Variation In Body Mass Research Articles

Melanin in a changing world: brown trout coloration reflects alternative reproductive strategies in variable environments

Melanins are the most widespread pigments in animals but their adaptive significance remains elusive. Recent studies suggest that intraspecific variation in melanin-based coloration reflects individual genetic-based alternative strategies to cope with environment variability, which could be crucial for their responses to climate changes. However, empirical evidence is still scarce. In this study, we tested how skin coloration in natural populations of brown trout Salmo trutta fario would reflect alternative reproductive strategies in different environments. We experimentally manipulated the flow regime (constant vs. variable) in artificial streams and compared the reproductive investment (body mass and plasma triglyceride variations), innate immunity (variations in plasma peroxidase and lysozyme activity) and reproductive success (number of mates and offspring) of differently colored brown trout over 2 reproductive seasons. Results show that darker males had a higher reproductive investment, but similar immune variations during reproduction compared to paler males. In addition, this reproductive investment was higher in variable environments. However, this did not translate into a higher reproductive success in variable environments, as darker males had a similar number of mates and offspring compared to their paler counterparts under a variable water flow. Since climate change will likely lead to an increased flow variability in the next decades, this suggests that darker brown trout could incur a higher energetic cost of reproduction and could be more impacted by climate changes than their paler counterparts. This highlights the need to take into account intraspecific variability to better forecast the response of natural populations to climate changes.

Body size, brain size, and sexual dimorphism in Homo naledi from the Dinaledi Chamber

Homo erectus and later humans have enlarged body sizes, reduced sexual dimorphism, elongated lower limbs, and increased encephalization compared to Australopithecus, together suggesting a distinct ecological pattern. The mosaic expression of such features in early Homo, including Homo habilis, Homo rudolfensis, and some early H. erectus, suggests that these traits do not constitute an integrated package. We examined the evidence for body mass, stature, limb proportions, body size and dental size dimorphism, and absolute and relative brain size in Homo naledi as represented in the Dinaledi Chamber sample. H. naledi stature and body mass are low compared to reported values for H. erectus, with the exception of some of the smaller bodied Dmanisi H. erectus specimens, and overlap with larger Australopithecus and early Homo estimates. H. naledi endocranial volumes (465–560 cc) and estimates of encephalization quotient are also similar to Australopithecus and low compared to all Homo specimens, with the exception of Homo floresiensis (LB1) and the smallest Dmanisi H. erectus specimen (D4500). Unlike Australopithecus, but similar to derived members of genus Homo, the Dinaledi assemblage of H. naledi exhibits both low levels of body mass and dental size variation, with an estimated body mass index of sexual dimorphism less than 20%, and appears to have an elongated lower limb. Thus, the H. naledi bauplan combines features not typically seen in Homo species (e.g., small brains and bodies) with those characteristic of H. erectus and more recent Homo species (e.g., reduced mass dimorphism, elongated lower limb).

The signature of human pressure history on the biogeography of body mass in tetrapods

AbstractAimExamining the biogeography of body size is crucial for understanding how animal communities are assembled and maintained. In tetrapods, body size varies predictably with temperature, moisture, productivity seasonality and topographical complexity. Although millennial‐scale human pressures are known to have led to the extinction of primarily large‐bodied tetrapods, human pressure history is often ignored in studies of body size that focus on extant species. Here, we analyse 11,377 tetrapod species of the Western Hemisphere to test whether millennial‐scale human pressures have left an imprint on contemporary body mass distributions throughout the tetrapod clade.LocationWestern Hemisphere.Time periodContemporary.Major taxa studiedTetrapods (birds, mammals, amphibians and reptiles).MethodsWe mapped the distribution of assemblage‐level median tetrapod body mass at a resolution of 110 km across the Western Hemisphere. We then generated multivariate models of median body mass as a function of temperature, moisture, productivity seasonality and topographical complexity, as well as two variables capturing the history of human population density and human‐induced land conversion over the past 12,000 years. We controlled for both spatial and phylogenetic autocorrelation effects on body mass–environment relationships.ResultsHuman pressures explain a small but significant portion of geographical variation in median body mass that cannot be explained by ecological constraints alone. Overall, the median body mass of tetrapod assemblages is lower than expected in areas with a longer history of high human population density and land conversion, but there are important differences among tetrapod classes.Main conclusionsAt this broad scale, the effect of human pressure history on tetrapod body mass is low relative to that of ecology. However, ignoring spatial variation in the history of human pressure is likely to lead to bias in studies of the present‐day functional composition of tetrapod assemblages, at least in areas that have long been influenced by humans.

