Differences In Allometry Research Articles

Clade-Specific Allometries in Avian Basal Metabolic Rate Demand a Broader Theory of Allometry.

AbstractMany attempts at providing a single-scale exponent and mechanism to explain metabolic rate assert a monolithic selective mechanism for allometries, characterized by a universal allometric scale power (usually chosen to be 0.75). To test for the deviations from universal allometric scaling, we gathered data from previously published metabolic measurements on 903 bird species and performed regressions of log(basal metabolic rate) and log(body mass) for (1) all birds and (2) 20 monophyletic clades within birds. We constructed two Bayesian linear mixed models-one included ecological variables and the other included data for mammals from Sieg et al. (2009). Overall allometric patterns differed significantly among clades of birds, and some clades were not consistent with the 0.75 scale power. We were unable to find apparent physiological, morphological, phylogenetic, or ecological characteristics among clades, predicting a difference in allometry or consistency with any previously proposed universal allometry. The Bayesian analysis illuminated novel bivariate, clade-specific differences in scaling slope-intercept space, separating large groups of birds and mammals. While significantly related to basal metabolic rate, feeding guild and migratory tendency had small effects compared to clade and body mass. We propose that allometric hypotheses, in general, must extend beyond simple overarching mechanisms to allow for conflicting and interacting influences that produce allometric patterns at narrower taxonomic scales-perhaps including other processes whose optimization may interfere with that of the system proposed by the metabolic theory of ecology.

Sex differences in allometry for phenotypic traits in mice indicate that females are not scaled males

Sex differences in the lifetime risk and expression of disease are well-known. Preclinical research targeted at improving treatment, increasing health span, and reducing the financial burden of health care, has mostly been conducted on male animals and cells. The extent to which sex differences in phenotypic traits are explained by sex differences in body weight remains unclear. We quantify sex differences in the allometric relationship between trait value and body weight for 363 phenotypic traits in male and female mice, recorded in >2 million measurements from the International Mouse Phenotyping Consortium. We find sex differences in allometric parameters (slope, intercept, residual SD) are common (73% traits). Body weight differences do not explain all sex differences in trait values but scaling by weight may be useful for some traits. Our results show sex differences in phenotypic traits are trait-specific, promoting case-specific approaches to drug dosage scaled by body weight in mice.

Egg size does not universally predict embryonic resources and hatchling size across annual killifish species

Egg size has a crucial impact on the reproductive success of a mother and the performance of her offspring. It is therefore reasonable to employ egg size as a proxy for egg content when studying variation in offspring performance. Here, we tested species differences in allometries of several egg content parameters with egg area. We measured individual eggs in five species of annual killifish (Cyprinodontiformes), a group of fish where egg banks permit population survival over dry season. Apart from comparing allometric scaling exponents, amounts and compositions of egg components across the different species, we assessed the explanatory power of egg area for egg wet and dry weight and for hatchling size. We found notable species-specific allometries between egg area and the other egg parameters (egg dry weight and water content, elemental composition and triglyceride content). Across species, egg area predicted egg wet weight with highest power. Within species, coefficients of determination were largest in A. elongatus, a large piscivorous species with large eggs. Our study shows that systematically using egg area as a proxy of egg content between different species can ignore relevant species-specific differences and mask within-species variability in egg content.

The effect of allometric partitioning on herbivory tolerance in four species in South China.

