CAN THEY KEEP UP? FECUNDITY, POLLEN FITNESS, AND THE EVOLUTIONARY DYNAMICS SURROUNDING REPRODUCTIVE SUCCESS IN SUBDIOECIOUS CANNABIS SATIVA L.

Candidate: Sydney Wizenberg
Supervisor: Dr. Lesley Campbell

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 sexual lability and genotype of Cannabis plants could influence estimates of relative pollen fitness. Broadly, plants with XY karyotypes had higher reproductive performance than plants with XX karyotypes, and plants with chemically induced cosexual phenotypes had lower rates of in vitro germination relative to naturally occurring cosexual phenotypes. My collected work aimed to answer basic science questions about sexual competition in subdioecious Cannabis sativa and explore the evolutionary dynamics surrounding reproductive success in this economically valuable crop