Authors' Response

Authors' Response: We appreciate our colleagues for their careful reading of our work in their manuscript clarification “methodological issues associated with the use of force plates when assessing push-ups power.” However, we believe that they misunderstood the primary purpose and the practical implications of our study (5). The authors pointed out that we inappropriately applied the method proposed by Cormie et al. (1) because the push-up involves rotational movement and needs support from both the hands and feet. We would like to reiterate that the purpose of our study was to develop a prediction model, but not a direct measurement of upper body strength and power in the field. Therefore, a compromise has to be reached between accuracy and feasibility. To make research findings more applicable to strength and conditioning professionals, we simplified our testing methods by only measuring the ground reaction force at the hands. However, it has been previously reported that most body mass was supported by the upper body (69 and 75% for the down and up position, respectively) during the push-up movement (4). Therefore, the variation of body mass supported by the feet is limited. In addition, if the authors carefully read the article they cited (1), they would have found that the load-power relationship for jump squat was no different between kinematic-kinetic and kinetic only methods. Besides, we are very well aware that using 2 synchronized force plates would provide more information. However, this approach would make it more difficult to conduct testing in the field. In fact, our results showed similar test-retest reliability as reported by Cormie et al. (1). We agree with the author's opinion that the body moves upward in a more linear motion during vertical jumps than push-ups. However, no human movement is perfectly vertical. The vertical jump movement also involves considerable anteroposterior and mediolateral ground reaction forces, which could be as high as 20% of the body mass (3). During our data collection procedure, we instructed the participants to place their hands in a similar relative position during the ballistic push-up testing. Furthermore, the bar path traveled during the barbell bench press exercise is not vertical or linear (2). In our study, we were able to demonstrate that over 80% of the variation in 1 repetition maximum bench press could be explained by our prediction equation. Although the standard error of the estimate needs to be strengthened by further standardizing the testing procedure, we believe that this is not a “transposed” technique. Finally, we hope that the authors consider both the scientific foundations as well as the practical applications of this new method to estimate upper-body strength and power. More importantly, we would like to emphasize the fact that strength and conditioning field does not show a lack of scientific research, but a lack of practical applications.

Getting fat or getting help? How female mammals cope with energetic constraints on reproduction

BackgroundFat deposits enable a female mammal to bear the energy costs of offspring production and thus greatly influence her reproductive success. However, increasing locomotor costs and reduced agility counterbalance the fitness benefits of storing body fat. In species where costs of reproduction are distributed over other individuals such as fathers or non-breeding group members, reproductive females might therefore benefit from storing less energy in the form of body fat.ResultsUsing a phylogenetic comparative approach on a sample of 87 mammalian species, and controlling for possible confounding variables, we found that reproductive females of species with allomaternal care exhibit reduced annual variation in body mass (estimated as CV body mass), which is a good proxy for the tendency to store body fat. Differential analyses of care behaviours such as allonursing or provisioning corroborated an energetic interpretation of this finding. The presumably most energy-intensive form of allomaternal care, provisioning of the young, had the strongest effect on CV body mass. In contrast, allonursing, which involves no additional influx of energy but distributes maternal help across different mothers, was not correlated with CV body mass.ConclusionsOur results suggest that reproducing females in species with allomaternal care can afford to reduce reliance on fat reserves because of the helpers’ energetic contribution towards offspring rearing.

