National scale climatic suitability
The MaxEnt model fit at the national scale had an average test AUC score of 0.98 (SD <0.01). The most important variable to the model was ‘number of frost days’ which made the highest relative percent contribution to the model (38.1%) followed by ‘annual total hours of sun’ (26.2%), whereas ‘autumn max temperature’ had the lowest contribution (2.9%). The model indicates suitable climatic conditions for P. muralis in maritime climates all along the south coast of the UK – from Norfolk in the southeast, to the south coast of Wales. Favourable conditions inland diminish towards a latitude of ~52°N, but are particularly evident in the Greater London Metropolitan area (Fig 2). P. muralis probability of presence responded positively to increasing total hours of sunlight and mean maximum spring, summer, autumn and winter temperature, although probability of presence diminished past a peak of 3°C with the latter. Probability of presence declined with increasing number of frost days (Fig 3).