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Amblypygids display high levels of sexual dimorphism, especially larger pedipalps in males compared to females. This study examines the difference in allometric rates as a potential cause of dimorphism in pedipalps and walking legs in three Heterophrynus species: Heterophrynus hatesii (Butler, 1873); Heterophrynus longicornis (Butler, 1873), and Heterophrynus elaphus (Pocock, 1903). Dimorphism is observed in all studied appendages, but higher allometric rates are shown in males more than females for only the pedipalps (for all three species) and the first walking legs (for only H. elaphus), with higher dimorphism in the pedipalp for H. hatesii and lower in H. elaphus. Dimorphism in pedipalps appears to be linked to species' mating system: larger dimorphism are observed in polygamous systems, whereas moderate and small dimorphisms are observed in monogamous and solitary species, respectively. Contrary to pedipalps, the evolution of walking legs seems to occur via natural selection rather than sexual selection. Key words: sexual size dimorphism, sexual shape dimorphism, allometry, selection, Amblypygi, Heterophrynus, Introduction Sexual size dimorphism is widespread in animals and varies greatly among species and sometimes populations (Emlen and Nijhout 2000; Fairbairn et al. 2007; Emlen 2008). It refers both to [...]

Tree height is one of the most important variables for quantitative assessment of forest stocks, but it is difficult to directly measure. Such allometric relationships of trees can vary between geographical regions, however, mainly due to climatic, edaphic, and floristic gradients. Based on the hypothesis that different forest types influence the generic modeling of tree height-diameter relationships on geographical scales, this study aimed to (i) fit equations to estimate tree height in Atlantic Forest types in the state of Rio de Janeiro, Brazil; (ii) compare efficiency and precision between generic and specific equations for forest types; and (iii) test the effect of different forest types and species on the height-diameter relationship. Four allometric models were tested for all forests (generic) and three main forest types (specific). Effects of tree size, forest types, and species on tree height estimation were analyzed using multiple linear models and mixed-effect linear models. A significant effect of forest type and species on tree height was seen, showing the need to apply local specific equations to minimize the effects that are not captured by generic equations. Differences in tree allometry between forest types were associated with temperature, rainfall, soil, and forest structure. These results confirm the effect of the local environment on the height-diameter relationship of trees as found over large scales in tropical forests. Key words: allometric models, environmental gradients, height modeling, categorical models, mixed-effect models. La hauteur des arbres est l'une des variables les plus importantes pour l'evaluation quantitative des stocks forestiers, mais elle est difficile a mesurer directement. Cependant, de telles relations allometriques pour les arbres peuvent varier entre les regions geographiques, surtout a cause de gradients climatiques, edaphiques et floristiques. En se fondant sur l'hypothese selon laquelle le type de foret influence la modelisation generique des relations entre la hauteur et le diametre des arbres a une echelle geographique, cette etude visait a (i) ajuster des equations d'estimation de la hauteur des arbres pour les types forestiers de l'Atlantique dans l'Etat de Rio de Janeiro, au Bresil; (ii) comparer l'efficacite et la precision des equations generiques et specifiques pour les types de forets; et (iii) tester l'effet de differents types forestiers et de differentes especes sur la relation entre la hauteur et le diametre. Quatre modeles allometriques ont ete testes pour l'ensemble des forets (modeles generiques) et pour trois principaux types forestiers (modeles specifiques). Les effets de la taille des arbres, des types forestiers et des especes sur l'estimation de la hauteur des arbres ont ete analyses a l'aide de modeles lineaires multiples et de modeles lineaires a effets mixtes. Nous avons observe un effet significatif du type forestier et de l'espece sur la hauteur des arbres, ce qui indique qu'il est necessaire d'appliquer des equations specifiques locales pour minimiser les effets qui ne sont pas pris en compte par les equations generiques. Les differences dans les relations allometriques des arbres entre les types forestiers etaient associees a la temperature, aux precipitations, au type de sol et a la structure forestiere. Ces resultats confirment la presence d'un effet de l'environnement local sur la relation entre la hauteur et le diametre des arbres, comme cela a ete constate a grande echelle dans les forets tropicales. [Traduit par la Redaction] Mots-cles : modeles allometriques, gradients environnementaux, modelisation de la hauteur, modeles categoriques, modeles a effets mixtes., 1. Introduction Tree height is one of the most important variables for quantitative assessment of stocks in tropical forests. Measuring standing tree heights in tropical forest inventories is expensive, however, [...]

Scaling studies on phenotypic characteristics like birth mass are useful to understanding life history attributes within species. The wide range in body mass of elk (Cervus elaphus) in North America and Europe allows robust estimation of scaling relationships. Our goal was to estimate the scaling relationship of maternal body mass and offspring birth mass. Data were extracted from the literature, which included captive elk fed a readily digestible diet rich in nutrients. The mass of the mother at birth and the birth mass of the young were recorded for 11 groups of mothers and their offspring. A simple linear regression was used to estimate an allometric relationship between maternal body mass and offspring birth mass ([R.sup.2] = 0.90). Birth mass scaled to the 0.78 power of maternal body mass. Understanding scaling relationships affecting maternal investment might have implications for understanding body size variation across the geographic range of elk., INTRODUCTION Understanding the factors that lead to variation in mass of an individual at birth is critical to understanding life history strategies of a species. In ungulates, for example, individuals [...]

White spruce (Picea glauca (Moench) Voss) and aspen (Populus tremuloides Michx.) from unmanaged stands in the boreal forest of Alberta, Canada, were examined for two of the main structural assumptions in the process-based model CROBAS: (i) a constant allometric relationship between foliage mass and crown length and (ii) a constant relationship between foliage mass and sapwood area. We evaluated these relationships at both at the whole-crown and within-crown levels. Results indicated that for both species, a constant allometric relationship between foliage mass and crown length was maintained at the whole-crown level over a period exceeding the peak mean annual increment of each species. Within the crowns of spruce, foliage mass accumulated faster near the tree apex as total crown length increased. For aspen, the increase in foliage mass per unit crown length for any section within the crown showed greater similarity to the relationship observed at the whole-crown level. The assumption of a constant relationship between foliage mass and sapwood area at the crown base generally held for spruce but showed considerable variation for any given diameter class. For aspen, this assumption did not appear to be appropriate. For both species, there was more foliage mass per unit sapwood area with increasing height from the ground for nearly all tree size classes. This latter finding was in conflict with the pipe model theory but could not be explained by the hydraulic theory of crown architecture, which predicts a decrease in the ratio of foliage mass to sapwood area with increasing path length. Key words: pipe model, crown allometry, foliage mass, Picea glauca, Populus tremuloides. A partir d'epinettes blanches (Picea glauca (Moench) Voss) et de peupliers faux-tremble (Populus tremuloides Michx.) provenant de peuplements boreaux non amenages de l'Alberta, nous avons etudie deux des principales hypotheses structurales du modele fonctionnel CROBAS : (i) une relation allometrique constante entre la masse foliaire et la longueur de la cime, et (ii) une relation constante entre la masse foliaire et la surface d'aubier. Nous avons evalue ces relations aux echelles de la cime entiere et de l'interieur de la cime. Les resultats indiquent que pour les deux especes, une relation allometrique constante entre la masse foliaire et la longueur de la cime a ete maintenue a l'echelle de la cime entiere au cours d'une periode depassant l'age d'atteinte de l'accroissement annuel moyen maximal de chaque espece. Dans les cimes d'epinette, la masse foliaire s'accumulait plus rapidement pres de l'apex de l'arbre a mesure que la longueur totale de la cime augmentait. Chez le peuplier, l'augmentation de la masse foliaire par unite de longueur de cime de toutes les sections de la cime ressemblait davantage a la relation observee a l'echelle de la cime entiere. L'hypothese d'une relation constante entre la masse foliaire et la surface d'aubier a la base de la cime a generalement ete validee pour l'epinette, mais sa variation etait considerable pour toutes les classes de diametre. Dans le cas du peuplier, cette hypothese ne semblait pas appropriee. Chez les deux especes, la masse foliaire par unite de surface d'aubier augmentait avec la hauteur par rapport au sol pour a peu pres toutes les classes de taille d'arbre. Ce dernier resultat contredit la theorie du modele tubulaire, mais ne peut etre explique par la theorie hydraulique de l'architecture de la cime qui predit une diminution du rapport entre la masse foliaire et la surface d'aubier avec l'augmentation de la distance de transport. [Traduit par la Redaction] Mots-cles : modele tubulaire, allometrie de la cime, masse foliaire, Picea glauca, Populus tremuloides., Introduction CROBAS (Makela 1997) is a process-based model that not only is based on the principle of carbon balance, but also incorporates principles related to the functional balance (Davidson 1969; [...]

