Pollinator limitation affects low reproductive success in populations of nectarless orchid in the Biebrza National Park

Emilia Brzosko,Izabela Tałałaj,Paweł Mirski,Beata Ostrowiecka,Edyta Jermakowicz,Ada Wróblewska

doi:10.5586/aa.1706

Abstract

The deficiency of pollinators is indicated as the main factor limiting fruit set in orchids. Nectariferous species are more successful in setting fruits than nectarless species. In the present study, we tested whether pollinator limitation lowers reproductive success in populations of <em>Cypripedium calceolus</em> on environmental islands in the Biebrza National Park, NE Poland. Moreover, we analyzed how population size and structure affect pollination success. Our observations and results of experiments document the low level of fruiting in populations of nectarless <em>C. calceolus</em> (9.2% on average) and strong pollen limitation. Generally, we noted a positive relationship between pollination success and all parameters of population size (measured by both occupied area and number of clumps or shoots) and parameters measuring floral display (number of flowers in population, number of flowers in clumps, spatial structure of flowering shoots). We suggest that information about factors influencing the reproductive success of this endangered species may be useful for planning appropriate conservation actions.

Highlights

For the maintenance of plant populations and their viability and stability, successful recruitment from seeds is essential
The fruit set noted after induced autogamy was very high and reached 88.9%, but no fruit was set in the experiment of spontaneous autogamy
Our results document the low level of fruiting in populations of nectarless C. calceolus existing on mineral islands in the Biebrza National Park

Summary

Introduction

For the maintenance of plant populations and their viability and stability, successful recruitment from seeds is essential. This success depends on the production of fruits/seeds, which is often recognized as a factor limiting the recruitment of new individuals [1,2,3]. A low level of fruiting (even below 10% in nonautogamous species) is indicated as a common characteristic of one of the largest families, Orchidaceae [4,5]. The deficiency of pollinators is indicated as the main factor limiting fruit set in orchids [2,6,7]. Despite pollinator restriction, fruiting can be increased in many orchid species if they are self-compatible, which enables reproductive assurance due to spontaneous or facilitated selfing [2].

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Results

Conclusion