Environmental drivers of roosting body mass variation in boreal Great Tits Parus major

Small wintering passerines adaptively modulate daily body mass acquisition as part of their energy management policy. However, whether birds optimize overnight mass loss or body mass at dawn remains poorly understood. We studied environmental correlates of individual variation in body mass at dusk, overnight mass loss and body mass at dawn in a wild population of Great Tits Parus major wintering in northern Fennoscandia. Body mass at dusk, overnight mass loss and body mass at dawn were independent of prevailing conditions despite extremely low night ambient temperatures. Body mass at dusk was higher in males than in females, and decreased throughout winter and when snowfall was higher in the previous month. Overnight mass loss increased with precipitation during the previous week and tended to be higher in mid‐winter, when nights were longest. However, birds reduced overnight mass loss with higher temperatures in the previous week and higher precipitation in the previous 2 weeks. Dawn body mass was strongly correlated with dusk body mass and overnight mass loss, and showed only mild associations with weather variables once dusk mass was accounted for. Body mass in roosting boreal Great Tits seems to be constrained by recent snowfall as the winter progresses, but otherwise appears to be mostly unaffected by previous and current temperatures, suggesting a regular use of facultative hypothermia.

Is incomplete estradiol suppression during aromatase inhibitor treatment in post-menopausal patients with breast cancer due to insufficient systemic drug concentrations?

1063 Background: Aromatase inhibitors (AI) suppress estrogen biosynthesis and are effective treatments for estrogen receptor (ER)-positive breast cancer. In a prospectively enrolled cohort we observed a subset of post-menopausal women who exhibit high plasma estradiol (E2) concentrations during AI treatment, which could potentially contribute to treatment failure. We tested the hypothesis that incomplete E2 suppression is due to insufficient systemic AI concentrations. Methods: Five hundred post-menopausal women with ER-positive breast cancer were randomized to daily exemestane (Exe) 25 mg or letrozole (Let) 2.5 mg. Plasma E2 was measured using GC/MS/MS (lower limit of quantification (LLOQ) = 1.25 pg/mL) at baseline and after 3 months. Let and Exe plasma concentrations measured after 1 or 3 months were compared with the magnitude of E2 depletion using four complementary statistical procedures to assess associations of drug concentrations with: 1) a binary outcome of E2 suppression below LLOQ (logistic regression), 2) 3-month E2 concentrations (linear regression), 3) absolute change from baseline in E2 concentrations (Spearman correlation), and 4) an ordinal outcome defined by E2: decreased to below LLOQ, decreased but not to LLOQ, stayed the same, or increased from baseline (cumulative logistic regression). Results: 397 patients with E2 and AI concentration measurements were evaluable (Exe n = 199, Let n = 198). Thirty (7.6%) patients (Exe n = 13, Let n = 17) had E2 concentrations above the LLOQ at 3 months (range: 1.42-63.8 pg/mL). Exe and Let concentrations were not associated with achievement of unmeasurable E2 concentrations, on-treatment E2 concentrations, E2 change from baseline, or ordinal groupings of E2 change (all p > 0.05). In a parallel analysis there was no association of estrone-sulfate and drug concentrations (data not shown). Conclusions: Our results suggest that circulating drug concentrations do not explain incomplete E2 suppression in women receiving AI therapy. Additional studies are underway to determine whether age, body mass and genetic variation in the aromatase enzyme influence AI treatment response.

Relationship Of Fat-free Mass And Fat Mass To Body Weight In College Female Athletes

