RESEARCH ARTICLE

F-75005 Paris, France Full list of author information is available at the end of the articledifferent reproductive modes within populations usually predict bi-modal distributions of predominant outcrossing or selfing [1-3]; but see, e.g., [4-8]. Selection against dele-terious recessive alleles is more effective in populations that reproduce more frequently via selfing than outcross-ing because selfing increases segregation of homozygotes, outcrossing can maintain higher loads of recessive dele-terious alleles, which should make those populations re-sistant to invasion by selfers and keep selfing rates low. In contrast to theoretical expectations, many natural populations of plants and animals exhibit mixed repro-ductive systems with partial selfing [9,10]. One means of reconciling empirical observations with theory is to recognize that the fitness components expressed under selfing or outcrossing might tradeoff with one another, e.g., [11-13], and thereby add an additional layer of com