Individual Variation in the Vigor of Self Pollen and Selfed Progeny in Hibiscus moscheutos (Malvaceae)

Abstract

In some self‐compatible species, self pollen tubes grow more slowly than outcross pollen, presumably leading to low selfing rates when mixtures of self and outcross pollen reach the stigma simultaneously. Here we show that the competitive ability of self pollen differed among individuals of Hibiscus moscheutos. Self pollen tubes grew slower than outcross pollen in three plants, faster than outcross pollen in four plants, and showed no difference in five other plants (based on rates of callose plug formation). Levels of inbreeding depression were examined by comparing progeny from self and outcross pollinations in seven maternal families. Self pollination led to reduced seed number in only one maternal family, and a slight decrease in seed size was seen in two maternal families. Considerable inbreeding depression occurred later in the life cycle, and the degree of inbreeding depression varied among maternal families of 6‐week‐old plants. Our results demonstrate the potential for unpredictable effects of pollen competition on individual selfing rates, which in turn may affect progeny vigor. This complex situation contrasts with previous reports of species in which outcross pollen consistently outcompetes self pollen (cryptic self‐incompatibility).

Reproductive Allocation and the Fitness Consequences of Selfing in Two Sympatric Species of Epilobium (Onagraceae) with Contrasting Mating Systems

“…One selfed and one outcrossed seedling were planted from the same maternal parent in each pot. This planting design has been used by others (Snow and Spira, 1993) and was chosen for the following reasons. First, it allows plants to compete, and is therefore a more realistic environment than plants growing alone.…”

Variability in Pollen Load: Implications for Reproduction and Seedling Vigor in a Rare Plant, Silene douglasii var. Oraria

“…Large pollen loads also affect offspring quality by increasing opportunities for competition and selection among pollen genotypes within the style or at fertilization (Mulcahy et al 1992;Snow and Spira 1993). Yet, while pollen intensity influences offspring vigor in a wide range of plants, the results for noncultivated species have been highly variable (Richardson and Stephenson 1992).…”

Influence of Seed Age and Inbreeding on Germination and Seedling Growth in Hibiscus moscheutos (Malvaceae)

“…Such knowledge could have applications to restoration efforts, particularly if selfed seeds deteriorate more rapidly than outcrossed seeds. Materials (Snow and Spira 1993). This species has a mixed mating system: its large, showy one-day flowers are pollinated by bees and a mixture of selfed and outcrossed seeds are produced (Spira et al 1992;Snow et al 1996).…”