Phenological responses to climate change do not exhibit phylogenetic signal in a subalpine plant community.

Phylogenetic relationships may underlie species-specific phenological sensitivities to abiotic variation and may help to predict these responses to climate change. Although shared evolutionary history may mediate both phenology and phenological sensitivity to abiotic variation, few studies have explicitly investigated whether this is the case. We explore phylogenetic signal in flowering phenology and in phenological sensitivity to temperature and snowmelt using a 39-year record of flowering from the Colorado Rocky Mountains, USA that includes dates of first, peak, and last flowering, and flowering duration for 60 plant species in a subalpine plant community. Consistent with other studies, we found evidence in support of phylogenetic signal in first flowering date. However, the strength and significance of that signal were inconsistent across other measures of flowering in this plant community: peak flowering date exhibited the strongest phylogenetic signal, followed by first flowering date; last flowering date and duration of flowering exhibited patterns indistinguishable from random trait evolution. In contrast to first and peak flowering date, phenological sensitivities of all flowering measures to temperature and snowmelt did not exhibit a phylogenetic signal. These findings show that within ecological communities, phylogenetic signal in phenology does not necessarily imply phylogenetic signal in phenological sensitivities to abiotic variation.