Abstract Detail

Reproductive Processes

Karron, Jeffrey [1], Christopher, Dorothy [2], Semski, Wendy [3], Trapnell, Dorset [4], Mitchell, Randall [5].

Pollen competition contributes to wide variation in male fertility in the field.

On average, hermaphroditic flowering plants achieve half of their reproductive success (RS) through male function and half through female function. Hermaphroditism is often thought to impose a constraint on the evolution of sexually-selected traits, since some trait combinations may fail to maximize fitness through either sexual function. However, this constraint may not apply to post-pollination processes, and males with faster pollen tube growth rates may sire seeds on more pollen recipients, leading to higher male fertility. We quantified male and female RS in experimental field populations of Mimulus ringens to test Bateman’s (1948) hypothesis that variation in male RS will exceed variation in female RS since it is likely to be limited by mating opportunities, rather than by resources. We found strong support for Bateman’s key predictions: 1) Male RS has a higher variance than female RS. 2) Male RS is strongly dependent on mate number, whereas female RS is only weakly influenced by mate number. The wide variance in male RS was not associated with flower size, flower shape, or pollen production. To explore whether post-pollination processes contribute to variation in male fertility we hand-pollinated 14 unrelated maternal plants with pollen mixtures containing equal proportions of pollen from six donors that differed markedly in male fertility in our field study. The three donors with high fertility in our field population disproportionately sired offspring on all maternal plants. These results suggest that male-male competition can be a potent selective force in hermaphroditic flowering plants.

1 - University Of Wisconsin-Milwaukee, Department Of Biological Sciences, Po Box 413, Milwaukee, WI, 53201, United States
2 - University Of Wisconsin - Milwaukee, Dept Of Biological Sciences, 3209 N Maryland Ave, Milwaukee, WI, 53211, United States
3 - UW-Milwaukee, Dept Of Bio Sci, P.O. Box 413, Milwaukee, WI, 53201, United States
4 - University Of Georgia, Plant Biology, 2502 Miller Plant Sciences Bldg , Athens, GA, 30602, United States
5 - University Of Akron, Department Of Biology, Dept Of Biology, Akron, OH, 44325, United States

Keywords:
pollen competition
male fertility
sexual selection
Reproductive Success
Pollination.

Presentation Type: Oral Paper
Number: RP3005
Abstract ID:249
Candidate for Awards:None