Brief Communication: Calculating hominin and nonhuman anthropoid femoral head diameter from acetabular size

Femoral head size provides important information on body size in extinct species. Although it is well‐known that femoral head size is correlated with acetabular size, the precision with which femoral head size can be estimated from acetabular size has not been quantified. The availability of accurate 3D surface models of fossil acetabular remains opens the possibility of obtaining accurate estimates of femoral head size from even fragmentary fossil remains [Hammond et al.,: Am J Phys Anthropol 150 (2013) 565–578]. Here we evaluate the relationship between spheres fit to surface models of the femoral head and acetabulum of a large sample of extant anthropoid primates. Sphere diameters are tightly correlated and scale isometrically. In spite of significant taxonomic and possibly functional differences in the relationship between femoral head size and acetabulum size, percent prediction errors of estimated femoral head size remain low regardless of the taxonomic composition of the reference sample. We provide estimates of femoral head size for a series of fossil hominins and monkeys. Am J Phys Anthropol 155:469–475, 2014. © 2014 Wiley Periodicals, Inc.     

Geometrical constraints in the scaling relationships between genome size, cell size and cell cycle length in herbaceous plants

Plant nuclear genome size (GS) varies over three orders of magnitude and is correlated with cell size and growth rate. We explore whether these relationships can be owing to geometrical scaling constraints. These would produce an isometric GS-cell volume relationship, with the GS-cell diameter relationship with the exponent of 1/3. In the GS-cell division relationship, duration of processes limited by membrane transport would scale at the 1/3 exponent, whereas those limited by metabolism would show no relationship. We tested these predictions by estimating scaling exponents from 11 published datasets on differentiated and meristematic cells in diploid herbaceous plants. We found scaling of GS-cell size to almost perfectly match the prediction. The scaling exponent of the relationship between GS and cell cycle duration did not match the prediction. However, this relationship consists of two components: (i) S phase duration, which depends on GS, and has the predicted 1/3 exponent, and (ii) a GS-independent threshold reflecting the duration of the G1 and G2 phases. The matches we found for the relationships between GS and both cell size and S phase duration are signatures of geometrical scaling. We propose that a similar approach can be used to examine GS effects at tissue and whole plant levels.     

Forest cover and fruit crop size differentially influence frugivory of select rainforest tree species in Western Ghats,India

Forest fragmentation and habitat loss are major disruptors of plant–frugivore interactions, affecting seed dispersal and altering recruitment patterns of the dependent tree species. In a heterogeneous production landscape (primarily tea and coffee plantations) in the southern Western Ghats, India, we examined effects of surrounding forest cover and fruit crop size on frugivory of four rainforest bird-dispersed tree species (N = 131 trees, ≥30 trees per species, observed for 623 hr). Frugivore composition differed among the four tree species with the large-seeded Canarium strictum and Myristica dactyloides being exclusively dependent on large-bodied avian frugivores, whereas medium-seeded Persea macrantha and Heynea trijuga were predominantly visited by small-bodied and large-bodied avian frugivores, respectively. Using the seed-dispersal-effectiveness framework, we identified effective frugivores and examined their responses to forest cover and fruit crop size. Results were idiosyncratic and were governed by plant and frugivore traits. Visitations to medium-seeded Persea had a positive relationship with forest cover but the relationship was negative for the large-seeded Myristica. In addition, two of the three effective frugivores for Persea responded to the interactive effect of forest cover and fruit crop size. Frugivore visitations to Heynea were not related to forest cover or fruit crop, and there were too few visitations to Canarium to discern any trends. These results highlight the context-specific responses of plant–frugivore interactions to forest cover and fruit crop size influenced by plant and frugivore traits.     

Patterns of frugivory of the Budongo Forest chimpanzees, Uganda

Frugivory patterns of the chimpanzees in the Budongo Forest Reserve, Uganda were studied between June 2000 and August 2001. Chimpanzee feeding habitats, movement, group size and food eaten were assessed using focal and scan sampling. It was found that fruits were scarce during the dry season, when chimpanzees appeared and moved in large groups over long distances and raided farms at the forest edge. Chimpanzee movement out of the forest to forage was influenced by seasonal fluctuations in availability of preferred foods as some cultivated crops are perennial. Presence of chimpanzees in a specific feeding habitat was related to the availability of edible fruits both within and between months, suggesting that the presence of food may influence chimpanzee movement patterns. Therefore, a good understanding of patterns of frugivory is essential for making informed decisions about conservation of chimpanzees and other frugivores like birds and monkeys in Budongo as different forest habitats are under varying human pressure because of logging and other forms of utilization.     

