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Population Genetics of Sika Deer
To establish whether populations of Sika deer from different parts of Purbeck are genetically distinct and thus isolated or part of a continuous population. In order to explore the degree of relatedness between different subpopulations within Purbeck, the sample of Sika above will be drawn from ten different subpopulations across the Isle of Purbeck (Figure 1). Thirty animals will be sampled from each sub population (approximately 15 males and 15 females per subpopulation). To establish whether the New Forest Populations are pure Sika or hybrids. There is only a single population of Sika deer in the New Forest, in a relatively isolated population in the southeastern corner. All samples will be drawn from this one population. To compare the genetic structure of the New Forest and Purbeck populations. Sika deer were first brought to British deer parks and private collections during the 1800's (Whitehead, 1964; Ratcliffe, 1967; Putman, 2000). Subsequent escapes or in some cases deliberate release of animals from these collections have resulted in Sika deer being widely distributed across Britain. These feral populations are of direct concern due to their impacts on forestry, agricultural crops and conservation habitats (as at Arne, above) and due to the widely recognised problem of hybridisation with native stocks of Red deer . There have been a number of separate introductions of Sika to the British Isles (Ratcliffe, 1967; Putman 2000). Although the vast majority of populations in the UK mainland would appear to have derived secondarily from the park collection at Powerscourt in County Wicklow, Eire, it seems probable that a small number of populations may have independent origins; it is possible that some may have been imported directly from Japan or mainland Asia. Many of these populations may have been of hybrid status even on initial introduction; subsequently other feral populations in the UK and elsewhere have repeatedly hybridised with Red deer. Some early studies on cranial morphometrics suggest that the vast majority of populations in mainland UK are now of hybrid status (Ratcliffe et al., 1992; Putman & Hunt, 1994). Understandably, given the heavily skewed geographical distribution of wild Sika deer, most work to date has concentrated on the abundant and widespread populations in Scotland. Here, more recent analyses, using the more sophisticated techniques of DNA analysis have confirmed that the majority of populations are of hybrid status (Abernethy, 1994; Goodman et al. 1999), although the central core of the expanding population of Sika at Peebles appears to be genetically pure Sika (and of an independent origin from others; Ratcliffe et al., 1992). By contrast relatively little work has been undertaken in 'typing' populations of sika in England, with lack of interest presumably reflecting their comparative scarcity. Yet ironically, this scarcity, and the fact that sika in England still tend to occur small, isolated populations, makes a study of their genetics and genetic diversity potentially of more interest than studies of what is now an almost continuous population distribution within Scotland. Early morphometric studies of Putman and Hunt (1994), using analyses based on a series of skull measurements found that while, again, the majority of sampled populations proved to be of hybrid status, the population in the New Forest in Hampshire did not cluster with other populations sampled, or with the Red deer marker. These early indications would suggest that the New Forest population may also be pure Sika. Craniometric techniques are not particularly sensitive however and this tentative conclusion awaits confirmation by the more sensitive analytical techniques of DNA profiling. No animals from the extensive population of Sika in the Isle of Purbeck were included in the earlier craniometric analyses. Science has moved on a good deal since this early work in England. DNA profiling techniques are now well-established and reliable and it is thus possible to repeat the earlier morphometric studies of Putman and Hunt, using a much more reliable and sensitive 'tool'. Clear genetic differences have also been determined between the native populations of the different Japanese islands (Ratcliffe et al., 1992; Goodman et al., 2001). Thus it should prove possible with modern techniques not only to determine whether or not any current populations are of pure, or of hybrid status, but also to suggest for each population the likely original founder population in Japan or mainland Asia. This may be of significance in determining the status of different UK populations (for many of which, as noted, documentary evidence of source of origin is completely missing (Ratcliffe, 1967). The current project aims to investigate the genetics of Sika deer within the Isle of Purbeck to determine whether or not these are of pure or hybrid status, and to determine the relationships with one another of the different subpopulations within Purbeck . DNA analyses of material from Sika in the New Forest will also be undertaken to determine the genetic status of New Forest Sika deer and confirm whether or not these are pure (non-hybrid) Sika.
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To establish whether the Purbeck populations are pure Sika or hybrids. DNA samples, taken from different Sika populations within the Isle of Purbeck, will be challenged with a number of genetic "probes" to look for a number of marker genes which we know to be possessed only by Red deer, or only by Sika deer. Pure Sika populations should have only Sika marker genes, and none characteristic of Red deer. Hybrid populations will show a combination of characteristically 'Red' and characteristically 'Sika' genes (Goodman et al., 1999). Simon Goodman has agreed to make available to us the same probes as he himself used in his own studies of hybridisation in Scottish populations.