Significant reductions of host abundance weakly impact infection intensity of Batrachochytrium dendrobatidis

Infectious diseases are considered major threats to biodiversity, however strategies to mitigate their impacts in the natural world are scarce and largely unsuccessful. Chytridiomycosis is responsible for the decline of hundreds of amphibian species worldwide, but an effective disease management strategy that could be applied across natural habitats is still lacking. In general amphibian larvae can be easily captured, offering opportunities to ascertain the impact of altering the abundance of hosts, considered to be a key parameter affecting the severity of the disease. Here, we report the results of two experiments to investigate how altering host abundance affects infection intensity in amphibian populations of a montane area of Central Spain suffering from lethal amphibian chytridiomycosis. Our laboratory-based experiment supported the conclusion that varying density had a significant effect on infection intensity when salamander larvae were housed at low densities. Our field experiment showed that reducing the abundance of salamander larvae in the field also had a significant, but weak, impact on infection the following year, but only when removals were extreme. While this suggests adjusting host abundance as a mitigation strategy to reduce infection intensity could be useful, our evidence suggests only heavy culling efforts will succeed, which may run contrary to objectives for conservation.

Download Full-text

Fungal infection, decline and persistence in the only obligate troglodytic Neotropical salamander

PeerJ ◽

10.7717/peerj.9763 ◽

2020 ◽

Vol 8 ◽

pp. e9763

Author(s):

Mizraim Olivares-Miranda ◽

Vance T. Vredenburg ◽

Julio C. García-Sánchez ◽

Allison Q. Byrne ◽

Erica B. Rosenblum ◽

...

Keyword(s):

Batrachochytrium Dendrobatidis ◽

Infection Intensity ◽

Sampling Technique ◽

Sympatric Species ◽

Amphibian Declines ◽

Small Range ◽

Museum Specimens ◽

Amphibian Species ◽

Extant Population ◽

Epidemic Wave

The fungal pathogen Batrachochytrium dendrobatidis (Bd) is implicated in global mass die-offs and declines in amphibians. In Mesoamerica, the Bd epidemic wave hypothesis is supported by detection of Bd in historic museum specimens collected over the last century, yet the timing and impact of the early stages of the wave remain poorly understood. Chiropterotriton magnipes, the only obligate troglodytic Neotropical salamander, was abundant in its small range in the decade following its description in 1965, but subsequently disappeared from known localities and was not seen for 34 years. Its decline is roughly coincident with that of other populations of Neotropical salamanders associated with the invasion and spread of Bd. To determine the presence and infection intensity of Bd on C. magnipes and sympatric amphibian species (which are also Bd hosts), we used a noninvasive sampling technique and qPCR assay to detect Bd on museum specimens of C. magnipes collected from 1952 to 2012, and from extant populations of C. magnipes and sympatric species of amphibians. We also tested for the presence of the recently discovered Batrachochytrium salamandivorans (Bsal), another fungal chytridiomycete pathogen of salamanders, using a similar technique specific for Bsal. We did not detect Bd in populations of C. magnipes before 1969, while Bd was detected at low to moderate prevalence just prior to and during declines. This pattern is consistent with Bd-caused epizootics followed by host declines and extirpations described in other hosts. We did not detect Bsal in any extant population of C. magnipes. We obtained one of the earliest positive records of the fungus to date in Latin America, providing additional historical evidence consistent with the Bd epidemic wave hypothesis. Genotyping results show that at least one population is currently infected with the Global Panzootic Lineage of Bd, but our genotyping of the historical positive samples was unsuccessful. The lack of large samples from some years and the difficulty in genotyping historical Bd samples illustrate some of the difficulties inherent in assigning causality to historical amphibian declines. These data also provide an important historical baseline for actions to preserve the few known remaining populations of C. magnipes.