Large-scale prediction of forest biomass is of interest for forest science, ecology, and issues related to climate change. Previous research has attempted to provide allometric models suitable for large-scale biomass prediction using different methods. We present a new approach for meta-analysis of existing biomass equations using mixed-effects modelling on simulated data. The resulting generalized meta-models can be calibrated for local conditions. This meta-analytical approach allows for directly benefiting from previous research to minimize data collection and properly take into account the unknown differences between different locations within large areas. The approach is demonstrated by developing pan-Mediterranean mixed-effects meta-models for Pinus brutia Ten. The fixed part of the meta-models enables sound aboveground biomass predictions throughout practically the full native range of the species. Significant improvement in the predictive performance can be further gained by using small local datasets for model calibration. The calibration procedure for location-specific biomass prediction is based on best linear unbiased predictor of random effects. The predictive performance of the meta-models under different sampling strategies is validated in an independent dataset. The results show that mixed-effects meta-models may enable accurate and robust large-scale biomass predictions. Calibration for specific locations based on minimal data collection effort performs better than fitting location-specific equations based on much larger samples. The advantages of mixed-effects meta-models are of interest not only for further biomass-related research and applications, but also for other modeling disciplines within forest science. Key words: meta-analysis, model calibration, best linear unbiased predictor, BLUP, random effects, allometric equations, sampling, Pinus brutia. La prediction de la biomasse a grande echelle presente un interet pour les sciences forestieres, l'ecologie et les questions reliees aux changements climatiques. Des travaux de recherche precedents ont tente de fournir des modeles allometriques convenables pour predire la biomasse a grande echelle a l'aide de differentes methodes. Nous presentons une nouvelle approche pour la meta-analyse des equations de biomasse existantes a l'aide de la modelisation a effets mixtes avec des donnees simulees. Les meta-modeles generalises ainsi produits peuvent etre calibres pour des conditions locales. Cette approche meta-analytique permet de beneficier directement des travaux de recherche precedents afin de minimiser la recolte de donnees et de tenir compte adequatement des differences inconnues entre differents endroits a l'interieur de vastes regions. Cette approche est illustree par la production de meta-modeles a effets mixtes pan-mediterraneens pour Pinus brutia Ten. La partie fixe des meta-modeles permet de faire des predictions valables de la biomasse aerienne dans pratiquement toute l'aire de repartition de l'espece. On peut ameliorer encore plus la performance predictive en utilisant de petits jeux de donnees locales pour calibrer les modeles. La procedure de calibration pour predire la biomasse specifique a un endroit s'appuie sur le meilleur predicteur lineaire non biaise des effets aleatoires. La performance predictive des meta-modeles avec differentes strategies d'echantillonnage est validee avec un jeu de donnees independantes. Les resultats montrent que les meta-modeles a effets mixtes peuvent permettre de faire des predictions exactes et robustes de la biomasse a grande echelle. La calibration specifique a un endroit basee sur un effort minimal de collecte de donnees donne de meilleurs resultats que l'ajustement d'equations specifiques a cet endroit en utilisant des echantillons beaucoup plus importants. Les avantages des meta-modeles a effets mixtes presentent un interet pour les applications et les travaux de recherche futurs relies a la biomasse mais aussi pour d'autres domaines de modelisation en sciences forestieres. [Traduit par la Redaction] Mots-cles : meta-analyse, calibration de modeles, meilleur predicteur lineaire non biaise (BLUP), effets aleatoires, equations allometriques, echantillonnage, Pinus brutia., Introduction Large-scale prediction of forest biomass has traditionally been the object of considerable interest within forest research for different reasons. Important issues such as carbon sequestration, forest productivity, forest management [...]

ABSTRACT. Morphological variation attributable to allometry in the freshwater gastropod Elimia livescens Menke, 1830 is described. Geometric morphometric analyses were used to examine shape variation and visual ontogenic deformation patterns [...]

Adequate quantification of canopy fuel load and canopy bulk density is required for assessment of the susceptibility of forest stands to crown fire and evaluation of silvicultural treatments aimed at reducing the risk of crowning. The use of tree biomass equations and vertical profile distributions of crown fuels provide the most accurate estimates of the canopy fuel characteristics. In this study, 100 pole-size maritime pine (Pinus pinaster Aiton) trees were destructively sampled in five different sites, covering a wide range of its geographical distribution in the Iberian Peninsula. To estimate crown fuel mass, allometric equations were fitted separately for needles, twigs, and fuel available for crown fire. Models were also fitted to characterize the vertical fuel distributions as a function of tree height. All models were fitted simultaneously to guarantee additivity among tree biomass components, and corrections were also made for heterocedasticity and autocorrelation. Diameter at breast height was the best explanatory variable for all the allometric models. The vertical distribution of crown biomass fractions along tree height depended on the crown size and tree dominance. The system of equations provides a good balance between accurate predictions and low data requirements, allowing quantification of canopy fuel characteristics at stand level. Resume: La quantification adequate de la charge de combustibles et de la densite apparente dans le couvert forestier est necessaire pour evaluer la susceptibilite des peuplements forestiers a un feu de cime et les traitements sylvicoles visant a reduire le risque d'embrasement des cimes. L'utilisation des equations de biomasse des arbres et des profils de repartition verticale des combustibles de cimes procure les estimations les plus precises des caracteristiques des combustibles dans le couvert forestier. Dans cette etude, 100 tiges de pin maritime (Pinus pinaster Aiton) au stade du perchis ont ete echantillonnees de facon destructive dans cinq stations differentes representatives d'une vaste partie de l'aire de repartition de l'espece dans la peninsule iberique. Pour estimer la masse des combustibles de cimes, des equations allometriques ont ete ajustees separement pour les aiguilles, les rameaux et les combustibles disponibles pour un feu de cime. Des modeles ont egalement ete ajustes pour caracteriser la repartition verticale des combustibles en fonction de la hauteur des arbres. Tous les modeles ont ete ajustes simultanement pour s'assurer de l'additivite parmi les composantes de la biomasse des arbres et des corrections ont ete apportees pour l'heterocedasticite et l'autocorrelation. Le diametre a hauteur de poitrine etait la meilleure variable independante pour tous les modeles allometriques. La repartition verticale des fractions de biomasse de la cime sur la hauteur d'un arbre dependait de la dimension de la cime et de la dominance de l'arbre. Le systeme d'equations constitue un bon equilibre entre la precision des predictions et la quantite de donnees necessaires et permet de quantifier les caracteristiques des combustibles dans le couvert forestier a l'echelle du peuplement. [Traduit par la Redaction], Introduction Many pine-dominated forests across the Mediterranean area are managed with the aim of maximizing biomass production, which makes them susceptible to high-severity wildfires. Better knowledge of the distribution of [...]

