Methods
The locations of known established P. muralis populations were
obtained from the Surrey Amphibian and Reptile Group website (Langham,
2019). We determined the current geographic extent of as many of these
populations as logistically possible using a combination of visual
surveys, canvassing of the local public at sites of interest, and press
releases in local and regional media encouraging members of the public
to report their wall lizard sightings (see Appendix 1). Of the 30 extant
populations recorded on the UK mainland, we visited 21 between three
field seasons (April-September) of 2016, 2017, and 2018 (Fig 1). We did
not visit the remaining nine locations because the lizard population
were either known to be very small, access was restricted, and/or site
locations were otherwise logistically challenging (i.e. distance from
other populations). Specific attention was given to assessing the extent
of P. muralis presence along railway habitat at West Worthing,
Sussex (50.818° N, 0.390° W) during a five-week period in June-July
2018. The railway acting as a linear transect, along which we could
assess the utility of railway habitat as a corridor for dispersal (Fig
S1 Appendix 1). We also collected wall lizard location data from
populations at two additional sites, Eastbourne (50.768° N, 0.291° E)
and Kingswear (50.349° N, 3.568° W). The former was confirmed to be an
established colony through a site visit, and the latter was reported to
RW by a member of the public responding to a citizen science campaign in
regional media. Sightings were confirmed for a further eight new
locations as a result of the citizen science campaign (Fig 1) (see
Appendix 1 for detailed methods).