Adult Allometry Research Articles

Clavicle length and shoulder breadth in hominoid evolution.

For a given body mass, hominoids have longer clavicles than typical monkeys, reflecting the lateral reorientation of the hominoid glenoid. Relative length of the clavicle varies among hominoids, with orangutans having longer clavicles than expected for body mass and gorillas and chimpanzees having shorter clavicles than expected. Modern humans conform to the general hominoid distribution, but Neandertals and Upper Paleolithic Homo sapiens have longer clavicles than expected for their size and exhibit marked positive allometry in clavicle length. Relative to clavicle length, adult and newborn humans have broader shoulders (biacromial breadths) than comparable apes, because the reduced elevation of the human shoulder swings the acromion laterally downward away from the head. Since broadened shoulders yield an increased risk of maternal and neonatal injury and/or death from shoulder dystocia during birth, we might expect hominins to manifest trends toward reduction in shoulder breadth and clavicle length. They do not, presumably because of countering selection pressures favoring a long clavicle in the adults. The marked sexual dimorphism seen in patterns of clavicular growth and static adult allometry in humans suggests that those selection pressures have disproportionately affected the males.

How did modern morphology evolve in the human mandible? The relationship between static adult allometry and mandibular variability in Homo sapiens

Key to understanding human origins are early Homo sapiens fossils from Jebel Irhoud, as well as from the early Late Pleistocene sites Tabun, Border Cave, Klasies River Mouth, Skhul, and Qafzeh. While their upper facial shape falls within the recent human range of variation, their mandibles display a mosaic morphology. Here we quantify how mandibular shape covaries with mandible size and how static allometry differs between Neanderthals, early H. sapiens, and modern humans from the Upper Paleolithic/Later Stone Age and Holocene (= later H. sapiens). We use 3D (semi)landmark geometric morphometric methods to visualize allometric trends and to explore how gracilization affects the expression of diagnostic shape features. Early H. sapiens were highly variable in mandible size, exhibiting a unique allometric trajectory that explains aspects of their ‘archaic’ appearance. At the same time, early H. sapiens share a suite of diagnostic features with later H. sapiens that are not related to mandibular sizes, such as an incipient chin and an anteroposteriorly decreasing corpus height. The mandibular morphology, often referred to as ‘modern’, can partly be explained by gracilization owing to size reduction. Despite distinct static allometric shape changes in each group studied, bicondylar and bigonial breadth represent important structural constraints for the expression of shape features in most Middle to Late Pleistocene hominin mandibles.

Relationships between host species and morphometric patterns in Fasciola hepatica adults and eggs from the northern Bolivian Altiplano hyperendemic region

The highest prevalences and intensities of human fasciolosis by Fasciola hepatica are found in the northern Bolivian Altiplano, where sheep and cattle are the main reservoir host species and pigs and donkeys the secondary ones. Morphometric comparisons of many linear measurements, areas and ratios of F. hepatica adults (from sheep, cattle and pigs) and eggs (from sheep, cattle, pigs and donkeys) in natural liver fluke populations of the Bolivian Altiplano, as well as of F. hepatica adults and eggs experimentally obtained in Wistar rats infected with Altiplanic sheep, cattle and pig isolates, were made using computer image analysis and an allometric model. Although morphometric values of adult flukes from natural populations of sheep, cattle, and pigs showed great overlap, there were clear differences in allometric growth. The allometries analyzed were: body area (BA) versus body length (BL), BA versus body width (BW), BA versus perimeter (Pe), BA versus distance between posterior end of body and ventral sucker (P–VS), BL versus BW, BL versus Pe, and BL versus P–VS. These allometries show a good fit in the seven pairs of variables in all the populations examined. Comparative statistical analysis of the allometries shows that fluke adult populations from sheep, cattle and pigs significantly differ in BL versus BW and BL versus P–VS functions. Statistical analysis of F. hepatica egg size shows characteristic morphometric traits in each definitive host species. In experimentally infected rats, fluke adult allometry and egg morphometry do not vary depending on the Altiplanic definitive host species isolate. Our study reveals that the definitive host species decisively influences the size of F. hepatica adults and eggs, and these influences do not persist in a rodent definitive host model.

Morphometric variation, sexual size dimorphism and character scaling in a marginal population of montandon's newt triturus montandoni from the Czech republic

This study presents for the first time the morphometric characteristics of the Montandon's newt Triturus montandoni population from the Jeseniky Mountains (Czech Republic), where the species reaches the northwest margin of its distribution range and occurs outside the Carpathians. All measurements were taken on live narcotized animals in ‐ 315). The snout‐vent length (SVL) was found to be the best univariate measure of overall body size, highly correlated with PCI (principal component). Overall ‘body shape’ as measured by PC2, was determined primarily by the relative length of limbs. Scaling of body characters against SVL (geometric mean regression slope) did not differ between sexes but suggested positive adult allometry for most characters. In absolute terms, males were smaller than females in all examined characters (although not significantly so in length of hind limbs). Males were characterized by relatively longer limbs, larger head, shorter tail and shorter axilla‐groin distance. The mean SVL in composite samples varied significantly over three years and between two localities, while the degree of sexual size dimorphism remained stable.

