The selection of social actions in families: III. Reproductively disabled individuals and organs

A wide variety of animals and plants produce a proportion of offspring that are partly or wholly sterile, or are fertile but sacrificed to sibs or mut ualist partners, or are diverted to nonreproductive tasks. All these indivi duals with reduced or zero fitness can be described collectively as being ' reproductively disabled'. Reproductively disabled individuals and organs ha ve received little attention; nonetheless, they provide a challenge to sele ction theory that is parallel to that recognized by Darwin for sterile cast es. In this paper, I examine a variety of disabilities, mostly in plants, a nd enquire as to whose fitness they benefit, and how. The results indicate, for the case of reproductively disabled individuals, that there is not muc h conflict between family participants For the case of individuals disabled by their position on a parent, parental manipulation controls the event. T he results also suggest that the level of self-incompatibility in plants is controlled by the pollen, and that in the development of endosperm there i s little conflict between parents and offspring. The diversity of outcomes appears to stem in part from the degree to which parents must consider info rmation transmitted by their offspring.