Allometry and prediction in hominoids: a solution to the problem of intervening variables.

To avoid misinterpretation of allometric exponents determined from interspecific allometric comparisons, specific conditions must be met with respect to the common reference variable. Body weight is considered to be the best general indication of overall size and is hence widely acknowledged to be the most suitable reference variable. However, because of the paucity of recorded body weights for museum specimens, various comparative studies have used other size indicators as intervening variables, although the allometric relationships to body size/weight were often unknown and possibly differed between species. Because of differences in the scaling properties of alternative intervening variables across the species investigated, conflicting conclusions may be drawn if different variables are chosen as substitutes for overall size. This is illustrated with two examples. In this study, series of skeletons with associated body weights of Gorilla, Pan, Pongo, and Homo were investigated. Both ontogenetic and static adult allometric relationships between several widely used reference variables and body weight were determined. Neither these variables nor additional estimators investigated in this study displayed allometric exponents and coefficients similar enough across species to justify direct interspecific comparison. To generate an alternative size estimator for both ontogenetic and static interspecific investigations, equations for combined sexes were derived to predict body weight from various long bone dimensions for individual hominoid species. From a total of 25 predictors, 12 prediction equations per species (six for nonadults and six for adults) were selected according to their relative suitability for reliable prediction of body weight. It is shown that the derived reference variable "predicted body weight" avoids problems of intervening variables, is valid for any interspecific ontogenetic and static allometric comparison, and displays less fluctuation in comparison to actual body weight.     

Pregnancy Weight Gain and Childhood Body Weight: A Within-Family Comparison

Background

Excessive pregnancy weight gain is associated with obesity in the offspring, but this relationship may be confounded by genetic and other shared influences. We aimed to examine the association of pregnancy weight gain with body mass index (BMI) in the offspring, using a within-family design to minimize confounding.

Methods and Findings

In this population-based cohort study, we matched records of all live births in Arkansas with state-mandated data on childhood BMI collected in public schools (from August 18, 2003 to June 2, 2011). The cohort included 42,133 women who had more than one singleton pregnancy and their 91,045 offspring. We examined how differences in weight gain that occurred during two or more pregnancies for each woman predicted her children''s BMI and odds ratio (OR) of being overweight or obese (BMI≥85th percentile) at a mean age of 11.9 years, using a within-family design. For every additional kg of pregnancy weight gain, childhood BMI increased by 0.0220 (95% CI 0.0134–0.0306, p<0.0001) and the OR of overweight/obesity increased by 1.007 (CI 1.003–1.012, p = 0.0008). Variations in pregnancy weight gain accounted for a 0.43 kg/m² difference in childhood BMI. After adjustment for birth weight, the association of pregnancy weight gain with childhood BMI was attenuated but remained statistically significant (0.0143 kg/m² per kg of pregnancy weight gain, CI 0.0057–0.0229, p = 0.0007).

Conclusions

High pregnancy weight gain is associated with increased body weight of the offspring in childhood, and this effect is only partially mediated through higher birth weight. Translation of these findings to public health obesity prevention requires additional study. Please see later in the article for the Editors'' Summary     

H广义线性模型中的参数估计的比较

本文研究H广义线性模型中未知参数的两种估计方法,一种是边际似然函数法,另一种是Lee和Nelder提出来的L-N法．对于一类具有两个随机效应的典型的Poisson-Gamma类模型,在一些正则性条件之下,我们已经证明了其中固定效应卢的L-N估计的强相合性及渐近正态性,并得到了其收敛于真值的速度．针对这类模型,本文进一步给出了其边际似然函数的解析表达式,并且通过Monte Carlo模拟,对模型中固定效应β的边际似然估计和L—N估计进行了比较,模拟表明L—N估计比边际似然估计在拟Poisson-Gamma模型中有着更加优良的表现,具有更高的精度。     

Allometry of diving capacities: ectothermy vs. endothermy

Body mass positively influences diving capacities in air-breathing vertebrates and has been identified as a key determinant for the evolution of diving. Our review on the relationship between body mass and dive duration (a major parameter of dive performances) encompassed for the first time a wide diversity of air-breathing vertebrates. We included a substantial number of nonavian and nonmammalian diving species belonging to various independent lineages (sea snakes, iguana, turtles and crocodiles). Our analyses suggest that the widely accepted size dependency of dive duration applies with significantly less force in ectotherms compared with endotherms; notably we failed to detect any effect of body mass in ectotherms. We hypothesize that the absence of tight physiological links between body mass and respiratory demands documented in ectotherms blurred our ability to detect the expected correlation. Further exploration of the evolution of diving physiology may well necessitate adopting novel perspectives to encompass both ectothermic and endothermic modes.     

A Monte Carlo Study of Robustness of Pretest and Shrinkage Estimators in Pooling Coefficients of Variation

Pooling data, when justified, is advantageous for estimating the true parameter. In this paper the problem of estimating the coefficient of variation is considered when it is a priori suspected that two coefficients of variation are the same. Various estimators based on pretest and shrinkage rules are considered. A comparison through the Simulated Mean Squared Error (SMSE) criterion is carried out among various proposed estimators of the target coefficient of variation. The relative simulated efficiencies of the restricted, shrinkage restricted and shrinkage pretest estimators are studied. It is found that the proposed estimators are quite robust when the sample sizes are not too large. The result of Monte Carlo study indicates that the proposed shrinkage pretest estimator is efficient than the usual estimator in a wider range.     