A fundamental feature of embryonic patterning is the ability to scale and maintain stable proportions despite changes in overall size, for instance during growth (1-6). A notable example occurs during [...]

A basic fact of life is that the size of an animal's brain depends to some extent on its body size. A long history of studies of vertebrate animals has [...]

Effects of growth acceleration on eye development have been examined in genetically modified salmonids. Growth hormone (GH) transgenic coho salmon (Oncorhynchus kisutch (Walbaum, 1792)) show dramatically elevated overall body growth and an absolute increase in eye size, but relative eye growth is shifted from negatively allometric to more isometric. Thus, transgenic fish possess significantly smaller eyes relative to nontransgenic fish of the same size. Ration-restricted limitation of growth in transgenic salmon to that of wild type restores relative eye growth rate, suggesting that effects on eyes are an indirect consequence of modification of growth rate rather than a direct effect of GH overexpression. Heart, spleen, and liver did not show changes in proportion among groups, whereas total brain size showed the same response as eye. Relative eye and brain size were also reduced in a fast-growing domesticated strain of rainbow trout (Oncorhynchus mykiss (Walbaum, 1792)), suggesting modifications of allometry are a more general effect of growth acceleration. GH mRNA levels from the transgene were elevated in eyes, whereas IGF-I mRNA was not, suggesting this organ may be regulated in a different fashion than other organs. Neural tissues with critical structural requirements for optimal function may be subject to less modification of growth rate than are other organ systems. Nous examinons les effets de l'acceleration de la croissance sur le developpement de l'ceil chez des salmonides genetiquement modifies. Des saumons coho (Oncorhynchus kisutch (Walbaum, 1792)) transgeniques pour l'hormone de croissance (GH), affichent une croissance corporelle globale spectaculairement acceleree et un accroissement absolu de la taille de l'oeil, mais la croissance relative de l'ceil change d'allometrique negative a plus isometrique. Ainsi, les poissons transgeniques possedent des yeux significativement plus petits relativement aux poissons non transgeniques de meme taille. La limitation de la croissance par restriction de la ration alimentaire chez les saumons transgeniques par rapport au type sauvage restaure le taux relatif de croissance de l'oeil, ce qui laisse croire que les effets sur les yeux sont une consequence indirecte de la modification du taux de croissance plutot qu'un effet direct d'une surexpression de GH. Le cceur, la rate et le foie n'affichent aucun changement de proportion entre les groupes, alors que la taille du cerveau entier connait la meme reaction que l'oeil. Les tailles relatives du cerveau et de l'ceil sont aussi reduites dans une lignee domestiquee de traites arcen-ciel a croissance rapide, ce qui fait penser que la modification de l'allometrie est un effet plus general de l'acceleration de la croissance. Les concentrations d'ARNm GH sont elevees dans les yeux des poissons transgeniques, alors que l'ARNm IGF-I ne l'est pas, ce qui indique que cet organe peut etre regule de maniere differente des autres organes. Les tissus neuraux qui possedent des besoins structuraux critiques pour un fonctionnement optimal peuvent etre sujets a une modification moindre de leur taux de croissance que les autres systemes d'organes. [Traduit par la Redaction], Introduction Growth rate and body size are important factors influencing the fitness of organisms in nature (Arendt 1997). Adjustments to growth rate in vertebrates can occur in response to biotic [...]

Territoriality is one of the best examples of interference competition and generally results in larger, dominant individuals gaining preferential access to food. However, the expectation of higher growth of dominant individuals among juvenile salmonids has received only mixed support. We used outdoor semi-natural stream channels stocked with varying sizes of young of the year juvenile salmonids under high and low food rations (i) to examine the mechanisms underlying variation in the benefits of dominance and (ii) to demonstrate that inconsistencies in the apparent benefits of dominance are a logical outcome of the allometry of growth and differential energy intake among fish of different size in a dominance hierarchy. Growth of dominants exceeded that of subordinates when food was abundant, but subordinates grew faster than dominants in low food treatments and when dominant fish increased in size and approached the capacity of their habitat. In general, size disparity within a dominance hierarchy may promote higher growth of subdominants because of the lower energetic requirements of smaller individuals, and the allometry of fish growth, relative to habitat capacity, can reverse the expected growth and condition of dominant and subordinate fish. La territorialite est l'un des meilleurs exemples de la competition par interference et elle produit generalement des individus plus grands et dominants qui ont un acces preferentiel a la nourriture. Bien qu'on s'attende a une croissance accrue chez les individus dominants parmi les jeunes saumons, les donnees n'appuient pas clairement cette attente. Nous avons utilise des canaux semi-naturels empoissonnes de jeunes salmonides de l'annee de tailles diverses dans des conditions elevees et basses de nourriture afin (i) d'examiner les mecanismes qui expliquent la variation dans les benefices de la dominance et (ii) de demontrer que les incoherences dans les benefices apparents de la dominance sont le resultat logique de l'allometrie de la croissance et de l'incorporation differentielle de l'energie chez les poissons de tailles differentes dans une hierarchie de dominance. La croissance des dominants depasse celle des subordonnes lorsque la nourriture est abondante, mais les subordonnes croissent plus vite que les dominants en conditions de nourriture restreinte et lorsque les poissons dominants augmentent en taille et s'approchent du stock limite de leur habitat. En general, la disparite des tailles dans une hierarchie de dominance peut promouvoir une croissance plus forte des subordonnes a cause des besoins plus faibles en energie des individus plus petits; l'allometrie de la croissance, en relation avec le stock limite de l'habitat, peut inverser la croissance et la condition auxquelles ont s'attend chez les poissons dominants et subordonnes. [Traduit par la Redaction], Introduction Territoriality is one of the best examples of interference competition and generally results in larger dominant individuals gaining preferential access to food, shelter, or mates. Territoriality occurs across a [...]

