PATTERNS OF FRUIT-SET: WHAT CONTROLS FRUIT-FLOWER RATIOS IN PLANTS?

Fruit-set values for 447 species of plants were examined for variations due to compatibility, breeding system, life form, latitude, type of fruit, and type of pollination. The results indicate significant differences between self-compatible and self-incompatible species in terms of 1) average fruit-set and 2) the effect of the independent variables. Breeding system, life form, and latitude were found to be the only significant independent variables for self-incompatible species, while fruit type and latitude were found to be significant for self-compatible plants. Although latitude was a significant variable for self-compatible and self-incompatible species, it was correlated with other variables and may actually have no direct effect on fruit-flower ratios in plants. Hypotheses explaining the effect of the significant independent variables on fruit-flower ratios were then examined and, when possible, predictions were tested. The results indicate that the selective-abortion and bet-hedging hypotheses may be important factors contributing to the low fruit-set in self-incompatible plants, while the male-function hypothesis may explain the lower fruit-flower ratios in hermaphrodites.