Sex differences in the jealousy-evoking nature of a rival's body build

This study among 185 college students showed that potential rivals with a relatively low waist-to-hip ratio (WHR) evoked more jealousy in women than in men. In contrast, rivals with a relatively high shoulder-to-hip ratio (SHR) evoked more jealousy in men than in women, particularly when the rival also had a high WHR. Rivals with a low as opposed to a high WHR were perceived as more socially dominant and attractive in both sexes, and as more physically dominant in the case of men. In addition, rivals of both sexes were perceived as more physically and socially dominant when they had a high SHR, and in the case of men as more attractive. In evaluating the rivals, women indicated that they had paid more attention to the rivals' waist, hips, and legs, and men indicated that they had paid more attention to the rivals' shoulders, chest, and belly. The results provide support for evolutionary psychological hypotheses that men and women pay attention to different bodily features in evaluating the potential threat imposed by a rival.     

Species–energy relationships and habitat complexity in bird communities

Species–energy theory is a commonly invoked theory predicting a positive relationship between species richness and available energy. The More Individuals Hypothesis (MIH) attempts to explain this pattern, and assumes that areas with greater food resources support more individuals, and that communities with more individuals include more species. Using a large dataset for North American birds, I tested these predictions of the MIH, and also examined the effect of habitat complexity on community structure. I found qualitative support for the relationships predicted by the MIH, however, the MIH alone was inadequate for fully explaining richness patterns. Communities in more productive sites had more individuals, but they also had more even relative abundance distributions such that a given number of individuals yielded a greater number of species. Richness and evenness were also higher in structurally complex forests compared to structurally more simple grasslands when controlling for available energy.     

Male Song Quality, Egg Size and Offspring Sex in Captive Canaries (Serinus canaria)

Life history theory predicts that females should vary their investment in offspring according to the quality of their mate. In birds, several studies have now shown that females do vary investment according to perceived male quality, by producing larger eggs, investing more in parental care or by manipulating the sex of their offspring. In a captive breeding colony of canaries, we first show that under normal conditions larger eggs in a clutch are more likely to hatch male offspring. In canaries, male song functions in female attraction and females respond more to complex structures in male song called sexy syllables. In a series of experiments, we go on to show first, that females exposed to playback of male song produce larger eggs than those who heard no song. Next, using synthetic songs, we show that females exposed to playback of more attractive songs containing sexy syllables, produced larger eggs than those exposed to simpler songs containing no sexy syllables. However, in a final analysis, we found no evidence from our experiments that females exposed to playback of more attractive songs also produced more male offspring.     

Sex-differential herbivory in androdioecious Mercurialis annua

Males of plants with separate sexes are often more prone to attack by herbivores than females. A common explanation for this pattern is that individuals with a greater male function suffer more from herbivory because they grow more quickly, drawing more heavily on resources for growth that might otherwise be allocated to defence. Here, we test this 'faster-sex' hypothesis in a species in which males in fact grow more slowly than hermaphrodites, the wind-pollinated annual herb Mercurialis annua. We expected greater herbivory in the faster-growing hermaphrodites. In contrast, we found that males, the slower sex, were significantly more heavily eaten by snails than hermaphrodites. Our results thus reject the faster-sex hypothesis and point to the importance of a trade-off between defence and reproduction rather than growth.     

Ecological divergence and talar morphology in gorillas

Gorillas occupy a variety of habitats from the west coast to eastern central Africa. These habitats differ considerably in altitude, which has a pronounced effect on forest ecology. Although all gorillas are obligate terrestrial knuckle‐walking quadrupeds, those that live in lowland habitats eat fruits and climb more often than do those living in highland habitats. Here we test the hypothesis that gorilla talus morphology falls along a morphocline that tracks locomotor function related to a more inverted or everted foot set. This proposed morphocline predicts that gorillas living in lowland habitats may have a talocrural joint configured to facilitate a more medially oriented foot during climbing, suggesting that they may be more adaptively committed to arboreality than gorillas living in highland habitats. To quantify the relative set of the foot in gorillas, we chose two three‐dimensional measurements of the talocrural joint: mediolateral curvature of the trochlea and relative surface area of the lateral malleolus. Our results show that, in comparison to their eastern counterparts, western gorillas have talar features that reflect a more medially directed sole of the foot. This morphology likely facilitates foot placement in a wider range of positions and minimization of shearing stresses across the joint when the foot is loaded on more curved or vertically oriented substrates as occurs during climbing and other arboreal behaviors. In contrast, eastern gorilla talar morphology is consistent with habitual placement of the foot with the sole directed more inferiorly, suggesting more effective loading during plantigrade push‐off on terrestrial substrates. Am J Phys Anthropol 153:526–541, 2014. © 2013 Wiley Periodicals, Inc.     

