Life-History Traits of the Miocene Hipparion concudense (Spain) Inferred from Bone Histological Structure

Histological analyses of fossil bones have provided clues on the growth patterns and life history traits of several extinct vertebrates that would be unavailable for classical morphological studies. We analyzed the bone histology of Hipparion to infer features of its life history traits and growth pattern. Microscope analysis of thin sections of a large sample of humeri, femora, tibiae and metapodials of Hipparion concudense from the upper Miocene site of Los Valles de Fuentidueña (Segovia, Spain) has shown that the number of growth marks is similar among the different limb bones, suggesting that equivalent skeletochronological inferences for this Hipparion population might be achieved by means of any of the elements studied. Considering their abundance, we conducted a skeletechronological study based on the large sample of third metapodials from Los Valles de Fuentidueña together with another large sample from the Upper Miocene locality of Concud (Teruel, Spain). The data obtained enabled us to distinguish four age groups in both samples and to determine that Hipparion concudense tended to reach skeletal maturity during its third year of life. Integration of bone microstructure and skeletochronological data allowed us to identify ontogenetic changes in bone structure and growth rate and to distinguish three histologic ontogenetic stages corresponding to immature, subadult and adult individuals. Data on secondary osteon density revealed an increase in bone remodeling throughout the ontogenetic stages and a lesser degree thereof in the Concud population, which indicates different biomechanical stresses in the two populations, likely due to environmental differences. Several individuals showed atypical growth patterns in the Concud sample, which may also reflect environmental differences between the two localities. Finally, classification of the specimens’ age within groups enabled us to characterize the age structure of both samples, which is typical of attritional assemblages.     

Tracing the evolution of fitness components in fossil bovids under different selective regimes

Hard tissue histology is a valuable tool to reconstruct life history traits in fossil ungulates. We estimated certain fitness components (age at weaning, age at maturity, life span and generation time) in two fossil bovids that evolved under different selective regimes, the insular Myotragus balearicus and the continental Gazella borbonica. Our results provide evidence that the mainland G. borbonica conforms to the predictions for ungulates of similar body size. However, the insular M. balearicus does not fit predictions from body mass scaling, as it shows an important delay in age at weaning and, especially, in age at first reproduction. The considerable differences in the onset of these fitness components reflect the differences in resource availability and in extrinsic mortality that exist between insular and continental ecosystems. The significant delay in life history traits in Myotragus most likely resulted in severe constraints on the ability of this insular mammal to respond to ecological disturbances.     

Genetic confounding of the relationship between father absence and age at menarche

Research in evolutionary psychology, and life history theory in particular, has yielded important insights into the developmental processes that underpin variation in growth, psychological functioning, and behavioral outcomes across individuals. Yet, there are methodological concerns that limit the ability to draw causal inferences about human development and psychological functioning within a life history framework. The current study used a simulation-based modeling approach to estimate the degree of genetic confounding in tests of a well-researched life history hypothesis: that father absence (X) is associated with earlier age at menarche (Y). The results demonstrate that the genetic correlation between X and Y can confound the phenotypic association between the two variables, even if the genetic correlation is small—suggesting that failure to control for the genetic correlation between X and Y could produce a spurious phenotypic correlation. We discuss the implications of these results for research on human life history, and highlight the utility of incorporating genetically sensitive tests into future life history research.     

Bone histology as an approach to providing data on certain key life history traits in mammals: Implications for conservation biology

The knowledge of the life histories of wild mammals is of crucial importance in the field of conservation management. The endangered status of many species calls for faster data collection that can be used in risk assessment and, ultimately, for designing conservation policies. This study is pioneering the potential of bone histology to provide data on life history traits crucial for conservation biology in long-lived mammals. Long bone cross-sections show pronounced annual cycles of growth arrest allowing application of skeletochronology (counts of lines of arrested growth ‘LAGs’). Consequently, the number of LAGs within the primary fast-growing bone tissue up to the outer cortical slow-growing bone tissue corresponds to the age at first reproduction; whereas the age at death can be estimated by the total number of rest lines throughout the whole of bone cross-section. Furthermore, the diameters of successive growth rings as well as the osteocyte lacuna density may shed light on growth rates. We use the endangered desert dwelling antelope Addax nasomaculatus as a case study. By analyzing different ontogenetic stages in five Addax individuals (three captive and two wild specimens) from a museum collection, we show that bone histology may be a reliable tool for determining certain key life history traits. In our sample, the wild Addax female attained reproductive maturity at three years, whereas the male specimens, both the captive and the wild ones, reached maturity at four years. This is congruent with data from other large antelopes with male-biased size dimorphism, but differs slightly from data on sexual maturity previously published for wild Addax. Moreover, quantification of osteocyte lacunae in both adult males provides a higher cell density in the captive one than in the wild one suggesting the strong effect of constant resources supply in individuals from zoos on growth rates. While age at first reproduction and longevity are essentials parameters to carry out demographic models, growth rates may allow evaluation of the health status of wild populations. This approach may provide useful data on life history traits when applied to bones collected in the wild.     

