Nuanced impacts and social perceptions of alpine newts Ichthyosaura alpestris in the UK

Abstract

Invasive species are major drivers of environmental change and their incidence appear to be growing worldwide. An understanding of the subtleties and complexities of invasion is important for conservation decision-making as not all introduced species become invasive, and the impacts of those that do can be highly context dependent. The alpine newt Ichthyosaura alpestris is a non-native species that is now widely distributed across the UK. An understanding of the drivers of introduction and spread of this species are in its infancy, and whilst anecdotal reports are indicative of negative ecological impacts, empirical evidence is lacking. This interdisciplinary thesis aims to address gaps in our knowledge using approaches in spatial and population ecology and the social sciences to better understand the conservation relevance of this species to UK amphibian populations. I first use species distribution and ecological niche models to investigate the invasive suitability of the UK for alpine newts, whilst also investigating the importance of evolutionary lineage for climate-based risk analyses. I then use targeted questionnaires to gather knowledge and opinions of those with most experience of this species. Finally, I conduct a multi-method and multi-biological scale field study quantifying the ecological impact of alpine newts in a wild amphibian system in Ceredigion, Wales. I find the UK to be highly climatically suitable for alpine newts and for species-level predictions, opposed to evolutionary lineage-level, to be most robust with current datasets. Targeted questionnaires provide highly valuable insights into the patterns and processes of alpine newt introduction in the UK but perceptions of impact and opinions towards management were strongly influenced by personal attitudes and experiences. Low prevalence of systematic population monitoring suggest current opinions towards management are based largely on perceptions rather than evidence. I find subtle but negative ecological impacts of alpine newts on native palmate newt populations in Wales, with trends of reduced palmate newt abundance at a landscape scale. The mechanisms at play are unclear with no clear differences seen in palmate newt population age structures or growth curves, but trends of reduced body condition may be a contributing factor. My thesis provides a broad and varied overview of the status and consequences of alpine newts living in the UK, a widespread but critically understudied non-native species. I provide the first empirical evidence of ecological impact of this species in a wild system and suggest the population in the Ceredigion region of Wales can be considered invasive according to both a biological and ecological impact definition. I advocate for a transparent and structured decision-making process for amphibian conservation efforts going forward.