Estimates of aboveground biomass and nutrient stocks are commonly derived using equations that describe tree dimensional relationships. Despite the widespread use of this approach, there is little information about whether equations specific to stand age are necessary for accurate biomass predictions. We developed equations for small trees (2-12 cm diameter) of six species in four young northern hardwood stands. We then compared our equations with equations used frequently in the literature that were developed in mature stands (Whittaker et al. 1974. Ecol. Monogr. 44: 233-252). Our equations for yellow birch (Betula alleghaniensis Britt.) predicted 11%-120% greater stem wood for individual trees com-pared with the equations from Whittaker et al. and, on average, 50% greater aboveground yellow birch biomass in the four stands that we studied. Differences were less pronounced for sugar maple (Acer saccharum Marsh.) and American beech (Fagus grandifolia Ehrh.); our equations predicted, on average, 9% greater aboveground stand biomass for sugar maple and 3% lower biomass for American beech compared with Whittaker et al. Our results suggest that stand age may be an important factor influencing the aboveground allometry and biomass of small yellow birch trees in these developing northern hardwood stands. Rsume: Des estimations de la biomasse aerienne et de la quantite de nutriments sont souvent calculees a l'aide d'equations decrivant des relations tridimensionnelles. Malgre l'utilisation generalisee de cette approche, il y a peu d'information concernant la necessite d'utiliser des equations qui tiennent compte de l'age du peuplement pour obtenir des previsions precises de la biomasse. Nous avons mis au point des equations pour les petits arbres (de 2 a 12 cm de diametre) de six especes provenant de quatre jeunes peuplements de feuillus nordiques. Nous avons ensuite compare nos equations a celles qui sont frequemment utilisees dans la litterature et qui ont ete mises au point a partir de peuplements matures (Whittaker et al. 1974. Ecol. Monogr. 44: 233-252). Dans le cas du bouleau jaune (Betula alleghaniensis Britt.), nos equations predisaient 11 % a 120 % plus de bois de tronc par arbre que les equations de Whittaker et al. et, en moyenne, 50 % plus de biomasse aerienne de bouleau jaune dans les quatre peuplements etudies. Ces differences etaient moins prononcees dans le cas de l'e-rable a sucre (Acer saccharum Marsh.) et du hetre a grandes feuilles (Fagus grandifolia Ehrh.); en effet nos equations predisaient, en moyenne, 9 % plus de biomasse aerienne du peuplement pour l'erable a sucre et 3 % moins de biomasse pour le hetre a grandes feuilles que les equations de Whittaker et al. Nos resultats indiquent que l'age du peuplement est un facteur qui peut avoir un effet important sur l'allometrie et la biomasse aerienne des bouleaux jaunes de petite taille dans ces jeunes peuplements de feuillus nordiques. [Traduit par la Redaction], Introduction Accurate descriptions of aboveground forest biomass are essential for characterizing ecosystem function and accounting for terrestrial C stocks. Estimates of forest biomass are commonly derived from allometric equations that [...]

* Premise of the study: Specific leaf area (SLA)is a critical component of the leaf economics spectrum, and many functional leaf traits have been empirically demonstrated to covary with SLA. However, a complete understanding of how change in leaf size influences SLA has not yet emerged. * Methods: To help develop a more complete understanding of the determinants of variability in SLA, we present a covariation model of leaf allometry that predicts a zero-sum interdependence of leaf thickness, density, and surface area on leaf mass. We test the model's predictions on measurements of 900 leaves from 44 angiosperm species. * Key results: We observe that 'diminishing returns,' the negative allometry (slope < 1) of surface area versus mass, does not hold universally across species. Rather, the scaling of SLA is linked to the relative allocation to thickness and density. Specifically, diminishing returns are observed when leaves grow thicker, more than their density decreases, with increasing mass. Finally, we confirm model predictions that the allometric dependence of area, thickness, and density on mass can be well approximated by a zero-sum allocational process. * Conclusions: Our work adds to the growing body of evidence that allometric covariation is a hallmark of the scaling behavior of complex plant and leaf traits. Moreover, because our model makes predictions based on allocational constraints, it provides a foundation to understand how deviations from zero-sum tradeoffs in allocation to leaf thickness, density, or area determine the allometry of SLA and, ultimately, underlie adaptive strategies within and across plant species. Key words: allometry; leaf density; leaf mass per area; leaf thickness; LMA; photosynthesis; SLA; specific leaf area. doi: 10.3732/ajb.1000118

It has been known for decades that the metabolic rate of animals scales with body mass with an exponent that is almost always 2/3, and often very close to 3/4. The 3/4 exponent emerges naturally from two models of resource distribution networks, radial explosion and hierarchically branched, which incorporate a minimum of specific details. Both models show that the exponent is 2/3 if velocity of flow remains constant, but can attain a maximum value of 3/4 if velocity scales with its maximum exponent, 1/12. Quarter-power scaling can arise even when there is no underlying fractality. The canonical 'fourth dimension' in biological scaling relations can result from matching the velocity of flow through the network to the linear dimension of the terminal 'service volume' where resources are consumed. These models have broad applicability for the optimal design of biological and engineered systems where energy, materials, or information are distributed from a single source. allometric | fractal | hierarchical | metabolic rate | network doi/ 10.1073/pnas.1009974107

The scaling of metabolic rates to body size is widely considered to be of great biological and ecological importance, and much attention has been devoted to determining its theoretical and empirical value. Most debate centers on whether the underlying power law describing metabolic rates is 2/3 (as predicted by scaling of surface area/volume relationships) or 3/4 ('Kleiber's law'). Although recent evidence suggests that empirically derived exponents vary among clades with radically different metabolic strategies, such as ectotherms and endotherms, models, such as the metabolic theory of ecology, depend on the assumption that there is at least a predominant, if not universal, metabolic scaling exponent. Most analyses claimed to support the predictions of general models, however, failed to control for phylogeny. We used phylogenetic generalized least-squares models to estimate allometric slopes for both basal metabolic rate (BMR) and field metabolic rate (FMR) in mammals. Metabolic rate scaling conformed to no single theoretical prediction, but varied significantly among phylogenetic lineages. In some lineages we found a 3/4 exponent, in others a 2/3 exponent, and in yet others exponents differed significantly from both theoretical values. Analysis of the phylogenetic signal in the data indicated that the assumptions of neither species-level analysis nor independent contrasts were met. Analyses that assumed no phylogenetic signal in the data (species-level analysis) or a strong phylogenetic signal (independent contrasts), therefore, returned estimates of allometric slopes that were erroneous in 30% and 50% of cases, respectively. Hence, quantitative estimation of the phylogenetic signal is essential for determining scaling exponents. The lack of evidence for a predominant scaling exponent in these analyses suggests that general models of metabolic scaling, and macro-ecological theories that depend on them, have little explanatory power. Key words: allometry; basal metabolic rate (BMR); field metabolic rate (FMR); Kleiber's law; metabolic theory of ecology (MTE); phylogenetic comparative analysis; phylogenetic generalized least squares; phylogenetically independent contrasts; phylogeny; power law; scaling.

