Dataset Information

Intrafloral Color Modularity in a Bee-Pollinated Orchid.

ABSTRACT: Flower color has been studied in different ecological levels of organization, from individuals to communities. However, it is unclear how color is structured at the intrafloral level. In bee-pollinated flowers, the unidirectional gradient in color purity and pollen mimicry are two common processes to explain intrafloral color patterns. Considering that floral traits are often integrated, usually reflecting evolutionary modules under pollinator-mediated selection, we hypothesize that such intrafloral color patterns are structured by intrafloral color modules as perceived by bee color vision system. Here, we studied the tropical bee-pollinated orchid Cattleya walkeriana, given its intrafloral color complexity and variation among individuals. Considering bee color vision, we investigated if intrafloral color modules arose among intrafloral patches (tip or base of the sepals, petals, and labellum). We expected a separate color module between the labellum patches (the main attractive structure in orchids) and petals and sepals. We measured the color reflectance and calculated the photoreceptor excitation, spectral purity, hue, and the chromatic contrast of the floral structures in the hexagon color model. Spectral purity (saturation) was higher in the labellum tip in comparison to petals and sepals, generating a unidirectional gradient. Labellum base presented a less saturated yellow UV-absorbing color, which may reflect a pollen mimicry strategy. C. walkeriana presented three intrafloral color modules corresponding to the color of petals and sepals, the color of the labellum tip, and the color of labellum base. These color modules were unrelated to the development of floral structures. Given the importance of intrafloral color patterns in bee attraction and guidance, our results suggest that intrafloral patterns could be the outcome of evolutionary color modularization under pollinator-mediated selection.

SUBMITTER: Aguiar JMRBV

PROVIDER: S-EPMC7693458 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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Publications

Intrafloral Color Modularity in a Bee-Pollinated Orchid.

Aguiar João Marcelo Robazzi Bignelli Valente JMRBV Maciel Artur Antunes AA Santana Pamela Cristina PC Telles Francismeire Jane FJ Bergamo Pedro Joaquim PJ Oliveira Paulo Eugênio PE Brito Vinicius Lourenço Garcia VLG

Frontiers in plant science 20201109

Flower color has been studied in different ecological levels of organization, from individuals to communities. However, it is unclear how color is structured at the intrafloral level. In bee-pollinated flowers, the unidirectional gradient in color purity and pollen mimicry are two common processes to explain intrafloral color patterns. Considering that floral traits are often integrated, usually reflecting evolutionary modules under pollinator-mediated selection, we hypothesize that such intrafl ...[more]

PMID: 33304366

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Project description:Unlabelled•Background and aimsAnimal-pollinated angiosperms have evolved a variety of signalling mechanisms to attract pollinators. Floral scent is a key component of pollinator attraction, and its chemistry modulates both pollinator behaviour and the formation of plant-pollinator networks. The neotropical orchid genus Gongora exhibits specialized pollinator associations with male orchid bees (Euglossini). Male bees visit orchid flowers to collect volatile chemical compounds that they store in hind-leg pouches to use subsequently during courtship display. Hence, Gongora floral scent compounds simultaneously serve as signalling molecules and pollinator rewards. Furthermore, because floral scent acts as the predominant reproductive isolating barrier among lineages, it has been hypothesized that chemical traits are highly species specific. A comparative analysis of intra- and inter-specific variation of floral scent chemistry was conducted to investigate the evolutionary patterns across the genus. •MethodsGas chromatography-mass spectrometry (GC-MS) was used to analyse the floral scent of 78 individuals belonging to 28 different species of Gongora from two of the three major lineages sampled across the neotropical region. Multidimensional scaling and indicator value analyses were implemented to investigate the patterns of chemical diversity within and among taxonomic groups at various geographic scales. Additionally, pollinator observations were conducted on a sympatric community of Gongora orchids exhibiting distinct floral scent phenotypes. •Key resultsA total of 83 floral volatiles, mainly terpenes and aromatic compounds, were detected. Many of the identified compounds are common across diverse angiosperm families (e.g. cineole, eugenol, ?-ocimene, ?-pinene and terpinen-4-ol), while others are relatively rare outside euglossine bee-pollinated orchid lineages. Additionally, 29 volatiles were identified that are known to attract and elicit collection behaviour in male bees. Floral scent traits were less variable within species than between species, and the analysis revealed exceptional levels of cryptic diversity. Gongora species were divided into 15 fragrance groups based on shared compounds. Fragrance groups indicate that floral scent variation is not predicted by taxonomic rank or biogeographic region. •ConclusionsGongora orchids emit a diverse array of scent molecules that are largely species specific, and closely related taxa exhibit qualitatively and quantitatively divergent chemical profiles. It is shown that within a community, Gongora scent chemotypes are correlated with near non-overlapping bee pollinator assemblies. The results lend support to the hypothesis that floral scent traits regulate the architecture of bee pollinator associations. Thus, Gongora provides unique opportunities to examine the interplay between floral traits and pollinator specialization in plant-pollinator mutualisms.

