Effects of precipitation on parasite burden along a natural climatic gradient in southern Africa - implications for possible shifts in infestation patterns due to global changes

To authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1600-0706.2009.18124.x Byline: Gotz Froeschke, Rainer Harf, Simone Sommer, Sonja Matthee Abstract: As a consequence of environmental change, it is expected that shifts in temperature and precipitation patterns will influence parasite communities and their hosts with unpredictable impact. Parasites play a vital role in ecosystems but there is only limited quantitative data which describe the effects of environmental parameters under natural conditions. We investigated the influence of rainfall, relative humidity and temperature on the prevalence, abundance and infection intensity of nematodes in southern Africa by studying the gastro-intestinal helminth community of the striped mouse Rhabdomys pumilio. Along a precipitation gradient from the Cape of South Africa to northern Namibia we trapped 470 mice over a geographical distance of about 1400 km. Faecal egg counts of 439 sampled individuals and dissections of 161 gastro-intestinal tracts revealed 15 different helminth species. The most abundant nematode species harboured in 62.6% of all infected mice were the oxyurid Syphacia obvelata followed jointly by two species (Heligmonina spira and Neoheligmonella capensis) of the subfamily Nippostrongylinae (43.7%). We found a significant positive correlation between mean annual precipitation (rainfall and relative humidity) and nematode infestation rates of animals and a negative correlation with temperature. In addition, we found associations between precipitation and different qualitative measurements of parasite burden (mean nematode species richness, mean number of nematode worms and infection intensity per individual host). The similarity in nematode species composition decreased with distance between all study sites. Our study indicates for the first time an association between climatic variables and parasite prevalence and abundance along a continuous natural climatic gradient in a small mammal. These results might be incorporated in the development of models which can predict possible threats for the balance of ecosystems and shifts in infestation patterns due to global changes. Author Affiliation: (1)Evolutionary Genetics, Leibniz-Institute for Zoo and Wildlife Research (IZW), Alfred-Kowalke-Stra[beta]e 17, DE-10315 Berlin, Germany (2)Animal Ecology and Conservation, Univ. of Hamburg, Martin-Luther-King-Platz 3, DE-20146 Hamburg, Germany (3)Dept. Conservation Ecology and Entomology, Private Bag X1, Univ. of Stellenbosch, Matieland, 7602, South Africa Article History: Paper manuscript accepted 9 October 2009 Article note: S. Sommer, Evolutionary Genetics, Leibniz-Institute for Zoo and Wildlife Research (IZW), Alfred-Kowalke-Stra[beta]e 17, DE-10315 Berlin, Germany. E-mail: sommer@izw-berlin.de