our analyses show that host breeding ecology strongly shapes pathogen-microbiome associations at a landscape scale, a trait that may influence resilience in the face of emerging infectious diseases.

Thermal biology of two tropical lizards from the Ecuadorian Andes and their vulnerability to climate change.

This study aims to analyze the thermal biology and climatic vulnerability of two closely related lizard species (Stenocercus festae and S. guentheri) inhabiting the Ecuadorian Andes at high altitudes. Four physiological parameters-body temperature (Tb), preferred temperature (Tpref), critical thermal maximum (CTmax), and critical thermal minimum (CTmin)-were evaluated to analyze the variation of thermophysiological traits among these populations that inhabit different environmental and altitudinal conditions. We also evaluate the availability of operative temperatures, warming tolerance, and thermal safety margin of each population to estimate their possible risks in the face of future raising temperatures. Similar to previous studies, our results suggest that some physiological traits (CTmax and Tb) are influenced by environmental heterogeneity, which brings changes on the thermoregulatory behavior. Other parameters (Tpref and CTmin), may be also influenced by phylogenetic constraints. Moreover, the fluctuating air temperature (Tair) as well as the operative temperatures (Te) showed that these lizards exploit a variety of thermal microenvironments, which may facilitate behavioral thermoregulation. Warming tolerance and thermal safety margin analyses suggest that both species find thermal refugia and remain active without reducing their performance or undergoing thermal stress within their habitats. We suggest that studies on the thermal biology of tropical Andean lizards living at high altitudes are extremely important as these environments exhibit a unique diversity of microclimates, which consequently result on particular thermophysiological adaptations.

Microbiological and cytological characterization of coelomic fluid from three captive endangered amphibian Gastrotheca species with edema syndrome: preliminary analysis.

OBJECTIVE: Edema syndrome is highly prevalent but under researched in captive frogs around the world. The objective of the present study was to characterize at a basic microbiological and cytological level of the bacteria of the edema fluid of 20 individuals of the genus Gastrotheca to determine the presence of possible anaerobic and aerobic bacteria. RESULTS: Fourteen types of bacteria were identified in the edema fluid, 12 of them at the species level (Pasteurella haemolytica, Hafnia alvei, Enterobacter agglomerans, Aeromonas hydrophila, Pseudomonas fluorescens, Burkholderia pseudomallei, Salmonella arizonae, Enterobacter gergoviae, Enterobacter sakazakii, Yersinia enterocolitica, Klebsiella oxytoca, and Klebsiella ozaenae) and two at the genus level (Enterococcus spp. and Streptococcus spp.). The most frequently identified cells were lymphocytes (37.7% in females and 46.4% in males), erythrocytes (23.5% in females and 17.5% in males) and neutrophils (4.2% in females and 2.8% in males). Finally, no relationship was found between the data obtained and the sex of the individuals studied.

Phylogenetic investigation of skin sloughing rates in frogs: relationships with skin characteristics and disease-driven declines.

Amphibian skin is highly variable in structure and function across anurans, and plays an important role in physiological homeostasis and immune defence. For example, skin sloughing has been shown to reduce pathogen loads on the skin, such as the lethal fungus Batrachochytrium dendrobatidis ( Bd), but interspecific variation in sloughing frequency is largely unknown. Using phylogenetic linear mixed models, we assessed the relationship between skin turnover rate, skin morphology, ecological traits and overall evidence of Bd-driven declines. We examined skin sloughing rates in 21 frog species from three continents, as well as structural skin characteristics measured from preserved specimens. We found that sloughing rate varies significantly with phylogenetic group, but was not associated with evidence of Bd-driven declines, or other skin characteristics examined. This is the first comparison of sloughing rate across a wide range of amphibian species, and creates the first database of amphibian sloughing behaviour. Given the strong phylogenetic signal observed in sloughing rate, approximate sloughing rates of related species may be predicted based on phylogenetic position. While not related to available evidence of declines, understanding variation in sloughing rate may help explain differences in the severity of infection in genera with relatively slow skin turnover rates (e.g. Atelopus).

Radiographic and histological evidence of metabolic bone disease in gliding leaf frogs (Agalychnis spurrelli).

