Rewardlessness in orchids: how frequent and how rewardless?

Shrestha, Mani; Dyer, Adrian G.; Dorin, Alan; Ren, Zong‐Xin; Burd, Martin

doi:10.1111/plb.13113

Cited by 34 publications

(34 citation statements)

References 62 publications

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“…Finally, we constructed a third table excluding plant species in both Asteraceae and Orchidaceae, given the prevalence of potential food deception in many orchids [76][77][78]. As before, the median soluble sugar content was updated, and the remaining flower species were subsequently reclassified as being high or low.…”

Section: Does Sugar Content Vary Among Colour Categories?mentioning

confidence: 99%

Australian native flower colours: Does nectar reward drive bee pollinator flower preferences?

et al. 2020

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Colour is an important signal that flowering plants use to attract insect pollinators like bees. Previous research in Germany has shown that nectar volume is higher for flower colours that are innately preferred by European bees, suggesting an important link between colour signals, bee preferences and floral rewards. In Australia, flower colour signals have evolved in parallel to the Northern hemisphere to enable easy discrimination and detection by the phylogenetically ancient trichromatic visual system of bees, and native Australian bees also possess similar innate colour preferences to European bees. We measured 59 spectral signatures from flowers present at two preserved native habitats in South Eastern Australia and tested whether there were any significant differences in the frequency of flowers presenting higher nectar rewards depending upon the colour category of the flower signals, as perceived by bees. We also tested if there was a significant correlation between chromatic contrast and the frequency of flowers presenting higher nectar rewards. For the entire sample, and for subsets excluding species in the Asteraceae and Orchidaceae, we found no significant difference among colour categories in the frequency of high nectar reward. This suggests that whilst such relationships between flower colour signals and nectar volume rewards have been observed at a field site in Germany, the effect is likely to be specific at a community level rather than a broad general principle that has resulted in the common signalling of bee flower colours around the world.

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Section: Does Sugar Content Vary Among Colour Categories?mentioning

confidence: 99%

Australian native flower colours: Does nectar reward drive bee pollinator flower preferences?

et al. 2020

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“…displaying attractive floral signals but offering no reward in return for the pollination service, has been studied for decades in orchids in an attempt to understand their evolutionary patterns (Jers akov a et al 2009;Shivanna & Tandon 2014). Approximately 30-40% of all orchid species are reported to be deceptive (Johnson & Schiestl 2016, but see Shrestha et al 2020), which suggests a crucial role for floral deception in species diversification (Cozzolino & Widmer 2005). The most common deceptive pollination systems are based on sexual (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…Approximately 30–40% of all orchid species are reported to be deceptive (Johnson & Schiestl 2016, but see Shrestha et al . 2020), which suggests a crucial role for floral deception in species diversification (Cozzolino & Widmer 2005). The most common deceptive pollination systems are based on sexual ( e.g .…”

Section: Introductionmentioning

confidence: 99%

Ecological factors affecting the fitness of the threatened orchid Anacamptis robusta (Orchidaceae): Habitat disturbance, interactions with a co‐flowering rewarding orchid and hybridization events

et al. 2020

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The food-deceptive species Anacamptis robusta is threatened in the Balearic Islands, and its habitat has recently been transformed through human disturbance. This study investigated how human disturbance affects the reproductive output of A. robusta and how its fitness is affected by competition with rewarding relatives, fungal infections and hybridization processes. • To evaluate the impact of habitat loss on plant fitness, data on reproductive measures were obtained in two well-conserved subpopulations and the unique disturbed subpopulation. Photo-trapping cameras were installed to determine the floral visitation rate. All flowering individuals in 2019 were georeferenced using differential GPS to examine the influence of geospatial patterns on the reproductive success of A. robusta. In addition, hand-pollination treatments were performed to evaluate the hybridization between A. coriophora and A. robusta and the origin of A. 9 albuferensis. • The human-disturbed subpopulation of A. robusta had a lower fruit set success than the subpopulations in well-conserved areas. The presence of A. coriophora is negatively affecting the reproductive output of A. robusta. Moreover, A. robusta can only act as the pollen donor during hybridization. • The complexity of the ecological system, which is enhanced by the strong pollinator dependence of the threatened species, must be considered when making conservation decisions. Although human disturbance directly affects plant population stability, other ecological issues must be considered, such as pollinator interaction, interspecific competition for pollinators, fungal infection and hybridization events.

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“…Even small quantities of nectar may constitute an important food source. Evidence that many orchids are truly rewardless is scarce and requires further research ( Shrestha et al, 2020 ). The observation of a Diamma species licking the bases of the calli on the labellum ( Kuiter, 2016 ) suggests that nectar may be produced directly on to the labellum, as in Caladenia concolor ( Reiter et al, 2018b , 2019 ) and C. nobilis ( Phillips et al, 2020 ).…”

Section: Discussionmentioning

confidence: 99%

Why Variation in Flower Color May Help Reproductive Success in the Endangered Australian Orchid Caladenia fulva

et al. 2021

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Caladenia fulva G.W. Carr (Tawny Spider-orchid) is a terrestrial Australian endangered orchid confined to contiguous reserves in open woodland in Victoria, Australia. Natural recruitment is poor and no confirmed pollinator has been observed in the last 30 years. Polymorphic variation in flower color complicates plans for artificial pollination, seed collection and ex situ propagation for augmentation or re-introduction. DNA sequencing showed that there was no distinction among color variants in the nuclear ribosomal internal transcribed spacer (ITS) region and the chloroplast trnT-trnF and matK regions. Also, authentic specimens of both C. fulva and Caladenia reticulata from the reserves clustered along with these variants, suggesting free interbreeding. Artificial cross-pollination in situ and assessment of seed viability further suggested that no fertility barriers existed among color variants. Natural fruit set was 15% of the population and was proportional to numbers of the different flower colors but varied with orchid patch within the population. Color modeling on spectral data suggested that a hymenopteran pollinator could discriminate visually among color variants. The similarity in fruiting success, however, suggests that flower color polymorphism may avoid pollinator habituation to specific non-rewarding flower colors. The retention of large brightly colored flowers suggests that C. fulva has maintained attractiveness to foraging insects rather than evolving to match a scarce unreliable hymenopteran sexual pollinator. These results suggest that C. fulva should be recognized as encompassing plants with these multiple flower colors, and artificial pollination should use all variants to conserve the biodiversity of the extant population.

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Rewardlessness in orchids: how frequent and how rewardless?

Cited by 34 publications

References 62 publications

Australian native flower colours: Does nectar reward drive bee pollinator flower preferences?

Australian native flower colours: Does nectar reward drive bee pollinator flower preferences?

Ecological factors affecting the fitness of the threatened orchid Anacamptis robusta (Orchidaceae): Habitat disturbance, interactions with a co‐flowering rewarding orchid and hybridization events

Why Variation in Flower Color May Help Reproductive Success in the Endangered Australian Orchid Caladenia fulva

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