Sarah Lenington

Social preferences for partners carrying ‘good genes’ in wild house mice

Female wild strain house mice (Mus musculus) can use olfactory cues to discriminate males carrying lethal t-alleles (+/t) from those that do not carry such alleles (+/+). When tested in an arena, female mice tend to avoid +/t males and preferentially direct approaches to +/+ males. The magnitude of a females avoidance of +/t males is related to the females own genotype. Females who are themselves +/t show greater avoidance than +/+ females. Male mice tend to be more aggressive toward females carrying t-alleles and are less likely to attempt copulations with such females than with +/+ females. I suggest that these social preferences may be related to mating preferences, providing an example of mating preference based on genetic quality. Furthermore, avoidance of +/t individuals as mates could account for the lower than expected frequency of t-alleles in natural populations.

The t Complex: A Story of Genes, Behavior, and Populations

Publisher Summary This chapter discusses the major molecular, behavioral, and population features of the t complex as an illustration of the relevance of data gathered at one level of analysis for interpretations at other levels. Behavior may be a major factor in determining the frequency of t haplotypes in wild mice. Genes within the t complex appear to have important effects on mating preference, parental investment, and aggressive behavior. There are probably two ways in which behavior regulates gene frequency. First, it seems likely that there is selection for t haplotypes because possession of a t mutation enhances male aggressive behavior. In all other respects, however, possession of a t haplotypes appears to lower fitness and mice appear to be capable of behaviorally altering the transmission of these otherwise deleterious genes to their progeny. Genes within the t complex have a large number of pleiotropic consequences for behavior. Understanding the behavioral consequences of t complex genotype can elucidate, in turn, the process controlling the frequency of these genes in natural populations.

Child abuse: The limits of sociobiology

Abstract A review of five population based studies indicates that rates of child abuse tend to be highest among young male children from poor families. Children from very large families, children from families with a history of marital disruption, and defective children are also at a high risk of abuse. Perpetrators are more apt to be fathers or stepparents than would be expected on the basis of their representation in families of abused children. Biological mothers are least apt to abuse their children. Although these data are consistent with an evolutionary model of child abuse, many of these findings are also consistent with alternative (especially economic) models for abuse. An attempt is made to develop testable predictions for child abuse that are consistent with evolutionary theory and inconsistent with more conventional models.

Female discrimination of male odors correlated with male genotype at the T locus: A response to T-locus or H-2-locus variability?

Female house mice (Mus musculus), derived from several populations of wild-caught mice, were tested for their ability to discriminate between males whose genotype at the T locus was +/+ and those whose genotype was +/t, using odor cues alone. Females spent more time near the odors or +/+ males than near the odors of +/t males. This preference was independent of the T-locus genotype of the female and the particular type of t allele carried by either the male or the female. A females preference, however, did appear to be related to the genotype of her parents. Females with one +/t parent were more likely to prefer +/t males than were females whose parents were both +/+. In a second experiment 18 females were tested with odors from soiled bedding of recombinant males whose genotype varied at the T locus but who were similar at the H-2 locus. As a control, these 18 females were also tested with bedding of wild-derived +/+ and +/tw semilethal males. Females tested with recombinant males preferred odors of males not carrying lethal t alleles over those of males carrying two lethal t alleles, indicating that T-locus variability, not H-2-locus variability, is responsible for odor differences between +/+ and +/t males. Female responses to odors of recombinanat males did not differ from those to odors of +/+ and +/tw semilethal males. Responses of mice to odor differences associated with T-locus variability may have evolved independently of responses to odor variability associated with the H-2 locus.

FEMALE PREFERENCE AND VARIABILITY AMONG t-HAPLOTYPES IN WILD HOUSE MICE

Many wild house mice are heterozygous (+/t) for a t-haplotype at the t-complex. Most t-haplotypes carry recessive lethal factors causing embryonic mortality of homozygotes Many different t-haplotypes coexist in mouse populations. Fetal death occurs when mice are homozygous for lethal haplotypes from the same complementation group. If the mouse carries two t-haplotypes from different complementation groups, it survives, but all such males are sterile. We gave +/tw12 and +/tw32 females a choice between +/tw12 and +/tw32 males Females preferred the male carrying a t-haplotype different from their own. This disassortative preference was stronger for +/tw12 than for +/tw32 females. We paired +/tw12 and +/tw32 females to males of each genotype and measured the number of fertile progeny produced. Fitness of +/tw32 females was slightly higher when they were mated to males of the opposite genotype; fitness of +/tw12 females was much higher when they were mated to +/tw32 than when mated to +/tw12 males. Hence, female preferences for genetically based male cues may track fitness consequences of mating. Female preference combined with a fitness advantage for disassortative mating among haplotypes may maintain the high degree of genetic variability in this region.