'Friendship' for fitness in chimpanzees?

It has been repeatedly suggested that primates trade social services for fitness benefits in their relationships with the opposite sex. We tested this proposal in a colony of captive chimpanzees, Pan troglodytes, by examining behavioural data on grooming, agonistic support and food sharing in relation to genetically established paternity. We found no support for the notion of trade. First, males did not sire more offspring with females that they actively groomed more frequently, that they supported more often or with which they shared food more frequently. Correspondingly, females did not give birth to more offspring sired by males from which they received more services. Second, males that showed more affiliative behaviour towards females in general did not sire more progeny. Furthermore, females did not bear more offspring sired by males to which they themselves directed more sociopositive behaviour. Results from this captive colony are compatible with those reported for chimpanzees under natural conditions. Copyright 1999 The Association for the Study of Animal Behaviour.     

Sex allocation predicts mating rate in a simultaneous hermaphrodite

Sexual selection theory for separate-sexed animals predicts that the sexes differ in the benefit they can obtain from multiple mating. Conventional sex roles assume that the relationship between the number of mates and the fitness of an individual is steeper in males compared with females. Under these conditions, males are expected to be more eager to mate, whereas females are expected to be choosier. Here we hypothesize that the sex allocation, i.e. the reproductive investment devoted to the male versus female function, can be an important predictor of the mating strategy in simultaneous hermaphrodites. We argue that within-species variation in sex allocation can cause differences in the proportional fitness gain derived through each sex function. Individuals should therefore adjust their mating strategy in a way that is more beneficial to the sex function that is relatively more pronounced. To test this, we experimentally manipulated the sex allocation in a simultaneously hermaphroditic flatworm and investigated whether this affects the mating behaviour. The results demonstrate that individuals with a more male-biased sex allocation (i.e. relatively large testes and small ovaries) are more eager to mate compared with individuals with a more female-biased sex allocation (i.e. relatively small testes and large ovaries). We argue that this pattern is comparable to conventional gender roles in separate-sexed organisms.     

New approach to the statistical analysis of cardiovascular data.

Fourier-based approaches to analysis of variability of R-R intervals or blood pressure typically compute power in a given frequency band (e.g., 0.01-0.07 Hz) by aggregating the power at each constituent frequency within that band. This paper describes a new approach to the analysis of these data. We propose to partition the blood pressure variability spectrum into more narrow components by computing power in 0.01-Hz-wide bands. Therefore, instead of a single measure of variability in a specific frequency interval, we obtain several measurements. The approach generates a more complex data structure that requires a careful account of the nested repeated measures. We briefly describe a statistical methodology based on generalized estimating equations that suitably handles this more complex data structure. To illustrate the methods, we consider systolic blood pressure data collected during psychological and orthostatic challenge. We compare the results with those obtained using the conventional methods to compute blood pressure variability, and we show that our approach yields more efficient results and more powerful statistical tests. We conclude that this approach may allow a more thorough analysis of cardiovascular parameters that are measured under different experimental conditions, such as blood pressure or heart rate variability.     

Pregnancy wantedness: attitude stability over time

In this analysis we have compared two attitudinal reports, from interviews two years apart, of the same event for consistency over time. We have looked at women's self-reports, and at their proxy reports for partners' attitudes as well. The inconsistent reports of women's own views tended to shift slightly toward more favorable reports at the second interview (15 percent more positive versus 10 percent more negative). More specifically, 7.5 percent of women who reported at Time 1 that their most recent births had been unwanted switched to more favorable reports at Time 2, and about the same percentage of women who reported Table 4, the findings would suggest that some of the groups typically considered to be most "at risk" were those who were also most apt to report inconsistently. This findings should signal some concern in the policy community. Net of other factors, there is no effect of income, but a number of at-risk groups remained significantly more likely than others to change their reports over time. Of particular concern is the finding that women who reported their pregnancies as mistimed or unwanted were so much more likely to change their reports over time than were women who initially said that their pregnancies had been well timed. When we look at the direction of change, it is clear that, with some exceptions, the more "at risk" groups were more likely to shift in a more negative direction, while the less "at risk" groups were less likely to do so; and at times they were more likely to report more favorably at the second interview. Although somewhat hampered by small sample sizes in the analysis of Time 1 mistimed and unwanted reports, results confirmed that certain subgroups were not only more apt to report inconsistently, they were also more likely to do so in specific directions. To the extent that future survey questions can emphasize to respondents that they should focus on the time of conception, and not on current status, inconsistency across groups may be reduced.     