Project description:Neotropical rainforests sustain some of the most diverse terrestrial communities on Earth. Euglossine (or orchid) bees are a diverse lineage of insect pollinators distributed throughout the American tropics, where they provide pollination services to a staggering diversity of flowering plant taxa. Elucidating the seasonal patterns of phylogenetic assembly and functional trait diversity of bee communities can shed new light into the mechanisms that govern the assembly of bee pollinator communities and the potential effects of declining bee populations. Male euglossine bees collect, store, and accumulate odoriferous compounds (perfumes) to subsequently use during courtship display. Thus, synthetic chemical baits can be used to attract and monitor euglossine bee populations. We conducted monthly censuses of orchid bees in three sites in the Magdalena valley of Colombia - a region where Central and South American biotas converge - to investigate the structure, diversity, and assembly of euglossine bee communities through time in relation to seasonal climatic cycles. In particular, we tested the hypothesis that phylogenetic community structure and functional trait diversity changed in response to seasonal rainfall fluctuations. All communities exhibited strong to moderate phylogenetic clustering throughout the year, with few pronounced bursts of phylogenetic overdispersion that coincided with the transition from wet-to-dry seasons. Despite the heterogeneous distribution of functional traits (e.g., body size, body mass, and proboscis length) and the observed seasonal fluctuations in phylogenetic diversity, we found that functional trait diversity, evenness, and divergence remained constant during all seasons in all communities. However, similar to the pattern observed with phylogenetic diversity, functional trait richness fluctuated markedly with rainfall in all sites. These results emphasize the importance of considering seasonal fluctuations in community assembly and provide a glimpse to the potential effects that climatic alterations may have on both pollinator communities and the ecosystem services they provide.

Project description:Flowers bear the function of filters supporting the attraction of pollinators as well as the deterrence of floral antagonists. The effect of epidermal cell shape on the visual display and tactile properties of flowers has been evaluated only recently. In this study we quantitatively measured epidermal cell shape, gloss and spectral reflectance of flowers pollinated by either bees or birds testing three hypotheses: The first two hypotheses imply that bee-pollinated flowers might benefit from rough surfaces on visually-active parts produced by conical epidermal cells, as they may enhance the colour signal of flowers as well as the grip on flowers for bees. In contrast, bird-pollinated flowers might benefit from flat surfaces produced by flat epidermal cells, by avoiding frequent visitation from non-pollinating bees due to a reduced colour signal, as birds do not rely on specific colour parameters while foraging. Moreover, flat petal surfaces in bird-pollinated flowers may hamper grip for bees that do not touch anthers and stigmas while consuming nectar and thus, are considered as nectar thieves. Beside this, the third hypothesis implies that those flower parts which are vulnerable to nectar robbing of bee- as well as bird-pollinated flowers benefit from flat epidermal cells, hampering grip for nectar robbing bees. Our comparative data show in fact that conical epidermal cells are restricted to visually-active parts of bee-pollinated flowers, whereas robbing-sensitive parts of bee-pollinated as well as the entire floral surface of bird-pollinated flowers possess on average flat epidermal cells. However, direct correlations between epidermal cell shape and colour parameters have not been found. Our results together with published experimental studies show that epidermal cell shape as a largely neglected flower trait might act as an important feature in pollinator attraction and avoidance of antagonists, and thus may contribute to the partitioning of flower-visitors.

Dataset Information

Intrafloral Color Modularity in a Bee-Pollinated Orchid.

Publications

Intrafloral Color Modularity in a Bee-Pollinated Orchid.

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