PARENT-OFFSPRING CONFLICT, SIBLING RIVALRY, AND BROOD SIZE PATTERNS IN PLANTS

Flowering plants show wide variation in the proportion of fertilized ovules that mature into seeds within individual fruits (9-11, 20, 39, 42, 44, 50, 74, 76, 77, 123). In most species a variable number of seeds die at different stages in their development (9, 11, 17, 33, 39, 44, 50, 65, 74, 76, 77). Thus, as in the case of many birds and some mammals (45, 49, 55, 56, 86, 88), the final brood size is considerably lower than the initial. The reduction in brood size or in the seediness of fruits has been viewed as a manifestation of genetic load (74, 80, 103, 124), resource depletion (50), predation or pathogen infestation (5, 6, 37, 42, 44, 50, 74), or maternal regulation of offspring quality (11, 21, 39, 50, 59-62, 71, 80, 107). Almost all of these explanations view brood reduction as a maternal adaptation to increase its own Darwinian fitness. However, developing fruits provide a perfect arena for the expression of