Harsh climate selects for small body size among Iceland's Arctic foxes

We studied the effect of the two environmental indices, the sub‐polar gyre (SPG), and winter and summer North Atlantic Oscillation (NAO), together with mean annual winter and summer temperatures and geographic location on mandible size and body mass of Arctic foxes in Iceland (6345 and 2732 specimens, respectively) during the year of their death. We predicted that when favorable conditions prevailed, large specimens would be selected for, and vice versa. Body size and body mass were significantly affected by the environmental parameters (i.e. SPG, NAO, ambient temperature and cloud cover) prevailing during the year of death. The effect of environmental conditions on body size was much stronger in the less productive region of eastern Iceland, apparently because in areas where food availability is meager, even a small difference in climate may tilt the balance from food sufficiency to food shortage. Western Iceland comprises only a quarter of the total surface area of the country, but its productive seashores are twice as long as those of all the rest of the country combined. It is interesting to note that the effect of the SPG, a marine phenomenon in the oceans surrounding Iceland, is reflected in the condition of the foxes more than the other climatic variables we used in this study, which are largely land‐related. Because Arctic foxes in Iceland feed largely on marine birds and invertebrates, the SPG seems to encompass more accurate information regarding the direct ocean forces that affect food availability to the foxes.     

Geographic variation in body size and sexual size dimorphism of a seed-feeding beetle

Body size of many animals varies with latitude: body size is either larger at higher latitudes (Bergmann's rule) or smaller at higher latitudes (converse Bergmann's rule). However, the causes underlying these patterns are poorly understood. Also, studies rarely explore how sexual size dimorphism varies with latitude. Here we investigate geographic variation in body size and sexual size dimorphism of the seed-feeding beetle Stator limbatus, collected from 95 locations along a 38 degrees range in latitude. We examine 14 variables to test whether clines in environmental factors are adequate to explain geographic patterns of body size. We found that body size and sexual size dimorphism of S. limbatus varied considerably with latitude; beetles were smaller but more dimorphic at lower latitudes. Body size was not correlated with a gradient in mean temperature, contrary to the commonly accepted hypothesis that clines are produced by latitudinal gradients in temperature. Instead, we found that three factors were adequate to explain the cline in body size: clinal variation in host plant seed size, moisture (humidity), and seasonality (variance in humidity, precipitation, and temperature). We also found that the cline in sexual size dimorphism was partially explainable by a gradient in moisture, though moisture alone was not sufficient to explain the cline. Other ecological or environmental variables must necessarily contribute to differences in selection on male versus female body size. The main implications of our study are that the sexes differ in the magnitude of clinal variation in body size, creating latitudinal variation in sexual size dimorphism, and that clines in body size of seed beetles are likely influenced by variation in host seed size, water availability, and seasonality.     

Geographical Variation in Body Size and Sexual Size Dimorphism in an Australian Lizard,Boulenger's Skink (Morethia boulengeri)

Ecogeographical rules help explain spatial and temporal patterns in intraspecific body size. However, many of these rules, when applied to ectothermic organisms such as reptiles, are controversial and require further investigation. To explore factors that influence body size in reptiles, we performed a heuristic study to examine body size variation in an Australian lizard, Boulenger''s Skink Morethia boulengeri from agricultural landscapes in southern New South Wales, south-eastern Australia. We collected tissue and morphological data on 337 adult lizards across a broad elevation and climate gradient. We used a model-selection procedure to determine if environmental or ecological variables best explained body size variation. We explored the relationship between morphology and phylogenetic structure before modeling candidate variables from four broad domains: (1) geography (latitude, longitude and elevation), (2) climate (temperature and rainfall), (3) habitat (vegetation type, number of logs and ground cover attributes), and (4) management (land use and grazing history). Broad phylogenetic structure was evident, but on a scale larger than our study area. Lizards were sexually dimorphic, whereby females had longer snout-vent length than males, providing support for the fecundity selection hypothesis. Body size variation in M. boulengeri was correlated with temperature and rainfall, a pattern consistent with larger individuals occupying cooler and more productive parts of the landscape. Climate change forecasts, which predict warmer temperature and increased aridity, may result in reduced lizard biomass and decoupling of trophic interactions with potential implications for community organization and ecosystem function.     

