Flower colour polymorphism in the Mediterranean Basin: occurrence, maintenance and implications for speciation

Narbona, Eduardo; Wang, Hui; Ortiz, Pedro; Arista, Montserrat; Imbert, Éric

doi:10.1111/plb.12575

Cited by 61 publications

(61 citation statements)

References 163 publications

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“…In addition to their importance in determining flower colour, floral pigments such as flavonoids and anthocyanins also play an important role in plant defence against environmental stresses, such as UV radiation and drought (Chalker-Scott 1999, Winkel-Shirley 2002, Coberly and Rausher 2008, Tucić et al 2009, Arista et al 2013, Landi et al 2015. Therefore, selective pressures, independent of pollinators, might also contribute to flower colour polymorphism maintenance (Narbona et al 2018).…”

Section: Researchmentioning

confidence: 99%

Are pollinators the agents of selection on flower colour and size in irises?

Souto‐Vilarós

Vuleta

Jovanović

et al. 2018

Oikos

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Plant–pollinator interactions are believed to play a major role in the evolution of floral traits. Flower colour and flower size are important for attracting pollinators, directly influencing reproduction, and thus expected to be under pollinator‐mediated selection. Pollinator‐mediated selection is also proposed to play a role in maintaining flower colour polymorphism within populations. However, pigment concentrations, and thus flower colour, are also under selective pressures independent of pollinators. We quantified phenotypic pollinator‐mediated selection on flower colour and size in two colour polymorphic Iris species. Using female fitness, we estimated phenotypic selection on flower colour and size, and tested for pollinator‐mediated selection by comparing selection gradients between flowers open to natural pollination and supplementary pollinated flowers. In both species, we found evidence for pollen limitation, which set the base for pollinator‐mediated selection. In the colour dimorphic Iris lutescens, while pigment concentration and flower size were found to be under selection, this was independent of pollinators. For the polymorphic Iris pumila, pigment concentration is under selective pressure by pollinators, but only for one colour morph. Our results suggest that pollinators are not the main agents of selection on floral traits in these irises, as opposed to the accepted paradigm on floral evolution. This study provides an opposing example to the largely‐accepted theory that pollinators are the major agent of selection on floral traits.

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Section: Researchmentioning

confidence: 99%

Are pollinators the agents of selection on flower colour and size in irises?

Souto‐Vilarós

Vuleta

Jovanović

et al. 2018

Oikos

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“…Abiotic factors are becoming increasingly recognized agents of natural selection on floral traits (Strauss & Whittall, ; Narbona et al ., ). For example, drought, ambient light conditions and temperature contribute to geographic variation in petal color phenotypes within multiple taxa (e.g.…”

Section: Introductionmentioning

confidence: 97%

Geographic variation in pollen color is associated with temperature stress

Koski

Galloway

2018

New Phytologist

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The evolution of flower color, especially petal pigmentation, has received substantial attention. Less understood is the evolutionary ecology of pollen pigmentation, though it varies among and within species and its biochemical properties affect pollen viability. We characterize the distribution of pollen color across 24 populations of the North American herb Campanula americana, and assess the degree to which this variation is genetically based. We identify abiotic factors that covary with pollen color and test whether germination of light and dark pollen is differentially affected by variable temperature and UV. Pollen color varies from white to deep purple in C. americana and is genetically determined. There was a longitudinal cline whereby pollen was darkest in western populations. Accounting for latitudinal variation, western populations experience elevated temperature and UV irradiance. Germination of light-colored pollen was reduced by 60% under high temperature, but dark pollen was unaffected. Exposure to UV reduced germination of light and dark pollen similarly. The cline in pollen color across the range may reflect adaptation to heat stress. This study supports thermal tolerance as a novel function of pollen pigmentation and contributes to growing evidence that abiotic factors can drive floral diversity.

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“…Our method could be particularly useful for studies attempting to unravel the ecological interactions and evolutionary forces molding flower color variation. Variation in floral anthocyanin content or pattering may be under selection by pollinators (Ortiz‐Barrientos, ; Sletvold, Trunschke, Smit, Verbeek, & Ågren, ) or nonpollinators alike (Narbona, Wang, Ortiz, Arista, & Imbert, ; Strauss & Cacho, ; Strauss & Whittall, ). Similarly, the accumulation of anthocyanins in vegetative organs or tissues such as leaves, stems, or pedicels is also influenced by direct or indirect selection of biotic and abiotic factors (Cooney, Schaefer, Logan, Cox, & Gould, ; Gould et al., ; Menzies et al., ).…”

Section: Discussionmentioning

confidence: 99%

Digital photography provides a fast, reliable, and noninvasive method to estimate anthocyanin pigment concentration in reproductive and vegetative plant tissues

Valle

Gallardo-López

Buide

et al. 2018

Ecology and Evolution

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Anthocyanin pigments have become a model trait for evolutionary ecology as they often provide adaptive benefits for plants. Anthocyanins have been traditionally quantified biochemically or more recently using spectral reflectance. However, both methods require destructive sampling and can be labor intensive and challenging with small samples. Recent advances in digital photography and image processing make it the method of choice for measuring color in the wild. Here, we use digital images as a quick, noninvasive method to estimate relative anthocyanin concentrations in species exhibiting color variation. Using a consumer‐level digital camera and a free image processing toolbox, we extracted RGB values from digital images to generate color indices. We tested petals, stems, pedicels, and calyces of six species, which contain different types of anthocyanin pigments and exhibit different pigmentation patterns. Color indices were assessed by their correlation to biochemically determined anthocyanin concentrations. For comparison, we also calculated color indices from spectral reflectance and tested the correlation with anthocyanin concentration. Indices perform differently depending on the nature of the color variation. For both digital images and spectral reflectance, the most accurate estimates of anthocyanin concentration emerge from anthocyanin content‐chroma ratio, anthocyanin content‐chroma basic, and strength of green indices. Color indices derived from both digital images and spectral reflectance strongly correlate with biochemically determined anthocyanin concentration; however, the estimates from digital images performed better than spectral reflectance in terms of r 2 and normalized root‐mean‐square error. This was particularly noticeable in a species with striped petals, but in the case of striped calyces, both methods showed a comparable relationship with anthocyanin concentration. Using digital images brings new opportunities to accurately quantify the anthocyanin concentrations in both floral and vegetative tissues. This method is efficient, completely noninvasive, applicable to both uniform and patterned color, and works with samples of any size.

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Flower colour polymorphism in the Mediterranean Basin: occurrence, maintenance and implications for speciation

Cited by 61 publications

References 163 publications

Are pollinators the agents of selection on flower colour and size in irises?

Are pollinators the agents of selection on flower colour and size in irises?

Geographic variation in pollen color is associated with temperature stress

Digital photography provides a fast, reliable, and noninvasive method to estimate anthocyanin pigment concentration in reproductive and vegetative plant tissues

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