POLLINATION DYNAMICS IN EPILOBIUM CANUM (ONAGRACEAE): CONSEQUENCES FOR GAMETOPHYTIC SELECTION

Area of Science:

• Plant reproductive biology
• Evolutionary botany
• Ecology

Background:

• Pollen tube competition is a known driver of gametophytic selection, influencing offspring genetic and phenotypic traits.
• Previous research relied on hand-pollination experiments, lacking quantification of natural pollen competition levels.

Purpose of the Study:

• To quantify the natural levels and intensity of pollen tube competition in a wild population of Epilobium canum.
• To investigate the relationship between pollen deposition patterns and the occurrence of pollen tube competition.
• To assess the variability of pollen tube competition among individual plants.

Main Methods:

• Field study of Epilobium canum population.
• Measurement of pollen deposition quantity and timing on stigmas.
• Estimation of pollen tetrads required for full seed set.
• Observation of pollen loads from hummingbird pollination.

Main Results:

• Approximately 20 pollen tetrads were needed for full seed set.
• Hummingbirds frequently deposited >20 tetrads, often in a single load.
• Pollen tube competition intensity varied significantly among plants, with some styles excluding up to 80% of pollen tubes.
• Competition was potentially weak unless at least 30 tetrads competed for ovules.

Conclusions:

• Natural pollen tube competition occurs in Epilobium canum, with varying intensity and frequency.
• Pollen deposition patterns, particularly multiple loads, can lead to pollen tube competition.
• Further research on pollination rates and progeny fitness is necessary to fully understand the ecological role of pollen tube competition.