Herbivory tolerance can offset the negative effects of herbivory on plants and plays an important role in both immigration and population establishment. Biomass reallocation is an important potential mechanism of herbivory tolerance. To understand how biomass allocation affects plant herbivory tolerance, it is necessary to distinguish the biomass allocations resulting from environmental gradients or plant growth. There is generally a tight balance between the amounts of biomass invested in different organs, which must be analyzed by means of an allometric model. The allometric exponent is not affected by individual growth and can reflect the changes in biomass allocation patterns of different parts. Therefore, the allometric exponent was chosen to study the relationship between biomass allocation pattern and herbivory tolerance. We selected four species (Wedelia chinensis, Wedelia trilobata, Merremia hederacea, and Mikania micrantha), two of which are invasive species and two of which are accompanying native species, and established three herbivory levels (0%, 25% and 50%) to compare differences in allometry. The biomass allocation in stems was negatively correlated with herbivory tolerance, while that in leaves was positively correlated with herbivory tolerance. Furthermore, the stability of the allometric exponent was related to tolerance, indicating that plants with the ability to maintain their biomass allocation patterns are more tolerant than those without this ability, and the tendency to allocate biomass to leaves rather than to stems or roots helps increase this tolerance. The allometric exponent was used to remove the effects of individual development on allocation pattern, allowing the relationship between biomass allocation and herbivory tolerance to be more accurately explored. This research used an allometric model to fit the nonlinear process of biomass partitioning during the growth and development of plants and provides a new understanding of the relationship between biomass allocation and herbivory tolerance.

Interspecific variation in tropical tree height and crown allometries in relation to life history traits

<p><strong>Abstract.</strong> Tree allometric relationships are widely employed to estimate forest biomass and production, and are basic building blocks of dynamic vegetation models. In tropical forests, allometric relationships are often modeled by fitting scale-invariant power functions to pooled data from multiple species, an approach that fails to reflect finite size effects at the smallest and largest sizes, and that ignores interspecific differences in allometry. Here, we analyzed allometric relationships of tree height (9884 individuals) and crown area (2425) with trunk diameter using species-specific morphological and life history data of 162 species from Barro Colorado Island, Panamá. We fit nonlinear, hierarchical models informed by species traits and assessed the performance of three alternative functional forms: the scale-invariant power function, and the saturating Weibull and generalized Michaelis-Menten (gMM) functions. The relationship of tree height with trunk diameter was best fit by a saturating gMM model in which variation in allometric parameters was related to interspecific differences in sapling growth rates, a measure of regeneration light demand. Light-demanding species attained taller heights at comparatively smaller diameters as juveniles and had shorter asymptotic heights at larger diameters as adults. The relationship of crown area with trunk diameter was best fit by a power function model incorporating a weak positive relationship between crown area and species-specific wood density. The use of saturating functional forms and the incorporation of functional traits in tree allometric models is a promising approach to improve estimates of forest biomass and productivity. Our results provide an improved basis for parameterizing tropical tree functional types in vegetation models.</p>

A meta‐analysis of zooplankton functional traits influencing ecosystem function

The use of functional traits to characterize community composition has been proposed as a more effective way to link community structure to ecosystem functioning. Organismal morphology, body stoichiometry, and physiology can be readily linked to large-scale ecosystem processes through functional traits that inform on interspecific and species-environment interactions; yet such effect traits are still poorly included in trait-based approaches. Given their key trophic position in aquatic ecosystems, individual zooplankton affect energy fluxes and elemental processing. We compiled a large database of zooplankton traits contributing to carbon, nitrogen, and phosphorus cycling and examined the effect of classification and habitat (marine vs. freshwater) on trait relationships. Respiration and nutrient excretion rates followed mass-dependent scaling in both habitats, with exponents ranging from 0.70 to 0.90. Our analyses revealed surprising differences in allometry and respiration between habitats, with freshwater species having lower length-specific mass and three times higher mass-specific respiration rates. These differences in traits point to implications for ecological strategies as well as overall carbon storage and fluxes based on habitat type. Our synthesis quantifies multiple trait relationships and links organisms to ecosystem processes they influence, enabling a more complete integration of aquatic community ecology and biogeochemistry through the promising use of effect traits.