Body mass differs widely across the sports spectrum in female athletes. While some sports are dominated by large athletes, other sports participants benefit from a smaller size and/or are limited by weight class. The most traditional measure of body composition has been %fat with less frequent emphasis on the major components of body composition: fat-free mass (FFM) and fat mass (FM). FFM is the functional component since as it is closely associated with maximal voluntary strength, while FM plays an important role in energy balance. With the ever increasing emphasis on control and manipulation of these components in modern sports, closer observation should be given to the relationship between FFM and FM accumulation. PURPOSE: To determine the relationship of FFM and FM to height and body mass across a wide-range of size typically observed in college female athletes. METHODS: One hundred and thirty-two NCAA Division-II female athletes (age = 19.9 ± 1.2 y, height =169.1 ± 7.9 cm, body mass = 67.8 ± 12.2 kg) volunteered to participate. Body composition was assessed using dual-energy x-ray absorptiometry (DEXA) to assess regional estimates of lean (bone, muscle, etc.) and fat tissue which allowed determination FFM and FM. RESULTS: Height was linearly correlated with body mass (r=0.58). FFM and FM were significantly related to height (r = 0.63 and 0.40, respectively) and body mass (r = 0.91 and 0.93, respectfully), with the relationships being linear in all four cases. FFM accumulated at approximately 0.35 kg/cm height and 0.50 kg/kg body mass; accounting for 91% of the variance in body mass, while FM accounted for only 9%. The greatest accumulation of FFM was at a height of 169 cm (0.402 kg/cm height) and body mass of 105 kg (0.663 kg/kg). The relationship between FFM and FM was significant (r = 0.71) and curvilinear. Accumulation of FM per kg of FFM increased at FFM > 55 kg. CONCLUSIONS: In female athletes, body mass appears to be the significant determinant of FFM accumulation. The accumulation of FM is determined by FFM, while the rate of accumulation of FM increases significantly at a threshold of 55 kg FFM.

Does selection on horn length of males and females differ in protected and hunted populations of a weakly dimorphic ungulate?

Weaponry in ungulates may be costly to grow and maintain, and different selective pressures in males and females may lead to sex‐biased natural survival. Sexual differences in the relationship between weapon growth and survival may increase under anthropogenic selection through culling, for example because of trophy hunting. Selection on weaponry growth under different scenarios has been largely investigated in males of highly dimorphic ungulates, for which survival costs (either natural or hunting related) are thought to be greatest. Little is known, however, about the survival costs of weaponry in males and females of weakly dimorphic species. We collected information on horn length and age at death/shooting of 407 chamois Rupicapra rupicapra in a protected population and in two hunted populations with different hunting regimes, to explore sexual differences in the selection on early horn growth under contrasting selective pressures. We also investigated the variation of horn growth and body mass in yearling males (n = 688) and females (n = 539) culled in one of the hunted populations over 14 years. The relationship between horn growth and survival showed remarkable sexual differences under different evolutionary scenarios. Within the protected population, under natural selection, we found no significant trade‐off in either males or females. Under anthropogenic pressure, selection on early horn growth of culled individuals showed diametrically opposed sex‐biased patterns, depending on the culling regime and hunters’ preferences. Despite the selective bias between males and females in one of the hunted populations, we did not detect significant sex‐specific differences in the long‐term pattern of early growth. The relationship between early horn growth and natural survival in either sex might suggest stabilizing selection on horn size in chamois. Selection through culling can be strongly sex‐biased also in weakly dimorphic species, depending on hunters’ preferences and hunting regulations, and long‐term data are needed to reveal potential undesirable evolutionary consequences.

Causes and consequences of variation in offspring body mass: meta-analyses in birds and mammals.

Early survival is highly variable and strongly influences observed population growth rates in most vertebrate populations. One of the major potential drivers of survival variation among juveniles is body mass. Heavy juveniles are better fed and have greater body reserves, and are thus assumed to survive better than light individuals. In spite of this, some studies have failed to detect an influence of body mass on offspring survival, questioning whether offspring body mass does indeed consistently influence juvenile survival, or whether this occurs in particular species/environments. Furthermore, the causes for variation in offspring mass are poorly understood, although maternal mass has often been reported to play a crucial role. To understand why offspring differ in body mass, and how this influences juvenile survival, we performed phylogenetically corrected meta-analyses of both the relationship between offspring body mass and offspring survival in birds and mammals and the relationship between maternal mass and offspring mass in mammals. We found strong support for an overall positive effect of offspring body mass on survival, with a more pronounced influence in mammals than in birds. An increase of one standard deviation of body mass increased the odds of offspring survival by 71% in mammals and by 44% in birds. A cost of being too fat in birds in terms of flight performance might explain why body mass is a less reliable predictor of offspring survival in birds. We then looked for moderators explaining the among-study differences reported in the intensity of this relationship. Surprisingly, sex did not influence the intensity of the offspring mass-survival relationship and phylogeny only accounted for a small proportion of observed variation in the intensity of that relationship. Among the potential factors that might affect the relationship between mass and survival in juveniles, only environmental conditions was influential in mammals. Offspring survival was most strongly influenced by body mass in captive populations and wild populations in the absence of predation. We also found support for the expected positive effect of maternal mass on offspring mass in mammals (rpearson = 0.387). As body mass is a strong predictor of early survival, we expected heavier mothers to allocate more to their offspring, leading them to be heavier and so to have a higher survival. However, none of the potential factors we tested for variation in the maternal mass-offspring mass relationship had a detectable influence. Further studies should focus on linking these two relationships to determine whether a strong effect of offspring size on early survival is associated with a high correlation coefficient between maternal mass and offspring mass.