Download Full-text

Endemic Infection of Batrachochytrium dendrobatidis in Costa Rica: Implications for Amphibian Conservation at Regional and Species Level

Diversity ◽

10.3390/d11080129 ◽

2019 ◽

Vol 11 (8) ◽

pp. 129 ◽

Cited By ~ 1

Author(s):

Héctor Zumbado-Ulate ◽

Kiersten N. Nelson ◽

Adrián García-Rodríguez ◽

Gerardo Chaves ◽

Erick Arias ◽

...

Keyword(s):

Costa Rica ◽

Batrachochytrium Dendrobatidis ◽

Infection Intensity ◽

Amphibian Conservation ◽

Conservation Strategies ◽

Amphibian Species ◽

Current Impact ◽

Taxonomic Groups ◽

Species Descriptions ◽

Effective Conservation

Batrachochytrium dendrobatidis (Bd) has been associated with the severe declines and extinctions of amphibians in Costa Rica that primarily occurred during the 1980s and 1990s. However, the current impact of Bd infection on amphibian species in Costa Rica is unknown. We aimed to update the list of amphibian species in Costa Rica and evaluate the prevalence and infection intensity of Bd infection across the country to aid in the development of effective conservation strategies for amphibians. We reviewed taxonomic lists and included new species descriptions and records for a total of 215 amphibian species in Costa Rica. We also sampled for Bd at nine localities from 2015–2018 and combined these data with additional Bd occurrence data from multiple studies conducted in amphibian communities across Costa Rica from 2005–2018. With this combined dataset, we found that Bd was common (overall infection rate of 23%) across regions and elevations, but infection intensity was below theoretical thresholds associated with mortality. Bd was also more prevalent in Caribbean lowlands and in terrestrial amphibians with an aquatic larval stage; meanwhile, infection load was the highest in direct-developing species (forest and stream-dwellers). Our findings can be used to prioritize regions and taxonomic groups for conservation strategies.

Download Full-text

Novel findings on the impact of chytridiomycosis on the cardiac function of anurans: sensitive vs. tolerant species

PeerJ ◽

10.7717/peerj.5891 ◽

2018 ◽

Vol 6 ◽

pp. e5891 ◽

Cited By ~ 3

Author(s):

Raquel F. Salla ◽

Gisele M. Rizzi-Possignolo ◽

Cristiane R. Oliveira ◽

Carolina Lambertini ◽

Lilian Franco-Belussi ◽

...

Keyword(s):

Cardiac Function ◽

Batrachochytrium Dendrobatidis ◽

Electrolyte Imbalance ◽

Amphibian Conservation ◽

Amphibian Species ◽

Cardiac Pumping ◽

Negative Effect ◽

Cardiac Relaxation ◽

The Impact

Background Understanding of the physiological effects of chytridiomycosis is crucial to worldwide amphibian conservation. Therefore, we analyzed the cardiac function of two anuran species (Xenopus laevis and Physalaemus albonotatus) with different susceptibilities to infection by the causative agent of chytridiomycosis, Batrachochytrium dendrobatidis (hereafter Bd). Methods We analyzed the in situ heart rate (fH - bpm), relative ventricular mass (RVM -%), and Ca2+ handling in heart of Bd infected animals compared to uninfected controls of both study species. Results Bd infection resulted in a 78% decrease in contraction force values in P. albonotatus when compared to the less susceptible X. laevis. This negative effect was even more evident (82%) for the cardiac pumping capacity. The time to reach peak tension was 125% longer in P. albonotatus than in X. laevis, and cardiac relaxation was 57% longer. Discussion These results indicate a delay in the cardiac cycle of P. albonotatus on a beat-to-beat basis, which was corroborated by the bradycardia observed in situ. In summary, Bd-sensitive species present impaired cardiac function, which could be a factor in mortality risk. The more pronounced effects of Bd in P. albonotatus may not only result from electrolyte imbalance, as previously reported, but also could be an effect of toxins produced by Bd. For X. laevis, the ability to promote cardiac adjustments seems to be an important homeostatic feature that allows greater tolerance to chytridiomycosis. This study provides new physiological mechanisms underlying the tolerance or susceptibility of amphibian species to chytridiomycosis, which determine their adaptability to survive in the affected environments.