Efficacy of generic allometric equations for estimating biomass: a test in Japanese natural forests

Accurate estimation of tree and forest biomass is key to evaluating forest ecosystem functions and the global carbon cycle. Allometric equations that estimate tree biomass from a set of predictors, such as stem diameter and tree height, are commonly used. Most allometric equations are site specific, usually developed from a small number of trees harvested in a small area, and are either species specific or ignore interspecific differences in allometry. Due to lack of site-specific allometries, local equations are often applied to sites for which they were not originally developed (foreign sites), sometimes leading to large errors in biomass estimates. In this study, we developed generic allometric equations for aboveground biomass and component (stem, branch, leaf, and root) biomass using large, compiled data sets of 1203 harvested trees belonging to 102 species (60 deciduous angiosperm, 32 evergreen angiosperm, and 10 evergreen gymnosperm species) from 70 boreal, temperate, and subtropical natural forests in Japan. The best generic equations provided better biomass estimates than did local equations that were applied to foreign sites. The best generic equations included explanatory variables that represent interspecific differences in allometry in addition to stem diameter, reducing error by 4-12% compared to the generic equations that did not include the interspecific difference. Different explanatory variables were selected for different components. For aboveground and stem biomass, the best generic equations had species-specific wood specific gravity as an explanatory variable. For branch, leaf, and root biomass, the best equations had functional types (deciduous angiosperm, evergreen angiosperm, and evergreen gymnosperm) instead of functional traits (wood specific gravity or leaf mass per area), suggesting importance of other traits in addition to these traits, such as canopy and root architecture. Inclusion of tree height in addition to stem diameter improved the performance of the generic equation only for stem biomass and had no apparent effect on aboveground, branch, leaf, and root biomass at the site level. The development of a generic allometric equation taking account of interspecific differences is an effective approach for accurately estimating aboveground and component biomass in boreal, temperate, and subtropical natural forests.

Differences in allometry and population structure between native and invasive populations of a tropical tree

Introduced species can establish self-replacing populations in introduction sites despite climatic differences between these sites and the native range. Schizolobium parahyba (Fabaceae) is a fast-growing tree from the Atlantic Forest in Brazil and is invasive in semideciduous forests. We studied the allometry and population structure of S. parahyba within its native and invaded ranges. We expected to find differences in allometric relationships and ontogenetic stage sizes between forest types. We measured individuals within native and invaded ranges and analysed height : diameter allometry using standardised major axis regression. We used the chi-squared test and permutational multivariate analysis of variance to compare the frequencies of individuals of each ontogenetic stage between native and invasive populations. We found that allometry differed between forest types for seedlings, but only marginally for adults. The population structure differed between ranges and suggests active recruitment of juvenile and subadult plants in invaded sites, where the species is naturalising.

Canine Evolution in Sabretoothed Carnivores: Natural Selection or Sexual Selection?

The remarkable elongated upper canines of extinct sabretoothed carnivorous mammals have been the subject of considerable speculation on their adaptive function, but the absence of living analogues prevents any direct inference about their evolution. We analysed scaling relationships of the upper canines of 20 sabretoothed feliform carnivores (Nimravidae, Barbourofelidae, Machairodontinae), representing both dirk-toothed and scimitar-toothed sabretooth ecomorphs, and 33 non-sabretoothed felids in relation to body size in order to characterize and identify the evolutionary processes driving their development, using the scaling relationships of carnassial teeth in both groups as a control. Carnassials display isometric allometry in both sabretooths and non-sabretooths, supporting their close relationship with meat-slicing, whereas the upper canines of both groups display positive allometry with body size. Whereas there is no statistical difference in allometry of upper canine height between dirk-toothed and scimitar-toothed sabretooth ecomorphs, the significantly stronger positive allometry of upper canine height shown by sabretooths as a whole compared to non-sabretooths reveals that different processes drove canine evolution in these groups. Although sabretoothed canines must still have been effective for prey capture and processing by hypercarnivorous predators, canine morphology in these extinct carnivores was likely to have been driven to a greater extent by sexual selection than in non-sabretooths. Scaling relationships therefore indicate the probable importance of sexual selection in the evolution of the hypertrophied sabretooth anterior dentition.

