Ben Thornes

The Genetic composition of Purbeck Sika

Tuesday 15th July 2014

Sika Deer Genetics’ is there evidence of recent or past hybridization with Red Deer?

Sika Cervus Nippon are native to Japan and East Asia, but are now naturalised in many parts of the world ‘ including England. It has become increasingly apparent, in Britain, and in other countries to which sika have been introduced, that sika may have considerable ecological and economic impacts. Feral sika populations in Britain have been shown to have the potential to cause significant damage to forestry, agricultural crops and conservation habitats. Additionally, there are concerns that sika hybridise freely with red deer Cervus elaphus and may therefore threaten the genetic integrity of native populations of red deer. There has been a substantial body of research on the extent of hydridization between sika and red deer in Scottish populations, but until now there had been little genetic analysis of the English populations of sika in comparison. Sika populations in England still have a patchy and discontinuous distribution; thus populations are still genetically isolated and may be expected to show higher variability in genetic type.

This study by Bournemouth University ecologist Anita Diaz used DNA based techniques to explore the genetic composition of sika in the New Forest, and that of sika from the Purbeck region of Dorset.

Sika were first introduced to Dorset around 1880 when they were released into the Melbury Park Estate, then subsequently to Brownsea Island in Poole Harbour in 1886. The Brownsea animals escaped to the mainland during the early 20th century and established feral herds in the surrounding area as did escapees from another captive population introduced to Hyde House, near Wareham. The origin of the sika introduced to Brownsea and to Hyde is not certain, but it is likely that like many other British populations of sika, they originated from captive stock bred at Powerscourt Park, Wicklow, Ireland and therefore are not pure sika. Subsequently, Purbeck now has one of the largest groups of feral sika in England, with an estimated number of 2000 individuals in the region.

Feral sika in the New Forest are considered to have descended from four animals: one pair that escaped from the collection of Lord Montagu at Beaulieu in 1904 into neighbouring Ashen Wood and another pair that were deliberately released into the same wood the following year. For the majority of the 20th century, sika were restricted to the woods to the south of the railway line running through the New Forest between Brockenhurst and Beaulieu road station. During the 1970s and 1980s sika spread to other parts of the New Forest with population size also increasing during this time with numbers exceeding 200-300 by the late 1980’s. Since then culling policy has changed, and the number of sika in the New Forest is held at below 150 animals.

Samples of New Forest deer were gathered in the form of neck muscle, ear or tongue tips obtained from a total of 54 sika and 13 red deer by the New Forest keepers during routine cull operations. Samples of sika tissue were collected from a total of 329 sika collected from various locations widely distributed around the Purbeck area, again during routine culling operations.

Samples were obtained from populations of red and sika deer that are considered to be pure bred, so therefore uncontaminated with introgressed genes from other species of Cervus. For this, red deer samples were collected in Fife (four animals) and Rum (five animals), and sika deer control samples came from three animals from the Nagasaki region of Japan, supplied as DNA extracts.

Samples were also obtained from suspected non-native red deer in East Anglia. These red deer are generally thought to have derived at least in part from stock that originated in deer parks and therefore are of uncertain genetic provenance. Five deer from East Anglia which were phenotypically ‘red’ were also analysed in this study to investigate whether the genetic analysis was able to detect sika DNA introgression in these animals.

The results of this analysis showed that sika and red deer in the New Forest were genetically distinct, which indicates that there is no large-scale in situ hybridisation occurring between these feral populations. In terms of the overall genetic composition, there was no significant difference between the sika in the New Forest and those in Purbeck. However, a further, more detailed analysis found that New Forest sika showed a lower level of introgression with red deer compared with Purbeck sika. The paper concludes that, overall, the New Forest sika deer do appear to be more genetically pure bred than the Purbeck sika.

To read the full article, click on the .pdf below.

To find out more about Dr. Anita Diaz and her research, click here.

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