The Effects of Ozone on Visual Attraction Traits of Erodium paularense (Geraniaceae) Flowers: Modelled Perception by Insect Pollinators

Abstract

Ozone (O3) effects on the visual attraction traits (color, perception and area) of petals are described for Erodium paularense, an endangered plant species. Plants were exposed to three O3 treatments: charcoal-filtered air (CFA), ambient (NFA) and ambient + 40 nL L−1 O3 (FU+) in open-top chambers. Changes in color were measured by spectral reflectance, from which the anthocyanin reflectance index (ARI) was calculated. Petal spectral reflectance was mapped onto color spaces of bees, flies and butterflies for studying color changes as perceived by different pollinator guilds. Ozone-induced increases in petal reflectance and a rise in ARI under NFA were observed. Ambient O3 levels also induced a partial change in the color perception of flies, with the number of petals seen as blue increasing to 53% compared to only 24% in CFA. Butterflies also showed the ability to partially perceive petal color changes, differentiating some CFA petals from NFA and FU+ petals through changes in the excitation of the UV photoreceptor. Importantly, O3 reduced petal area by 19.8 and 25% in NFA and FU+ relative to CFA, respectively. In sensitive species O3 may affect visual attraction traits important for pollination, and spectral reflectance is proposed as a novel method for studying O3 effects on flower color.

Air pollution: a threat to insect pollination

“…Flower color, size, and shape are visual cues used by pollinators to detect flowers during foraging (Dafni and Kevan 1997;van der Kooi et al 2019). In Erodium paularense, even current ozone levels are apparently high enough to reduce petal size, modify petal reflectance, and alter the anthocyanin reflectance index therein (Prieto-Benitez et al 2021). A modeling approach suggests that these changes in reflectance induce a partial change in the color perception of flies and butterflies but not of bees (Prieto-Benitez et al 2021).…”

“…In Erodium paularense, even current ozone levels are apparently high enough to reduce petal size, modify petal reflectance, and alter the anthocyanin reflectance index therein (Prieto-Benitez et al 2021). A modeling approach suggests that these changes in reflectance induce a partial change in the color perception of flies and butterflies but not of bees (Prieto-Benitez et al 2021). In addition to floral cues, the visual cues of the vegetative parts of the plant, particularly pigments, are also affected by ozone (Blande 2021), but the degree to which this influences pollinator attraction is unclear.…”

“…A modeling approach suggests that these changes in reflectance induce a partial change in the color perception of flies and butterflies but not of bees (Prieto‐Benitez et al . 2021). In addition to floral cues, the visual cues of the vegetative parts of the plant, particularly pigments, are also affected by ozone (Blande 2021), but the degree to which this influences pollinator attraction is unclear.…”

Ozone and Temperature May Hinder Adaptive Capacity of Mediterranean Perennial Grasses to Future Global Change Scenarios

“…Taking advantage of the OTC experimental design, the effects of temperature increase were also tested at the same time as the O 3 effect following [ 48 ]. Climate warming is one of the most important threats for plant species from the Mediterranean basin mountains, including the Spanish Central System mountain range [ 49 ].…”