Data from: Phenological and fitness responses to climate warming depend upon genotype and competitive neighborhood in Arabidopsis thaliana

1. Increasing temperatures during climate change are known to alter the
phenology across diverse plant taxa, but the evolutionary outcomes of
these shifts are poorly understood. Moreover, plant temperature-sensing
pathways are known to interact with competition-sensing pathways, yet
there remains little experimental evidence for how genotypes varying in
temperature responsiveness react to warming in realistic competitive
settings. 2. We compared flowering time and fitness responses to warming
and competition for two near isogenic lines (NILs) of Arabidopsis thaliana
transgressively segregating temperature-sensitive and -insensitive alleles
for major-effect flowering time genes. We grew focal plants of each
genotype in intraspecific and interspecific competition in four treatments
contrasting daily temperature profiles in summer and fall under
contemporary and warmed conditions. We measured phenology and fitness of
focal plants to quantify plastic responses to season, temperature, and
competition and the dependence of these responses on flowering time
genotype. 3. The temperature-insensitive NIL was constitutively
early-flowering and less fit, except in a future-summer climate in which
its fitness was higher than the later flowering, temperature-sensitive NIL
in low competition. The late-flowering NIL showed accelerated flowering in
response to intragenotypic competition and to increased temperature in the
summer but delayed flowering in the fall. However, its fitness fell with
rising temperatures in both seasons, and in the fall its marginal fitness
gain from decreasing competition was diminished in the future. 4.
Functional alleles at temperature-responsive genes were necessary for
plastic responses to season, warming, and competition. However, the
plastic genotype was not the most fit in every experimental condition,
becoming less fit than the temperature-canalized genotype in the warm
summer treatment. 5. Climate change is often predicted to have deleterious
effects on plant populations, and our results show how increased
temperatures can act through genotype-dependent phenology to decrease
fitness. Furthermore, plasticity is not necessarily adaptive in rapidly
changing environments since a non-plastic genotype proved fitter than a
plastic genotype in a warming climate treatment.