Rotating Arrays of Orchid Flowers: A Simple and Effective Method for Studying Pollination in Food Deceptive Plants

Daniela Scaccabarozzi,Kingsley W Dixon,Salvatore Cozzolino,Andrea Galimberti

doi:10.3390/d12080286

Daniela Scaccabarozzi, Kingsley W Dixon + Show 2 more

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https://doi.org/10.3390/d12080286

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Abstract

Floral deception has been observed in several genera in angiosperms, but is most common in the Orchidaceae. Pollination mechanisms in food deceptive plants are often difficult to assess, as visitation frequency by insects requires numerous hours of field observations to ascertain. Here, for the first time, we describe in detail and validate a simple and effective method that extends previous approaches to increase the effectiveness of pollination studies of food deceptive orchids. We used an orchid of southwest Australia, Diuris brumalis (Orchidaceae), that visually mimics model plants belonging to the genus Daviesia (Faboideae). Arrays of orchid flowers were placed and moved systematically in proximity to model plants, resulting in rapid attraction of the pollinators of D. brumalis. We compared pollinaria removal (as an indicator of pollination success) in naturally growing orchids with pollinaria removal in arrays of orchid flowers in the same sites. We showed that the proposed method greatly enhances pollinator attractiveness in food deceptive systems with very low pollination rates, and we compared its efficiency with other similar methods. The approach can be used for observing pollinator behavioural patterns and confirming effective pollinators for food deceptive species with low insect visitation rates.

Highlights

Floral deception has been observed in several hundred genera of angiosperms [1], but is most common in the Orchidaceae where approximately 8000 species are believed to not have floral rewards for pollinators [2,3]. Deceitful orchids lure their pollinators by many mechanisms that include generalised food deception, through target mimicry of other flowers that do produce food such as nectar or pollen, mimicking carrion odour and providing insect brood-sites or shelters, as well as by sexual deceit, utilising pheromone attraction of insects [4]
Despite food deception being a predominant strategy among deceptive orchids [8], especially in Australia, it has been less studied relative to sexual deceit of specialised male pollinators
During a study of the food deceptive orchid Diuris brumalis D.L.Jones in southwest Australia, we developed an alternative strategy to consistently attract pollinators which were difficult to observe due to their low visitation rates and fleeting floral visitation times [28]

Summary

Introduction

Floral deception has been observed in several hundred genera of angiosperms [1], but is most common in the Orchidaceae where approximately 8000 species are believed to not have floral rewards for pollinators [2,3]. Deceitful orchids lure their pollinators by many mechanisms that include generalised food deception, through target mimicry of other flowers that do produce food such as nectar or pollen, mimicking carrion odour and providing insect brood-sites or shelters, as well as by sexual deceit, utilising pheromone attraction of insects [4].

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