酶解鹿茸血ACE抑制活性及其与抗氧化活性关系的研究

实验采用木瓜蛋白酶和Alcalase碱性蛋白酶水解鹿茸血,在不同的时间取样,分别测定血管紧张素转化酶(ACE)抑制率、二苯代苦味肼基自由基(DPPH.)清除率和羟自由基(.OH)清除率。结果表明Alcalase蛋白酶水解产物ACE抑制活性和DPPH.清除活性较强,其水解3h的产物ACE抑制率为90.63%,DPPH.清除率为14.40%;木瓜蛋白酶水解5h的产物.OH清除率最高,为96.7%。用SPSS10.0软件分析结果,发现ACE抑制率与DPPH.清除率具有显著相关性。     

Postnatal long bone growth in terrestrial placental mammals: Allometry,life history,and organismal traits

The ontogenetic allometry of long bone proportions is poorly understood in Mammalia. It has previously been suggested that during mammalian ontogeny long bone proportions grow more slender (positive allometry; length ∝ circumference^>1.0), although this conclusion was based upon data from a few small‐bodied taxa. It remains unknown how ontogenetic long bone allometry varies across Mammalia in terms of both taxonomy and body size. We collected long bone length and circumference data for ontogenetic samples of 22 species of mammals spanning six major clades and three orders of magnitude in body mass. Using reduced major axis bivariate regressions to compare bone length to circumference, we found that isometry and positive allometry are the most widespread patterns of growth across mammals. Negative allometry (i.e., bones growing more robust during ontogeny) occurs in mammals but is largely restricted to cetartiodactyls. Using regression slope as a proxy for long bone allometry, we compared long bone allometry to life history and organismal traits. Neonatal body mass, adult body mass, and growth rate have a negative relationship with long bone allometry. At an adult mass of roughly 15–20 kg, long bone growth shifts from positive allometry to mainly isometry and negative allometry. There were no significant relationships between ontogenetic long bone allometry and either cursoriality or basal metabolic rate. J. Morphol. © 2012 Wiley Periodicals, Inc.     

Robust Estimators on Laboratory Measurements of Fat and Protein in Milk

A total of 57 estimators of location were compared on data from routine laboratory measurements of fat and protein content in milk. Measurements in milk delivered from farmers to 6 different Norwegian dairies were used as a basis for a Monte Carlo study. The results indicated that the better robust estimators give an important increase in precision relative to the sample mean.     

A Comparative Statistical Analysis of Genetic Distances. I - Estimation of Distances and of their Variances: Distribution of the Estimators

We present a Monte-Carlo simulation analysis of the statistical properties of absolute genetic distance and of Nei's minimum and standard genetic distances. The estimation of distances (bias) and of their variances is analysed as well as the distributions of distance and variance estimators, taking into account both gamete and locus samplings. Both of Nei's statistics are non-linear when distances are small and consequently the distributions of their estimators are extremely asymmetrical. It is difficult to find theoretical laws that fit such asymmetrical distributions. Absolute genetic distance is linear and its distributions are better fit by a normal distribution. When distances are medium or large, minimum distance and absolute distance distributions are close to a normal distribution, but those of the standard distance can never be considered as normal. For large distances the jack-knife estimator of the standard distance variance is bad; another standard distance estimator is suggested. Absolute distance, which has the best mathematical properties, is particularly interesting for small distances if the gamete sample size is large, even when the number of loci is small. When both distance and gamete sample size are small, this statistic is biased.     

Allometry and performance: the evolution of skull form and function in felids

Allometric patterns of skull‐shape variation can have significant impacts on cranial mechanics and feeding performance, but have received little attention in previous studies. Here, we examine the impacts of allometric skull‐shape variation on feeding capabilities in the cat family (Felidae) with linear morphometrics and finite element analysis. Our results reveal that relative bite force diminishes slightly with increasing skull size, and that the skulls of the smallest species undergo the least strain during biting. However, larger felids are able to produce greater gapes for a given angle of jaw opening, and they have overall stronger skulls. The two large felids in this study achieved increased cranial strength by increasing skull bone volume relative to surface area. Allometry of skull geometry in large felids reflects a trade‐off between the need to increase gape to access larger prey while maintaining the ability to resist unpredictable loading when taking large, struggling prey.     

Allometry and chromosomal speciation of the casiraguas Proechimys (Mammalia, Rodentia)

Morphometric characters (linear measurements) of the skull and mandible of the rodent Proechimys occurring in Venezuela and Columbia were investigated through multivariate techniques in order to describe static allometry and to relate allometric patterns to the recent evolution of these taxa. At least five species originated during the recent Pleistocene period in the upper Orinoco basin, all characterized by different karyotypes, one of them (P. guairae) being a Rassenkreis of karyomorphs. Species are characterized by unique static allometric patterns and the study of these patterns suggests a phylogenetic rather than an ecogenetic origin for these patterns; modifications in the shape of the skull and the mandible have originated during phyletic speciation and there is no apparent sign of functional adaptation.     