Download Full-text

Skin microbiome correlates with bioclimate and Batrachochytrium dendrobatidis infection intensity in Brazil’s Atlantic Forest treefrogs

Scientific Reports ◽

10.1038/s41598-020-79130-3 ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Katharina Ruthsatz ◽

Mariana L. Lyra ◽

Carolina Lambertini ◽

Anat M. Belasen ◽

Thomas S. Jenkinson ◽

...

Keyword(s):

Bacterial Community ◽

Atlantic Forest ◽

Bacterial Communities ◽

Batrachochytrium Dendrobatidis ◽

Abiotic Factors ◽

Experimental Studies ◽

Infection Intensity ◽

Skin Microbiome ◽

Host Pathogen ◽

The Impact

AbstractIn Brazil’s Atlantic Forest (AF) biodiversity conservation is of key importance since the fungal pathogen Batrachochytrium dendrobatidis (Bd) has led to the rapid loss of amphibian populations here and worldwide. The impact of Bd on amphibians is determined by the host's immune system, of which the skin microbiome is a critical component. The richness and diversity of such cutaneous bacterial communities are known to be shaped by abiotic factors which thus may indirectly modulate host susceptibility to Bd. This study aimed to contribute to understanding the environment-host–pathogen interaction determining skin bacterial communities in 819 treefrogs (Anura: Hylidae and Phyllomedusidae) from 71 species sampled across the AF. We investigated whether abiotic factors influence the bacterial community richness and structure on the amphibian skin. We further tested for an association between skin bacterial community structure and Bd co-occurrence. Our data revealed that temperature, precipitation, and elevation consistently correlate with richness and diversity of the skin microbiome and also predict Bd infection status. Surprisingly, our data suggest a weak but significant positive correlation of Bd infection intensity and bacterial richness. We highlight the prospect of future experimental studies on the impact of changing environmental conditions associated with global change on environment-host–pathogen interactions in the AF.

Download Full-text

Locality, time and heterozygosity affect chytrid infection in yellow-bellied toads

Diseases of Aquatic Organisms ◽

10.3354/dao03543 ◽

2020 ◽

Vol 142 ◽

pp. 225-237

Author(s):

P Oswald ◽

A Rodríguez ◽

J Bourke ◽

N Wagner ◽

N de Buhr ◽

...

Keyword(s):

Genetic Diversity ◽

Breeding Season ◽

Batrachochytrium Dendrobatidis ◽

Infection Intensity ◽

Sampling Period ◽

Infection Prevalence ◽

Infection Status ◽

Population Declines ◽

Amphibian Species ◽

High Genetic Diversity

The chytrid fungus Batrachochytrium dendrobatidis (Bd) infects numerous amphibian species worldwide and is suggested to drive population declines and extinction events. We report a study of Bd infection at the northernmost distribution of the European yellow-bellied toad Bombina variegata. A total of 577 individuals from ponds in 16 study sites were sampled for DNA and Bd throughout the breeding season. Microsatellite genotyping revealed 3 genetic clusters for the host B. variegata with an overall low genetic diversity. One of the clusters displayed a low microsatellite heterozygosity, a high inbreeding coefficient as well as high Bd infection prevalence and intensities. Multi-model estimates identified site, time of sampling, and heterozygosity to be important predictors of an individual’s Bd infection status, and identified a strong effect of site on individual Bd infection intensity. The study site effects are suggestive of localized infection peaks, and the increase of individual Bd infection probabilities towards the end of the sampling period suggests cumulative infection during the breeding season. This study highlights the need for regular monitoring of Bd infection variables at multiple localities and times to gain insights into Bd dynamics. Due to the detected relationship between individual Bd infection status and heterozygosity, conservation measures should focus on the maintenance of high genetic diversity and connectivity within and among amphibian populations.

