Selection in the city: Rapid and fine scale evolution of urban eastern water dragons

Oceanic archipelagos have long been treated as a petri dish for studies of
evolutionary and ecological processes. Like archipelagos, cities exhibit
similar patterns and processes, such as the rapid phenotypic divergence of
a species between urban and non-urban environments. However, on a local
scale, cities can be highly heterogenous, where geographically close
populations can experience dramatically different environmental
conditions. Nevertheless, we are yet to understand the evolutionary and
ecological implications for populations spread across a heterogenous
cityscape. To address this, we compared neutral genetic divergence to
quantitative trait divergence within three native riparian and four city
park populations of an iconic urban adapter, the eastern water dragon. We
demonstrated that selection is likely acting to drive divergence of
snout-vent length and jaw width across native riparian populations that
are geographically isolated and across city park populations that are
geographically close yet isolated by urbanisation. City park populations
as close as 0.9 kms exhibited signs of selection driven divergence to the
same extent as native riparian populations isolated by up to 114.5 kms.
These findings suggest that local adaptation may be occurring over
exceptionally small geographic and temporal scales within a single
metropolis, demonstrating that city parks can act as archipelagos for the
study of rapid evolution.