Spatial and temporal population genetics of Swiss red foxes (Vulpes vulpes) following a rabies epizootic

• Main Author: Wandeler, Peter
• Format: Dissertation
• Language: English
• Published: Cardiff University 2004

Infectious disease can affect the demography of natural populations and, as a consequence, can alter the genetic variation within and between those populations. This study investigated long-term effects of rabies-induced mortality on the demography and genetic variation in two Swiss red fox populations over ten to fourteen generations. In Switzerland, the last rabies epizootic persisted from 1967 to 1999 and was continuously monitored by collecting fox carcasses throughout the country. Alongside records of rabies tests and post-mortem data, tooth samples were systematically archived for ageing. In this study, DNA from 666 individual teeth was extracted. For 279 extracts, the concentration of nuclear DNA was estimated in a quantitative PCR and found to be negatively correlated with storage time. After excluding samples with insufficient DNA concentration for reliable genotyping, 382 samples were screened using between nine and seventeen canine and red fox specific microsatellites. Tooth samples were combined with 189 modern tissue samples. By assessing the age structure continuously throughout and after the rabies epizootic for the first population, population census size and age structure were found to be altered by the high rabies-induced mortality. In contrast, no long-term trends in genetic diversity were identified although a high variation of Ho, He, F s was discovered both in short-term and longer-term. A strong isolation-by-distance pattern was revealed for the second population by comparing individual pairwise genetic with spatial distances using modern samples. Furthermore, genetic data demonstrated that dispersal was sex-biased and diverted by the topography of the landscape. When investigating isolation-by-distance patterns within the same population in 1971-73 and 1982-84 at lower population densities, density-dependant dispersal was observed. In conclusion, this study revealed no loss of genetic diversity in red foxes following a rabies epizootic despite a population bottleneck, yet highlights population density as an important factor to determine local spatial genetic structure.