Associations of water balance and thermal sensitivity of toads with macroclimatic characteristics of geographical distribution

Interspecific variation in patterns of geographical distribution of phylogenetically related species of amphibians might be related to physiological adaptation to different climatic conditions. In this way, a comparative study of resistance to evaporative water loss, rehydration rates and sensitivity of locomotor performance to variations on hydration level and temperature was performed for five species of Bufonidae toads (Rhinella granulosa, R. jimi, R. ornata, R. schneideri and R. icterica) inhabiting different Brazilian biomes. The hypotheses tested were that, when compared to species inhabiting mesic environments, species living at hot and dry areas would show: (1) greater resistance to evaporative water loss, (2) higher rates of water uptake, (3) lower sensitivity of locomotor performance to dehydration and (4) lower sensitivity of locomotor performance at higher temperatures and higher sensitivity of locomotor performance at lower temperatures. This comparative analysis showed relations between body mass and interspecific variation in rehydration rates and resistance to evaporative water loss in opposite directions. These results might represent a functional compensation associated with relatively lower absorption areas in larger toads and higher evaporative areas in smaller ones. Moreover, species from the semi-arid Caatinga showed locomotor performance less sensitive to dehydration but highly affected by lower temperatures, as well greater resistance to evaporative water loss, when compared to the other species from the mesic Atlantic Forest and the savannah-like area called Cerrado. These results suggest adaptation patterns to environmental conditions.

Early‐life density‐dependence effects on growth and survival in subantarctic fur seals

AbstractUnderstanding the regulation of natural populations has been a long‐standing research program in ecology. Current knowledge on marine mammals and seabirds is biased toward the adult component of populations and lacking are studies investigating the juvenile component. Our goal was to estimate demographic parameters on the pre‐weaning stage of a subantarctic fur seal (Arctocephalus tropicalis) population on Amsterdam Island, suspected to be regulated by density‐dependence. The influence of abundance on growth parameters (length and weight) and survival was assessed over a study period spanning 16 years. We evidenced a negative trend in population growth rate when density increased. Density‐dependence models were favored for pup body size and mass growth. Abundance had a clear influence on body length at high population‐density, pups grew slower and were smaller at weaning than pups born in years with low population density. Abundance partly explained pup body mass variation and a weak effect was detected on pre‐weaning survival. The causal mechanisms may be increased competition for food resources between breeding females, leading to a reduction of maternal input to their pups. Our results suggested that pup favored survival over growth and the development of their diving abilities in order to withstand the extreme fasting periods that are characteristic of this fur seal population. This analysis provides significant insight of density‐dependent processes on early‐life demographic parameters of a long lived and top‐predator species, and more specifically on the pre‐weaning stage with important consequences for our understanding of individual long‐term fitness and population dynamics.

Impact of Early Nutrition on Body Composition in Children Aged 9.5 Years Born with Extremely Low Birth Weight.

