Tuesday, 21 May 2013

Chytridiomycosis and Seasonal Mortality of Tropical Stream

Assessing the effects of diseases on wildlife populations can be difficult in the absence of observed mortalities, but it is crucial for threat assessment and conservation. We performed an intensive capture-mark-recapture study across seasons and years to investigate the effect of chytridiomycosis on demographics in 2 populations of the threatened common mist frog (Litoria rheocola) in the lowland wet tropics of Queensland, Australia. Infection prevalence was the best predictor for apparent survival probability in adult males and varied widely with season (0–65%). Infection prevalence was highest in winter months when monthly survival probabilities were low (approximately 70%). Populations at both sites exhibited very low annual survival probabilities (12–15%) but high recruitment (71–91%), which resulted in population growth rates that fluctuated seasonally. Our results suggest that even in the absence of observed mortalities and continued declines, and despite host–pathogen co-existence for multiple host generations over almost 2 decades, chytridiomycosis continues to have substantial seasonally fluctuating population-level effects on amphibian survival, which necessitates increased recruitment for population persistence. Similarly infected populations may thus be under continued threat from chytridiomycosis which may render them vulnerable to other threatening processes, particularly those affecting recruitment success.

Chytridiomycosis and Seasonal Mortality of Tropical Stream-Associated Frogs 15 Years after Introduction of Batrachochytrium dendrobatidis - PHILLOTT - 2013 - Conservation Biology - Wiley Online Library

No Bd in Speleomantes

A new paper by Frank Pasmans and coauthors in the open access journal PLoS ONE shows that there is no Bd in Speleomantes salamanders. Pasmans et al. use experiments to show that Speleomantes salamanders appear to be resistant to Bd. http://www.plosone.org/article/metrics/info%3Adoi%2F10.1371%2Fjournal.pone.0063639

Wednesday, 15 May 2013

California frogs once used for pregnancy tests carry deadly fungus - latimes.com

Frogs that were imported for pregnancy tests and set loose in California carry a deadly fungus responsible for wiping out vast numbers of amphibians worldwide, scientists have found.
Populations of African clawed frogs (Xenopus laevis) have thrived for decades in the state’s drainage ditches and ponds, but their link with the deadly Batrachochytrium dendrobatidis fungus was unverified until a research team from Stanford University and San Francisco State University recently tested museum samples for the fungus.

California frogs once used for pregnancy tests carry deadly fungus - latimes.com

Fatal fungus found in third major amphibian group, caecilians | Natural History Museum

It is known as the amphibian chytrid fungus and can cause a deadly disease that is decimating some of the world's frogs, toads, newts and salamanders. However, the fungus had not been detected in the other lesser-known major group of amphibians, the caecilians, until now.

Fatal fungus found in third major amphibian group, caecilians | Natural History Museum

Tuesday, 14 May 2013

PLOS ONE: Widespread Occurrence of Batrachochytrium dendrobatidis in Contemporary and Historical Samples of the Endangered Bombina pachypus along the Italian Peninsula

Batrachochytrium dendrobatidis is considered a main driver of the worldwide declines and extinctions of amphibian populations. Nonetheless, fundamental questions about its epidemiology, including whether it acts mainly as a “lone killer” or in conjunction with other factors, remain largely open. In this paper we analysed contemporary and historical samples of the endangered Apennine yellow-bellied toad (Bombina pachypus) along the Italian peninsula, in order to assess the presence of the pathogen and its spreading dynamics. Once common throughout its range, B. pachypus started to decline after the mid-1990s in the northern and central regions, whereas no declines have been observed so far in the southern region. We show that Batrachochytrium dendrobatidis is currently widespread along the entire peninsula, and that this was already so at least as early as the late 1970s, that is, well before the beginning of the observed declines. This temporal mismatch between pathogen occurrence and host decline, as well as the spatial pattern of the declines, suggests that the pathogen has not acted as a “lone killer”, but in conjunction with other factors. Among the potentially interacting factors, we identified two as the most probable, genetic diversity of host populations and recent climate changes. We discuss the plausibility of this scenario and its implications on the conservation of B. pachypus populations.
PLOS ONE: Widespread Occurrence of Batrachochytrium dendrobatidis in Contemporary and Historical Samples of the Endangered Bombina pachypus along the Italian Peninsula

Friday, 10 May 2013

Bd on Sardinia

A new paper out on-line at Diversity and Distributions, co-authored by members of RACE and the NGO Zirichiltaggi describes geographic and host patterns of infection in Sardinian amphibians. Infection was only detected in two of the species found on the island, one endemic and threatened and one near-endemic and considered not threatened by the IUCN. Based on species-specific patterns of habitat use, the authors also conclude that infection is predominantly maintained through intraspecific transmission. Buona lettura!

Monday, 6 May 2013

Chytrid fungus '40,000 years old' | Story & Education Stories | The Australian

History, novelty, and emergence of an infectious amphibian disease Understanding the evolutionary history of microbial pathogens is critical for mitigating the impacts of emerging infectious diseases on economically and ecologically important host species. We used a genome resequencing approach to resolve the evolutionary history of an important microbial pathogen, the chytrid Batrachochytrium dendrobatidis (Bd), which has been implicated in amphibian declines worldwide. We sequenced the genomes of 29 isolates of Bd from around the world, with an emphasis on North, Central, and South America because of the devastating effect that Bd has had on amphibian populations in the New World. We found a substantial amount of evolutionary complexity in Bd with deep phylogenetic diversity that predates observed global amphibian declines. By investigating the entire genome, we found that even the most recently evolved Bd clade (termed the global panzootic lineage) contained more genetic variation than previously reported. We also found dramatic differences among isolates and among genomic regions in chromosomal copy number and patterns of heterozygosity, suggesting complex and heterogeneous genome dynamics. Finally, we report evidence for selection acting on the Bd genome, supporting the hypothesis that protease genes are important in evolutionary transitions in this group. Bd is considered an emerging pathogen because of its recent effects on amphibians, but our data indicate that it has a complex evolutionary history that predates recent disease outbreaks. Therefore, it is important to consider the contemporary effects of Bd in a broader evolutionary context and identify specific mechanisms that may have led to shifts in virulence in this system. Chytrid fungus '40,000 years old' | Story & Education Stories | The Australian

Saturday, 4 May 2013

No Bd in Lyciasalamandra (but Bd occurs in Turkey)

A new paper by Bayram Göçmen et al. published in the journal Salamandra (link) suggests that there is no Bd in the terrestrial salamanders of the genus Lyciasalamandra. Earlier this year, Chiari et al. reported in a paper published in Amphibia-Reptilia that there was no Bd in terrestrial Hydromantes salamanders and last year Lötters et al. published a paper in Salamandra showing that there was no Bd in the terrestrial Salamandra atra. Is it a general rule that there is no Bd in terrestrial salamanders?