Can They Keep Up? Fecundity, Pollen Fitness, and Reproductive Success in Subdioecious, Sexually Labile Cannabis Sativa L

Abstract

Pollen grains are male gametophytes, haploid intergeneration organisms, that function as vectors for gamete dispersal. Pollen compete to fertilize ovules, potentially influencing differential reproductive success - a key condition for microevolution. Variation in the abundance and fertility of pollen produced by plants sets the stage for intense competition among pollen-derived sperm cells for the often limited supply of ovules. To explore this, I developed a methodological framework for collecting pollen, quantifying its abundance, and characterizing its relative fitness. I applied this framework to test if differences in the sex expression of Cannabis plants could influence estimates of relative reproductive performance. Broadly, unisexual male plants produced more pollen than cosexual plants, and plants with chemically induced cosexual phenotypes had lower rates of pollen viability than naturally occurring cosexual phenotypes. My collected work aimed to answer basic science questions about male reproductive performance and the adaptive value of unisexual phenotypes in subdioecious Cannabis sativa.