The effects of leaf size,leaf habit,and leaf form on leaf/stem relationships in plant twigs of temperate woody species

Question: Do thick‐twigged/large‐leaf species have an advantage in leaf display over their counterparts, and what are the effects of leaf habit and leaf form on the leaf‐stem relationship in plant twigs of temperature broadleaf woody species? Location: Gongga Mountain, southwest China. Methods: (1) We investigated stem cross‐sectional area and stem mass, leaf area and leaf/lamina mass of plant twigs (terminal branches of current‐year shoots) of 89 species belonging to 55 genera in 31 families. (2) Data were analyzed to determine leaf‐stem scaling relationships using both the Model type II regression method and the phylogenetically independent comparative (PIC) method. Results: (1) Significant, positive allometric relationships were found between twig cross‐sectional area and total leaf area supported by the twig, and between the cross‐sectional area and individual leaf area, suggesting that species with large leaves and thick twigs could support a disproportionately greater leaf area for a given twig cross‐sectional area. (2) However, the scaling relationships between twig stem mass and total leaf area and between stem mass and total lamina mass were approximately isometric, which indicates that the efficiency of deploying leaf area and lamina mass was independent of leaf size and twig size. The results of PIC were consistent with these correlations. (3) The evergreen species were usually smaller in total leaf area for a given twig stem investment in terms of both cross‐sectional area and stem mass, compared to deciduous species. Leaf mass per area (LMA) was negatively associated with the stem efficiency in deploying leaf area. (4) Compound leaf species could usually support a larger leaf area for a given twig stem mass and were usually larger in both leaf size and twig size than simple leaf species. Conclusions: Generally, thick‐twigged/large‐leaf species do not have an advantage over their counterparts in deploying photosynthetic compartments for a given twig stem investment. Leaf habit and leaf form types can modify leaf‐stem scaling relationships, possibly because of contrasting leaf properties. The leaf size‐twig size spectrum is related to the LMA‐leaf life span dimension of plant life history strategies.     

The influence of prey size and abundance, and individual phenotype on prey choice by the three-spined stickleback, Gasterosteus aculeatm L.

Prey selection behaviour of three-spined sticklebacks, Gasterosteus aculeatus L., was studied in two experiments. Where possible, the experimental apparatus satisfied the assumptions of the simplest optimal diet model (the basic prey model); prey were presented sequentially, the fish could not search for and handle prey at the same time, and net energy gain, handling time and encounter rate were fixed. Experiment 1 presented fish with a range of Asellus sizes so that pursuit ( p ) and handling ( h ) time could be related to prey size. Published energy values of Asellus together with pursuit and handling times were used to calculate E /( p+h ) for Asellus measuring 3,4,5,6,7 and 9 mm. Pursuit times did not differ with prey size but handling times did. E /( p+h ) was very variable particularly at the larger prey sizes. Experiment 2 presented fish with two sequences of prey differing in the encounter rate with the most profitable prey sizes. Fish did not select the diet predicted by the basic prey model tending to always ignore the largest prey even when net energy gain would have been maximized by including them in the diet. Further analysis showed that the probability of a prey size being taken was a function of prey size, fish stomach fullness and encounter rate. It is concluded that the basic prey model is too simple to capture the behaviour of the fish. One of its main faults is that the changing state of the fish through the feeding bout is ignored.     

Evolution of reversed sexual size dimorphism and role partitioning among predatory birds, with a size scaling of flight performance

