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, a...