Allometry Varies among 6-Year-Old Pinus taeda (L.) Clones in the Virginia Piedmont

Clonal forestry is becoming a reality in the southeastern United States owing to recent improvements in somatic embryogenesis for Pinus taeda (L.). Differences in aboveground and belowground carbon allocation between individual genotypes could have significant implications forproductivity and carbon sequestration and cycling in clonal plantations. We assessed biomass partitioning, allometry, coarse root morphology, and crown size of 10 P. taeda clones at age 6 in the Virginia Piedmont in control and operationally fertilized plots. Clonal effects were observedfor biomass partitioning to foliar, branch, stem, taproot, and lateral root fractions; allometric relationships including root/shoot, stem/foliage, branch/foliage, and stem/taproot ratios; root morphology; and crown size. Clonal differences in biomass partitioning were the result of both differencesin allometry and differences in growth rates. Growth efficiency (stem/foliage ratio) showed a twofold difference among the two most disparate clones even after standardizing for different growth rates. Clone-by-fertilizer interactions were observed for total, aboveground, and belowground biomassand for root depth sampled up to 1 m. Differences in partitioning and allometry were not clearly tied to tree or stem growth rates, indicating that there may be opportunities to select and deploy clones with rapid stem volume growth rates that have biomass partitioning patterns tailored tovarious precision-silviculture applications.

우리나라 남해에 분포하는 붕장어(Conger myriaster)의 연령과 성장

【Age and growth of whitespotted conger Conger myriaster were estimated using right sagittal otoliths from 495 fish collected from February, 2004, to January, 2005, in the southern coastal waters of Korea. Examination of the outer margin of the otoliths showed that opaque zones formed once a year and annual rings formed from April to June. The ages of the specimens examined ranged from 3 to 8 years. Whitespotted conger spawn from December to March. Allometry between preanal length and total weight can be expressed as $TW=0.0350{\times}PL^{2.9173}$ ( $R^2=0.89$ ). There was no significant difference in allometry between females and males (P>0.05). The estimated VBF growth equation was $L_t=415.2(1-e^{-0.1457(t+0.4654)})$ .】

Is the reproduction of Donax trunculus affected by their sites of origin contrasted by their level of contamination?

The reproductive cycle of bivalves is regulated by several natural environmental factors but exposure to chemical pollutants can also interfere and may result in advanced or delayed spawning season. To our knowledge, the gametogenic cycle of the suspension-feeder bivalve Donax trunculus has not yet been used as biomonitoring tool in ecotoxicological surveys. The aim of this study was to examine over a year physiological reproductive endpoints (sex-ratio, gametogenic and energy reserve cycles) and biological indices (condition index, allometry) in D. trunculus originating from two sites differing by their level of contamination. Specimens were collected bimonthly from November 2008 to October 2009 from a polluted site (Radès Méliane) and a comparatively reference site (Sidi Jehmi) in the Gulf of Tunis (Tunisia). Five stages were depicted by histological examination of gonads: undifferentiated, developing, mature, spawn and spent. Differences in the gametogenic cycle according to the site of origin of bivalves were observed. The spawning period began in March and was maximum in May in bivalves from both sites, but the percentage of spawning animals was higher in the polluted site vs the reference site. The spawning period was shorter in animals from the polluted site comparatively to the reference site. Energy reserves (glycogen, lipids) were higher in March and May comparatively to the other studied periods in bivalves from both sites. Lower energy reserves levels were usually observed in animals from the polluted site compared to the reference site. Seasonal variations of the condition index were associated to the reproductive and nutritive status of bivalves. Differences in allometry were depicted between bivalves from both studied sites. If we try to link allometry, energy reserves and reproduction, it can be hypothesized that for bivalves from the reference site, energy reserves are allocated to gametogenesis and length growth. For bivalves from the polluted site, energy reserves could be devoted to tolerance to chemical stress and to reproductive processes. Therefore, D. trunculus appears as a suitable sentinel species for the assessment of the ecotoxicological risk of contaminants such as endocrine disruptors.

