Selection on pollen donors by Echium vulgare (Boraginaceae)

Abstract

Fewer than 25% of the ovules of Echium vulgare in the field develop into viable seeds, even with no pollen limitation. The loss of ovules could enhance the fitness of the maternal parent, if less fit embryos are selectively aborted. Two pollination experiments were performed to examine the selectivity of maternal parents on self-pollen and different cross-pollen sources. Pollinated with one pollen genotype per flower, self-pollen was, on average, as successful in siring seeds as cross-pollen. However, the relative success of self-pollen compared to outcross-pollen differed significantly among the maternal parents. These results suggest that, under certain conditions, selfing can produce a greater number of seeds than cross-pollination. Pollen donors differed significantly in outcrossing success. The plants that were more successful in selfing were also more successful pollen donors in outcross-pollinations. No significant interaction between maternal parent and paternal genotype was found. Pollinations with a pollen mixture produced selfed and outcrossed seeds in the same ratios as the singledonor experiment. Overall, only slight differences were found between the single-and mixed-donor experiments. Pollen tube growth did not show a significant correlation with the success of the parental genotypes in the mixeddonor experiment, indicating that pollen tube growth is not the determining factor controlling the paternity of the seeds. These results are discussed with reference to possible mediating mechanisms.

Seed paternity in flowering plants: an evolutionary perspective

“…In Campsis radicans, up to 33% of viable seeds from mixed pollinations were fathered by self pollen, while nearly none would be fathered using loads of purely self pollen (Bertin & Sullivan 1988). In Aquilegia caerulea (Montalvo 1992) and Echium vulgare (Melser et al 1997), the proportion of selfed seeds after mixed pollinations reflects the ratio of seed set after pure self and pure outcross pollinations. Thus, none of these studies provides strong evidence that post-pollination selection excludes self pollen from fertilization.…”

Pollen‐tube growth rate and seed‐siring success among Betula pendula clones

“…Bjo$ rkman et al, 1995 ;Snow & Spira, 1996) provide evidence for non-random fertilization, the association between pollen tube growth and seed-siring success has not been straightforward (Melser et al, 1997 ; J. I. Hormaza & M. Herrero, unpublished ; see also Thomson et al, 1994). Melser et al (1997) found that the parental combinations that sired relatively many seeds did not have high pollen-tube growth rates in Echium vulgare. In P. avium the speed of pollen germination on the stigma was not a determinant factor affecting fertilization success (J. I. Hormaza & M. Herrero, unpublished).…”

Impact of introduced honey bees on native pollination interactions of the endemic Echium wildpretii (Boraginaceae) on Tenerife, Canary Islands

“…On the other hand, inbreeding effects in life stages other than seed viability cannot be ruled out. In a close relative, Echium vulgare L., no effect of selfing was found at the stage of seed production (Mensler et al, 1997). Yet, late-acting inbreeding depression in male and female function of offspring derived from selfing has been reported (Mensler et al, 1999).…”