Ecogeographic size variations in Sifakas: a test of the resource seasonality and resource quality hypotheses

Ecogeographic size variations have been documented in some but not all sifakas. Few morphometric or body weight data have been available for two critically endangered subspecies of diademed sifakas: Perrier's sifakas (Propithecus diadema perrieri) and silky sifakas (Propithecus diadema candidus). The objectives of our study were to determine size variations in sifakas and if these variations are related to resource quality and/or resource seasonality. P. d. perrieri and P. d. candidus were captured, weighed, and measured in northern Madagascar. Body weights and morphometrics were compared with other subspecies of diademed sifakas and indris (Indri indri). Differences in body weights and morphometrics between taxa are particularly pronounced for P. d. perrieri compared to P. d. diadema, P. d. edwardsi, and I. indri. Most morphometrics varied in comparisons between P. d. candidus and the other Indriidae (P. d. diadema, P. d. edwardsi, and I. indri). Average body size in sifakas is positively correlated with annual rainfall and negatively correlated with length of dry season. Sifaka body size is not correlated with protein-to-fiber ratios. Thus, size variations in sifakas are related to resource seasonality rather than resource quality. The relationships between the temporal availability of food resources and sifaka body size reflect complex and regionally varying causalities. Detailed, longitudinal information on the ecological factors underlying food selection and nutrient requirements in sifakas are needed to determine the relationship between ecogeographic variables and body size in sifakas.     

Insulin‐like growth factor 1 relieves the constraints on the growth of young wild passerines

To gain a selective advantage for survival in stochastic environments, the growth of different body parameters of juvenile animals should be constantly adjusted according to prevailing conditions. Hormones, especially insulin‐like growth factor 1 (IGF‐1), are an important part of physiological mechanisms mediating life‐history variability in free‐living animals when connecting available resources (e.g. food) with pathways of somatic growth. We used an IGF‐1 injection treatment in free‐living European Pied Flycatcher Ficedula hypoleuca nestlings to mimic experimentally the differentiation of growth conditions for chicks with a similar genetic background. We showed that there is probably a physiological trade‐off for young animals between the growth rates of structural size and body mass, where IGF‐1 could be part of the physiological modulatory system of this trade‐off. By weakening internal constraints that limit growth, IGF‐1 could help to relieve the trade‐off between these competing body size parameters.     

Body size varies with abundance,not climate,in an amphibian population

Body size variation among animals has many possible correlates, temporal as well as geographic. Adult male body size was analysed over the course of 23 yr (1989–2011) in a population of Fowler’s toads Anaxyrus fowleri at Long Point, Ontario. We used an information theoretic approach to identify the most likely models to explain body length variation in relation to abundance, age and environmental variables, including temperature. Male toads overall averaged 53.6 ± 0.1 (SE) mm (n = 1976) but average body length from year to year varied from 50.9 ± 0.2 to 61.4 ± 1.3 mm (n = 23 yr), a difference of 18.7%. Abundance was the only variable significantly correlated with body size variation (R²= 0.713, p = < 0.001). A significant 10‐yr trend in increased body size (R²= 0.874, p = < 0.001) was coincident with a previously detected negative trend in abundance. A 0.05°C yr^?1 increase in environmental temperature over the course of our study was not significantly correlated with the toads’ body size. Body size variation in these toads is likely related to density‐dependent resource availability for growth in the terrestrial stage. Temporal changes in average body size within populations in relation to density may be a significant component of phenotypic variation.     

Providing water for goats in arid landscapes: effects on feeding effort with regard to time period, herd size and secondary compounds

In arid regions, herbivores contend with a wide range of variables that influence their foraging ability. These may include plant secondary compounds (e.g. tannins and oxalates), water availability, time of day, and herd size. To determine the relative importance of these variables for goats living in a semi-desert, we measured the remaining food resources after foraging events (giving up densities-GUDs) as an index of foraging effort in artificial food patches. Time of day and the availability of drinking water had the greatest effect on GUDs. Goats achieved lower GUDs (i.e. ate more) in the afternoon than they did during the morning. We suggest this was due to missed opportunity costs of future foraging opportunities being lower in the afternoon. Ultimately, this implies that goats made short-term foraging decisions based on estimates of future feeding opportunities. When water was available, feeding effort increased and GUDs dropped almost 50%. For goats living in an arid environment, food and water are strong complementary resources. The presence of low to moderate levels of tannic or oxalic acid in food was a slight deterrent, raising the GUDs similarly. Larger herds ate more and thus obtained lower GUDs. In addition, there was an interaction of herd size and water, suggesting that in arid environments, the effect of water intensifies with population density. Our approach allowed us to quantify and rank the effects that disparate environmental factors had on the goats' foraging costs: water>time of day>herd size>plant secondary compounds. These findings ultimately demonstrate how the provision of water may increase grazing impacts by herbivores in arid landscapes.     