Allometry of the Long Bones of Closely Related Macaques

In an attempt to investigate the relationships between ontogenetic, static adult and interspecific allometry, long limb bones of closely related macaques (Macaca mulatta, Macaca fascicularis, Macaca fuscata fuscata and Macaca fuscata yakui) were studied. Sex differences of intralimb allometry were also investigated. Principal component analyses were applied to the maximum length of bones to provide multivariate assessments of relationships between ontogenetic and static adult allometries. Static adult and ontogenetic allometries were different in M. fuscata and M. mulatta, but coincided in M. fascicularis. In interspecific comparison of ontogenetic and static adult allometries, M. fascicularis showed a unique allometric tendency. Analyses of bivariate allometries revealed that sexual dimorphism was a result of ontogenetic scaling (time hypermorphosis). The difference between subspecies of Japanese macaques (M. fuscata fuscata and M. fuscata yakui) was also explained by ontogenetic scaling. A vertical transposition was observed in the ontogenetic patterns of interlimb allometries among the three species. This relationship produced an interspecific positive allometry of the hindlimb compared with the forelimb, which differed from the general trend among nonhuman primates.

Bioenergetics Model for Larval and Juvenile Walleyes: An in Situ Approach with Experimental Ponds

Abstract We used an in situ approach to redefine allometric parameters of consumption and metabolism in a percid bioenergetics model for young-of-year (age-0) walleyes Stizostedion vitreum (0.0021–0.8237 g wet weight; 8–49 mm total length) in ponds across a range of densities (10–50 fish·m–3). Of three methods used to estimate evacuation rates, only the one based on whole-gut fullness of larvae and stomach fullness of juveniles in food-free enclosures proved reliable, The intercepts for allometry of maximum consumption and resting metabolism for age-0 walleyes were higher than the intercepts for adults; however, slopes of age-0 and adult allometry were similar. Activity costs (ACT = ratio of active metabolism to resting metabolism) for age-0 walleyes varied across body weights and with fish density; patterns of activity costs at different fish densities reflected patterns of food availability. Activity and p-values (proportion of maximum consumption realized) were correlated with powers of zooplankton bio...

The Ontogeny of Sexual Dimorphism: Quantitative Models and a Case Study in Labrisomid Blennies (Teleostei: Paraclinus)

Studies of sexual dimorphism commonly focus on male morphology, often viewing males as divergent both evolutionarily and ontogenetically. For example, in continuously grow- ing vertebrates such as lizards and fishes, it has been assumed that adult dimorphism arises from growth rate changes in male characters at the onset of maturity. However, there has been little explicit treatment of the ontogenetic origin of morphological sex differences. I present here a method for testing hypotheses of sex-specific allometric change, and offer an example of its application in four species of labrisomid blennies. I develop three hierarchical models to test for allometric divergence: (1) the null model, in which adult allometries of both sexes are simply an extension of the juvenile allometries (model A); (2) a model in which either adult males or females (but not both) diverge from the juvenile trajectory (model B); and (3) a model in which adults of both sexes diverge from the juvenile allometry (model C). Growth that fits either of the two latter models results in shape dimorphism. Although size dimorphism may occur in all three cases, it is not explicitly treated here. The models were tested with size-series of four species of fish (Paraclinus, Labrisomidae). To further explore overall shape similarity among males, females, and juveniles, a multivariate analysis of shape (independent of size) was applied. Analysis of 42 mensural characters showed that divergence from juvenile allometry occurred as frequently in female traits as in male traits. Multivariate analysis showed that in all four species, female shape diverges more from juvenile shape than does male shape. In addition, similarity among adult dimorphic character states often resulted from quite different growth patterns, suggesting that resemblance of adult characters among related species is insufficient evidence to conclude character homology. Interpretations of sexual dimorphism, currently emphasizing male morphology, may be biased and may underestimate the importance of selection on the female form as a cause of sexual dimorphism. (Allometry; homology; homoplasy; Labrisomidae; ontogeny; Paraclinus; sexual dimorphism; sexual selection.)

Metabolic Allometry of Larval and Juvenile Yellow Perch (Perca flavescens): In Situ Estimates and Bioenergetic Models

Measurements of in situ food consumption and growth rates of young-of-the-year (YOY) yellow perch, Perca flavescens, indicated that extrapolations of the metabolic allometry of adult perch to larval and juvenile perch were inappropriate. YOY active metabolism had the same weight dependent slope as adults but was 4.4 times adult standard respiration. Adult active respiration is typically 1–2 times standard. YOY consumption rates were also higher than predicted from adult allometry. Model simulations demonstrate that consumption and growth dynamics of larval and juvenile fish are more sensitive to variation in temperature and prey availability than are adults.

Allometric analysis of dental variation in a human population

There exists an extensive literature that deals with interspecific allometry, eg, brain size-body size relationships among species. Yet comparatively little attention has been paid to intraspecific or static adult allometry. An intraspecific allometric analysis was conducted on the complete permanent dentition of a prehistoric American Indian population (N = 156). Mesiodistal and buccolingual measurements were logarithmically transformed and regressed on log transformations of femur length, an estimate of body size. When measurements of antimeric teeth were introduced together into common regressions on femur length, 20 of the 32 slopes were significantly different from zero. Thirty-one of the slopes ranged between zero and one and clustered between 0.2 and 0.4. Hence, negative allometry describes the tooth size-body size association, ie, taller individuals in general possess absolutely but not relatively larger teeth than shorter individuals. In addition, no significant sex differences for the regression slopes were observed. Though significantly correlated, tooth size and body size variables are too weakly associated to permit accurate predictions from regression equations. Evolutionary implications of intraspecific dental allometry are discussed.