Marine mammal faeces as a source of DNA

[Extract] Remote collection of skin biopsies from free-ranging marine mammals has been to date, the most effective and noninvasive means of tissue collection for DNA studies (Amos & Hoelzel 1990; Brown et al. 1991; Weinrich et al. 1991). Although it has been shown that DNA extraction from faeces is possible (Hoss et al. 1992), there are no records of DNA extraction from the faeces of marine mammals, perhaps because it is expected their faeces have a shorter life span compared with the faeces of (dry) land mammals. We have been able to extract DNA from the faeces of a free-ranging dugong (Dugong dugon).\ud \ud We present a sequence from this DNA, a region of the mitochondrial DNA which we have used for a genetic population structure study of the dugong. Extraction of DNA from faeces of marine mammals provides an attractive alternative to biopsy sampling. It is less invasive and more economical. The dugong faecal sample was collected from Borroloola (15°8'S 136°7'E) as part of a feeding study (A.R. Preen, pers. comm., 1995). Dugong feeding trails are easily recognizable and their faeces float to the surface of the water. Several intact faeces were collected after floating for an undetermined time (a few hours?) and individually contained in plastic bags. It was about 3h before they were frozen and, although they stayed cold, they were defrosted during a 2 day transit, refrozen, then thawed for DNA extraction

Absence of evidence for isolation by distance in an expanding cane toad (Bufo Marinus) population and individual-based analysis of microsatellite genotypes

The cane toad (Bufo marinus) was introduced in 1935 in Australia, where it spread rapidly. We have tested for isolation by distance by analysing at a local geographical scale a continuous population using seven microsatellite markers and an individual-based method. The matrix of pairwise individual differentiation was not significantly correlated with that of geographical distance. Regression analyses gave a low positive slope of 0.00072 (all individuals) or a negative slope of 0.0017 (individuals with a distance higher than the previously estimated mean dispersal distance). The absence of evidence for isolation by distance favours the hypothesis that the substantial differentiation and autocorrelation previously observed at enzyme loci, mainly results from discontinuities in the colonization process with founder effects occurring at the time of the establishment of new populations