To explain the adaptive significance of sex role partitioning and reversed sexual size dimorphism among raptors, owls and skuas, where females are usually larger than males, we combine several previous hypotheses with some new ideas. Owing to their structural and behavioural adaptations for prey capture, predatory birds have better prospects than other birds of defending their offspring against nest predators. This makes sex role partitioning advantageous; one parent guards the offspring while the other forages for the family. Further, among predators hunting alert prey such as vertebrates, two mates because of interference may not procur much more food than would one mate hunting alone. By contrast, two mates feeding on less alert prey may together obtain almost twice as much food as one mate hunting alone. For these reasons, partitioning of breeding labours might be adaptive only in predatory birds. An initial imbalance favours female nest guarding and male foraging: the developing eggs might be damaged if the female attacks prey; their mass might reduce her flight performance; she must visit the nest to lay; and the male feeds her before she lays (‘courtship feeding’). Increased female body size should enhance egg production, incubation, ability to tear apart prey for the young, and, in particular, offspring protection in predatory birds. Efficient foraging during the breeding period then becomes most important for the male. This imposes great demands on aerial agility in males, particularly among predators of agile prey. Flight performance decreases with increasing size in five of six aspects explored. The male must therefore not be too large in relation to the most important prey. For these reasons, he should be smaller than the female. Among predatory birds, size dimorphism increases with the proportion of birds in the diet, which may be explained as follows. Adult birds have mainly one type of predators: other predatory birds. Because almost only these specialists exploit adult birds, they carry out most of the cropping of this prey. A predator of easier prey competes with many other kinds of predators, which considerably reduce prey abundance in its territory. This is not so for predators of adult birds. Further, because birds are extremely agile, the specialized predator can hunt efficiently only within a limited size range of birds, whose flight skill it can match. Increased size dimorphism among these predators therefore should be particularly important for enlarging the combined food base of the pair. A bird specialist may consume much of the available prey in the suitable size range during the breeding period. When the predator's young are large enough to defend themselves, the female aids better by hunting than by guarding the chicks. It is advantageous among bird specialists if she hunts prey of other sizes than does the male, who has by then reduced prey abundance in his prey size class. But among predatory birds hunting easier prey the female gains little by hunting outside the male's prey spectrum, because other kinds of predators will have reduced the prey abundance outside as well as inside the male's preferred size range. Intra-pair food separation through large sexual size dimorphism therefore should be particularly advantageous among predators of birds. This may be the main reason why the degree of size dimorphism increases with the dietary proportion of birds.     

The origins of allometry: size and shape polymorphism in the common waterstrider, Gerris remigis Say (Heteroptera, Gerridae)

Changes in size, whether ontogenetic or phylogenetic, tend to be associated with changes in shape. This allometry can arise through two different evolutionary mechanisms: (1) selection acting primarily on overall size may be associated with changes in shape because of physiological and mechanical constraints or differential responses of different body components; or (2) selection acting primarily on shape (on the size of specific body components) may be associated with changes in overall size because of genetic correlations, and thus correlated responses, of other body components. To assess the relative importance of these two mechanisms, shape polymorphism is examined along two axes of size dimorphism (sex and wing morphology) in the common waterstrider, Gerris remigis Say. Eight measurements were made of body and appendage components of 234 adults, from three independent populations. Univariate and multivariate analyses reveal that both sexes and wing morphs differ significantly in size and shape. Shape differentiation along the two axes of size dimorphism is found to be dissimilar, partially independent of size, and strongly correlated with the ecological specialization of the various morphs. These observations suggest that selection is acting directly on shape, and thus that allometry in this species primarily reflects shape-mediated changes in size (mechanism 2), rather than size-mediated changes in shape. The role of developmental processes in facilitating this shape differentiation is discussed.     

Incisor size and diet revisited: The view from a platyrrhine perspective

Allometric relationships between incisor size and body size were determined for 26 species of New World primates. While previous studies have suggested that the incisors of Old World primates, and anthropoids in general, scale isometrically with body size, the data presented here indicate a negative allometric relationship between incisor size and body size among New World species. This negative allometry was exhibited by platyrrhines when either upper or lower incisor row length was regressed against body weight, and when either least-squares or bivariate principal axis equations were used. When upper incisor length was plotted against skull length, negative allometry could be sustained using both statistical techniques only when the full sample of 26 species was plotted. The choice of variables to represent incisor size and body size, and the choice of a statistical technique to effect the allometric equation, had a more pronounced impact on the location of individual species with regard to lines of best fit. Platyrrhines as a group have smaller incisors relative to body size than do catarrhines, regardless of diet. Among New World primates, small incisors represent a plausible primitive condition; species with relatively large incisors manifest a phyletic change associated with a dietary shift to foods that require increased incisal preparation. The opposite trend characterizes Old World primates. In spite of the taxonomic differences in relative incisor size between platyrrhine and catarrhine primates, inferences about diet derived from an allometric equation for all anthropoids should prove reliable as long as the species with unknown diet does not lie at the upper end of the body size range for platyrrhines or catarrhines.     