Allometry of some woody plant species in a Brazilian savanna after two years of a dry season fire

Studies of allometry are important in explaining effects of fire and herbivory, for estimating biomass in forests, and so on. There has been extensive research on plant allometry in temperate and tropical forests, showing that plant architecture often adjusts to the elastic similarity model, but not in Brazilian savannas (cerrado). We studied allometry of Dalbergia miscolobium, Diospyros hispida, Erythroxylum suberosum, Miconia albicans, M. ligustroides, Schefflera vinosa, and Xylopia aromatica in a cerrado sensu stricto area that was affected by a fire in August 2006. We expected that the study species would not adjust to any of the allometric models considered common for forest species ("constant stress", "elastic similarity", and "geometric growth"), and that there would be differences in allometry in burnt and unburnt patches. We sampled two species in 60 5 × 5 m contiguous plots placed in three transects, and five species in 100 5 × 5 m contiguous plots placed in five transects, where we measured the diameters at soil level (DSL) and the heights of all shoots. We used standardized major axis regressions on log-transformed data. The regression slope between the height and DSL was higher than 1.0 (p < 0.05) for four species, showing a greater height than would be expected under geometric growth, not predicted by theoretical models. We found significant differences (p < 0.05) in regression slopes and/or correlation coefficients between burnt and unburnt plots for five species, indicating that fire may influence plant allometry in the Brazilian cerrado, and that such a response is highly variable between species.

Differences in growth and light requirement of two sympatric congeneric tree species in an Indonesian floodplain forest

A prominent hypothesis to account for the maintenance of the woody species diversity in tropical forests is niche differentiation with respect to resources (Ashton 1969, Connell 1978). According to the hypothesis, species can coexist when each species is specialized for a specific set of growth conditions. Spatial and temporal variations in the forest understorey light conditions can be an important niche gradient. If species are adapted to a certain light condition for optimizing growth and share different optimal light conditions with each other, they can coexist by reducing direct competition; i.e. the regeneration niche differentiation sensu Grubb (1977). Species difference in rate of exclusion of trees in suboptimal light conditions due to mortality also contributes to species coexistence. Many scientists have emphasized the importance of the spatial and temporal variations in understorey light conditions on species coexistence in tropical forests (Clark & Clark 1992, Kohyama & Hotta 1990, Poorter & Arets 2003). Allometry and architecture of a tree reflect strategies of space occupation in a forest (King 1990, Kohyama & Hotta 1990, Poorter & Werger 1999). Thus, tree allometry and architecture provide information on species coexistence. Yamada et al. (2005) analysed interspecific differences in allometry and architecture of two sympatric congeneric species, Pterospermum diversifolium and P. javanicum, in a Bornean floodplain forest and concluded that the sapling growth strategy of P. diversifolium appears to be dynamic, emphasizing the opportunistic use of light following a disturbance, whereas that of P. javanicum appears to be static, emphasizing better leaf display for current light conditions. Based on these results, they proposed equilibrium coexistence mechanisms between the two species in a community. The advantage of these strategies depends on context, and thus the two species may coexist by adopting different regeneration niches based on differing understorey light conditions; P. diversifolium was hypothesized to outperform P. javanicum in bright microsites, and on the other hand, P. javanicum is hypothesized to outperform P. diversifolium in shaded microsites.

