Using DNA to sum up the Scottish adder

12/06/2018 in Conservation

RZSS WildGenes Scottish adder - photo by Pete Minting

Above: Wild adders at home in the Scottish countryside - photo © Pete Minting

At the RZSS WildGenes lab we have been working on producing a bank of genetic data that can be used to help fight the illegal trade of python skins, commonly sourced from South East Asia, for use in the high-end fashion industry. A little closer to home, and although not generally threatened by a handbag-shaped future, reptile species in Scotland are also coming under threat. 

The common European adder (Vipera berus) is Britain’s only venomous snake. It can be found on the British mainland and some islands, but is absent from Ireland (https://www.arc-trust.org/adder). The adder was once a common sight across large parts of the countryside but like many reptile species in recent decades, the adder has suffered significant declines in both its range and population size. It is thought that modern agricultural practices have resulted in habitat degradation and fragmentation, leading to smaller and more isolated populations of this enigmatic reptile. In other countries, collection for the pet trade or for venom extraction have also been recorded as major contributing factors to the decline of the Vipera species.

As adder numbers have declined the remaining populations have become increasingly isolated and it is now feared that these fragmented populations may also have low levels of genetic diversity. Small, fragmented groups with limited genetic diversity are also vulnerable to external factors such as disease, which in turn can exacerbate declines, even leading to local extinctions. In other areas, such as Sweden, increasing genetic diversity has been shown to be a key component for the rescue of adder populations. In the UK however, little is known about genetic diversity levels and how these might be influencing declines. A genetic assessment to determine the current levels of genetic diversity across adder populations in Scotland could provide the essential data to inform conservation practices.

RZSS WildGenes sloughed snake skin

Above: A dried sample of a sloughed adder skin in the lab. You can still see the shape of the head  and clear skin pattern on this specimen but others are shed in fragments - photo © Konstantinos Kalaentzis

 

Most genetic studies on snakes to date have used DNA from biological samples, such as muscle tissue, blood, or buccal swabs. To collect DNA via this method is very time consuming as the animal must first be caught and this often requires significant time and skill to ensure minimal impact on the individual adders. However, there are alternative sampling methods that can limit disturbance to the individuals or populations, such as the collection of sloughed skins. As reptiles, adders regularly shed their skin and these sloughed remnants can be found fragmented or whole around hibernation sites. They are also more easily found than other biological samples such as road kills or adder faeces and can dry quickly in warm weather, helping to preserve them. At WildGenes, the team is working to develop an efficient protocol for extracting DNA from this resource, found naturally in the Scottish countryside. By establishing an optimised method for extracting DNA from sloughed snake skins, we can then look towards carrying out a more thorough genetic analysis of adder populations in Scotland, using non-invasive sampling. We look forward to updating you on our progress with this work in the future.

All the best,

Gill and Konstantinos (Erasmus+ placement student)

 

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