Genetic benefits from mate choice could be attained by choosing mates with high heritable quality ("good genes") and that are genetically compatible ("compatible genes"). We clarify the conceptual and empirical framework for estimating genetic benefits of mate choice, stressing that benefits must be measured from offspring fitness because there are no unequivocal surrogates for genetic quality of individuals or for compatibility of parents. We detail the relationship between genetic benefits and additive and nonadditive genetic variance in fitness, showing that the benefits have been overestimated in previous verbal treatments. We point out that additive benefits readily arise from nonadditive gene action and that the idea of "heritable nonadditive benefits" is a misconception. We review the empirical evidence of the magnitude of benefits of good genes and compatible genes in animal populations, and we outline the most promising future directions for empirical research on the genetic benefits of mate choice.

A distinctive feature of human behaviour is the widespread occurrence of cooperation among unrelated individuals. Explaining the maintenance of costly within-group cooperation is a challenge because the incentive to free ride on the efforts of other group members is expected to lead to decay of cooperation. However, the costs of cooperation can be diminished or overcome when there is competition at a higher level of organizational hierarchy. Here we show that competition between groups resolves the paradigmatic 'public goods' social dilemma and increases within-group cooperation and overall productivity. Further, group competition intensifies the moral emotions of anger and guilt associated with violations of the cooperative norm. The results suggest an important role for group conflict in the evolution of human cooperation and moral emotions.

a b s t r a c tDespite its importance for the long-term viability of populations and functioning of ecosystems, the genetic diversity of populations is seldom given explicit consideration in conservation prioritization. Research on the species-genetic diversity correlation (SGDC) suggests that species diversity within a community and intrapopulation genetic diversity are positively correlated, due to the parallel influences of environmental characteristics (area, connectivity, and environmental heterogeneity) on both levels of diversity. A positive locality scale SGDC (i.e. α-SGDC) thus provides potential for simultaneous conservation of both species diversity within a locality and intrapopulation genetic diversity. However, caution is needed, since in some situations environmental characteristics can influence species diversity and genetic diversity differently, resulting in a negative α-SGDC. In such cases there can be a conflict between conservation of species diversity within localities and genetic diversity within populations. SGDCs provide useful information also for conservation planning, which considers compositional differences between localities, since the mechanisms behind α-SGDCs can also drive correlations between differentiation of community and genetic compositions (i.e. β-SGDCs). We suggest that emphasizing locality area and connectivity between similar localities in conservation planning best conserves both species and intrapopulation genetic diversity, and that focusing on highly complementary species richness may compromise conservation of genetic diversity.

Mating between related individuals results in inbreeding depression

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Summary1. Sexual selection through mate choice, and in particular female choice for indirect fitness benefits for their offspring, is a major paradigm that currently seems to enjoy almost unequivocal acceptance. A large body of theoretical work has been built to explain the evolution of mate choice in the absence of direct benefits, and the empiricists have enthusiastically verified the various assumptions and predictions of the theory. 2. However, the relative importance of mate choice for indirect benefits in comparison to choice for direct benefits or to other mechanisms of sexual selection such as malemale competition or sensory exploitation remains a controversial issue, and this seems to be forgotten in many empirical studies. 3.Here we discuss what mate choice is, and how mating bias resulting from mate choice can be distinguished from mating biases resulting from other mechanisms such as male-male competition or sensory exploitation. We will argue that the evidence for active mate choice for indirect benefits is not as compelling as the current paradigm suggests, and that the current emphasis on active mate choice for indirect benefits has resulted in a distorted view of the nature of sexual selection. We emphasize that unlike the other mechanisms, active mate choice must come with a cost to females. 4. We conclude by suggesting what we feel are three important areas that require further study before active mate choice for indirect fitness benefits should be concluded. Sexual selection is a powerful evolutionary force that has been the subject of much investigation for the past 150 years -and still is

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The negative fitness consequences of close inbreeding are widely recognized, but predicting the long-term effects of inbreeding and genetic drift due to limited population size is not straightforward. As the frequency and homozygosity of recessive deleterious alleles increase, selection can remove (purge) them from a population, reducing the genetic load. At the same time, small population size relaxes selection against mildly harmful mutations, which may lead to accumulation of genetic load. The efficiency of purging and the accumulation of mutations both depend on the rate of inbreeding (i.e., population size) and on the nature of mutations. We studied how increasing levels of inbreeding affect offspring production and extinction in experimental Drosophila littoralis populations replicated in two sizes, N = 10 and N = 40. Offspring production and extinction were measured over 25 generations concurrently with a large control population. In the N = 10 populations, offspring production decreased strongly at low levels of inbreeding, then recovered only to show a consistent subsequent decline, suggesting early expression and purging of recessive highly deleterious alleles and subsequent accumulation of mildly harmful mutations. In the N = 40 populations, offspring production declined only after inbreeding reached higher levels, suggesting that inbreeding and genetic drift pose a smaller threat to population fitness when inbreeding is slow. Our results suggest that highly deleterious alleles can be purged in small populations already at low levels of inbreeding, but that purging does not protect the small populations from eventual genetic deterioration and extinction.