Distribution of T-haplotypes in natural populations of wild house mice

Data obtained from published studies and from mice trapped for use in our laboratory were analyzed to determine the relationship between frequency of t -haplotypes in wild house mice ( Mus musculus ) and other variables such as sex, age at capture, and kind of t -haplotype found in the population. In addition, the frequency of t -alleles in populations from which mice had been sampled repeatedly was examined to determine whether, within populations, frequency of t -haplotypes tends to change over time. Populations in which semilethal haplotypes predominated had higher frequencies of heterozygous animals than populations in which the predominant haplotype was a lethal. Furthermore, frequencies of t -haplotypes were higher in males than in females. However, no difference in frequency of t -alleles was found between mice trapped as juveniles and individuals of the same sex trapped as adults. Furthermore, only one of 14 populations from which mice were trapped repeatedly showed evidence of a change in frequency of heterozygotes over time. The relevance of these data for potential processes controlling the frequency of t -haplotypes in wild populations is discussed.

Analysis of a genetic recognition system in wild house mice

Wild female house mice have strong preferences for odors of male mice whose t-complex genotype is +/+ rather than for males carrying deleterious mutations (+/t) at the t complex. In this review of a large number of studies examining the basis for this preference, we suggest the following: first, preferences of +/+ females are greatly influenced by environmental factors and probably do not have a large genetic component: second, preferences of +/t females are less dependent upon environmental factors and hence may have a strong genetic component: third, the lethal factors within the t complex are involved in both the production of the cue by males and the expression of the preference in females: and fourth, there may be a second gene or genes within the t complex involved in the expression of female preference.

Dominance and reproductive behavior of wild house mice in a seminatural environment correlated with T-locus genotype

SummaryBehavior of mice whose T-locus genotype was either +/+ or +/t was observed in a seminatural environment. Heterozygous females were less likely to be dominant, less likely to go into behavioral estrus, and less likely to become pregnant than were +/+ females. The relative fitness of +/t as compared with +/+ females was 0.32:1.00. In contrast, +/t males produced 35% more young than did +/+ males. The higher fitness of +/t males was primarily due to a greater production of young on the part of +/t as compared with +/+ subordinate males. Little evidence was found under these naturalistic conditions, of non-random mating with respect to T-locus genotype. The indication of overdominance for +/t males makes it unlikely that heterozygote disadvantage will be sufficient to account for the frequency of t-alleles in natural populations.

Genetic basis for male aggression and survivorship in wild house mice (Mus domesticus)

Work on the genetic region of the house mice known as the t-complex has produced the hypothesis that mice heterozygous for t-haplotypes (+/t) may have a selective advantage over wild-type (+/+) males owing to the greater aggressiveness of +/t males. We tested this hypothesis by examining the behavior of +/+ and +/t mice placed in four large outdoor enclosures. We found that +/t males were dominant over +/+ males. Furthermore, in the outdoor enclosures +/t males had higher survivorship than +/+ males, both as adults and juveniles. However, males of the two genotypes did not differ in home range size. We suggest that t-haplotypes may be, in part, maintained in mouse populations because of a selective advantage in heterozygous males.

The Evolution of Polyandry in Shorebirds

The existence of polyandry has posed a difficult problem for theories attempting to account for the evolution of mating systems. The theory of sexual selection predicts competition among males, greater female than male parental investment, and more sexual promiscuity on the part of males than females (Darwin, 1871; Fisher, 1930; Orians, 1969; Trivers, 1972; Emlen and Oring, 1977). Polyandrous mating systems, particularly in extreme cases such as the Northern Jacana (Jacana spinosa) (Jenni and Collier, 1972), seem to violate each of these predictions. Females are larger and more aggressive than males, parental care is performed only by males, and females copulate with several males whereas each male copulates with only one female.