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

ABSTRACT

Background

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:

• Fecundity
• nearest neighbour distance
• pollination
• plant fitness
• spatial aggregation

Acknowledgments

I am grateful to Nona Mellaerts for invaluable assistance with field work and Giampiero Ciaschetti for advice in the field. I thank an anonymous reviewer and Richard Abbott for their thoughtful comments on the manuscript.

Disclosure statement

No potential conflict of interest was reported by the author.

Additional information

Funding

This work was funded by a Starting Investigator Research Grant (Programma STAR) from the University of Naples Federico II and Compagnia San Paolo.