Download Full-text

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

PeerJ ◽

10.7717/peerj.3594 ◽

2017 ◽

Vol 5 ◽

pp. e3594 ◽

Cited By ~ 5

Author(s):

Sandra V. Flechas ◽

Ailin Blasco-Zúñiga ◽

Andrés Merino-Viteri ◽

Valeria Ramírez-Castañeda ◽

Miryan Rivera ◽

...

Keyword(s):

Bacterial Community ◽

Batrachochytrium Dendrobatidis ◽

Ex Situ ◽

Rrna Gene ◽

Natural Habitats ◽

Amphibian Species ◽

Skin Bacteria ◽

In Captivity ◽

In The Wild ◽

Microbial Symbionts

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.

Download Full-text

Shifts in temperature influence howBatrachochytrium dendrobatidisinfects amphibian larvae

10.1101/165985 ◽

2017 ◽

Author(s):

Paul W. Bradley ◽

Michael D. Brawner ◽

Thomas R. Raffel ◽

Jason R. Rohr ◽

Deanna H. Olson ◽

...

Keyword(s):

Batrachochytrium Dendrobatidis ◽

Temperature Shift ◽

Amphibian Species ◽

Change Models ◽

Rana Aurora ◽

Amphibian Larvae ◽

Western Toads ◽

Anaxyrus Boreas ◽

Potential Shifts ◽

Increased Susceptibility

AbstractMany climate change models predict increases in mean temperature, and increases in frequency and magnitude of temperature fluctuations. These potential shifts may impact ectotherms in several ways, including how they are affected by disease. Shifts in temperature may especially affect amphibians, a group with populations that have been challenged by several pathogens. Because amphibian hosts invest more in immunity at warmer than cooler temperatures and parasites may acclimate to temperature shifts faster than hosts (creating lags in optimal host immunity), researchers have hypothesized that a temperature shift from cold-to-warm might result in increased amphibian sensitivity to pathogens, whereas a shift from warm-to-cold might result in decreased sensitivity. Support for components of this climate-variability based hypothesis have been provided by prior studies of the fungusBatrachochytrium dendrobatidis(Bd) that causes the disease chytridiomycosis in amphibians. We experimentally tested whether temperature shifts before Bd exposure alter susceptibility to Bd in the larval stage of two amphibian species – western toads (Anaxyrus boreas) and northern red legged frogs (Rana aurora). Both host species harbored elevated Bd infection intensities under constant cold (15° C) temperature in comparison to constant warm (20° C) temperature. Additionally, both species experienced an increase in Bd infection abundance when shifted to 20° C from 15° C, compared to a constant 20° C but they experienced a decrease in Bd when shifted to 15° C from 20° C, compared to a constant 15° C. These results are in contrast to prior studies of adult amphibians that found increased susceptibility to Bd infection after a temperature shift in either direction, highlighting the potential for species and stage differences in the temperature-dependence of chytridiomycosis.

Download Full-text

Assessing Habitat Vulnerability and Loss of Naturalness: Applying the GLOBIO3 Model in the Czech Republic

Sustainability ◽

10.3390/su13105355 ◽

2021 ◽

Vol 13 (10) ◽

pp. 5355

Author(s):

Vilém Pechanec ◽

Ondřej Cudlín ◽

Miloš Zapletal ◽

Jan Purkyt ◽

Lenka Štěrbová ◽

...

