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Because of maternal mtDNA inheritance, mtDNA mutations detrimental only in males are not expected to be selected against, an effect termed the \"mother's curse.\" However, if there is positive-assortative mating, equivalent to what was called \"inbreeding\" by Wade and Brandvain (2009), then selection can act to reduce the frequency of these male-specific detrimental mtDNA mutants. On the other hand, as shown here negative-assortative mating, or \"outbreeding, \"paradoxically can result in an increase in the frequency of male-specific detrimental mtDNA mutants. The implications of these findings are briefly discussed.

The mode in which sexual organisms choose mates is a key evolutionary process, as it can have a profound impact on fitness and speciation. One way to study mate choice in the wild is by measuring trait correlation between mates. Positive assortative mating is inferred when individuals of a mating pair display traits that are more similar than those expected under random mating while negative assortative mating is the opposite. A recent review of 1134 trait correlations found that positive estimates of assortative mating were more frequent and larger in magnitude than negative estimates. Here, we describe the scale-of-choice effect (SCE), which occurs when mate choice exists at a smaller scale than that of the investigator's sampling, while simultaneously the trait is heterogeneously distributed at the true scale-of-choice. We demonstrate the SCE by Monte Carlo simulations and estimate it in two organisms showing positive (Littorina saxatilis) and negative (L. fabalis) assortative mating. Our results show that both positive and negative estimates are biased by the SCE by different magnitudes, typically toward positive values. Therefore, the low frequency of negative assortative mating observed in the literature may be due to the SCE's impact on correlation estimates, which demands new experimental evaluation.

When nonrandom mating alters offspring numbers or the distribution of offspring phenotypes, it has the potential to impact the population growth rate. Similarly, sex-specific demographic parameters that influence the availability of mating partners can leave a signature on the population growth rate. We develop a general framework to explore how mating patterns and sex differences influence the population growth rate. We do this by constructing a two-sex integral projection model to explore ways in which altering the mating behavior from random to nonrandom mating (assortative, disassortative, or selection for size) and altering demographic parameters in one or both sexes (growth, survival, and parental contribution to offspring phenotype) affect the population growth rate. We demonstrate our framework using data from a population of Columbian ground squirrels. Our results suggest that the population growth rate is substantially affected when nonrandom mating is linked to sex differences in demographic parameters or parental contributions to offspring phenotype, but interestingly, the effect of the mating pattern alone is rather small. Our results also suggest that the population growth rate of Columbian ground squirrels would increase with the degree of disassortative mating and with the degree of the mating advantage of large individuals.

The MHC is highly polymorphic in most vertebrates and the suggested selective mechanisms responsible for the maintenance of this variation are several, including maternal-fetal interaction, parasite resistance, and negative-assortative mating. Evidence for these mechanisms is reviewed and estimates of the amount of selection in a number of studies are given. Although there is much yet to be understood about the mechanism and extent of balancing selection at MHC, new advances in molecular genetic technology and increasing interest in MHC from many types of biologists promise answers in the near future.

The negative control design can be used to provide evidence for whether a prenatal exposure–outcome association occurs by in utero mechanisms. Assortative mating has been suggested to influence results from negative control designs, although how and why has not yet been adequately explained. We aimed to explain why mutual adjustment of maternal and paternal exposure in regression models can account for assortative mating. We used directed acyclic graphs to show how bias can occur when modeling maternal and paternal effects separately. We empirically tested our claims using a simulation study. We investigated how increasing assortative mating influences the bias of effect estimates obtained from models that do and do not use a mutual adjustment strategy. In models without mutual adjustment, increasing assortative mating led to increased bias in effect estimates. The maternal and paternal effect estimates were biased by each other, making the difference between them smaller than the true difference. Mutually adjusted models did not suffer from such bias. Mutual adjustment for maternal and paternal exposure prevents bias from assortative mating influencing the conclusions of a negative control design. We further discuss issues that mutual adjustment may not be able to resolve.

Coevolution of plants and pollinators has been suggested as a mechanism driving diversification of plant-pollinator mutualisms. There is increasing recognition that predators or competitors can influence the abundance and behavior of pollinators and indirectly affect the fitness of plants. However, existing theories on plant-pollinator diversification focus exclusively on mutualistic interactions between plants and pollinators. Here we used simulations to evaluate whether predation on pollinators promotes coevolutionary diversification of plant-pollinator mutualisms. We developed an individual-based simulation model in which the blooming season of plants and the active seasons of pollinators and predators can evolve. In simulations without predators, plant-pollinator coevolution caused diversification in blooming/active seasons for both plants and pollinators, but this diversification resulted in polymorphisms, not speciation. The introduction of predators promoted a split of plant and pollinator populations into reproductively isolated subpopulations with corresponding blooming and active seasons or a directional shift of blooming and active seasons, increasing the possibility of plant-pollinator cospeciation. This result suggests that predation on pollinators can promote sympatric and allopatric divergence of plant-pollinator mutualisms. Joint action of antagonistic and mutualistic interactions may be fundamentally important for diversification in coevolutionary interactions.

The purpose of this research was to determine if the correlation between perpetration and being a victim of sexual coercion is due to a lack of self-control, a coercive lifestyle, or dysfunctional romantic relationships. Two hundred and sixty-two college students completed measures of perpetration and being a victim of sexual coercion, lack of self-control, coercive lifestyle, romantic partner’s coercive lifestyle, and partner’s perpetration and being a victim of sexual coercion. Support was not found for the lack of self-control and coercive lifestyle explanations; support was found for the dysfunctional relationships explanation. Multiple regression analyses found that the self-control variable that best (negatively) predicted both perpetration and being a victim of sexual coercion was valuing long-term, committed romantic relationships. Interventions to prevent perpetration and being a victim of sexual coercion should focus not only on the individual victim/perpetrator but also on promoting functional romantic relationships.

Two 3-wave panel studies were conducted to test for transmission of negative affect in naturally occurring dyads. In Study 1, symptoms of depression and negative affect were measured in 1 53 dating couples at 6-week intervals. In a similar second study, these same variables were measured in 170 college roommate dyads. Within both dating couples and roommates, symptoms of depression and negative affect were typically correlated at all points of measurement. However, structural equation analyses that controlled for prior negative affect and initial similarity on negative affect provided no evidence of emotional transmission in dating couples. There was minimal evidence for emotional transmission in roommate dyads. The intradyadic similarity in negative affect was greater than what would be expected by chance, but unrelated to the length of the relationship, as predicted by the assortative mating effect. [PUBLICATION ABSTRACT]