Genetic Scorecard Indicator - Great Crested Newt

The Highland population is known to be distinct from the rest of the British population (O’Brien et al., 2015). Recent studies suggest that the number of occupied sites in the Highlands has increased by around 25% due to targeted interventions incorporating genetic knowledge (O’Brien et al., 2021). 

Population definitions:

Populations are defined based on biogeography and genetic evidence. There is a wide and near continuous distribution of great crested newts within England, Wales and Southern Scotland. To allow for local adaptation, this has been assessed based on the four zones that form the basis of UK seed zones. The disjunct and genetically distinct population the Scottish Highlands has been considered as a separate population.

Ne500: The proportion of populations that have an effective population size of more than 500. 

PM: Proportion of populations that existed in 2000 that still exist in 2025.

Functional variation

The Highland population within Scotland shows some functional variation from the rest of its British range (Miró et al., 2017). The population has limited numbers and the distance between it and the main population is far enough to effectively prevent geneflow between the two. This coupled with the small population size makes it vulnerable. 

Divergent lineages

There is a genetically distinct lineage found within the Highlands and due to interventions, it has experienced an increase in population size (O’Brien et al., 2021). Should this population be lost, the overall UK population would lose genetic diversity.

Hybridisation/Introgression

Within the UK, there is evidence of hybridisation with the introduced Italian crested newt (Triturus carnifex) in southern England leading to some introgression (Beebee & Griffiths, 2000; Brede 2015). 

Low turnover - constraints on adaptive opportunities

The species typically produces over 200 eggs in a breeding season. Although egg and larval mortality are high, in the absence of introduced fish and other pressures T. cristatus is able to establish large populations quickly (Jehle et al., 2011; O’Brien et al., 2021).

For most of the great crested newt population, the risk of loss of genetic diversity is negligible except for the Highland population which holds fewer than the Ne 500 threshold. There are multiple protections in place for the species, however there are still declines and at-risk populations. 

In situ genetic threat level

Confidence in in situ threat level

There is a negligible ex situ population found within two institutions in the UK of an estimated five individuals according to the IUCN Red List 2023 report.

Great crested newts are fully protected under the following acts and legislation: Schedule 5 of the Wildlife and Countryside 1981 Act, The Habitats Regulation 1995, and the Habitats Directive 1992. 

Population

Demographic

Genetic