Influence of distance from conspecific and heterospecific co-flowering plants on pollination and fecundity in the nectarless orchid dactylorhiza sambucina

ABSTRACTBackground The relative influence of both conspecific and heterospecific plant density on the fecundity of generalist rewardless plants is unclear.Aims To test whether distance from both conspecific and heterospecific plants influence pollen removal, deposition, and fruit set in the nectarless orchid, Dactylorhiza sambucina that co-flowers with the rewarding Ranunculus apenninus.Methods I experimentally translocated D. sambucina inflorescences and measured pollen removal and deposition rates. I measured plant height and distance to D. sambucina and R. apenninus plants in 30 D. sambucina patches of varying density. I quantified the proportion of pollen removed, pollinia deposited, and fruit set and tested whether these vary according to plant height and distance to both D. sambucina and R. apenninus.Results Translocated inflorescences outside the population had a higher proportion of pollen removal than control plants within the population, while pollinia deposition rates did not differ. Increased D. sambucina height increased pollen removal rates, while increasing distance from R. apenninus resulted in both increased pollen deposition and fruit set.Conclusion Pollination and fecundity of a nectarless orchid may increase with increasing distance from rewarding heterospecifics. This study improves our understanding of how the fecundity of rewardless plants is influenced by co-flowering plants.KEYWORDS: Fecunditynearest neighbour distancepollinationplant fitnessspatial aggregationDisclaimerAs a service to authors and researchers we are providing this version of an accepted manuscript (AM). Copyediting, typesetting, and review of the resulting proofs will be undertaken on this manuscript before final publication of the Version of Record (VoR). During production and pre-press, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal relate to these versions also. AcknowledgementsI am grateful to Nona Mellaerts for invaluable assistance with field work and Giampiero Ciaschetti for advice in the field. This work was funded by a Starting Investigator Research Grant (Programma STAR) from the University of Naples Federico II and Compagnia San Paolo.I thank an anonymous reviewer and Richard Abbott for their thoughtful comments on the manuscript.Additional informationFundingThe work was supported by the Programma STAR .