Growth and mortality are related to adult tree size in a Malaysian mixed dipterocarp forest

Tree stature is an important ecological and silvicultural characteristic and the high diversity of many tropical forests is associated with a broad range in species stature. A measure of adult size, the 95th percentile of trunk diameter of all diameters ≥0.1 × maximum observed diameter ( D95 0.1) was found to be independent of species abundance and highly correlated with maximum height. D95 0.1 was determined for 573 species with at least 20 trees with diameters ≥0.1 × maximum observed diameter in old-growth, lowland evergreen forest on the 50-ha forest dynamics plot at Pasoh Forest Reserve, Malaysia. These species, comprising 98.3% of all trees ≥1 cm diameter in the plot, were then divided into five life forms of differing stature; shrubs ( D95 0.1 < 5 cm), treelets (5 cm ≤ D95 0.1 < 12 cm), understory trees (12 cm ≤ D95 0.1 < 25 cm), canopy trees (25 cm ≤ D95 0.1 < 60 cm) and emergents ( D95 0.1 ≥ 60 cm). Each life form showed a distinctive pattern of mortality versus trunk diameter, but all showed higher mortality in the largest diameter class per life form. Mean growth rates increased with trunk diameter within each life form, consistent with reported increases in irradiance with height at Pasoh. Among trees of similar diameter, growth rates increased across life forms from the smallest to largest. These differences in growth rate among life forms may be due to associated differences in allometry, photosynthetic capacity and reproductive allocation.

Sexually dimorphic proportions of the harbour porpoise (Phocoena phocoena) skeleton

Sexual differences in growth, allometric growth patterns and skeletal proportions were investigated by linear measurements of skeletal parts on 225 harbour porpoises (Phocoena phocoena) from the inner Danish and adjacent waters. Females show larger asymptotic sizes and extended period of growth compared with males. Measurements of the skull and flipper bones show negative allometry, whereas those of the bones of the body generally show positive allometry. There are no statistically significant intersexual differences in allometry except for the pelvic bones, where the males show stronger positive allometry. Throughout the range of individual sizes, females have significantly larger skulls and shorter vertebral columns than males for similarly sized individuals. In fully grown specimens, the condylobasal length of females makes up a smaller proportion of total length, and the vertebrae make up a larger proportion as compared with males. As these characters show negative and positive allometry, respectively, it is suggested that males finish their development at an earlier stage than females, retaining more paedomorphic proportions of the skeleton. Paedomorphosis in fully grown males relative to females is also found in the vertebral epiphyses that mature later in males than females, although the males finish growth at a younger age.

Quantitative morphological variation in Sagitta setosa Müller, 1847 (Chaetognatha) and two closely related taxa

This paper reviews the quantitative morphological variation published for Sagitta setosa Müller, 1847 and two other species described within the S. serosa-complex, viz., S. euxina Moltschanoff, 1909 from the Black Sea, and S. batava Biersteker &amp; Van der Spoel, 1966 from the Scheldt Estuary (Netherlands). Data on total (body) length, caudal length, numbers of teeth and hooks, ovary length, and dimensions of fins are compared between these three taxa. Additionally, samples from the North Sea, Mediterranean, and Black Sea are compared to look for geographic differences. Specimens from the Mediterranean were smallest with relatively long caudal segments, and few teeth and hooks, whereas specimens from the Black Sea were largest with relatively short caudal segments and many teeth and hooks. Specimens from the North Sea were intermediate with regards to these characters, but ranges overlapped and there were no obvious differences in allometry. These differences may be ecophenotypic, as the warm and salty Mediterranean Sea and cool and brackish Black Sea are at opposite ends of the environmental spectrum. The dimensions related to the fins showed clearer distinction between samples from different geographical areas, and slight differences in allometry. However, few data were available and little is known about the variance within each geographical area. We found more variation in quantitative characters within S. setosa from different parts of its range than between S. setosa and either S. batava, or S. euxina. Sagitta batava conformed to S. setosa in terms of all the morphological characters considered. The data for S. setosa derived from Biersteker &amp; Van der Spoel (1966) were atypical and were found to be based on misidentifications of S. elegans. Therefore, we concluded that S. batava cannot be considered a separate taxon. For S. euxina, the data were inconclusive. Quantitative data completely overlapped between S. setosa from the Black Sea and S. euxina, but few data of S. setosa from the Black Sea were available. Because samples were either composed entirely of S. setosa or S. euxina (depending on sampling season and depth)and there was a large variation in body lengths and relative ovary lengths, we consider it possible that these samples represent seasonal variants of one and the same species.