Geographic clines in body weight of Norwegian red deer: a novel explanation of Bergmann's rule?

Variation in body weight of red deer in Norway was investigated along two climatic gradients: one with increasing latitude, and the other with proximity to the coast. Deer of all sex/age classes were significantly heavier in the northern parts of their range compared with the south and were also significantly heavier at inland localities compared with the coast. Body weights were negatively correlated with temperature and precipitation throughout the years. These clines in body weight apparently support Bergmann's rule, and may reflect selection for large size in cold environments. However, we interpret the results in the light of recent work on plant physiology which indicates higher quality forage at high latitudes, and in cooler and drier climates: conditions which are likely lo enhance growth in the north and inland. Evidence that individual deer which migrate inland, following the snow melt, are heavier is also presented and discussed in terms of an adaptive behaviour that maximises the intake of digestible energy and high quality nutrients.     

Rates of molecular evolution in tree ferns are associated with body size,environmental temperature,and biological productivity

Variation in rates of molecular evolution (heterotachy) is a common phenomenon among plants. Although multiple theoretical models have been proposed, fundamental questions remain regarding the combined effects of ecological and morphological traits on rate heterogeneity. Here, we used tree ferns to explore the correlation between rates of molecular evolution in chloroplast DNA sequences and several morphological and environmental factors within a Bayesian framework. We revealed direct and indirect effects of body size, biological productivity, and temperature on substitution rates, where smaller tree ferns living in warmer and less productive environments tend to have faster rates of molecular evolution. In addition, we found that variation in the ratio of nonsynonymous to synonymous substitution rates (dN/dS) in the chloroplast rbcL gene was significantly correlated with ecological and morphological variables. Heterotachy in tree ferns may be influenced by effective population size associated with variation in body size and productivity. Macroevolutionary hypotheses should go beyond explaining heterotachy in terms of mutation rates and instead, should integrate population‐level factors to better understand the processes affecting the tempo of evolution at the molecular level.     

BERGMANN'S RULE,SEASONALITY, AND GEOGRAPHIC VARIATION IN BODY SIZE OF HOUSE SPARROWS

Body size of House Sparrows is positively correlated with seasonality (annual temperature range) in both North America and Europe. Previously used climatic variables gave inconsistent or contrasting results for the two continental samples. The physiological advantage of large size in seasonal environments appears to be increased fasting ability, but this may be offset somewhat, particularly for females, by other factors, e.g., competitive interactions that influence rates of energy intake or ability to initiate breeding in the spring. It is proposed that minimization of maintenance energy costs on a per individual basis, and thus small size, is advantageous in equable (and predictable) environments.     

Body size clines in the European badger and the abundant centre hypothesis

Aim To test the abundant centre hypothesis by analysing the physical and climatic factors that influence body size variation in the European badger (Meles meles). Location Data were compiled from 35 locations across Europe. Methods We used body mass, body length and condylo‐basal length (CBL) as surrogates of size. We also compiled data on latitude, several climatic variables, habitat type and site position relative to the range edge. We collapsed all continuous climatic variables into independent vectors using principal components analysis (PCA), and used a general linear model to explain the morphometric variation in badger populations across the species’ range. Results Body mass and body length were nonlinearly and significantly related to latitude. In contrast, CBL was linearly related to latitude. Body mass changed nonlinearly along the temperature (PC1) gradient, with the highest values observed at mid‐range. Furthermore, body mass, body length and CBL differed significantly among habitats, with badgers showing larger size in temperate habitats and core areas relative to peripheral zones. Main conclusions Our analysis supports the nonlinear pattern predicted by the abundant centre hypothesis only for body mass and body length. These results imply that individuals are largest and heaviest at the centre of the climatic range of badger distribution. Variation of CBL with latitude follows a linear trend, consistent with Bergmann’s rule. Our results provide mixed support for the abundant centre hypothesis, and suggest food availability/quality to be the main mechanism underlying body size clines in this species.     