The limits of protein sequence comparison?

Modern sequence alignment algorithms are used routinely to identify homologous proteins, proteins that share a common ancestor. Homologous proteins always share similar structures and often have similar functions. Over the past 20 years, sequence comparison has become both more sensitive, largely because of profile-based methods, and more reliable, because of more accurate statistical estimates. As sequence and structure databases become larger, and comparison methods become more powerful, reliable statistical estimates will become even more important for distinguishing similarities that are due to homology from those that are due to analogy (convergence). The newest sequence alignment methods are more sensitive than older methods, but more accurate statistical estimates are needed for their full power to be realized.     

Structural characterization of the partially folded intermediates of an immunoglobulin light chain leading to amyloid fibrillation and amorphous aggregation

Immunoglobulin light chain deposition diseases involve various types of extracellular deposition of light chain variable domains, including amyloid fibrils and amorphous deposits. The decreased thermodynamic stability of the light chain is believed to be the major factor leading to fibrillation. However, the differences in the nature of the deposits among the light chain deposition diseases raise the question of whether the mechanisms leading to fibrillar or amorphous aggregation is different. In this study, we generated two partially folded intermediates of the light chain variable domain SMA in the presence of guanidine hydrochloride (GuHCl) and characterized their conformations. The more unfolded intermediate formed fibrils most rapidly, while the more native-like intermediate predominantly led to amorphous deposits. The results also show that the monomeric, rather than the dimeric state, was critical for fibrillation. The data also indicate that fibril elongation involves addition of a partially unfolded intermediate, rather than the native state. We postulate that a more highly unfolded intermediate is more suited to undergo the topological rearrangements necessary to form amyloid fibrils than a more structured one and that this also correlates with increased destabilization. In the case of light chain aggregation, it appears that more native-like intermediate conformations are more prone to form amorphous deposits.     

Amplifiers and the handicap principle in sexual selection: a different emphasis

Population genetic models have shown that female choice is a potential cause of the evolution of male display. In these models the display is assumed to be the immediate object of female choice. Here I present an explicit genetic model that shows that male display can evolve as a consequence of female choice even when the display is not the immediate object of choice. When females initially base their preferences on the existence of variance in a cue that is correlated with male viability, a rare display can evolve to fixation if it amplifies the previously recognized differences in males, (i.e. if it increases the resolution power of females with respect to the original cue). By definition, amplifying displays (or amplifiers) increase mating success of the more viable males and decrease mating success of the less viable males. Therefore, the higher the frequency of the preferred, more viable males, the more likely it is that amplifiers will evolve to fixation. The evolution of an amplifier is further facilitated by a genetic association that is built up between the amplifier allele and the more viable allele. If the expression of the amplifier is limited to the more viable males, the amplifier will evolve to fixation provided only that the change in total fitness to the more viable males (higher mating success, lower viability), is positive.     

Hunting behavior of wild chimpanzees in the Taï National Park

Hunting is often considered one of the major behaviors that shaped early hominids' evolution, along with the shift toward a drier and more open habitat. We suggest that a precise comparison of the hunting behavior of a species closely related to man might help us understand which aspects of hunting could be affected by environmental conditions. The hunting behavior of wild chimpanzees is discussed, and new observations on a population living in the tropical rain forest of the Taï National Park, Ivory Coast, are presented. Some of the forest chimpanzees' hunting performances are similar to those of savanna-woodlands populations; others are different. Forest chimpanzees have a more specialized prey image, intentionally search for more adult prey, and hunt in larger groups and with a more elaborate cooperative level than savanna-woodlands chimpanzees. In addition, forest chimpanzees tend to share meat more actively and more frequently. These findings are related to some theories on aspects of hunting behavior in early hominids and discussed in order to understand some factors influencing the hunting behavior of wild chimpanzees. Finally, the hunting behavior of primates is compared with that of social carnivores.     

Profitability of prey determines the response of population abundances to enrichment

Theoretical and empirical evidence in a one-predator two-prey system consistently indicates a regular trend that the less profitable (therefore, less vulnerable) prey increases in abundance with enrichment. The response in the abundance of the more profitable (more vulnerable) prey to enrichment has, however, remained unclear. Previous theoretical models have assumed the less profitable prey as inedible, though its actual profitability is unknown. Here, relaxing this assumption, we show that the response of the more profitable prey abundance to enrichment depends critically on the profitability of the less profitable prey. Specifically, the more profitable prey increases in abundance with enrichment if the profitability of the less profitable prey is lower than a critical value so that it cannot support the predator population by itself even at high densities (in this case, the prey is referred to as 'unpalatable') and decreases otherwise. This establishes a more general rule which unifies the previous works and resolves the indeterminacy on the response of the more profitable prey.     

