A test of Sensory Drive in plant–pollinator interactions: heterogeneity in the signalling environment shapes pollinator preference for a floral visual signal

Abstract

Sensory Drive predicts that habitat-dependent signal transmission and perception explain the diversification of communication signals. Whether Sensory Drive shapes floral evolution remains untested in nature. Pollinators of Argentina anserina prefer small ultraviolet (UV)absorbing floral guides at low elevation but larger guides at high. However, mechanisms underlying differential preference are unclear. High elevation populations experience elevated UV irradiance and frequently flower against bare substrates rather than foliage, potentially impacting signal transmission and perception.At high and low elevation extremes, we experimentally tested the effects of UV light (ambient vs reduced) and floral backgrounds (foliage vs bare) on pollinator choice for UV guide size. We examined how different signalling environments shaped pollinator-perceived flower colour using visual system models.At high elevation, pollinators preferred locally common large UV guides under ambient UV, but lacked preference under reduced UV. Flies preferred large guides only against bare substrate, the common high elevation background. Ambient UV amplified contrast of large UV guides with floral backgrounds, and flowers contrasted more with bare ground than foliage.Results support that local signalling conditions contribute to pollinator preference for a floral visual signal, a key tenet of Sensory Drive. Components of Sensory Drive could shape floral signal evolution in other plants spanning heterogeneous signalling environments.

Achromatic Cues Are Important for Flower Visibility to Hawkmoths and Other Insects

“…Bukovac et al (2017) modelled flower salience against more than 500 natural backgrounds and found that background colour has the potential to significantly change a flower's colour contrast. A recent study by Finnell and Koski (2021) showed that bee and fly colour preferences for ultraviolet flower markings depends on the type of background, though this preference difference depended on chromatic and not achromatic properties. The findings from Menzel et al (1997) that desert plants exhibit lower achromatic contrast than plants in the Mediterranean due to differences in background and not flower colour also suggests that achromatic aspects of backgrounds are important.…”

Can trait matching inform the design of pollinator‐friendly urban green spaces? A review and synthesis of the literature

“…Sensory signaling is one of the underlying factors mediating the attraction of pollinators to flowering plants, thereby leading to the establishment of biotic interactions and ecological networks (Finnell & Koski, 2021; Sun et al, 2018). These intrinsic signals, which may be visual or olfactory, determine which pollinators are attracted to which plant species based on the signal receptive ability of the pollinators (van der Kooi et al, 2021).…”

Determining factors of flower coloration

“…Different altitudes also vary in ambient light and background. In Colorado (USA), ambient UV light increased with altitude and different altitudes had different backgrounds (foliage or bare), which impacted the conspicuity and preference for fly and bee pollinators (Finnell & Koski 2021).…”