Thompson, B J, Smith, DB, Jacobson, BH, Fiddler, RE, Warren, A J, Long, BC, O'Brien, MS, Everett, KL, Glass, RG, and Ryan, ED. The influence of ratio and allometric scaling procedures for normalizing uppper body power output in division I collegiate football players. J Strength Cond Res 24(9): 2269-2273, 2010-The purpose of the present study was to examine the differences in upper body power output among lineman and nonlineman division I collegiate football players and to examine the influence of 2 normalization procedures: (a) simple ratio scaling and (b) standardized allometric scaling. Ten lineman (mean [+ or -] SD: age = 19.3 [+ or -] 1.6 years; height = 187.7 [+ or -] 4.7 cm; mass = 127.7 [+ or -] 13.3 kg) and 14 nonlineman (19.6 [+ or -] 1.4 years; 181.8 [+ or -] 5.2 cm; 92.3 [+ or -] 10.6 kg) performed a multiple repetition bench press power test at 50% of their 1 repetition maximum. Peak power (PP) was determined from a Tendo weightlifting analyzer that was attached to the barbell. The PP values were then analyzed under 3 conditions that included: (a) no scaling (absolute values), (b) ratio scaling (PP body [mass.sup.-1]), and (c) allometric scaling (PP body [mass.sup.-067]). The results indicated that the larger lineman demonstrated greater absolute PP values (p = 0.02); however, ratio scaling favored the smaller nonlineman group (p = 0.04). There were no differences in PP values between positions after the standardized allometric scaling procedure (p = 0.60). These findings indicated that the standardized allometric scaling procedure may be a more effective method for normalizing PP values among elite division I collegiate football players.

The ontogeny of skull allometry has been the subject of research in didelphid, microbiotheriid, and dasyurid marsupials. We described and compared postweaning stages of cranial development in the woolly opossum Caluromys philander, a member of a distinct lineage of didelphids. We identified 31 qualitative morphological changes between juveniles and adults, many related to the trophic apparatus. Early development of the paracanine fossa in the snout, correlated with the presence of well-developed canines in juveniles, represents a remarkable difference between the ontogeny of C. philander and other marsupials. We performed bivariate and multivariate analyses of allometry on a data set composed of 14 cranial measurements and 45 specimens. Allometric scaling showed that braincase is relatively small in adulthood, whereas other neurocranial components, particularly the orbit, grew isometrically along its length. The palate becomes elongated by the combination of the isometry of its length and the negative allometry of its width. The rostrum lengthened, but its height remained proportionally constant. In relative terms the temporal fossa expanded inward following the marsupial model that combines the negative allometry of the braincase and the isometry of the zygomatic breadth. The mandible increased in robustness. The skull ontogeny of C. philander shares 4 allometric trends with 2 didelphids (Didelphis albiventris and Lutreolina crassicaudata) and two australidelphians (Dromiciops gliroides and Dasyurus albopunctatus). Three of these trends, breadth of palate, breadth of braincase, and height of occipital plate, were allometrically negative, whereas height of the dentary was positive. These common allometric trends may be interpreted as symplesiomorphic for marsupials, suggesting a high degree of conservatism in the skull development of Caluromys and other marsupials. DOI: 10.1644109-MAMM-A-291.1. Key words: anatomy, Caluromyinae, ontogeny, skull allometry

The production of heterotrophic biomass is an important aspect of overall ecosystem functioning. However, single-celled organisms or microscopic metazoans are often ignored in studies of secondary production, despite being very abundant and possessing high mass-specific population growth rates, relative to the more widely studied larger taxa. Here, we focused on how life history parameters scale with body size of ciliates and meiofauna (body mass range from ~0.001 to 90 mg C/individual) and integrated experimental and survey data to calculate secondary production of these groups. First, we derived a single allometric scaling relationship between the intrinsic rate of population increase and body mass in a laboratory experiment. We then used this relationship to calculate secondary production for over 260 of these small species in the field, using survey data from two contrasting streams; one of which was nutrient rich, the other nutrient poor. Results from laboratory cultures showed that the scaling relationship between body mass and both daily intrinsic rate of population increase and generation time followed a power law. The relationship between body mass and annual secondary production was consistent in both streams, but the number of taxa was greater in the more productive site. Both ciliates and meiofauna had high rates of biomass production, with annual P/B ratios (production divided by biomass) for the whole assemblage exceeding 11 in both streams. We conclude that a large fraction of benthic production is overlooked when protozoans and microscopic metazoans are excluded from estimates of biomass turnover. Key words: biomass; Ciliata; generation time; intrinsic rate of population increase; invertebrates; meiofauna; metabolic theory of ecology; MTE; power law; production.

The scaling of respiratory metabolism with body mass is one of the most pervasive phenomena in biology. Using a single allometric equation to characterize empirical scaling relationships and to evaluate alternative hypotheses about mechanisms has been controversial. We developed a method to directly measure respiration of 271 whole plants, spanning nine orders of magnitude in body mass, from small seedlings to large trees, and from tropical to boreal ecosystems. Our measurements include the roots, which have often been ignored. Rather than a single power-law relationship, our data are fit by a biphasic, mixed-power function. The allometric exponent varies continuously from 1 in the smallest plants to 3/4 in larger saplings and trees. Therefore, our findings support the recent findings of Reich et al. [Reich PB, Tjoelker MG, Machado JL, Oleksyn J (2006) Universal scaling of respiratory metabolism, size, and nitrogen in plants. Nature 439:457-461] and West, Brown, and Enquist [West GB, Brown J H, Enquist BJ (1997) A general model for the origin of allometric scaling laws in biology. Science 276:122 -126.]. The transition from linear to 3/4-power scaling may indicate fundamental physical and physiological constraints on the allocation of plant biomass between photosynthetic and nonphotosynthetic organs over the course of ontogenetic plant growth. allometry | metabolic scaling | mixed-power function | whole-plant respiration | simple-power function doi/ 10.1073/pnas.0902554107

Increased encephalization, or larger brain volume relative to body mass, is a repeated theme in vertebrate evolution. Here we present an extensive sampling of relative brain sizes in fossil and extant taxa in the mammalian order Carnivora (cats, dogs, bears, weasels, and their relatives). By using Akaike Information Criterion model selection and endocranial volume and body mass data for 289 species (including 125 fossil taxa), we document clade-specific evolutionary transformations in encephalization allometries. These evolutionary transformations include multiple independent encephalization increases and decreases in addition to a remarkably static basal Carnivora allometry that characterizes much of the suborder Feliformia and some taxa in the suborder Caniformia across much of their evolutionary history, emphasizing that complex processes shaped the modern distribution of encephalization across Carnivora. This analysis also permits critical evaluation of the social brain hypothesis (SBH), which predicts a close association between sociality and increased encephalization. Previous analyses based on living species alone appeared to support the SBH with respect to Carnivora, but those results are entirely dependent on data from modern Canidae (dogs). Incorporation of fossil data further reveals that no association exists between sociality and encephalization across Carnivora and that support for sociality as a causal agent of encephalization increase disappears for this clade. Akaike Information Criterion | allometry | encephalization | Mammalia | phylogeny

Previous efforts to use the Euler equation to estimate maximum population growth rates (variously symbolized as either r, [r.sub.m], or [r.sub.max]) have used simplified models of survivorship that neglect differences in survivorship schedules among species. In particular, several recent analyses have used either an exponential model of survivorship or a step function model in which all individuals live until a fixed age of death. Using a flexible alternative based on the beta distribution and a compiled data set of mammalian survivorship curves for 58 species, we explore the influence of survivorship shape and scale on the estimation of r. We show that the Euler equation paired with an exponential model of survivorship can be used to calculate an unbiased estimate of r over a large range of body sizes, whereas the more commonly used step function survivorship model results in severely inflated estimates of r, especially for mammals with large maximum population growth rates. Finally, we demonstrate that, despite producing different absolute estimates of r, the three survivorship models examined yield similar allometric scaling coefficients relating r to biomass. These allometric scaling relationships are highly sensitive to the inclusion or exclusion of bats (Chiroptera), which exhibit life-history traits (long life spans, small litter sizes, and relatively long litter intervals) inconsistent with their small body size. Key words: allometry; beta distribution; Cole approximation; Euler equation; life history; maximum population growth rate; metabolic theory; survivorship.

