Crested Newt Hybridization in UK

Posted by Annie Hatt on 21/07/2015

Great crested newts (Tritiurus cristatus) are well known within ecological consultancy as they are a protected species which often crop up within areas of proposed development. They are sensitive creatures which are vulnerable to water changes and therefore suffer due to natural forces including; ponds overgrowing, shallowing and eutrophication, as well as non-natural forces; industrial water pollution, destruction and drainage of ponds, introduced predatory fish and habitat fragmentation. But there may be another force to add into the mix…

It has been known that an Italian crested species (Triturus carnifex) was introduced into an area in Surrey, most likely escaping from the pet trade. Not only are these individuals more tolerant to water changes, they also do not need cover within the pond, do not always require vegetation to lay eggs, thrive in disturbed habitat and as a result is thought to outcompete the native T. cristatus and become the dominant species.     To complicate the matter further hybrid individuals of T. cristatus and T. carnifex have now been identified morphologically and molecularly. Hybridization of these two subspecies have been identified previously in other areas of the world including; on the boarders of Germany and Austria, however the impacts are thought to only be local rather than regional (Beebee and Griffiths 2005), and within the Netherlands. Here the hybrid was found, although it is thought the native species T. cristatus, selects against mating with the alien species T. carnifex, evidence of hybrids have been found as well as evidence of T. cristatus DNA within alien populations, through molecular studies. This suggests alien individuals outcompete the native individuals resulting in change in female preference.

Although long term effects in the UK are hard to identify, the introduction of the T. carnifex along with the hybridization of the two species is sure to have a detrimental effect on our already declining great crested newt populations. Serious thought needs to be given to control measures and containing these introduced individuals, as well as research into any further distributions of T. carnifex to prevent them further outcompeting our native species.