What’s in flower? Phenological temperature sensitivities in a restricted alpine flora

Casey Kirchhoff, Ken Green, Susanna E. Venn, David Keith, William K Cornwell

As climate warming continues, cues for shifts in plant reproductive timing will be a key mediator of species success. To examine the links between temperature and flowering time in the Australian alpine, we used climate records and 18,000 flowering observations spanning 12 years for 52 alpine plant species from the Snowy Mountains, Australia. We modelled three phenological traits (flowering onset, peak, and end) against climate to determine species that exhibit an expansion, contraction or shift in their temporal niche. Ninety-four percent of species in our dataset were phenologically sensitive to temperature. Flowering onset was most influenced by October mean temperature, with mean flowering onset occurring earlier under warmer temperatures. Flowering peak and end were most phenologically sensitive to September mean temperature. Plant and phenological traits exhibited phylogenetic signal, although this was weak for temperature sensitivity. Apparent relationships between floral traits and temperature sensitivity were explained by shared ancestry rather than repeated evolutionary associations. Our findings demonstrate the importance of accounting for phylogeny when investigating the phenological temperature sensitivity of plants, and that flowering phenology in this flora is highly responsive to early spring temperatures. As spring rapidly warms, alpine flowering will partially shift to be earlier, with reproductive success depending on the breeding systems and phenology of associated pollinators.