Physiological responses of growing Large White boars in three management environments

Growth and physiological responses in Large White boars were studied under three different management environments at the Teaching and Research Farm of the Federal University of Technology, Akure. The management environments were shed with concrete floor (SCF), open space with concrete floor (OSCF) and open space with earth floor (OSEF). Two studies were carried out, one between December 1990 and March 1991 and the other from December 1991 to April 1992. Meteorological parameters in all management environments were monitored simultaneously with physiological variables. Growth of the animals was assessed by monitoring body weights of the animals. Data analysis showed that mean ambient temperatures, mean relative humidity and net radiation differed significantly (P<0.05) among the management environments. Ambient temperature and net radiation of the pigs were highest (P<0.05) in the OSEF environment, which also had the lowest (P<0.05) relative humidity. Although growth rates did not differ significantly among environments, body weight was lowest (P<0.05) in the OSEF environment. Mean respiratory rates and rectal temperatures were lowest (P<0.05) in the SCF environment. The study shows correlations between some meteorological parameters and body weights. Pigs under shade and in concrete-floored pens were more comfortable and had higher body weight and lower respiratory rates and rectal temperatures.     

Growth,development, and sexual dimorphism in vervet monkeys (Cercopithecus aethiops) at four sites in Kenya

Body weight and ten body segment measurements were collected from 367 wild-trapped vervet monkeys (Cercopithecus aethiops) in central and southern Kenya. The animals represent between 70 and 95% of the animals in each of 30 troops at four geographical locations separated by 80 to 380 km. The capture sites differed in altitude, mean annual rainfall and temperature. Two questions are addressed: (1) what are the differences in male and female growth patterns, and (2) what is the relationship between size, climate, and availability of food? Each animal was assigned to an age class based on dental examination. Means for all variables do not diverge for males and females from birth to age class 4 (15–18 months). After this, male and female growth rates diverge. This sexual dimorphism in growth pattern may reflect timing of entry into the reproductive community. A nested analysis of variance (ANOVA) was employed to compare sites, groups within sites and individuals within groups. Statistically significant differences between sites in body weight and body segment measurements are found for adult females. Except for tail length, these differences do not follow Bergmann's or Allen's Rules correlating size differences and temperature, but rather may reflect proximity to cultivated areas or tourist lodges with greater access to human food. Am J Phys Anthropol 103:19–35, 1997. © 1997 Wiley-Liss, Inc.     

Population characteristics predict responses in moose body mass to temporal variation in the environment

1. A general problem in population ecology is to predict under which conditions stochastic variation in the environment has the stronger effect on ecological processes. By analysing temporal variation in a fitness-related trait, body mass, in 21 Norwegian moose Alces alces (L.) populations, we examined whether the influence of temporal variation in different environmental variables were related to different parameters that were assumed to reflect important characteristics of the fundamental niche space of the moose. 2. Body mass during autumn was positively related to early access to fresh vegetation in spring, and to variables reflecting slow phenological development (low June temperature, a long spring with a slow plant progression during spring). In contrast, variables related to food quantity and winter conditions had only a minor influence on temporal variation in body mass. 3. The magnitude of the effects of environmental variation on body mass was larger in populations with small mean body mass or living at higher densities than in populations with large-sized individuals or living at lower densities. 4. These results indicate that the strongest influence of environmental stochasticity on moose body mass occurs towards the borders of the fundamental niche space, and suggests that populations living under good environmental conditions are partly buffered against fluctuations in environmental conditions.     

Birth seasonality in cotton-top tamarins (saguinus oedipus) despite constant food supply and body weight

Goldizen et al. (1988) reported that wild saddle-back tamarins (Saguinus fuscicollis, Callitrichidae) show birth seasonality that is correlated with food supply and body weight. They suggested a sequence of ultimate causality in which shortage of food leads to reduced body weight which leads to timing of weaning and lactation when resources are more abundant. Cotton-top tamarins in captivity show birth seasonality despite constant food supply and body weight. Although natural availability of fruit and insects (which are key foods for tamarins) is related to rainfall, birth seasonality and body weight in captive cotton-top tamarins are unrelated to rainfall. The most likely proximate mechanism for seasonality of births in tamarins is photo-period, given existing data on populations living in natural and artificial lighting.     