Size-dependent prey selection in piscivorous pikeperch Sander lucioperca and Volga pikeperch Sander volgensis shaped by bimodal prey size distribution

Prey size and species selection of pikeperch Sander lucioperca and Volga pikeperch Sander volgensis were investigated in relation to predator size in the shallow Lake Balaton, Hungary. Although their gape sizes were similar, S. lucioperca shifted to piscivory earlier and consumed fewer, but larger, prey than S. volgensis. Prey species preference of the two piscivores also differed. A bimodal prey size distribution resulted in a reclining sigmoid curve for the life span predator size to prey size relationship with inflexion points between 266 and 284 mm predator standard length (L(S) ) in S. lucioperca. In S. volgensis, as well as in S. lucioperca L(S) ≤ 350 mm, prey size increased monotonically with predator L(S) , following a power trend for all prey size variables. Prey depth to predator L(S) relationship varied significantly with prey species and prey number in both piscivores, and prey depth tended to be smaller in predators consuming more than one prey. Both predator species characteristically selected less active, benthic prey fishes in spite of their spiny fin rays, and small- and mid-sized predators selected for small prey. Relatively large prey were also eaten, however, especially by the smallest and largest S. lucioperca.     

Lipid content of terrestrial arthropods in relation to body size,phylogeny, ontogeny and sex

Energy storage in arthropods has important implications for survival and reproduction. The lipid content of 276 species of adult arthropods with wet mass in the range 0.2–6.13 g is determined to assess how lipid mass scales with body mass. The relative contribution of lipids to total body mass is investigated with respect to phylogeny, ontogeny and sex. The lipid content of adult insects, arachnids, and arthropods in general shows an isometric scaling relationship with respect to body mass (M) (M_{arthropod lipid} = ?1.09 ×M_dry^1.01 and M_{arthropod lipid} = ?1.00 ×M_lean^0.98). However, lipid allocation varies between arthropod taxa, as well as with sex and developmental stage within arthropod taxa. Female insects and arachnids generally have higher lipid contents than males, and larval holometabolous insects and juvenile arachnids have higher lipid contents than adults.     

Early life histories of the London poor using δ13C and δ15N stable isotope incremental dentine sampling

High resolution incremental isotopic analysis of the dentine from early forming teeth, especially first molars (M1s), provides a means to assess the effects of poor childhood nutrition and healthcare on individuals in an assemblage where there are no infants to study. This approach is applied to an 18th and 19th century cemetery population associated with St Saviour's Almshouse burial ground in Southwark, London, to assess whether, or how, early dietary history, including weaning age, influenced health and nutritional status. The results show a general pattern in which non‐breast milk foods were introduced before or by 6 months of age, as indicated by elevated δ¹⁵N during this period. Almost all individuals for which we also have second molar (M2) records, showed lower δ¹⁵N values from a very young age (>1 year) until approximately 8–10 years, compared to adult values. The overall results show a significant difference in δ¹³C (p = 0 to 4sf, F = 17.327) and a weaker statistical difference in δ¹⁵N between males and females (p = 0.019, F = 5.581). One possible cause of this is a difference in the diet of males and females early in life, or alternatively, a greater susceptibility of males to nutritional deprivation compared to females. The latter argument is strengthened by a significant difference in the incidence of enamel hypoplasia between the males and females, with 7.7% of male teeth showing defects, compared to 3.9% of females. Am J Phys Anthropol 154:585–593, 2014. © 2014 Wiley Periodicals, Inc.     

On size and area: Patterns of mammalian body size extremes across landmasses

We describe a biogeographic pattern in which mammalian body size extremes scale with landmass area. The relationship between the largest and the smallest mammal species found on different landbridge islands, mountaintops and continents shows that the size of the largest species increases, while that of the smallest species decreases, with increase in the area of the landmass. We offer two possible explanations: (1) that the pattern is the result of sampling artefacts, which we call the ‘statistical artefact hypothesis’, or (2) that the pattern is the result of processes related to the way body size affects the number of individuals that a particular species can pack in a given area, which we call the ‘area-scaling hypothesis’. Our results point out that the pattern is not a statistical artefact resulting from random sampling, but can be explained by considering the scaling of individual space requirements and its effect on population survival on landmasses of different area. This revised version was published online in July 2006 with corrections to the Cover Date.     

