Mechanisms of male-male interference during dispersal of orchid pollen

Siring success of flowering plants depends on the fates of male gametophytes, which compete for access to stigmas, stylar resources and ovules. Although rarely considered, pollen may often compete during dispersal, affecting the processes required for export to stigmas; pollen pickup, transport and deposition. We quantified dispersal interference by tracking bee dispersal of stained Anacamptis morio (Orchidaceae) pollen from individual donor flowers and inferred the affected dispersal mechanisms based on the fit of a process-based model. During individual trials, all recipient flowers were either emasculated, precluding interference with donor pollen, or intact, adding potentially interfering pollen to the pollinator. The presence of competing pollinaria on bees reduced pickup of additional pollinaria, doubled the overall proportion of lost donor pollen and reduced total pollen export by 27%. Interference specifically increased loss of donor pollen between successive flower visits and v..., We quantified massula dispersal in a glasshouse at the Ecological Field Station of Uppsala University at Skogsby on Öland, Sweden. Bees without A. morio pollinaria were captured while foraging near the Field Station and maintained in individual vials in a refrigerator. We also collected A. morio inflorescences with intact pollinaria and clean stigmas from a nearby population and placed them in water-filled vials for use in the experiment.  On each donor inflorescence, we stained both pollinia of one flower by injecting rhodamine pink histochemical stain into the anther sacs with a syringe, which generally dyes all of a pollinium’s massulae. Stain was allowed to dry > 20 min before an inflorescence was used in the experiment. We also collected a neighboring flower from the inflorescence, for which we counted the massulae of one pollinium as an estimate of pollen availability in the stained flower. Massula production correlates very strongly between adjacent flowers within inflorescenc...,

Variable
Description

Trial_type
Type of trial (Intact  pollinaria in recipient flowers or Emasculated recipient flowers)

Trial
Trial number

M_init
Initial number of donor massulae

R
Final number of donor pollinaria on bee

Visit
Sequence number of recipient flower in trial

Deposition
Number of donor massulae deposited on stigma of recipient flower