Pollinator diversity and reproductive success of Epipactis helleborine (L.) Crantz (Orchidaceae) in anthropogenic and natural habitats.

Agnieszka Rewicz,Radomir Jaskuła,Grzegorz Tończyk,Tomasz Rewicz

doi:10.7717/peerj.3159

Abstract

BackgroundEpipactis helleborine is an Eurasian orchid species which prefers woodland environments but it may also spontaneously and successfully colonise human-made artificial and disturbed habitats such as roadsides, town parks and gardens. It is suggested that orchids colonising anthropogenic habitats are characterised by a specific set of features (e.g., large plant size, fast flower production). However, as it is not well known how pollinator diversity and reproductive success of E. helleborine differs in populations in anthropogenic habitats compared to populations from natural habitats, we wanted to compare pollinator diversity and reproductive success of this orchid species between natural and anthropogenic habitat types.MethodsPollination biology, reproductive success and autogamy in populations of E. helleborine from anthropogenic (roadside) and natural (forest) habitats were compared. Eight populations (four natural and four human-disturbed ones) in two seasons were studied according to height of plants, length of inflorescences, as well as numbers of juvenile shoots, flowering shoots, flowers, and fruits. The number and diversity of insect pollinators were studied in one natural and two human-disturbed populations.ResultsReproductive success (the ratio of the number of flowers to the number of fruits) in the populations from anthropogenic habitats was significantly higher than in the natural habitats. Moreover, plants from anthropogenic habitats were larger than those from natural ones. In both types of populations, the main insect pollinators were Syrphidae, Culicidae, Vespidae, Apidae and Formicidae. With respect to the type of pollinators’ mouth-parts, chewing (39%), sponging (34%) and chewing-sucking (20%) pollinators prevailed in anthropogenic habitats. In natural habitats, pollinators with sponging (55%) and chewing mouth-parts (32%) dominated, while chewing-sucking and piercing-sucking insects accounted for 9% and 4% respectively.DiscussionWe suggest that higher reproductive success of E. helleborine in the populations from anthropogenic habitats than in the populations from natural habitats may result from a higher number of visits by pollinators and their greater species diversity, but also from the larger size of plants growing in such habitats. Moreover, our data clearly show that E. helleborine is an opportunistic species with respect to pollinators, with a wide spectrum of pollinating insects. Summarising, E. helleborine is a rare example of orchid species whose current range is not declining. Its ability to make use of anthropogenically altered habitats has allowed its significant spatial range expansion, and even successful colonisation of North America.

Highlights

Orchidaceae is one of the most diverse and species-rich (20,000–30,000 species) plant families (Baumann, Kunkele & Lorenz, 2010; Djordjević et al, 2016a), with many species that are seriously endangered and require conservation efforts to maintain their populations.Destruction of natural habitats is causing extinction of many orchid species (Swarts & Dixon, 2009)
Orchids that colonise anthropogenic habitats are characterised by a specific set of features: fast growth resulting in large plant size and fast flower production (Forman et al, 2009)
In the populations from the anthropogenic habitats, the most frequent families were Syrphidae (57), Vespidae (48) and Apidae (43). In both types of habitats, Diptera and Hymenoptera clearly dominated, with 41% and 52% of all the pollinators observed in the populations from the anthropogenic habitats, and with 59% and 37% observed in the population from the natural habitat (Fig. 3)

Summary

Introduction

Orchidaceae is one of the most diverse and species-rich (20,000–30,000 species) plant families (Baumann, Kunkele & Lorenz, 2010; Djordjević et al, 2016a), with many species that are seriously endangered and require conservation efforts to maintain their populations.Destruction of natural habitats is causing extinction of many orchid species (Swarts & Dixon, 2009). It is suggested that orchids colonising anthropogenic habitats are characterised by a specific set of features (e.g., large plant size, fast flower production). As it is not well known how pollinator diversity and reproductive success of E. helleborine differs in populations in anthropogenic habitats compared to populations from natural habitats, we wanted to compare pollinator diversity and reproductive success of this orchid species between natural and anthropogenic habitat types. We suggest that higher reproductive success of E. helleborine in the populations from anthropogenic habitats than in the populations from natural habitats may result from a higher number of visits by pollinators and their greater species diversity, and from the larger size of plants growing in such habitats.

Methods

Results

Conclusion