Pollen limitation and its influence on natural selection through seed set

Area of Science:

• Ecology
• Evolutionary Biology
• Plant Reproductive Biology

Background:

• Pollen limitation can intensify plant competition, theoretically increasing selection on traits related to pollen receipt.
• Previous empirical evidence testing this hypothesis has yielded inconsistent results.
• Understanding this relationship is crucial for predicting plant adaptation and community dynamics.

Purpose of the Study:

• To mathematically demonstrate that increased pollen limitation inherently leads to stronger selection, all else being equal.
• To empirically test the relationship between pollen limitation and selection strength across multiple plant species and within a specific population (Lobelia cardinalis).
• To investigate if pollinator-mediated selection is associated with pollen limitation in Lobelia cardinalis.

Main Methods:

• Analysis of existing published studies correlating pollen limitation and selection.
• Field study measuring natural selection and pollen limitation over three years in an Ontario population of Lobelia cardinalis.
• Field study measuring natural selection and pollen limitation over one year in two Michigan populations of Lobelia cardinalis.

Main Results:

• A positive relationship between selection strength and pollen limitation was observed across species and within Lobelia cardinalis.
• This relationship extended to vegetative traits among species, which was an unexpected finding.
• Pollinator-mediated selection in Lobelia cardinalis showed no consistent relationship with pollen limitation across most trait types.

Conclusions:

• The study provides strong support for the hypothesis that increased pollen limitation drives stronger natural selection.
• The findings highlight the pervasive influence of pollen limitation on plant evolution, even affecting non-reproductive traits.
• The lack of a consistent link between pollinator-mediated selection and pollen limitation in Lobelia cardinalis warrants further investigation.