Prenatal sex ratios influence sexual dimorphism in a reptile.

The prenatal environment influences offspring traits in a variety of ways and in a wide range of taxa. For example, maternal allocation of steroids to the eggs influences offspring traits in birds, and in some mammals the intrauterine position influences morphological, behavioural, and physiological traits due to sex-related steroid transfer between sibling fetuses. We show that similar phenomena occur in the common lizard (Lacerta vivipara), a viviparous reptile. Females developing in male-biased clutches had a more masculine allometry (relatively larger heads) at parturition than females developing in female-biased clutches. Males were correspondingly feminized in female-biased clutches. The effects could either be due to diffusion of steroids produced by the offspring or by a general tendency for females to allocate steroids according to the sex ratio of her clutch. Subsequent to parturition, the sexes differed in their growth trajectories depending on sex ratio environment. In males, the difference in allometry between sex ratio environments remained over time, whereas in females the corresponding effect disappeared.

Allometry and plasticity of meristem allocation throughout development in Arabidopsis thaliana

Summary The three principal fates of axillary meristems in flowering plants are branching or vegetative growth, reproduction, and inactivity. We examined the relationship between allocation to each of these fates and plant size in five genotypes of Arabidopsis thaliana. Nutrient availability was used to obtain a range of plant size. Allocation to each meristem fate was recorded at weekly intervals throughout development and at final developmental stage. There were significant allometric relationships between meristem allocation and plant size for each meristem fate throughout development in each genotype. Allometry and plasticity tended to be strongest early in development. In addition, although there were differences in allometry between genotypes, meristem allocation through development was generally consistent across genotypes. We interpret the results of this study as an adaptive response to nutrient availability. Increased allocation to growth meristems in high nutrient treatments early in development should maximize both size and the total number of meristems that can be committed to reproduction later in development. This suggests that the pattern of meristem allocation is a component of an adaptive strategy through development in Arabidopsis thaliana.

Genetic influence on caste in the ant Camponotus consobrinus

Genetic influences on polyethism within social insect colonies are well known, suggesting that the determination of caste (soldiers and minor workers) may also be genetically mediated. The Australian sugar ant Camponotus consobrinus is suitable for such a study, having soldiers and minor workers that follow a complex allometry. Further, although most C. consobrinus colonies are monogynous, 13 of 42 surveyed using microsatellites were found to be polygynous. Thus, although a minority of colonies were polygynous, the great majority of queens live in polygynous colonies. From the 29 monogynous colonies studied, we inferred that the queens are monandrous. Ants from four polygynous colonies were assigned to families on the basis of microsatellite genotypes, after measurements had been taken of head width and scape length. These measurements reflect a complex allometry interpretable as soldier and minor worker growth curves with a large changeover zone. Genetic influence on caste determination was examined by testing for differences between families within colonies in the distribution of scape lengths, residuals from the overall colony allometric curve, and proportions of soldiers and minor workers (as determined by head width falling above or below the inflection point of the overall colony allometric curve). Families in all four colonies differed significantly in caste proportions and in head-width distributions, and three of the four colonies showed significant differences between families in residuals from the overall colony growth curve. Nested ANOVAs using head widths and scape-length residuals showed that when the effect of family is removed, intercolony differences in allometry are negligible. This evidence indicates genetic rather than environmental causes for the observed differences between families. We speculate that this variation may reflect some selective advantage to within-colony heterogeneity between families or that selective differences are few between a wide array of family growth patterns.