Amphibians are one of the most threatened animal groups in the world. Nearly one third of all species are under acute threat. One of the main reasons for their decline is a fungus which has a nearly worldwide distribution. Under the lead of researcher from the Museum für Naturkunde in Berlin nearly 800 amphibians belonging to over 60 species were searched for the disease. Analyses revealed that the fungus could find suitable environmental conditions in West Africa but does not occur yet. Therefore this biodiversity hotspot is beside Madagascar the only chytrid free region in the world.</span>
Under the direction of scientists of the Museum für Naturkunde in Berlin nearly 800 amphibians were analysed in search of the chytrid fungus (Batrachochytrium dendrobatidis). It is assumed that it is responsible for the amphibian decline in many regions of the world. In infected individuals the fungus settles itself into the skin and blocks respiration therein which kills the animals in the end. Chytrid is widespread in Africa and every year new positive records are reported from countries in southern, eastern and central Africa. The current study did not detect chytrid in western Africa despite extensive tests of 62 species from seven countries. This is especially remarkable because an analysis of environmental factors showed clearly that the fungus would find suitable conditions in western Africa. Thus its occurrence should be highly likely.
The international team used a number of different methods and analysed the samples partly genetically, partly histologically in different laboratories which all had experience in detecting chytrid. These consistent negative results were compared to against results derived from modelling environmental parameters from regions where positive records exist. This shows clearly that the occurrence of chytrid is very likely in West Africa. One explanation for this lack, according to Johannes Penner, first author of the study, could be the Dahomy Gap. This natural gap in the distribution of rain forests in West Africa (in the countries Togo and Benin) is probably a natural barrier for the dispersal of the of the fungus.
Therefore West Africa is the last tropical region beside Madagascar where chytrid does not exist. So it could be that the global amphibian decline spares the region? “Unfortunately this is not the case!” says Dr. Mark-Oliver Rödel, Curator of Herpetology at the Museum für Naturkunde. “Unfortunately the conversion and destruction of natural habitats are still the main cause for the amphibian decline”. This also still happens on a large scale in western Africa.
However, it would be one big step if it would be possible to avoid the anthropogenic dispersion of chytrid into western Africa. The researchers also discuss potential routes of the fungus into the region (e.g. via the trade of frogs for the food market) and suggest various precautionary measures. For example the transport of potential fungus infected materials between the regions should be controlled and materials prophylactically disinfected. In addition an early warning system would be useful to detect the appearance of the fungus in Ghana, a potential entry point. Within the combination of all factors contributing to the global amphibian decline, this would eliminate a significant one from western Africa.
Johannes Penner, Gilbert B. Adum, Matthew T. McElroy, Thomas Doherty-Bone, Mareike Hirschfeld, Laura Sandberger, Ché Weldon, Andrew A. Cunningham, Torsten Ohst, Emma Wombwell, Daniel M. Portik, Duncan Reid, Annika Hillers, Caleb Ofori-Boateng, William Oduro, Jörg Plötner, Annemarie Ohler, Adam D. Leaché & Mark-Oliver Rödel (2013) Title: West Africa - A Safe Haven for Frogs? A Sub-Continental Assessment of the Chytrid Fungus (Batrachochytrium dendrobatidis). PLOS ONE http://dx.plos.org/10.1371/journal.pone.0056236