鹿茸血肽疏水性分离及抗氧 化和ACE抑制作用的研究

实验采用DA201-C型大孔吸附树脂对Alcalase蛋白酶水解鹿茸血3 h的水解液进行吸附,采用25%、50%、75%、100%乙醇分级洗脱,收集各组分进行氨基酸组成分析,发现各洗脱组分具有不同疏水性值,同时测定各组分的血管紧张素转化酶(ACE)抑制活性和二苯代苦味肼基自由基(DPPH·)清除活性:75%乙醇洗脱组分的ACE抑制活性最高,为54.71%,且ACE抑制活性与组分疏水性值显著相关;100%乙醇洗脱组分的DPPH清除率最高.     

Reconciling Genetic and Demographic Estimators of Effective Population Size in the Anuran Amphibian Bufo Calamita

We used genetic and demographic methods to estimate the variance effective population sizes (N _e) of three populations of natterjack toads Bufo calamita in Britain. This amphibian breeds in temporary pools where survival rates can vary among families. Census population sizes (N) were derived from spawn string counts. Point and coalescent-based maximum likelihood estimates of N _e based on microsatellite allele distributions were similar. N _e/N ratios based on genetic estimates of N _e ranged between 0.02 and 0.20. Mean demographic estimates of N _e were consistently higher (2.7–8.0-fold) than genetic estimates for all three populations when variance in breeding success was evaluated at the point where females no longer influence their progeny. However, discrepancies between genetic and demographic estimators could be removed by using a model that included extra variance in survivorship (above to Poisson expectations) among families. The implications of these results for the estimation of N _e in wild populations are discussed.     

Allometry and sexual selection of male weaponry in Wellington tree weta, Hemideina crassidens

Both male and female Wellington tree weta, Hemideina crassidens,use cavities in trees as diurnal shelters. That these galleriesare often limiting in nature offers males the opportunity toincrease their reproductive success by monopolizing galleriesand the females residing in them. Male H. crassidens, can matureat either the 8th, 9th, or 10th instar, whereas females matureat the 10th instar only, and male head (and mandible) size positivelycovaries with ultimate instar number. It has been suggestedthat males fight for control of galleries by using their enlargedmandibles as weapons, and males with larger mandibles controlgalleries with more females. In the present study, I presenta statistical examination of sexual dimorphism, showing thattraits related to head size are on average significantly largerin males, whereas traits related to body size are on averagesignificantly larger in females. I tested three predictionsaddressing the hypothesis that sexual selection is driving megacephalyin male H. crassidens. First, as predicted, traits related tohead size show a positive allometric relationship with bodysize in males but not in females. Second, adapting a novel statisticaltechnique based on maximum likelihood and bootstrapping revealedthat males, but not females, exhibit a multimodal distributionin head and body size traits. This is likely a consequence ofmales maturing at one of three instars, which results in positivecovariance between the ultimate instar number and morphologicaltraits. Third, as predicted, single adult males with largerheads reside in galleries housing larger groups of adult females.     

Allometry of egg and hatchling mass in birds and reptiles: roles of developmental maturity, eggshell structure and phylogeny

The factors determining hatchling mass (HM) are investigated in a wide range of birds and reptiles using regression analysis, analysis of covariance and comparative analysis by independent contrasts. In birds, initial egg mass (IEM) at laying is the most important factor affecting HM and phylogenetic relatedness has no significant effects on HM. Developmental maturity of the avian neonates did not affect the proportion of IEM converted into HM. For all reptile species, IEM also significantly affected HM but phylogenetic relatedness did not. By contrast, allometric relationships between IEM and HM in the different orders of reptiles were affected by shell type. The robustness of allometric relationships across taxa in birds and reptiles suggests that there is a physiological link between IEM and HM, which contrasts with that observed for the relationship between egg mass and incubation period. This result has significant implications for the inter-relationships between IEM and embryonic growth, which are discussed for birds and reptiles.     

Allometry and variability of resource allocation to reproduction in a wild reindeer population

The differential allocation of energy to either reproductionor survival represents a major conflict with important implicationsfor patterns of life history. Here, we explore how covariationbetween maternal body weight and fetal weight vary accordingto fetal sex in a wild reindeer (Rangifer tarandus) populationduring two contrasting years. Maternal weights differed duringthe 2 years, probably because of a difference in populationdensity. We could not detect any change in the allocation toreproduction depending on female phenotypic distribution. Malefetuses were heavier than female fetuses, with the same relativedimorphism in both years. There was no support for a correlationbetween the sex of the fetus carried by a female and her weight.Our results suggest that the level of resource allocation toreproduction during the prenatal period is strongly determinedby female body weight and the allometric relationship betweenbody weight and metabolic rate. We discuss the consequencesof our results for population dynamics. We call for an integrationof inter- and intraspecific allometric approaches to betterunderstand constraints and variation in life-history traits.