Nonrandom Mating in Wild Radish: Variation in Pollen Donor Success and Effects of Multiple Paternity Among One‐ to Six‐donor Pollinations

Abstract

Nonrandom mating in plants may involve differential success of self‐ vs. outcross pollen, of pollen from relatives vs. nonrelatives, and of pollen from several compatible donors. Of these, the last is least understood. Wild radish plants were crossed with six pollen donors in all possible combinations to investigate differences in pollen donor performance and to compare multiply sired fruits with different numbers and identities of fathers. Pollen donors differed in number of seeds sired, position of seeds sired within fruits, and mass of seeds sired. Performance in single pollination was not a good predictor of performance in mixed pollination. Performance in two‐donor pollinations was a better predictor of the outcome of multidonor pollinations. Multiply sired fruits were selectively filled, but not all multiply sired fruits were equal. Both the number and identity of donors affected fruit filling. These results and others with wild radish suggest that variation in pollen donor ability to sire seeds is relatively common in wild radish. Since wild radish plants in the field typically receive pollen from several donors, there may be considerable opportunity for selection at this stage of the life cycle in wild radish.

Under how wide a set of conditions will nonrandom mating occur in Raphanus sativus (Brassicaceae)?

“…In greenhouse experiments with wild radish (e.g., Marshall and Ellstrand, 1986;Marshall, 1991;Marshall, 1998) and other species (Mitchell and Marshall, 1998), compatible pollen donors vary in seed siring success, supporting the hypothesis that pollen competition and mate choice can be important in plants. However, because greenhouse conditions may lack important sources of variability for field plants, questions remain about the interpretation of patterns of nonrandom mating seen only in the greenhouse.…”

“…For example, previous studies with wild radish have shown that whenever a mixture of pollen from two or more compatible donors is applied to stigmas, mating is nonrandom (Marshall and Ellstrand, 1988;Marshall, 1991Marshall, , 1998Marshall and 1 Manuscript received 20 March 2003; revision accepted 20 June 2003. The authors thank Joy J. Avritt for assistance in the greenhouse and suggestions on experimental design, Patricia J. Gegick for help with various laboratory techniques, Eric L. Charnov for invaluable discussions and advice, Jerusha Reynolds for helpful comments and for Fig.…”

“…1. This organism is excellent for this because (1) nonrandom mating is known to occur Ellstrand, 1986, 1988;Marshall, 1991Marshall, , 1998, (2) maternal condition is known to affect seed paternity (Marshall and Ellstrand, 1988;Marshall and Fuller, 1994;Marshall and Diggle, 2001), and (3) a previous study of pollen availability and paternity showed that seed paternity was unchanged across a range of pollen load sizes (Marshall et al, 2000). A total of 360 pollinations was performed.…”

Variation of pollen limitation in the early flowering Mediterranean geophyte Narcissus assoanus (Amaryllidaceae)

“…The inbreeding hypothesis could be tested by investigating the fertility of crosses at different spatial scales (Waser 1993). It is also possible that by increasing the number of male parents used in crosses fertility could have been increased (Marshall 1991). Another intriguing possibility concerns ovule maturation schedules within flowers of Narcissus species.…”

Selection on pollen donors by Echium vulgare (Boraginaceae)

“…Such deviations in seed numbers from different pollen sources have been established for a number of species (Raphanus raphanistrum in Mazer et al 1986;Ellstrand and Marshall 1986;Marshall and Ellstrand 1988;Marshall 1991;Marshall and Folsom 1992; Campsis radicans in Bertin 1982Bertin , 1985Bertin , 1988; Chamaecrista fasciculata in Fenster 1991). However, the ovules of these species are not uniformly arranged.…”