Bone alterations due to metabolic bone disease in captive animal populations can have a negative impact on repopulation and research initiatives. This investigation has the purpose of describing the principal radiographic and anatomopathological findings present in nine gliding leaf frogs (Agalychnis spurrelli) kept in captivity with alterations in their spines and long bones. The observed histopathological findings were in the canalis vertebralis, paraspinal muscle and long bones, and included deformed bones with alteration of the adjacent tissues, alterations in the ossification process, bone degeneration and resorption, decreased number of osteocytes and deposition of osteoid and fibrous material in the compact bone tissue. Additionally, the spinal cord showed compressed white matter, chronic meningitis in the duramater, alteration in the number of glial cells and loss of delimitation between the gray and white matter. Radiographical changes were found mainly in the long bones and included moth-eaten osteolysis, solid periosteal reaction, bone deformities, cortical tunneling and inflammation of adjacent soft tissues. Also, pathological fractures of the femur and urostyle were observed together with spinal column deviations with increased bone density.

The effect of captivity on the skin microbial symbionts in three Atelopus species from the lowlands of Colombia and Ecuador.

Many amphibian species are at risk of extinction in their natural habitats due to the presence of the fungal pathogen Batrachochytrium dendrobatidis (Bd). For the most highly endangered species, captive assurance colonies have been established as an emergency measure to avoid extinction. Experimental research has suggested that symbiotic microorganisms in the skin of amphibians play a key role against Bd. While previous studies have addressed the effects of captivity on the cutaneous bacterial community, it remains poorly studied whether and how captive conditions affect the proportion of beneficial bacteria or their anti-Bd performance on amphibian hosts. In this study we sampled three amphibian species of the highly threatened genus, Atelopus, that remain in the wild but are also part of ex situ breeding programs in Colombia and Ecuador. Our goals were to (1) estimate the diversity of culturable bacterial assemblages in these three species of Atelopus, (2) describe the effect of captivity on the composition of skin microbiota, and (3) examine how captivity affects the bacterial ability to inhibit Bd growth. Using challenge assays we tested each bacterial isolate against Bd, and through sequencing of the 16S rRNA gene, we identified species from thirteen genera of bacteria that inhibited Bd growth. Surprisingly, we did not detect a reduction in skin bacteria diversity in captive frogs. Moreover, we found that frogs in captivity still harbor bacteria with anti-Bd activity. Although the scope of our study is limited to a few species and to the culturable portion of the bacterial community, our results indicate that captive programs do not necessarily change bacterial communities of the toad skins in a way that impedes the control of Bd in case of an eventual reintroduction.

Stepping inside the niche: microclimate data are critical for accurate assessment of species' vulnerability to climate change.

To assess a species' vulnerability to climate change, we commonly use mapped environmental data that are coarsely resolved in time and space. Coarsely resolved temperature data are typically inaccurate at predicting temperatures in microhabitats used by an organism and may also exhibit spatial bias in topographically complex areas. One consequence of these inaccuracies is that coarsely resolved layers may predict thermal regimes at a site that exceed species' known thermal limits. In this study, we use statistical downscaling to account for environmental factors and develop high-resolution estimates of daily maximum temperatures for a 36 000 km(2) study area over a 38-year period. We then demonstrate that this statistical downscaling provides temperature estimates that consistently place focal species within their fundamental thermal niche, whereas coarsely resolved layers do not. Our results highlight the need for incorporation of fine-scale weather data into species' vulnerability analyses and demonstrate that a statistical downscaling approach can yield biologically relevant estimates of thermal regimes.

Widespread amphibian extinctions from epidemic disease driven by global warming.

As the Earth warms, many species are likely to disappear, often because of changing disease dynamics. Here we show that a recent mass extinction associated with pathogen outbreaks is tied to global warming. Seventeen years ago, in the mountains of Costa Rica, the Monteverde harlequin frog (Atelopus sp.) vanished along with the golden toad (Bufo periglenes). An estimated 67% of the 110 or so species of Atelopus, which are endemic to the American tropics, have met the same fate, and a pathogenic chytrid fungus (Batrachochytrium dendrobatidis) is implicated. Analysing the timing of losses in relation to changes in sea surface and air temperatures, we conclude with 'very high confidence' (> 99%, following the Intergovernmental Panel on Climate Change, IPCC) that large-scale warming is a key factor in the disappearances. We propose that temperatures at many highland localities are shifting towards the growth optimum of Batrachochytrium, thus encouraging outbreaks. With climate change promoting infectious disease and eroding biodiversity, the urgency of reducing greenhouse-gas concentrations is now undeniable.