Patterns of joint size dimorphism in the elbow and knee of catarrhine primates

Differences in body size between conspecific sexes may incur differences in the relative size and/or shape of load-bearing joints, potentially confounding our understanding of variation in the fossil record. More specifically, larger males may experience relatively greater limb joint stress levels than females, unless an increase in weight-related forces is compensated for by positive allometry of articular surface areas. This study examines variation in limb joint size dimorphism (JSD) among extant catarrhines to: 1) determine whether taxa exhibit JSD beyond that expected to simply maintain geometric similarity between sexes, and 2) test whether taxa differ in JSD (relative to body size dimorphism) with respect to differences in limb use and/or phylogeny. "Joint size" was quantified for the distal humerus and distal femur of 25 taxa. Analysis of variance was used to test for differences between sexes (in joint size ratios) and among taxa (in patterns of dimorphism). Multiple regression was used to examine differences in JSD among taxa after accounting for variation in body size dimorphism (BSD) and body size. Although degrees of humeral and femoral JSD tend to be the same within species, interspecific variation exists in the extent to which both joints are dimorphic relative to BSD. While most cercopithecoids exhibit relatively high degrees of JSD (i.e., positive allometry), nonhuman hominoids exhibit degrees of JSD closer to isometry. These results may reflect a fundamental distinction between cercopithecoids and hominoids in joint design. Overall, the results make more sense (from a mechanical standpoint) when adjustments to BSD are made to account for the larger effective female body mass associated with bearing offspring. In contrast to other hominoids, modern humans exhibit relatively high JSD in both the knee and elbow (despite lack of forelimb use in weight support). Estimates of BSD based on fossil limb bones will vary according to the extant analogue chosen for comparison.     

Transcriptional and chromatin-based partitioning mechanisms uncouple protein scaling from cell size

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Differences in fecal particle size between free‐ranging and captive individuals of two browser species

Data from captive animals indicated that browsing (BR) ruminants have larger fecal particles—indicative of lesser chewing efficiency—than grazers (GR). To answer whether this reflects fundamental differences between the animal groups, or different reactions of basically similar organisms to diets fed in captivity, we compared mean fecal particle size (MPS) in a GR and a BR ruminant (aurox Bos primigenius taurus, giraffe Giraffa camelopardalis) and a GR and a BR hindgut fermenter (Przewalski's horse Equus ferus przewalskii, lowland tapir Tapirus terrestris), both from captivity and from the wild. As would be expected owing to a proportion of finely ground, pelleted feeds in captive diets, MPS was smaller in captive than free‐ranging GR. In contrast, MPS was drastically higher in captive than in free‐ranging BR of either digestion type. Thus, the difference in MPS between GR and BR was much more pronounced among captive than free‐ranging animals. The results indicate that BR teeth have adapted to their natural diet so that in the wild, they achieve a particle size reduction similar to that of GR. However, although GR teeth seem equally adapted to food ingested in captivity, the BR teeth seem less well suited to efficiently chew captive diets. In the case of ruminants, less efficient particle size reduction could contribute to potential clinical problems like “rumen blockage” and bezoar formation. Comparisons of MPS between free‐ranging and captive animals might offer indications for the physical suitability of zoo diets. Zoo Biol 27:70–77, 2008. © 2007 Wiley‐Liss, Inc.     

Canine size, shape, and bending strength in primates and carnivores

Anthropoid primates are well known for their highly sexually dimorphic canine teeth, with males possessing canines that are up to 400% taller than those of females. Primate canine dimorphism has been extensively documented, with a consensus that large male primate canines serve as weapons for intrasexual competition, and some evidence that large female canines in some species may likewise function as weapons. However, apart from speculation that very tall male canines may be relatively weak and that seed predators have strong canines, the functional significance of primate canine shape has not been explored. Because carnivore canine shape and size are associated with killing style, this group provides a useful comparative baseline for primates. We evaluate primate maxillary canine tooth size, shape and relative bending strength against body size, skull size, and behavioral and demographic measures of male competition and sexual selection, and compare them to those of carnivores. We demonstrate that, relative to skull length and body mass, primate male canines are on average as large as or larger than those of similar sized carnivores. The range of primate female canine sizes embraces that of carnivores. Male and female primate canines are generally as strong as or stronger than those of carnivores. Although we find that seed-eating primates have relatively strong canines, we find no clear relationship between male primate canine strength and demographic or behavioral estimates of male competition or sexual selection, in spite of a strong relationship between these measures and canine crown height. This suggests either that most primate canines are selected to be very strong regardless of variation in behavior, or that primate canine shape is inherently strong enough to accommodate changes in crown height without compromising canine function.