Floral UV Features of Plant Species From a Neotropical Savanna.

Priscila Tunes,Elza Guimarães,Maria Gabriela Gutierrez Camargo

doi:10.3389/fpls.2021.618028

Priscila Tunes, Elza Guimarães + Show 1 more

Open Access

https://doi.org/10.3389/fpls.2021.618028

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Abstract

Despite the wide interest in flower colours, only after the end of the nineteenth-century studies started to comprise floral UV reflection, which is invisible to humans but visible to the major groups of pollinators. Many flowers and inflorescences display colour patterns, an important signal for pollinators, promoted by the presence of at least two different colours within flowers or inflorescences, including colours in the UV waveband. For Neotropical savanna plant species, we characterised floral UV features using UV-photography and reflectance measurements. We tested (i) whether floral UV features were constrained by their shared ancestry, (ii) whether floral UV features were associated with pollinators, and (iii) whether floral UV features were associated with floral traits mediating these interactions, including floral resource, type of attraction unit and presence/absence of non-UV colour patterns. Of 80 plant species, ca. 70% were UV-patternless, most of them UV-absorbing. Approximately 30% presented one of three types of UV-patterns: bullseye, contrasting corolla markings oriented toward floral resources or contrasting reproductive structures, which were all considered as floral guides. Floral UV features were phylogenetically constrained and were associated with pollinators, floral resources and attraction unit, but not with non-UV colour patterns. UV-patternless flowers were associated with most of the pollination systems, while UV-patterned flowers were mainly associated with bee-pollination. UV-absorbing flowers comprised the only category with hawkmoth- and butterfly-pollinated flowers, and a high percentage of hummingbird-pollinated species. Nocturnal pollinated species were also commonly UV-absorbing, except for one UV-reflecting bat-pollinated species and one beetle-pollinated species with UV-reflecting stigmas. All types of floral UV features were associated with nectar; however, flowers with contrasting reproductive structures were mainly associated with pollen. There was an association between UV-absorbing species and the presence of inflorescences and intermediate attraction units. Our results evince that phylogenetic relatedness can constraint floral UV features’ diversification, but combinations of evolutionary and ecological processes may be expected in this scenario.

Highlights

Floral colour has always called humankind’s attention, and throughout time it was explored in several studies including genetic, ecological, and evolutionary approaches
We used plant species from a Neotropical savanna to characterise floral UV features and tested (i) whether floral UV features were constrained by their shared ancestry, (ii) whether floral UV features were related to pollinators, and (iii) whether floral UV features were associated with floral traits mediating these interactions, including floral resource, type of attraction unit and the presence/absence of non-UV colour patterns
Features: (R) UV-reflecting; (A) UV-absorbing; (BE) bullseye; (CM) contrasting corolla markings oriented toward floral resources or reproductive structures (UV-reflecting markings in a flower with predominantly UV-absorbing corolla, and vice versa) and (CR) contrasting reproductive structures (UV-reflecting reproductive structures in a flower with UV-absorbing corolla, and vice versa) (Figures 1–5, Supplementary Figure 1, and Supplementary Table 2)

Summary

Introduction

Floral colour has always called humankind’s attention, and throughout time it was explored in several studies including genetic, ecological, and evolutionary approaches. It is important to highlight that from a pollinator’s perspective, the UV wavelengths are only one of the wavebands perceived by animals that have UV photoreceptors (Kevan, 1979; Cronin et al, 2014). It acts together with the information from other photoreceptors that may perceive longer wavelengths, encompassing human-visible blue, green and red wavebands to create a colour (Chittka et al, 1994)

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