Didelphid marsupials specialized in arboreal locomotion have morphological features convergent with primates, and hence are an ideal group to test hypotheses about the evolution of arboreality. We analyzed the relative contributions of allometric, phylogenetic, and adaptive aspects to the climbing performance of 7 species of didelphid marsupials of the Atlantic Forest of Brazil. These species encompass a diversity of body sizes, use of the vertical strata, and lineages within didelphid marsupials. Climbing performance was evaluated by measuring the velocity in climbing 3 nylon ropes of 0.6, 0.9, and 1.25 cm diameter. The cycle of maximum velocity was chosen to measure relative stride length, frequency, and relative velocity. As expected, arboreal species (Gracilinanus microtarsus, Marmosops incanus, Micoureus paraguayanus, and Caluromys philander) had higher relative climbing velocities than more terrestrial species (Didelphis aurita, Philander frenatus, and Metachirus nudicaudatus). Stride frequency was mostly associated with phylogeny and vertical use of the forest, but relative velocities generally were determined by a combination of stride length and frequency. Differences in climbing performance originated early in the diversification of the group, but continued to evolve because significant differences also were detected at the subfamily, tribe, and genus levels, which seems to parallel the evolution of grasping abilities in primates. Key words: Didelphimorphia, locomotion, neotropical forest, performance, velocity, vertical stratification

The effect of selection for growth rate on relative growth of the rabbit body components was studied. Animals from the 18th generation of a line selected for growth rate were compared with a contemporary control group formed with offspring of embryos that were frozen at the seventh generation of selection of the same line. A total of 313 animals were slaughtered at 4, 9, 13, 20, and 40 wk old. The offal, organs, tissues, and retail cuts were weighed, and several carcass linear measurements were recorded. Huxley's allometric equations relating the weights of the components with respect to BW were fitted. Butterfield's quadratic equations relating the degree of maturity of the components and the degree of maturity of BW were also fitted. In most of the components studied, both models lead to similar patterns of growth. Blood was isometric or early maturing and skin was late maturing or isometric depending on the use of Huxley's or Butterfield's model. Full gas trointestinal tract, liver, kidneys, thoracic viscera, and head were early maturing, and the chilled carcass and reference carcass were late maturing. The retail cuts of the reference carcass showed isometry (forelegs) or late maturing growth (breast and ribs, loin, hind legs, and abdominal walls). Dissectible fat of the carcass and meat of the hind leg had a late development, whereas bone of the hind leg was early maturing. Lumbar circumference length was later maturing than the carcass length and thigh length. Sex did not affect the relative growth of most of the components. Butterfield's model showed that males had an earlier development of full gastrointestinal tract and later growth of kidneys than females. No effect of selection on the relative growth of any of the components studied was found, leading to similar patterns of growth and similar carcass composition at a given degree of maturity after 11 generations of selection for growth rate. Key words: allometry, carcass composition, growth rate, rabbit, selection

Allometric relationships are important sources of information for many types of anthropological and biological research. The baseline for all allometric relationships is isometry (or geometric similarity), the principal that shape is invariant of size. Here, we formally test for geometric similarity in modern humans, looking at the maximum lengths of four long bones (humerus, radius, femur, and tibia). We use Jolicoeur's multivariate allometry method to examine globally distributed samples of human populations, both collectively and individually. Results indicate that humans are not geometrically similar, although morphological deviations from isometry are small. KEY WORDS allometry; geometric similarity; long bones

A fundamental but unanswered biological question asks how much energy, on average, Earth's different life forms spend per unit mass per unit time to remain alive. Here, using the largest database to date, for 3,006 species that includes most of the range of biological diversity on the planet--from bacteria to elephants, and algae to sapling trees--we show that metabolism displays a striking degree of homeostasis across all of life. We demonstrate that, despite the enormous biochemical, physiological, and ecological differences between the surveyed species that vary over [10.sup.20]-fold in body mass, mean metabolic rates of major taxonomic groups displayed at physiological rest converge on a narrow range from 0.3 to 9 W [kg.sup.-1]. This 30-fold variation among life's disparate forms represents a remarkably small range compared with the 4,000- to 65,000-fold difference between the mean metabolic rates of the smallest and largest organisms that would be observed if life as a whole conformed to universal quarter-power or third-power allometric scaling laws. The observed broad convergence on a narrow range of basal metabolic rates suggests that organismal designs that fit in this physiological window have been favored by natural selection across all of life's major kingdoms, and that this range might therefore be considered as optimal for living matter as a whole. allometry | body size | breathing | scaling | energy consumption

Environmental factors during juvenile growth such as temperature and nutrition have major effects on adult morphology and life-history traits. In Drosophila melanogaster, ovary size, measured as ovariole number, and body size, measured as thorax length, are developmentally plastic traits with respect to larval nutrition. Herein we investigated the genetic basis for plasticity of ovariole number and body size, as well the genetic basis for their allometric relationship using recombinant inbred lines (RILs) derived from a natural population in Winters, California. We reared 196 RILs in four yeast concentrations and measured ovariole number and body size. The genetic correlation between ovariole number and thorax length was positive, but the strength of this correlation decreased with increasing yeast concentration. Genetic variation and genotype-by-environment (G x E) interactions were observed for both traits. We identified quantitative trait loci (QTL), epistatic, QTL-by-environment, and epistatic-by-environment interactions for both traits and their scaling relationships. The results are discussed in the context of multivariate trait evolution.

Taylor's spatial scaling law concerns the relation between the variance and the mean population counts within areas of a given size. For a range of area sizes, the log of the variance often is an approximately linear function of the mean with a slope between 1 and 2, depending on the range of areas considered. In this paper, we investigate this relationship theoretically for random quadrat samples within a large area. The model makes a distinction between the local point process determining the position of each individual and the population density described by a spatial covariance function. The local point process and the spatial covariance of population density both contribute to the general relationship between the mean and the variance in which the slope may begin at 1, increase to 2, and decrease to 1 again. It is demonstrated by an example that the slope theoretically may exceed 2 by a small amount for very regular patterns that generate spatial covariance functions that increase in certain intervals. We also show how properties of population dynamics in space and time determine this relationship. Key words: covariance function; migration; point process; population counts, population density; population dynamics; Taylor's spatial scaling law.

