Female gametophyte development

Great attention has been drawn toward research on female gametophyte (FG) development, and many mutants have been identified with abnormal formation. Although studies are being conducted on the function and expression of individual regulatory genes, only a few projects have focused on gene regulatory networks. Here, we briefly reviewed the molecular mechanisms and factors that affect FG development and discuss our ongoing investigations with gymnosperms. The progress that has already been reported in this field serves as a strong foundation for future examinations of those gene networks that control steps in plant reproduction.     

Reproductive Inhibition of Female Peromyscus leucopus: Female Competition and Behavioral Regulation

Maturational delay of young female mice as the result of exposureto grouped female odors and reproductive inhibition as the resultof exposure to isolated adult females have both been observed(Drickamer, 1974; Skryja, 1978). Each has the potential to reducethe growth rate of populations. Reductions in a female's reproductionfacilitated by social stimulation from other females, whileeffective in reducing population growth, may in the case, ofmaturational delay and reproductive inhibition be an epiphenomenonor exadaptation of selection for improved relative reproductivesuccess in the females possessing these abilities. The ultimateoutcome of these selective processes may be the buffering ofpopulation numbers, but the selective forces may operate tomaximize a female's relative reproductive success. A females'relative reproductive success can be maximized by either increasingher own reproduction or decreasing the reproductive output ofother females. A body of evidence exists to suggest that inPeromyscus mamculatus and Peromyscus leucopus, females are physiologicallyconstrained and unable to increase their own reproduction. Ifthe assumption of physiological restraint is correct, then themost effective way for females to maximize their relative reproductivesuccess is to reduce the reproductive output of their competitors.In this paper, maturational delay and reproductive inhibitionas they affect both the adult female and young females are discussed.Examination of these effects reveals that while they can beeffective in population regulation, their main function andthe selective process that produced them is at the level ofindividual reproduction.     

Female transfer in baboons

Eight of 19 identified adult females transferred over 7 years in a study of intertroop relations among Papio ursinus at Suikerbosrand. Only one of the eight was cycling at the time of transfer. Five of the seven recent mothers who transferred had lost their infants shortly before transferring. Females who transferred received no more aggression before or after their transfer than females who did not transfer. The most important factors determining this extraordinarily high rate of female transfer include subtrooping and absence of predation.     

Female control of paternity

Of the two components of sexual selection, female choice is much less obvious than male-male competition, and hence has always been considered to be of secondary importance. However, recent field observations and new theory have brought about a radical change of emphasis. It now appears that although a female's choice of who fathers her offspring often occurs in a subtle manner, it may be widespread and take place through a variety of behavioural and physiological mechanisms, including the manipulation of male behaviour and the selection of sperm within the female reproductive tract.     

Female transfer in primates

Intergroup transfer by males is nearly universal among social primates. Furthermore, among the most frequently studied monkeys-savanna baboons and Japanese and rhesus macaques—females typically remain in their natal groups, so troops are composed of related matrilines. These facts strongly support two major theories: (l) that kin selection is a powerful force in patterning sociality (if one is to live in a group, one should prefer a group of one’s relatives); and (2) that the ultimate explanation for intergroup transfer is the avoidance of inbreeding depression (though both sexes would prefer to live with kin, one sex has to disperse to avoid inbreeding and for a variety of reasons the losing sex is generally male). Substantial rates of transfer by females in social species with routine male transfer would cast doubt on both ideas. In fact, evidence reviewed here indicates that female transfer is not unusual and among folivorous primates (e.g., Alouatta,the Colobinae) it seems to be routine. In addition to casting doubt on the demographic significance of inbreeding avoidance and favoring mutualistic and/or game theory interpretations of behavior over nepotistic ones, this finding supports the hypothesis that predator detection is the primary selective pressure favoring sociality for many primates. Finally, while female bonding [sensuWrangham, R. W. (1980), Behaviour75:262–299] among primates appears to be less common than generally believed, the observed correlation between female transfer and morphological adaptations to folivory provides empirical support for Wrangham’s model for the evolution of female-bonded groups.