CLONAL REPEATABILITY OF IN-VITRO POLLEN-TUBE GROWTH-RATES IN OENOTHERA-ORGANENSIS (ONAGRACEAE)

The concept that pollen selection is an important force driving angiosperm evolution has received a lot of attention in recent years. In order for pollen competition to have evolutionary significance, heritable variation for pollen tube growth rate must exist. In this study, I tested the clonal repeatability, a measure of broad-sense heritability, of in vitro pollen tube growth rate in Oenothera organensis. Although I found significant phenotypic differences in pollen tube growth rate, the calculated clonal repeatability value of 9.4% indicates that heritability of pollen tube growth rate in this species is quite low. In contrast, both flower identity and plant identity had highly significant effects on pollen tube growth rate, suggesting that the environment may be more important than genotype in determining pollen performance in this species.