The cranial base is one of the major foci of interest in functional craniology. The evolution and morphogenesis of this structure are still poorly known and rather controversial because of multifactorial influences and polyphasic stages. Endocranial dynamics are associated anteriorly with the upper facial structures, laterally with the mandibular system and midsagittally with brain development. In the present study, we investigated the endocranial morphology of modern humans using 3D landmark-based approaches, i.e. geometric morphometrics and Euclidean distance matrix analysis. The structure of endocranial variation is poorly integrated, with only weak reciprocal influences among the three fossae. Some major variations are associated with changes in the posterior fossa, with possible consequences on the anterior areas. These main patterns of integration are hypothesized to be influenced by the connective tensors of the dura layers. Static allometry and sex differences are largely related to the ontogenetic sequences, characterized by early maturation of the anterior fossa with respect to the middle and posterior regions (i.e., relatively shorter posterior part of the planum sphenoideum and vertical lengthening of the clivus in males). The relative independence between the endocranial fossae, as well as their structural connection through the meningeal tensors, must be carefully considered in studies on the evolutionary dynamics, since they lead to mosaic changes through phylogeny. KEY WORDS cranial base; endocranial fossae; functional craniology; morphological integration

A decrease in the surface area per unit volume is a well known constraint setting limits to the size of organisms at both the cellular and whole-organismal levels. Similar constraints may apply to social groups as they grow in size. The communal three-dimensional webs that social spiders build function ecologically as single units that intercept prey through their surface and should thus be subject to this constraint. Accordingly, we show that web prey capture area per spider, and thus number of insects captured per capita, decreases with colony size in a neotropical social spider. Prey biomass intake per capita, however, peaks at intermediate colony sizes because the spiders forage cooperatively and larger colonies capture increasingly large insects. A peaked prey biomass intake function would explain not only why these spiders live in groups and cooperate but also why they disperse only at large colony sizes, thus addressing both sociality and colony size range in this social spider. These findings may also explain the conspicuous absence of social spiders from higher latitudes and higher elevations, areas that we have previously shown to harbor considerably fewer insects of the largest size classes than the lowland tropical rainforests where social spiders thrive. Our findings thus illustrate the relevance of scaling laws to the size and functioning of levels of organization above the individual. Anelosimus | cooperation | group foraging | sociality | allometry

Mammalian chewing rate scales inversely to body mass (M); however, controversy exists over the value of the scaling exponent. Different mechanisms explain different values of the scaling exponent; hence, a better estimate of the exponent would provide insight into the mechanisms governing chewing rate across mammalian species. We evaluated the relationship between mean chewing cycle duration (CD; i.e., the inverse of mean chewing rate) and M in 132 species and removed phylogenetic effects by using an independent contrast method currently used in evolutionary biology studies. A one-third-power law resulted when independent contrasts were not used; however, a one-third- to one-fourth-power law resulted when independent contrasts were used to remove phylogenetic effects. We hypothesize that variation in the scaling exponent is due to natural selection acting to increase metabolic efficiency; and variation in the complexity of mandibular kinematics, motor control asymmetry, and mandibular biomechanics, which may act to increase CDs above the 'ideal' one-fourth-power law. Future studies should consider effects due to jaw-movement kinematics, motor control issues, and biomechanics. Key words: allometry, chewing rate, independent contrasts, mastication, phylogeny, rhythmic movements

For squirrels, physical size varies with ancestry, locomotion, and sex. Body length has little variation associated with subfamilies or tribes but varies significantly among genera within tribes. Thus, patterns in body size among genera represent more recent evolutionary pressures. Flying squirrels weigh less than similarly sized tree or ground squirrels but ecological profile and ancestry are confounded for flying squirrels. Tail length has clear relationships with ecological profile in squirrels. Tail length is shorter in ground squirrels, longer in tree squirrels, and longest in flying squirrels. In addition, in arboreal squirrels, females have longer tails, relative to body length, than those of males. This latter result suggests that reproductive constraints can influence external features of morphology. Key words: allometry, body size, flying squirrels, gliding locomotion, ground squirrels, tail length, tree squirrels

The sciurid tribe Marmotini has a distinctive, highly specialized reproductive profile characterized by annually produced litters of many offspring, each of small mass and fast growth rate. However, not all genera of marmotines follow the reproductive profile of the tribe. In fact, included in the tribe are squirrels with the highest and lowest energetic investment into reproduction of the entire family. Because of its large litter size, Ammospermophilus has the largest energetic investment into reproduction of nearly all squirrels. Also, Ammospermophilus is not limited to 1 litter per year. At the opposite extreme, Marmota has the smallest energetic investment into reproduction of all squirrels. Of the other 4 marmotine genera, reproduction in Cynomys is similar to that of Marmota, whereas that of Tamias is similar to that of Ammospermophilus; reproduction in Sciurotamias and Spermophilus may reflect their phylogenetic positions. Litter size in the basal Sciurotamias (2.5) is the lowest for all marmotines and is closest to that of other squirrel taxa. Consistent with the probable paraphyly of the genus, spermophiline data are the most variable and many reproductive characters sort along the probable clades within Spermophilus. For spermophilines, a litter size of 4 is probably basal and the larger litter sizes of 6-8 in some clades are derived. Two other derived features are the low offspring biomass in Marmota and a short time between conception and weaning in a spermophiline clade of predominantly New World species. Overall, reproductive investment within marmotines has followed 2 patterns: the larger marmotines (Cynomys and Marmota) have a reduced annual energetic investment compared with a higher reproductive investment in the smaller marrnotines (Ammospermophilus and Tamias). Thus, body size is a key aspect in the diversification of reproductive patterns in the Marmotini. Key words: allometry, gestation, ground squirrels, lactation, litter size, Marmotini, reproductive effort, reproductive investment

The distinctive features of reproduction in squirrels are the lack of allometric influences on the duration of reproductive investment; the strong allometric influences on offspring mass; and a trade-off between number and size of young, suggesting an important developmental component to reproduction. Lengths of gestation and lactation do not vary with body size but neonatal and weaning mass do. Apparently, the major constraint on reproduction in squirrels is not resources per se (food, calories, minerals, or water) but rather the length of time such resources are available. Squirrels adjust growth rate to fit the timing of resource abundance. Within the familial reproductive pattern, arboreal squirrels invest more into reproduction than do ground squirrels. Flying squirrels (Pteromyini) have a larger temporal investment into reproduction but a smaller energetic investment compared with other squirrels. Ground squirrels do not have a distinct reproductive profile, because marmotine and nonmarmotine ground squirrels differ. Marmotine ground squirrels have a small temporal investment and a large energetic investment on a per litter but not on an annual basis. Nonmarmotine ground squirrels have a reproductive pattern similar to that of tree squirrels, a pattern intermediate between marmotines and flying squirrels. Within this locomotor-ecological framework, reproductive patterns differ among subfamilies. Tribes differ in having few (2-4) versus many (4-8) young, and in the relative allocation of investment into gestation versus lactation. Specific environmental influences on reproduction in squirrels occur at lower taxonomic levels within the framework of a broad reproductive pattern set by earlier radiations into particular locomotor and nest-site niches. Key words: flying squirrels, gestation, ground squirrels, lactation, litter size, reproduction, reproductive effort, reproductive investment, Sciuridae, tree squirrels

Research indicates that increases in total leaf area ([A.sub.T]) may fail to keep pace with increases in total leaf mass ([M.sub.L]) across plants differing in size (e.g., as measured by stem diameter, D). This 'diminishing returns' hypothesis predicts that the scaling exponent for [A.sub.T] vs. ME will be less than one and that the exponent for specific leaf mass (i.e., [A.sub.T] / [M.sub.I]) vs. D will be negative. These predictions were examined using data from 46 plants ranging between 0.125 cm D [less than or equal to] 0.485 m across 25 woody dicot species. Standardized major axis slopes were used to quantify scaling exponents and random effects models were used to quantify species and size effects on the numerical values of exponents. The exponents for [A.sub.T] vs. [M.sub.L] and [A.sub.T] / [M.sub.L] vs. D differed among species and different species groupings. In general, the exponent for [A.sub.T] vs. [M.sub.L] was less than one and the exponent for [A.sub.T] / [M.sub.L] VS. D was negative, as predicted. However, random effects models indicated that species effects overshadowed size effects, although size effects were statistically significant. The diminishing returns hypothesis therefore receives statistical support, i.e., although the numerical values of exponents are 'species-dependent,' they are less than unity, as predicted by theory. Key words: allometry; functional foliar traits; leaf area; leaf economics; leaf mass; leaf number; random effects models; scaling relationships; specific leaf area.

