Role of Wind and Insects in the Pollination of Ephedra (Gnetales) in Contrasting Habitats of Northwestern Argentina.

BACKGROUND AND AIMS: Species of Ephedra (Gnetales) produce sugar-rich pollination drops on their ovules, which capture wind-borne pollen but may also attract insects. The relative importance of wind and insects as pollen vectors may vary with habitat characteristics. We evaluated the relative contributions of wind and insects to the reproductive success of three Ephedra species-E. multiflora, E. breana and E. triandra-inhabiting contrasting environments in northwestern Argentina, from the open, high-elevation Puna to the structurally complex Monte Desert ecoregion.

METHODS

We conducted open pollination and insect-exclusion experiments, characterized insect visitor assemblages and visitation frequencies, quantified pollen loads carried by insects, and analysed the sugar composition of pollination drops.

KEY

RESULTS

Insect exclusion had no significant effect on reproductive success in any species. The most frequent visitors to female cones were flies, ants and parasitoid wasps. Visitation frequency was similar among species, though visitor assemblages differed in composition. All insect groups carried low pollen loads, whereas total sugar concentration of pollination drops was high in all three species, within the range reported for biotically pollinated plants.

CONCLUSIONS

Our results indicate that in all three Ephedra species successful pollination can occur independently of insects. In the open Puna, pollen transport is predominantly mediated by wind whereas in the more sheltered habitats of E. triandra, transfer appears to occur through both wind and gravity. Insects consuming pollination drops behave as opportunistic visitors, with no detectable contribution to reproductive success. This study provides the first experimental comparison of pollination modes among Ephedra species in contrasting habitats and highlights insect-exclusion experiments as the most robust evidence for detecting ambophily, while observational evidence, such as insect visitation records or pollination drop sugar composition, can complement and help interpret these findings.