To evaluate body composition, metabolism and growth as well as their interaction with early nutrition in former extremely low birth weight infants (ELBW), we assessed qualitative and quantitative nutritional intake during initial hospitalization and infantile growth parameters in 61 former ELBW infants with a birth weight <1000 g. In two follow-up exams, physical and biochemical development were measured at 5.7 and at 9.5 years. At the second follow-up, in addition to biochemical reassessment, body composition was analyzed by dual-energy x-ray absorptiometry (DEXA). Protein intake between birth and discharge was associated with weight gain in the first six months of life (r = 0.51; p < 0.01). Weight catch-up preceded height catch-up. Protein intake in early infancy correlated highly significantly with abdominal fat mass (r = 0.49; p < 0.05), but not with lean body mass at 9.5 years (r = 0.30; not significant (n.s.). In contrast to nutrient intake, birth weight was associated with lean body mass (r = 0.433; p < 0.001). Early protein and carbohydrate intake were associated with high-density lipoprotein (HDL)-cholesterol, and early catch-up growth correlated with fasting insulin at follow-up. Stepwise linear regression demonstrated that protein intake predicted fat mass (p < 0.05), whereas only gender and birth weight standard deviation score (SDS) contributed significantly to lean body mass variation (p < 0.05). Our results suggest an important impact of early nutrient intake on body composition and metabolism in later childhood in ELBW children.

The role of climate factors in geographic variation in body mass and wing length in a passerine bird

BackgroundGeographic variation in body size is assumed to reflect adaptation to local environmental conditions. Although Bergmann’s rule is usually sufficient to explain such variation in homeotherms, some exceptions have been documented. The relationship between altitude, latitude and body size, has been well documented for some vertebrate taxa during the past decades. However, relatively little information is available on the effects of climate variables on body size in birds.MethodsWe collected the data of 267 adult Eurasian Tree Sparrow (Passer montanus) specimens sampled at 48 localities in China’s mainland, and further investigated the relationships between two response variables, body mass and wing length, as well as a suit of explanatory variables, i.e. altitude, latitude, mean annual temperature (MAT), annual precipitation (PRC), annual sunshine hours (SUN), average annual wind speed (WS), air pressure (AP) and relative humidity (RH).ResultsOur study showed that (1) although the sexes did not differ significantly in body mass, males had longer wings than females; (2) body mass and wing length were positively correlated with altitude but not with latitude; (3) body mass and wing length were negatively correlated with AP and RH, but not significantly correlated with WS. Body mass was positively correlated with SUN and inversely correlated with MAT. Wing length was not correlated with MAT in either sex, but was positively correlated with SUN and negatively correlated with PRC in male sparrows; (4) variation in body mass could be best explained by AP and SUN, whereas variation in wing length could be explained by RH and AP in both sexes. In addition, variation in male sparrows can be explained by SUN, WS and PRC but not in females.ConclusionsTwo different proxies of body size, body mass and wing length, correlated with same geographic factors and different climate factors. These differences may reflect selection for heat conservation in the case of body mass, and for efficient flight in the case of wing length.

Rapid adaptive phenotypic change following colonization of a newly restored habitat

Real-time observation of adaptive evolution in the wild is rare and limited to cases of marked, often anthropogenic, environmental change. Here we present the case of a small population of reed warblers (Acrocephalus scirpaceus) over a period of 19 years (1996–2014) after colonizing a restored wetland habitat in Malta. Our data show a population decrease in body mass, following a trajectory consistent with a population ascending an adaptive peak, a so-called Ornstein–Uhlenbeck process. We corroborate these findings with genetic and ecological data, revealing that individual survival is correlated with body mass, and more than half of the variation in mean population fitness is explained by variation in body mass. Despite a small effective population size, an adaptive response has taken place within a decade. A founder event from a large, genetically variable source population to the southern range margin of the reed warbler distribution likely facilitated this process.

Breeding limits foraging time: evidence of interrupted foraging response from body mass variation in a tropical environment

