Molecular Ecology zyxwvuts 1996,5, 81-87 zyxwvuts Microsatellite differentiation between Phillip Island and mainland Australian populations of the red fox z Vulpes zyxwvut vulpes J. A. LADE,*+ N. D. MURRAY,* C. A. MARKS$ and N. A. ROBINSONt *Department of Genetics and Human Variation, La Tmbe University, Bundoora, Victoria 3083, Australia, tVictorian lnstitute of Animal Science, 475 Mickleham Road, Attroood, Victoria 3049, Australia and $Department of Conservation and Natural Resources, Keith Turnbull Research Institute, PO Box 48, Frankston, Victoria 3199, Australia Abstract Predation by the red fox Vulpes auZpes is believed to be threatening the little penguin EudyptuZa minor on Phillip Island in Victoria. Polymorphism at seven microsatellite loci was examined to estimate the extent of differentiation between Phillip Island and main- land populations of V mrlpes. Loss of alleles has occurred on Phillip Island where foxes first appeared zyxwvuts = zyxwvut 88 years ago compared with mainland populations. Genetic differentia- tion between the Phillip Island and mainland populations was high. The relatively high differentiation found between the two populations could be due to either low migration rates, the effect of the composition of founder animals or both effects. Further ecological and historical information about the populations is needed to explore the likely signifi- cance of these effects. Keywords: Eudyptula minor, gene flow, genetic variation, miaosatellites, population genetics, Vulpes vulpes Received 3 April 1995; revision received 26 July 2995; accepted 24 September 1995 Introduction Predation by the European red fox Vulpes vulpes in Australia is believed to have contributed to the decline or extinction of a number of native mammalian and avian populations including the Eastern barred bandicoot Perameles gunnii, long footed potoroo Potomus longipes, mountain pigmy-possum Burramys parous, brush-tailed rock-wallaby Petrogale penicillata, malleefowl Leipoa ocellata and little penguin Eudyptula minor (Mansergh & Marks 1993). zyxwvutsrqp V: vulpes was first released in Australia around 1870 and spread throughout much of the continent by the 1940s (Rolls 1969). There zyxwvutsr are some indications that the early and rapid movement of foxes in Australia was assisted by deliberate spread of the animals by humans in an attempt to control rabbit populations (Rolls 1969; Saunders et al. 1994). The present distribution of V. oulpes covers all of mainland Australia except the tropical north (Jarman 1986). Correspondence: Jennifer Anne Lade. Victorian Institute of Animal Science, 475 Mickleham Road, Attwood, Victoria 3049, Australia. Fax: 61 32174299. In Europe V vulpes has been observed to form breeding groups consisting of several related females and an unre- lated male (Voigt 1987). However, adult pairs occupy tem- tones in most rural and and zone habitats in Australia (C. Marks, personal observations). Dispersal of both sexes from the den generally occurs between six to nine months of age in Australia (Saunders et al. 1994). Males have been known to disperse between 3 and 44km and females between 2 and 39km from the natal den in the UK (Trewhella et al. 1988). A positive correlation between mean dispersal distance and home range size has been detected for both sexes suggesting that dispersing foxes travel in increments of home range diameters (Trewhella et al. 1988). The role offoxes in the decline of little penguin populations on Phillip Island The distribution of little penguins, Eudyptula minor, throughout Australia and New Zealand is limited to remote regions of the mainland coast and islands which are inaccessible to mammalian predators. A large breeding colony exists on Phillip bland, Victoria. The red fox was first sighted on Phillip Island in 1907 (Gliddon 1977). In 0 1996 Blackwell Science Ltd