QTLs for grain carbon isotope discrimination in field-grown barley.

In several crops including cereals, carbon isotope discrimination (Delta) has been associated with drought tolerance in terms of water-use efficiency and yield stability in drought-prone environments. By using a complete genetic map generated from 167 recombinant inbred lines from a cross between Tadmor and Er/Apm, QTLs associated with grain Delta have been detected in barley grown in three Mediterranean field environments, two differing only in water availability. Ten QTLs were identified: one was specific to one environment, two presented interaction with the environment, six presented main effects across three or two environments and one presented both effects. Heading date did not contribute to the environment (E) and G x E effects acting on Delta. Seasonal rainfall and the ratio of rainfall to evapo-transpiration made large contributions to the environmental effect, but their influence on G x E was weaker. Eight QTLs for Delta co-located with QTLs for physiological traits related to plant water status and/or osmotic adjustment, and/or for agronomic traits previously measured on the same population. Some perspectives in terms of characterising drought tolerance are evoked.

DNA analyses support the hypothesis that infanticide is adaptive in langur monkeys.

Although the killing of dependent infants by adult males is a widespread phenomenon among primates, its causes and consequences still remain hotly debated. According to the sexual selection hypothesis, infanticidal males will gain a reproductive advantage provided that only unrelated infants are killed and that the males increase their chances of siring the next infants. Alternatively, the social pathology hypothesis interprets infanticide as a result of crowded living conditions and, thus, as not providing any advantage. Based on DNA analyses of wild Hanuman langurs (Presbytis entellus) we present the first evidence that male attackers were not related to their infant victims. Furthermore, in all cases the presumed killers were the likely fathers of the subsequent infants. Our data, therefore, strongly support the sexual selection hypothesis interpreting infanticide as an evolved, adaptive male reproductive tactic.

Ecology of female social relationships: Hanuman langurs (Presbytis entellus) and the van Schaik model.

The ecological model of Carel van Schaik provides clear predictions for female-female relationships in relation to scramble or contest within-group competition and contest between-group competition. These predictions were applied to data from a 12-year field study on Hanuman langurs (Presbytis entellus) that ranged freely around Jodhpur (India). It appears that hierarchical relationships between females (unstable, inconsistent, individualistic, with low rates of agonistic coalitions) reflect scramble within-group competition. Such competition, however, results in individual evolutionary advantages (differential feeding time; differential reproductive success) so that dominance effects mirror contest within-group competition. Between-group contest competition at Jodhpur is strong (low predator pressure, high population density, good food defensibility, essential role of females during intergroup encounters, loud vocalization of males). The results are discussed in the light of langur feeding habits.

Homosexual mounting in free-ranging female Hanuman langurs (Presbytis entellus).

Female-female mounting was studied for 3233 hr in a bisexual one-male troop of free-ranging Hanuman langurs in northwestern India over a period of 6 years. The population breeds throughout the year and female-female mounts (n = 524) occurred during all months. All 15 adult females mounted and were mounted, although only 20% of the individuals exhibited more than half of all mounter activity and 33% more than half of all mountee activity. Various similarities with heterosexual mounting suggest that sexual arousal is a stimulus of the activity. Cycling, pregnant, and lactating females acted as mounters as well as mountees. However, ovulating individuals were greatly overrepresented concerning their likelihood of mounting and being mounted. Females of any given rank in the dominance hierarchy showed mounter as well as mountee activity, although mounters were higher ranking than mountees in 84% of cases. Young mounters were overrepresented and middle- to old-aged mounters underrepresented, whereas no such differences existed for mountees. Mounting relations among four young adult paternal half-sisters who occupied top positions in the dominance hierarchy were significantly overrepresented. Although the ultimate function of homosexual female mounting is not fully understood, it is suspected to be connected with intrasexual competition: If "pseudocopulations" induce mountees to reduce the number of solicitations addressed to the male, the probability of insemination decreases and mounters thus reduce the number of future competitors.