Birds should store body reserves if starvation risk is anticipated; this is known as an ‘interrupted foraging response’. If foraging remains unrestricted, however, body mass should remain low to limit the predation risk that gaining and carrying body reserves entails. In temperate environments mass gain in female birds during breeding is often attributed to egg formation and mass loss after incubation to flight adaptation or the effect of reproductive workload, rather than as a result of an adaptive interrupted foraging response to the limited foraging time or unpredictable foraging conditions that breeding demands. In tropical environments, foraging conditions vary more within the breeding season than in temperate environments, and so studies in tropical environments are more suited to decouple the potentially confounded effects of increase in body reserves versus egg formation on the body mass of breeding birds. In this study, we test whether breeding results in an interrupted foraging response in a tropical savannah system using body mass data collected over a 15‐year period from female common bulbuls Pycnonotus barbatus. This species breeds both in the wet and dry season, despite fewer resources being available in the dry season. Breeding stage predicted female body mass: body mass peaked abruptly during incubation, but was not closely associated with the egg‐laying stage, and declined during brood rearing. Breeding females were heavier in the dry season than in the wet season. In the dry season, heavier birds were more likely to incubate eggs or brood chicks. These observations suggest that increased body reserves are required to buffer the consequence of limited foraging time or impoverished foraging conditions, which may be most pronounced during incubation and in the dry season, respectively. Such mass increases are consistent with an interrupted foraging response, which may apply to temperate zone birds experiencing foraging restrictions during breeding.

Ontogenetic and life history trait changes associated with convergent ecological specializations in extinct ungulate mammals

Investigating life history traits in mammals is crucial to understand their survival in changing environments. However, these parameters are hard to estimate in a macroevolutionary context. Here we show that the use of dental ontogenetic parameters can provide clues to better understand the adaptive nature of phenotypic traits in extinct species such as South American notoungulates. This recently extinct order of mammals evolved in a context of important geological, climatic, and environmental variations. Interestingly, notoungulates were mostly herbivorous and acquired high-crowned teeth very early in their evolutionary history. We focused on the variations in crown height, dental eruption pattern, and associated body mass of 69 notoungulate taxa, placed in their phylogenetic and geological contexts. We showed that notoungulates evolved higher crowns several times between 45 and 20 Ma, independently of the variation in body mass. Interestingly, the independent acquisitions of ever-growing teeth were systematically accompanied by eruption of molars faster than permanent premolars. These repeated associations of dental innovations have never been documented for other mammals and raise questions on their significance and causal relationships. We suggest that these correlated changes could originate from ontogenetic adjustments favored by structural constraints, and may indicate accelerated life histories. Complementarily, these more durable and efficient dentitions could be selected to cope with important ingestions of abrasive particles in the context of intensified volcanism and increasing aridity. This study demonstrates that assessing both life history and ecological traits allows a better knowledge of the specializations of extinct mammals that evolved under strong environmental constraints.

Evaluation of hydration status by urine, body mass variation and plasma parameters during an official half-marathon

The aim of this study was to verify the agreement of urine, body mass variations and plasma parameters to determine the hydration status of 14 male runners (29±4 years and 54.3±5.5 mLO2/kg/min) in an official 21.1 km road race. The mean dry-bulb temperature and air relative humidity during the road race were 25.1±2.1 °C and 54.7±2.2%, respectively. The volume of water ingested by the runners was monitored using marked volumetric plastic bottles provided at the hydration stations located at 0, 2.5, 5.0, 7.5, 10.5, 14.0, 16.0 and 18.5 km from the starting line. Hydration status was assessed using urine specific gravity (USG), urine osmolality (UOSM) and plasma osmolality (POSM). Furthermore, body mass variation (∆BM) was assessed by comparing body mass (BM) immediately prior and after the race. Total sweat was estimated by ∆BM, added water volume ingested and deducted blood volume collected. The sweat rate was calculated through total sweat and total exercise time. The mean water intake was 0.82±0.40 L, and the mean sweat rate and total sweating were 1440.11±182.13 mL/h and 2.67±0.23 L. After the race, the BM reduced by 1.7±0.4 kg. The ∆BM was -2.41±0.47%, and the plasma volume variation was -9.79±4.6% between pre- and post-running measurements. Despite the POSM increased post-race compared to pre-race, the UOSM and USG did not change. No significant correlations were found between POSM variation with UOSM variation (r=-0.08; P=0.71), USG variation (r=-0.11; P=0.78) or ∆BM (r=0.09; P=0.77). In conclusion, this study shows that both ∆BM and ∆POSM indicated a hypohydration state after exercise even though the ∆BM did not correlate significantly with ∆POSM. These results demonstrate that ∆BM is a practical method and can be sufficiently sensitive to evaluate the hydration state, but it should be utilized with caution.

