Floral bullseyes and stratospheric ozone

Abstract

As well as guiding pollinators to the centre of flowers, areas of the corolla that absorb UV radiation may help to protect floral reproductive parts from solar UV radiation that would otherwise be reflected onto them. In their recent article, 'Floral pigmentation has responded rapidly to global change in ozone and temperature', Koski et al.¹ compared herbarium specimens collected between 1941 and 2017 to investigate whether the size of the UV-absorbing area in the centre of flowers (called 'bullseyes', UV proportion, or UVP) has changed relative to the size of the flower over this period. The article, and a subsequent feature², describe an increase in UVP of ∼2% per year across all taxa examined. However, the study's main conclusion that this trend can be partially related to changes in ozone and temperature does not withstand close examination.