Data from: Linear reaction norms of thermal limits in Drosophila: predictable plasticity in cold but not in heat tolerance

1. Thermal limits of ectotherms have been studied extensively and are
believed to be evolutionary constrained, leaving ectotherms at risk under
future climate change. Phenotypic plasticity may extend the thermal
limits, but we lack detailed characterizations of thermal limit reaction
norms as well as an understanding of the interspecific variation of these
reaction norms. 2. Here we investigated the interspecific variation in
phenotypic plasticity of thermal limits in 13 Drosophila species. We
obtained high-resolution reaction norms for upper and lower thermal limits
across the permissive developmental thermal range (12.5 – 30°C). The
estimated phenotypes were then associated (while accounting for phylogeny)
with climatic parameters from the species’ distributional range. 3. All
species showed linear reaction norms for cold tolerance (CTmin) and heat
tolerance (CTmax) across developmental acclimation temperatures. We
observed strong beneficial cold acclimation to lower temperatures in all
species. Conversely, the heat acclimation response was non-existent in
some species, and decreasing or increasing with increasing developmental
acclimation temperatures in other species. The degree of phenotypic
plasticity of CTmin and CTmax was neither related to the basal thermal
limits (trade-off hypothesis) nor to climatic parameters connected to
latitudinal distributions (latitudinal hypothesis). 4. A substantial and
linear developmental plasticity of lower thermal limits is a general
characteristic of Drosophila species, which allows for straightforward
application in species distribution models. In general, upper thermal
limits also show linear norms of reaction, but their adaptive significance
is limited and highly variable among species, making general predictions
across species rather impossible. 5. High resolution estimates of norms of
reaction of thermal limits can considerably increase our understanding of
the capacity of ectotherms to acclimate to different thermal environments.
However, our understanding of the environmental drivers of the evolution
of phenotypic plasticity and thus of the interspecific differences remains
ambiguous, potentially constrained by limited microclimate information.