The role of weather and density dependence on population dynamics of Alpine-dwelling red deer.

The dynamics of red deer Cervus elaphus populations has been investigated across different environmental conditions, with the notable exception of the European Alps. Although the population dynamics of mountain-dwelling ungulates is typically influenced by the interaction between winter severity and density, the increase of temperatures and the reduction of snowpack occurring on the Alps since the 1980s may be expected to alter this pattern, especially in populations dwelling at medium - low elevations. Taking advantage of a 29-year time series of spring count data, we explored the role of weather stochasticity and density dependence on growth rate and vital rates (mortality and weaning success), and the density-dependent variation in body mass in a red deer population of the Italian Alps. The interaction between increasing values of density and snow depth exerted negative and positive effects on growth and mortality rates, respectively, while weaning success was negatively affected by increasing values of density, female-biased sex ratio and snow depth. Body mass of males and females of different age classes declined as population size increased. Our data support the role of winter severity and density dependence as key components of red deer population dynamics, and provide insight into the species' ecology on the European Alps. Despite the recent decline of snowpack on the Alpine Region, the negative impacts of winter severity and population abundance on growth rrate (possibly mediated by the density-dependent decline in body mass) confirms the importance of overwinter mortality in affecting the population dynamics of Alpine-dwelling red deer.

Assessment of an east-west phenotypic variation in body height, body form and body mass among prehistoric hunter-gatherers of Patagonia and Tierra del Fuego, chile

espanolResumen: Historicamente grupos marinos y terrestres de Fuego-Patagonia fueron descritos como fenotipicamente distintos. Este estudio examina la presencia de esta variacion fenotipica, la cual de existir, podria ser resultado de factores extrinsecos, como son los procesos adaptativos de corto o largo plazo e intrinsecos como son los factores geneticos. La muestra se compone de 51 individuos adultos. Se incluyeron seis mediciones post-craneales: longitud maxima del humero (MHL); longitud maxima del radio (MRL); longitud bicondilar del femur (BFL); longitud maxima de la tibia (MTL); ancho bi-iliaco (BIB), y; diametro antero-posterior de la cabeza femoral (FHD). Tambien se calcularon el indice braquial, el crural, la masa corporal, el indice de masa y la estatura. En general, los individuos terrestres tenian huesos de la extremidad inferior mas largos y eran por ende mas altos y pesados. Los individuos marinos tenian los huesos mas cortos y eran mas bajos y livianos. Los individuos de economia mixta mostraron valores intermedios. Esto sugiere la presencia de una gradiente fenotipica de este a oeste, que es mas marcada en individuos masculinos, y que puede haber resultado de diferencias extrinsecas y/o intrinsecas. Sin embargo, dado el tamano pequeno de la muestra, estos resultados deben ser considerados con cautela. EnglishAbstract: Fuego-Patagonia’s marine and terrestrial groups were historically described as phenotypically distinct but, studies of these phenotypic differences have yet to be conducted. This study evaluates phenotypic variation in Fuego-Patagonia. Phenotypic disparities result from extrinsic and intrinsic factors and therefore can reveal differences in both long and short term adaptations as well as genetic differences. Fifty-one adults were assessed. A total of six post-cranial measurements were included: maximum length of the humerus (MHL); maximum length of the radius (MRL); Bicondylar length of the femur (BFL); Maximum length of the tibia (MTL); bi-iliac breadth (BIB), and; antero-posterior diameter of the femoral head (FHD). Brachial index, crural index, body mass, body mass index and stature were then calculated. In general, terrestrial individuals had longer lower limb bones and were the tallest and heaviest. Marine individuals had the shortest bones and were shorter and lighter. Mixed-economy individuals showed mostly intermediate values. The trends are more marked in males than in females. The results suggests the presence of an east-to-west phenotypic gradient in the region that may have resulted from intrinsic and/or extrinsic differences between the groups. But, the sample size of this study is small, and thus the results should be cautiously considered.