FrogLog and Bd

There are several interesting articles on Bd in the new issue of FrogLog (e.g. an update on the global Bd mapping project). http://www.amphibians.org/wp-content/uploads/2013/07/froglog-107-low-res.pdf

Bd becomes more virulent as it spreads

A new paper published in the Proceedings of the Royal Society (here's the link to the paper) shows that Bd become more virulent as it spread through the Americas.

Temperature determines how amphibian populations respond to Bd

A team lead by Ben Doddington shows in a new paper that was recently published in Ecology that temperature determines the response of amphibian populations to Bd. Link to the abstract of the paper.

Monitoring Strategy for Eight Amphibian Species in French Guiana, South America

Although dramatic amphibian declines have been documented worldwide, only few of such events have been quantitatively documented for the tropical forests of South America. This is due partly to the fact that tropical amphibians are patchily distributed and difficult to detect. We tested three methods often used to monitor population trends in amphibian species in a remote lowland tropical forest of French Guiana. These methods are capture-mark-recapture (CMR), estimation of the number of calling males with repeated counts data and distance sampling, and rates of occupancy inferred by presence/absence data. We monitored eight diurnal, terrestrial amphibian species including five Dendrobatidae and three Bufonidae. 

Monitoring Strategy for Eight Amphibian Species in French Guiana, South America

Site occupancy models in the analysis of environmental DNA presence/absence surveys: a case study of an emerging amphibian pathogen

Site occupancy models in the analysis of environmental DNA presence/absence surveys: a case study of an emerging amphibian pathogen

1. The use of environmental DNA (eDNA) to detect species in aquatic environments such as ponds and streams is a powerful new technique with many benefits. However, species detection in eDNA-based surveys is likely to be imperfect, which can lead to underestimation of the distribution of a species.
2. Site occupancy models account for imperfect detection and can be used to estimate the proportion of sites where a species occurs from presence/absence survey data, making them ideal for the analysis of eDNA-based surveys. Imperfect detection can result from failure to detect the species during field work (e.g. by water samples) or during laboratory analysis (e.g. by PCR).
3. To demonstrate the utility of site occupancy models for eDNA surveys, we reanalysed a data set estimating the occurrence of the amphibian chytrid fungus Batrachochytrium dendrobatidis using eDNA. Our reanalysis showed that the previous estimation of species occurrence was low by 5–10%. Detection probability was best explained by an index of the number of hosts (frogs) in ponds.
4. Per-visit availability probability in water samples was estimated at 0·45 (95% CRI 0·32, 0·58) and per-PCR detection probability at 0·85 (95% CRI 0·74, 0·94), and six water samples from a pond were necessary for a cumulative detection probability >95%. A simulation study showed that when using site occupancy analysis, researchers need many fewer samples to reliably estimate presence and absence of species than without use of site occupancy modelling.
5. Our analyses demonstrate the benefits of site occupancy models as a simple and powerful tool to estimate detection and site occupancy (species prevalence) probabilities despite imperfect detection. As species detection from eDNA becomes more common, adoption of appropriate statistical methods, such as site occupancy models, will become crucial to ensure that reliable inferences are made from eDNA-based surveys.