Ecological interactions of the sexually deceptive orchid Orchis galilaea

Nisrine Machaka-Houri,Ahmad Houri,Khouzama M Knio,Duncan B Westbury

doi:10.1080/17429145.2018.1478005

Abstract

ABSTRACTPlant species dependent on highly specific interactions with pollinators are vulnerable to environmental change. Conservation strategies therefore require a detailed understanding of pollination ecology. This two-year study examined the interactions between the sexually deceptive orchid, Orchis galilaea, and its pollinator Lasioglossum marginatum. Relationships were investigated across three different habitats known to support O. galilaea (garrigue, oak woodland, and mixed oak/pine woodland) in Lebanon. Visitation rates to flowers were extremely low and restricted to male bees. The reproductive success of O. galilaea under ambient conditions was 29.3% (±2.4), compared to 89.0% (±2.1) in plants receiving cross-pollination by hand. No difference in reproductive success was found between habitat types, but values of reproductive success were positively correlated to the abundance of male bees. Pollination limitation can have negative impacts on the population growth of orchids, and this study provides clear evidence for more holistic approaches to habitat conservation to support specific interactions.

Highlights

Orchidaceae is one of the largest and most diverse families of the flowering plants in the plant kingdom, containing an estimated 25,000–30,000 species (Kull and Hutchings 2006)
The main aim of this study was to investigate the interactions between O. galilaea and its pollinator L. marginatum, and to investigate the relationship between L. marginatum abundance and the reproductive success of O. galilaea
Field observations confirmed that O. galilaea is pollinated exclusively by male L. marginatum bees, and that female L. marginatum did not visit O. galilaea despite their greater abundance across sites

Summary

Introduction

Orchidaceae is one of the largest and most diverse families of the flowering plants in the plant kingdom, containing an estimated 25,000–30,000 species (Kull and Hutchings 2006). Many orchid species from the Mediterranean region do not possess nectar, attracting pollinators through food deception (Dactylorhiza genus), shelter deception (Serapias genus), or sexual deception (Ophrys genus) (Dressler 1993; Vereecken et al 2010; Kindlmann and Roberts 2012). Throughout the Mediterranean region, orchids in the genus Ophrys mainly exhibit this behavior, and in Lebanon, Orchis galilaea is the only known sexually deceptive orchid belonging to the Orchis genus. This is Lebanon’s only narrow endemic orchid species (Cozzolino and Widmer 2005). Polylectic species that forms the largest colonies of any bee in the halictine tribe (McGinley 1986)

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