Plant Ecology and Evolution 150(3): 279-292, doi: 10.5091/plecevo.2017.1313
Effects of floral display, conspecific density and rewarding species on fruit set in the deceptive orchid Orchis militaris (Orchidaceae)
Thomas Henneresse, Renate A Wesselingh‡, Daniel Tyteca‡ UCLouvain, Louvain-la-Neuve, Belgium
© Botanic Garden Meise and Royal Botanical Society of Belgium. all rights reserved Citation:
Henneresse T, Wesselingh RA, Tyteca D (2017) Effects of floral display, conspecific density and rewarding species on fruit set in the deceptive orchid Orchis militaris (Orchidaceae). Plant Ecology and Evolution 150(3): 279-292. https://doi.org/10.5091/plecevo.2017.1313 |  |
Abstract
Background and aims – About one third of orchid species do not produce any floral reward but have developed various strategies to attract pollinators. The most common system is food deception, which takes place through two types of attraction mechanisms: Batesian floral mimicry and generalised food deception. In rewardless species, fruit set is generally low and various factors, such as floral display size or density, are known to positively or negatively influence fruit set. This study aimed to clarify the deceptive pollination system in Orchis militaris and to investigate the effect of individual, population and environmental factors on fruit set in this orchid species.
Methods – The effects of floral display size, con- and heterospecific density and rewarding species diversity were studied both at the scale of the individual plant (fourteen sites) and of the population (22 sites). Generalised linear (mixed) models and multivariate analysis were performed to examine which factors affect fruit set.
Key Results – At the individual scale, the probability of setting fruit was influenced by several factors and their interaction, including floral display size, conspecific density, and heterospecific total density and richness. Fruit set was higher in medium-height vegetation than in short vegetation. Globularia bisnagarica was the only species whose density was significantly (and negatively) correlated with fruit set. At the population scale, none of the studied factors was significantly correlated to fruit set.
Conclusions – In Orchis militaris, generalised food deception is the most likely strategy of pollinator attraction. This orchid species may benefit from the proximity of rewarding plants through the magnet-species effect, depending on the size of its floral display. The effect of con- and heterospecific density and rewarding species richness seem scale-dependent.
Methods – The effects of floral display size, con- and heterospecific density and rewarding species diversity were studied both at the scale of the individual plant (fourteen sites) and of the population (22 sites). Generalised linear (mixed) models and multivariate analysis were performed to examine which factors affect fruit set.
Key Results – At the individual scale, the probability of setting fruit was influenced by several factors and their interaction, including floral display size, conspecific density, and heterospecific total density and richness. Fruit set was higher in medium-height vegetation than in short vegetation. Globularia bisnagarica was the only species whose density was significantly (and negatively) correlated with fruit set. At the population scale, none of the studied factors was significantly correlated to fruit set.
Conclusions – In Orchis militaris, generalised food deception is the most likely strategy of pollinator attraction. This orchid species may benefit from the proximity of rewarding plants through the magnet-species effect, depending on the size of its floral display. The effect of con- and heterospecific density and rewarding species richness seem scale-dependent.
Keywords
SPECIES RICHNESS; CONSPECIFIC DENSITY; DECEPTIVE ORCHID; FOOD DECEPTION; FRUIT SET; GENERALISED FOOD DECEPTION; ORCHIDACEAE; ORCHIS MILITARIS; POLLINATION FACILITATION; REWARD