How much variance can be explained by ecologists and evolutionary biologists?

117

133

Sex allocation theory offers excellent opportunities for studying the precision of adaptation. One of the best-supported areas in the field of sex allocation is Hamilton's theory of local mate competition, which predicts female-biased offspring sex ratios when populations are structured such that mating takes place locally before females disperse. As predicted by local mate competition theory, females of numerous species, especially parasitoid wasps, have been shown to lay a less female-biased sex ratio as the number of females simultaneously laying eggs on a patch increases. It has usually been assumed that this sex ratio adjustment comes through individuals adjusting their behavior directly in response to the presence of other females. Here we show that in the parasitoid wasp Nasonia vitripennis, this shift in offspring sex ratios is primarily caused by the presence of eggs laid by other females and to a lesser extent by the presence of other females. We confirm that females are behaving as predicted by theory, but the way in which they do so is not as straightforward as is often assumed. Instead, even when there are multiple females on a patch, individuals still use the cues that are more commonly associated with sex ratio adjustment in response to sequential visits to a patch by females. This result provides a possible explanation for the observed variation in N. vitripennis sex ratios. More generally, it confirms the need to consider the mechanistic basis of a behavior to understand fully its adaptive value.

Section: Resultsmentioning

confidence: 85%

Information constraints and the precision of adaptation: Sex ratio manipulation in wasps

Shuker

West²

2004

117

133

“…Our global GLM that contained all recorded predictors of human-to-human transmission in all viruses as fixed effects had R 2 = 0.446, a value that is relatively high for an evolutionary or ecological study (30). A model incorporating duration of infection, outer envelope status, segmentation (i.e., segmented or nonsegmented), mode of transmission, and mortality rate had the lowest AICc (Table 1).…”

Section: Resultsmentioning

confidence: 98%

Virological factors that increase the transmissibility of emerging human viruses

Geoghegan

Senior

Giallonardo

et al. 2016

131

133

The early detection of pathogens with epidemic potential is of major importance to public health. Most emerging infections result in dead-end "spillover" events in which a pathogen is transmitted from an animal reservoir to a human but is unable to achieve the sustained human-to-human transmission necessary for a full-blown epidemic. It is therefore critical to determine why only some virus infections are efficiently transmitted among humans whereas others are not. We sought to determine which biological features best characterized those viruses that have achieved sustained human transmission. Accordingly, we compiled a database of 203 RNA and DNA human viruses and used an information theoretic approach to assess which of a set of key biological variables were the best predictors of human-to-human transmission. The variables analyzed were as follows: taxonomic classification; genome length, type, and segmentation; the presence or absence of an outer envelope; recombination frequency; duration of infection; host mortality; and whether or not a virus exhibits vector-borne transmission. This comparative analysis revealed multiple strong associations. In particular, we determined that viruses with low host mortality, that establish long-term chronic infections, and that are nonsegmented, nonenveloped, and, most importantly, not transmitted by vectors were more likely to be transmissible among humans. In contrast, variables including genome length, genome type, and recombination frequency had little predictive power. In sum, we have identified multiple biological features that seemingly determine the likelihood of interhuman viral transmissibility, in turn enabling general predictions of whether viruses of a particular type will successfully emerge in human populations.virus | evolution | transmission | comparative analysis | spill-over

“…Compared with the PC of body masculinity used in the previous analyses, this assessment of landmark joint configuration is less dependent on hip and breast fat distribution. Because female bodily attractiveness is largely associated with fat distribution (8,11,30), we expected that joint configuration would be a better indicator of attractiveness and phenotypic quality in males than in females. The locations (x-y-z coordinates) of 18 landmarks were estimated using NX12 scanning software and the [TC] 2 body scanner.…”

Section: Resultsmentioning

confidence: 99%

“…However, a study that tested directly for publication bias (29) did not find a significant difference in effect sizes (adjusted for sample size) between published and unpublished studies. Another report shows that the effect sizes in the study of FA are within the range of other fields in ecology and evolutionary biology (30). Considering the strong theoretical rationale for expecting bodily characteristics to function as reliable signals of quality, it is notable that no published study has demonstrated significant relationships between human body attractiveness, or shape-based secondary sex characteristics, and FA.…”

mentioning

confidence: 94%

Fluctuating asymmetry and preferences for sex-typical bodily characteristics

Brown

Price

Kang

et al. 2008

Body size and shape seem to have been sexually selected in a variety of species, including humans, but little is known about what attractive bodies signal about underlying genotypic or phenotypic quality. A widely used indicator of phenotypic quality in evolutionary analyses is degree of symmetry (i.e., fluctuating asymmetry, FA) because it is a marker of developmental stability, which is defined as an organism's ability to develop toward an adaptive end-point despite perturbations during its ontogeny. Here we sought to establish whether attractive bodies signal low FA to observers, and, if so, which aspects of attractive bodies are most predictive of lower FA. We used a 3D optical body scanner to measure FA and to isolate size and shape characteristics in a sample of 77 individuals (40 males and 37 females). From the 3D body scan data, 360°videos were created that separated body shape from other aspects of visual appearance (e.g., skin color and facial features). These videos then were presented to 87 evaluators for attractiveness ratings. We found strong negative correlations between FA and bodily attractiveness in both sexes. Further, sextypical body size and shape characteristics were rated as attractive and correlated negatively with FA. Finally, geometric morphometric analysis of joint configurations revealed that sex-typical joint configurations were associated with both perceived attractiveness and lower FA for male but not for female bodies. In sum, body size and shape seem to show evidence of sexual selection and indicate important information about the phenotypic quality of individuals.3D morphometrics ͉ body shape ͉ developmental stability ͉ sexual dimorphism ͉ sexual selection I n humans, as in other species, sex differences in size and shape are attributed to divergent effects of morphology on the survival or reproductive success of each sex (1-10). For human females, smaller waist relative to hips (WHR), larger breasts, and longer legs relative to height have been attributed to fecundity selection and are perceived as attractive by males (8,11,12). In human males, greater height, larger size, and shorter legs relative to height are believed to have arisen through sexual selection by enhancing success in male-male rivalry (6, 7) and by being more attractive to females (6, 12). In addition, pronounced secondary sex characteristics may be preferred because they are signals of a pathogen-resistant genotype (13). However, recent theoretical models suggest that high-quality signalers may be more resistant, equally resistant, or less resistant to pathogens, depending on life history trade-offs between reproductive effort, survival, and fecundity (14, 15). For example, high-quality males that produce costly signals may compromise their future survival but nonetheless be more fit than their low-quality competitors.If sex-typicality of body size and shape are attractive to the opposite sex because they indicate phenotypic quality, then these conspicuous sex-specific signals are expected to correlate negativ...