Data from: The evolution of thermal performance in native and invasive populations of Mimulus guttatus

The rise of globalization has spread organisms beyond their natural range,
allowing further opportunity for species to adapt to novel environments
and potentially become invaders. Yet, the role of thermal niche evolution
in promoting the success of invasive species remains poorly understood.
Here, we use thermal performance curves (TPCs) to test hypotheses about
thermal adaptation during the invasion process. First, we tested the
hypothesis that if species largely conserve their thermal niche in the
introduced range, invasive populations may not evolve distinct TPCs
relative to native populations, against the alternative hypothesis that
thermal niche and therefore TPC evolution has occurred in the invasive
range. Second, we tested the hypothesis that clines of TPC parameters are
shallower or absent in the invasive range, against the alternative
hypothesis that with sufficient time, standing genetic variation, and
temperature-mediated selection, invasive populations would re-establish
clines found in the native range in response to temperature gradients. To
test these hypotheses, we built TPCs for 18 native (United States) and 13
invasive (United Kingdom) populations of the yellow monkeyflower, Mimulus
guttatus. We grew clones of multiple genotypes per population at six
temperature regimes in growth chambers. We found that invasive populations
have not evolved different thermal optima or performance breadths,
providing evidence for evolutionary stasis of thermal performance between
the native and invasive ranges after over 200 years post-introduction.
Thermal optimum increased with mean annual temperature in the native
range, indicating some adaptive differentiation among native populations
which was absent in the invasive range. Further, native and invasive
populations did not exhibit adaptive clines in thermal performance breadth
with latitude or temperature seasonality. These findings suggest that
thermal performance curves remained unaltered post-invasion, and that
invasion may proceed via broad thermal tolerance and establishment in
already climatically suitable areas rather than rapid evolution upon
introduction.