This study investigated the effects of using different size variables for interpretations of relative orbit size and mandibular robusticity. Thirty-three skull measurements taken on 385 platyrrhines representing 12 of 16 New World monkey genera (in addition to body mass and total body length) were used singly and in combinations (by taking the geometric mean of all measurements) as size variables to produce relative size indices of orbit area and mandibular thickness. These indices were then compared to investigate which size variables proved effective at differentiating nocturnal from diurnal taxa and hard object from soft object feeders based upon results from previous biomechanical studies. It was found that certain groups of size variables consistently produced the a priori expectations and resulted in lower coefficients of variation. The general principles shared by these size variables were that they sampled anatomically remote regions of the skull that appear to be functionally independent from the trait being evaluated and they were nearly always geometric mean combinations composed of a relatively high number ([greater than or equal to] 12) of large measurements. Suggestions are also presented for amending these principles for use with incomplete material such as fossils. KEY WORDS size adjustment; mandibular robusticity; orbit size; allometry

Among the most studied relationships in ecology are those of population density with (1) body size and (2) species distribution. The first relationship, in conjunction with metabolic rate, determines the energy flows through species communities, whereas the second relationship shows how local communities are influenced by the species history of dispersal and establishment. Traditionally, these two relationships have been examined separately. Here, I explored how diatom density was affected by cell size (biovolume) and species distribution in benthic and planktonic stream habitats all the way from individual localities and hydrologic systems (regions) to the entire United States. At all scales, density was predominantly a negative function of biovolume and a positive function of distribution. Biovolume was more strongly related to density in the benthos than in the phytoplankton. Partial regressions revealed that biovolume, by itself, explained a substantially higher percentage of the variance in density at local than at regional and continental scales. Conversely, species distribution was a much more important descriptor of density at larger scales and a slightly better predictor than biovolume at local scales. At large scales density was explained primarily by distribution and, to a lesser extent and only in the benthos, by the covariance of distribution and biovolume, whereas biovolume was a marginal predictor in all habitats. This discovery suggests that the strong relationships between density and body size, reported for populations ranging from unicellular algae to mammals, may be less direct than previously thought but mediated by large-scale species distributions. Key words: abundance-distribution; allometric scaling laws; density-body size; diatoms; macroecology; NAWQA.

Plant mortality and birth rates are critical components of plant life history affecting the stability of plant populations and the ecosystems they form. Although allometric theory predicts that both plant birth and mortality rates should be size-dependent, this prediction has not yet been tested across plants ranging the full size spectrum. Here we show that both population mortality and population birth rates scale as the--1/4 power and plant lifespan as the 1/4 power of plant mass across plant species spanning from the tiniest phototrophs to the largest trees. Whereas the controls on plant lifespans are as yet poorly understood, our findings suggest that plant mortality rates have evolved to match population birth rates, thereby helping to maintain plant communities in equilibrium and optimizing plant life histories. birth | lifespan | mortality | phototrophic organisms | population growth

The hands and feet of primates fulfill a variety of biological roles linked with food acquisition and positional behavior. Current explanations of shape differences in cheiridial morphology among prosimians are closely tied to body size differences. Although numerous studies have examined the relationships between body mass and limb morphology in prosimians, no scaling analysis has specifically considered hand and foot dimensions and intrinsic proportions. In this study, we present such an analysis for a sample of 270 skeletal specimens distributed over eight prosimian families. The degree of association between size and shape was assessed using nonparametric correlational techniques, while the relationship between each ray element length and body mass (from published data and a body mass surrogate) was tested for allometric scaling. Since tarsiers and strepsirrhines encompass many taxa of varying degrees of phylogenetic relatedness, effective degrees of freedom were calculated, and comparisons between families were performed to partially address the problem of statistical nonindependence and 'phylogenetic inertia.' Correlational analyses indicate negative allometry between relative phalangeal length (as reflected by phalangeal indices) and body mass, except for the pollex and hallux. Thus, as size increases, there is a significant decrease in the relative length of the digits when considering all prosimian taxa sampled. Regression analyses show that while the digital portion of the rays scales isometrically with body mass, the palmar/plantar portion of the rays often scales with positive allometry. Some but not all of these broadly interspecific allometric patterns remain statistically significant when effective degrees of freedom are taken into account. As is often the case in interspecific scaling, comparisons within families show different scaling trends in the cheiridia than those seen across families (i.e., lorisids, indriids, and lemurids exhibit rather different allometries). The interspecific pattern of positive allometry that appears to best characterize the metapodials of prosimians, especially those of the foot, parallels differences found in the morphology of the volar skin. Indeed, relatively longer metapodials appear to covary with flatter and more coalesced volar pads, which in turn slightly improve frictional force for animals that are at a comparative disadvantage while climbing because of their larger mass. Despite the essentially isometric relationship found between digit length and body mass across prosimians, examination of the residual variation reveals that tarsiers and Daubentonia possess, relative to their body sizes, remarkably long fingers. Such marked departures between body size and finger length observed in these particular primates are closely linked with specialized modes of prey acquisition and manipulation involving the hands. Am J Phys Anthropol 133:828-840, 2007. KEY WORDS allometry; body mass; cheiridia; strepsirrhines; lemurs; galagos; lorises; tarsiers

Managing ecosystems for resilience--the capacity to maintain function in response to perturbation--is among the most pressing ecological and socioeconomic imperatives of our time. The variability of biological and ecological systems […]

More than 5,000 measurements from 1,943 plant species were used to explore the scaling relationships among the foliar surface area and the dry, water, and nitrogen/phosphorus mass of mature individual leaves. Although they differed statistically, the exponents for the relationships among these variables were numerically similar among six species groups (ferns, graminoids, forbs, shrubs, trees, and vines) and within 19 individual species. In general, at least one among the many scaling exponents was foliar traits | plant allometry | scaling relations

Many scarab beetles produce rigid projections from the body called horns. The exaggerated sizes of these structures and the staggering diversity of their forms have impressed biologists for centuries. Recent comparative studies using DNA sequence-based phylogenies have begun to reconstruct the historical patterns of beetle horn evolution. At the same time, developmental genetic experiments have begun to elucidate how beetle horns grow and how horn growth is modulated in response to environmental variables, such as nutrition. We bring together these two perspectives to show that they converge on very similar conclusions regarding beetle evolution. Horns do not appear to be difficult structures to gain or lose, and they can diverge both dramatically and rapidly in form. Although much of this work is still preliminary, we use available information to propose a conceptual developmental model for the major trajectories of beetle horn evolution. We illustrate putative mechanisms underlying the evolutionary origin of horns and the evolution of horn location, shape, allometry, and dimorphism. allometry development | phenotypic plasticity | sexual selection | weapons