Data from: Evolution of thermal tolerance and its fitness consequences: parallel and non-parallel responses to urban heat islands across three cities

The question of parallel evolution—what causes it, and how common it
is—has long captured the interest of evolutionary biologists. Widespread
urban development over the last century has driven rapid evolutionary
responses on contemporary timescales, presenting a unique opportunity to
test the predictability and parallelism of evolutionary change. Here we
examine rapid urban evolution in an acorn-dwelling ant species, focusing
on the urban heat island signal and the ant’s tolerance of these altered
urban temperature regimes. Using a common-garden experimental design with
acorn ant colonies collected from urban and rural populations in three
cities and reared under five temperature treatments in the laboratory, we
assessed plastic and evolutionary shifts in the heat and cold tolerance of
F1 offspring worker ants. In two of three cities, we found evolved losses
of cold tolerance, and compression of thermal tolerance breadth. Results
for heat tolerance were more complex: in one city, we found evidence of
simple evolved shifts in heat tolerance in urban populations, though in
another, the difference in urban and rural population heat tolerance
depended on laboratory rearing temperature, and only became weakly
apparent at the warmest rearing temperatures. The shifts in tolerance
appeared to be adaptive, as our analysis of the fitness consequences of
warming revealed that while urban populations produced more sexual
reproductives under warmer laboratory rearing temperatures, rural
populations produced fewer. Patterns of natural selection on thermal
tolerances supported our findings of fitness tradeoffs and local
adaptation across urban and rural acorn ant populations, as selection on
thermal tolerance acted in opposite directions between the warmest and
coldest rearing temperatures. Our study provides mixed support for
parallel evolution of thermal tolerance under urban temperature rise.