Ecological divergence and medial cuneiform morphology in gorillas

Gorillas are more closely related to each other than to any other extant primate and are all terrestrial knuckle-walkers, but taxa differ along a gradient of dietary strategies and the frequency of arboreality in their behavioral repertoire. In this study, we test the hypothesis that medial cuneiform morphology falls on a morphocline in gorillas that tracks function related to hallucial abduction ability and relative frequency of arboreality. This morphocline predicts that western gorillas, being the most arboreal, should display a medial cuneiform anatomy that reflects the greatest hallucial abduction ability, followed by grauer gorillas, and then by mountain gorillas. Using a three-dimensional methodology to measure angles between articular surfaces, relative articular and nonarticular areas, and the curvatures of the hallucial articular surface, the functional predictions are partially confirmed in separating western gorillas from both eastern gorillas. Western gorillas are characterized by a more medially oriented, proportionately larger, and more mediolaterally curved hallucial facet than are eastern gorillas. These characteristics follow the predictions for a more prehensile hallux in western gorillas relative to a more stable, plantigrade hallux in eastern gorillas. The characteristics that distinguish eastern gorilla taxa from one another appear unrelated to hallucial abduction ability or frequency of arboreality. In total, this reexamination of medial cuneiform morphology suggests differentiation between eastern and western gorillas due to a longstanding ecological divergence and more recent and possibly non-adaptive differences between eastern taxa.     

Book notes

The costs and benefits of polygyny have been widely debated and vary according to local sociopolitical context, the level of female autonomy, and economic considerations such as the mode of production. This study aims to understand perceptions of polygyny as a function of household demography, particularly the number of female kin present in the household who can provide labor that is largely substitutable to that of a co-wife. The presence of these helpers is proposed to shift the cost-benefit structure of polygyny, in which having more female kin available is associated with a more negative view of the practice. Interview and census data from 106 Himba women, who are traditional, seminomadic pastoralists, were used to test this prediction. Among married women who reside patrilocally, the presence of more elder daughters was associated with a more negative view of polygyny. Among unmarried women, who reside in their natal homes, it is the total number of adult female kin that predicts perception of polygyny. In addition, unmarried women are significantly more likely to report fights over resources as a source of co-wife conflicts when they have more dependent children, but no such association was found among married women.     

Frequency-dependent conspecific attraction to food patches

In many ecological situations, resources are difficult to find but become more apparent to nearby searchers after one of their numbers discovers and begins to exploit them. If the discoverer cannot monopolize the resources, then others may benefit from joining the discoverer and sharing their discovery. Existing theories for this type of conspecific attraction have often used very simple rules for how the decision to join a discovered resource patch should be influenced by the number of individuals already exploiting that patch. We use a mechanistic, spatially explicit model to demonstrate that individuals should not necessarily simply join patches more often as the number of individuals exploiting the patch increases, because those patches are likely to be exhausted soon or joining them will intensify future local competition. Furthermore, we show that this decision should be sensitive to the nature of the resource patches, with individuals being more responsive to discoveries in general and more tolerant of larger numbers of existing exploiters on a patch when patches are resource-rich and challenging to locate alone. As such, we argue that this greater focus on underlying joining mechanisms suggests that conspecific attraction is a more sophisticated and flexible tactic than currently appreciated.     

The Roles of Whole-Genome and Small-Scale Duplications in the Functional Specialization of Saccharomyces cerevisiae Genes

Researchers have long been enthralled with the idea that gene duplication can generate novel functions, crediting this process with great evolutionary importance. Empirical data shows that whole-genome duplications (WGDs) are more likely to be retained than small-scale duplications (SSDs), though their relative contribution to the functional fate of duplicates remains unexplored. Using the map of genetic interactions and the re-sequencing of 27 Saccharomyces cerevisiae genomes evolving for 2,200 generations we show that SSD-duplicates lead to neo-functionalization while WGD-duplicates partition ancestral functions. This conclusion is supported by: (a) SSD-duplicates establish more genetic interactions than singletons and WGD-duplicates; (b) SSD-duplicates copies share more interaction-partners than WGD-duplicates copies; (c) WGD-duplicates interaction partners are more functionally related than SSD-duplicates partners; (d) SSD-duplicates gene copies are more functionally divergent from one another, while keeping more overlapping functions, and diverge in their sub-cellular locations more than WGD-duplicates copies; and (e) SSD-duplicates complement their functions to a greater extent than WGD–duplicates. We propose a novel model that uncovers the complexity of evolution after gene duplication.