Keyword(s):

Land Use ◽

Czech Republic ◽

Habitat Quality ◽

Species Abundance ◽

Biodiversity Loss ◽

Infrastructure Development ◽

Natural Habitats ◽

The Czech Republic ◽

New Equation ◽

The Impact

Global and regional biodiversity loss is caused by several drivers including urban development, land use intensification, overexploitation of natural resources, environmental pollution, and climate change. The main aim of our study was to adapt the GLOBIO3 model to the conditions of the Czech Republic (CR) to assess loss of naturalness and biodiversity vulnerability at the habitat level on a detailed scale across the entire CR. An additional aim was to assess the main drivers affecting the biodiversity of habitat types. The GLOBIO3 model was adapted to CZ-GLOBIO by adapting global to local scales and using habitat quality and naturalness data instead of species occurrence data. The total mean species abundance (MSA) index of habitat quality, calculated from the spatial overlay of the four MSA indicators by our new equation, reached the value 0.62. The total value of MSA for natural and near-natural habitats was found to be affected mainly by infrastructure development and fragmentation. Simultaneously, intensity of land use change and atmospheric nitrogen deposition contributed primarily to the low total value of MSA for distant natural habitats. The CZ-GLOBIO model can be an important tool in political decision making to reduce the impact of the main drivers on habitat biodiversity in the CR.

Download Full-text

“We Make Our Community”: Youth Forging Environmental Identities in Urban Landscapes

Sustainability ◽

10.3390/su13147736 ◽

2021 ◽

Vol 13 (14) ◽

pp. 7736

Author(s):

Erin Gallay ◽

Alisa Pykett ◽

Constance Flanagan

Keyword(s):

High School Students ◽

Urban Areas ◽

Local Environment ◽

Natural World ◽

Urban Landscapes ◽

Youth Of Color ◽

School Students ◽

Environmental Leadership ◽

And Gender ◽

The Impact

Insofar as race, class, and gender have profound effects on people’s environmental experiences, and consequently their activism, the environmental field needs more work on the environmental experiences and insights of groups whose voices have been missing, including youth of color who live in urban areas in the U.S. In this paper, we focus on African American and Latinx students engaged in environmental projects in their urban communities and the impact of such projects on promoting pro-environmental leadership, agency, and behavior. We draw from written reflections and focus group interviews of several hundred 4th–12th graders (majority middle- and high-school students) who participated in place-based civic science projects. Thematic analyses of student responses found that students engaged in work on local environmental issues cultivated an appreciation for the natural world and an understanding of human-nature interdependence and the ties between the local environment and their communities’ health. Through taking action with others in their communities, students viewed themselves as contributors to their communities and started to form environmental identities in ways that are not traditionally measured. Findings point to the need for forms of environmental education that are contextually grounded and centered on environmental justice in urban areas.

Download Full-text

Invasive Scots Pine, Pinus sylvestris, Replacing Corema, Corema conradii, Heathland in the Annapolis Valley, Nova Scotia

The Canadian Field-Naturalist ◽

10.22621/cfn.v119i2.112 ◽

2005 ◽

Vol 119 (2) ◽

pp. 237 ◽

Cited By ~ 5

Author(s):

Paul M. Catling ◽

Susan Carbyn

Keyword(s):

Pinus Sylvestris ◽

Scots Pine ◽

Vascular Plants ◽

Dominant Species ◽

Vascular Plant ◽

Agricultural Crops ◽

Deschampsia Flexuosa ◽

Natural Habitats ◽

Annapolis Valley ◽

The Impact

Examination of air photos from 1930, 1970 and 2002 revealed stands of the European Scots Pine (Pinus sylvestris) invading remnants of natural Corema (Corema conradii) heathland in the Annapolis valley. To document the impact of the introduced pines, four natural habitats were compared with two adjacent habitats already invaded by the pines. All surveyed habitats had been dominated by Corema heath based on air photos taken in 1930. Twenty 1 m2 quadrats were used to record presence and cover of vascular plants at each site. The invasive alien pines reduce the native cover to 12%. Vascular plant biodiversity is reduced to less than 42% and the cover of the heathland dominant, Corema conradii, is reduced from over 100 % to less than 2%. with Deschampsia flexuosa becoming the dominant species. The modified ecosystem and loss of biodiversity has economic impacts through loss of pollinators of agricultural crops and loss of germplasm of native crop relatives.

Download Full-text