Does pollen limitation limit plant ranges? Evidence and implications

Area of Science:

• Ecology
• Plant Biology
• Conservation Biology

Background:

• Sexual reproduction is crucial for plant fitness, dispersal, and adaptation.
• Reproductive success, particularly in plants, can be constrained by insufficient pollination.
• Pollen limitation is known to restrict plant distributions in some cases, but its prevalence at range edges is unclear.

Purpose of the Study:

• To investigate whether pollen limitation intensifies towards the edges of plant species' geographical ranges.
• To determine the general importance of pollination as a factor limiting plant distributions.

Main Methods:

• A phylogenetically controlled meta-analysis was conducted using global databases of pollen-supplementation experiments and plant occurrence data.
• Examined trends in pollen limitation relative to latitude and range limits (equatorward vs. poleward).
• Compared meta-analysis findings with results from targeted field experiments at plant range edges.

Main Results:

• Significant overall pollen limitation was detected across the studies analyzed.
• However, little evidence was found to support an increase in pollen limitation towards plant range edges.
• Pollen limitation did not differ significantly towards the tropics or between equatorward and poleward range limits.

Conclusions:

• Pollination appears to contribute to plant range limits less frequently than other ecological interactions.
• The findings suggest that pollination is not a universally dominant factor constraining plant distributions.
• Other ecological factors likely play a more significant role in defining the geographical boundaries of plant species.