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).