Size‐based interactions across trophic levels in food webs of shallow Mediterranean lakes

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Spatial variations in size, weight and condition factor of the females of Acartia clausi (Copepoda: Calanoida) along a salinity gradient in two contrasting estuaries of the Basque coast (Bay of Biscay)

Variations in prosome length and width, dry weight and condition factor of female Acartia clausi copepods were studied at three salinities (35, 34 and 33 psu) in the euhaline region of two estuaries (Bilbao and Urdaibai) of the Basque coast, with different level of anthropogenic impact. Effect of the environmental variables upon the morphology of A. clausi females on a small geographic scale is discussed. In general, biometric variables showed no significant differences between the two estuaries, but dry weight and condition factor were significantly higher in the estuary of Urdaibai at 35 and 34 psu, whilst at 33 psu they were higher in Bilbao. Body dimensions decreased significantly with decreasing salinity in both estuaries, however, no similar trends were observed for dry weight and condition factor. Temperature appeared the main variable to account size variations, but once eliminated seasonal effect of the temperature body size was related with oxygen concentration in the estuary of Bilbao and with salinity in Urdaibai. This study reveals that morphological characteristics of A. clausi not are only dependent on the temperature, but also, within a limited geographical zone, on local differences in environmental variables, mainly salinity and oxygen concentration.     

Individual variation in body color in the field cricket Teleogryllus occipitalis (Orthoptera: Gryllidae)

Body color of animals may affect individual fitness through direct effects on various processes, such as predatory avoidance, thermoregulation, UV resistance, and mating behavior. Body color variation of the field cricket Teleogryllus occipitalis (Audinet‐Serville) (Orthoptera: Gryllidae) is often observed. We quantified the individual variation in body color of this species by measuring the luminance of hind leg femur. Thereafter, we examined whether the body color was a heritable trait or not using parent–offspring analysis. In addition, the effect of body color of both parents on body size, sex ratio, and survival rate of progeny was investigated. The results showed that maternal body color was not heritable, whereas paternal body color was correlated with the body color of the progeny. Body size and sex ratio were not correlated with body color of parents. Although paternal body color did not affect the survival rate of the progeny beyond the stage of final instar nymph, progeny survival rate significantly increased with darkness of maternal body.     

Climate and mammalian life histories

Mammals display considerable geographical variation in life history traits. To understand how climatic factors might influence this variation, we analysed the relationship between life history traits – adult body size, litter size, number of litters per year, gestation length, neonate body mass, weaning age and age at sexual maturity – and several environmental variables quantifying the seasonality and predictability of temperature and precipitation across the distribution range of five terrestrial mammal groups. Environmental factors correlated strongly with each other; therefore, we used principal components analysis to obtain orthogonal climatic predictors that could be used in multivariate models. We found that in bats, primates and even‐toed ungulates adult body size tends to be larger in species inhabiting cold, dry, seasonal environments, whereas in carnivores and rodents a smaller body size is characteristic of warm, dry environments, suggesting that low food availability might limit adult size. Species inhabiting cold, dry, seasonal habitats have fewer, larger litters and shorter gestation periods; however, annual fecundity in these species is not higher, implying that the large litter size of mammals living at high latitudes is probably a consequence of time constraints imposed by strong seasonality. On the other hand, the number of litters per year and annual fecundity were greater in species inhabiting environments with higher seasonality in precipitation. Lastly, we found little evidence for specific effects of environmental variability. Our results highlight the complex effects of environmental factors in the evolution of life history traits in mammals. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111 , 719–736.     

Effect of reproductive state and body size on food consumption in captive Galago senegalensis braccatus

Measurements of food consumption for different types of foods were made for seven Galago senegalensis braccatus. Differences because of reproductive state in females and body size were found. Lactating females consumed more food in total and had greater energy and protein intake than they did during other reproductive states. Near-term pregnant females consumed less food, energy, and protein than they did during other reproductive states. Body size affected food intake, with smaller animals ingesting more per unit metabolic weight than larger subjects.