Life history of an invasive and unexploited population of Nile tilapia (Oreochromis niloticus) and geographical variation across its native and non-native ranges

Although the life history traits of Nile tilapia, Oreochromis niloticus have been studied since the early 20^th century, the potential range of life history parameters in unexploited populations and geographical variability in life history traits are still poorly understood. We explored life history traits (age composition, growth rate, mortality, size, and age at maturity) of an invasive and unexploited population in the Tabaru River, Yonaguni-jima Island, southwestern Japan, through comparisons with exploited populations across the species’ global distribution. Analysis of sectioned otoliths from 307 fish revealed that growth and maximum age were sexually dimorphic (females growing less but having greater longevity). Large-scale comparisons with exploited populations revealed that the unexploited Tabaru River population had a greater life span than exploited populations in other regions, but the growth rate was in the middle of the range of observed values. Although a high variation in life history parameters was observed among populations (L _∞, K, maximum age), we found no significant variation in life history traits by latitude or between African and non-African populations. Such a combination of long life span and high variability in life history traits in response to environmental and fishing pressures may aid the success of non-native Nile tilapia in various environments.     

Natural History of Malignant Bone Disease in Hepatocellular Carcinoma: Final Results of a Multicenter Bone Metastasis Survey

Background

Bone is an uncommon site of metastasis in patients with advanced hepatocellular carcinoma (HCC). Therefore, there are few studies concerning the natural history of bone metastasis in patients with HCC.

Patients and Methods

Data on clinicopathology, survival, skeletal-related events (SREs), and bone-directed therapies for 211 deceased HCC patients with evidence of bone metastasis were statistically analyzed.

Results

The median age was 70 years; 172 patients were male (81.5%). The median overall survival was 19 months. The median time to the onset of bone metastasis was 13 months (22.2% at HCC diagnosis); 64.9% patients had multiple bone metastases. Spine was the most common site of bone metastasis (59.7%). Most of these lesions were osteolytic (82.4%); 88.5% of them were treated with zoledronic acid. At multivariate analysis, only the Child Score was significantly correlated with a shorter time to diagnosis of bone metastases (p = 0.001, HR = 1.819). The median survival from bone metastasis was 7 months. At multivariate analysis, HCC etiology (p = 0.005), ECOG performance status (p = 0.002) and treatment with bisphosphonate (p = 0.024) were associated with shorter survival after bone disease occurrence. The site of bone metastasis but not the number of bone lesions was associated with the survival from first skeletal related event (SRE) (p = 0.021) and OS (p = 0.001).

Conclusions

This study provides a significant improvement in the understanding the natural history of skeletal disease in HCC patients. An early and appropriate management of these patients is dramatically needed in order to avoid subsequent worsening of their quality of life.     

Maternal High Fat Diet Affects Offspring’s Vitamin K-Dependent Proteins Expression Levels

Studies suggest bone growth & development and susceptibility to vascular disease in later life are influenced by maternal nutrition, during intrauterine and early postnatal life. There is evidence for a role of vitamin K-dependent proteins (VKDPs) including Osteocalcin, Matrix-gla protein, Periostin, and Gas6, in bone and vascular development. This study extends the analysis of VKDPs previously conducted in 6 week old offspring, into offspring of 30 weeks of age, to assess the longer term effects of a maternal and postnatal high fat (HF) diet on VKDP expression. Overall a HF maternal diet and offspring diet exacerbated the bone changes observed. Sex specific and tissue specific differences were observed in VKDP expression for both aorta and femoral tissues. In addition, significant correlations were observed between femoral OCN, Periostin Gas6, and Vkor expression levels and measures of femoral bone structure. Furthermore, MGP, OCN, Ggcx and Vkor expression levels correlated to mass and fat volume, in both sexes. In summary the current study has highlighted the importance of the long-term effects of maternal nutrition on offspring bone development and the correlation of VKDPs to bone structure.     

Can Soil Seed Banks Serve as Genetic Memory? A Study of Three Species with Contrasting Life History Strategies

We attempted to confirm that seed banks can be viewed as an important genetic reservoir by testing the hypothesis that standing (aboveground) plants represent a nonrandom sample of the seed bank. We sampled multilocus allozyme genotypes from three species with different life history strategies: Amaranthus retroflexus, Carduus acanthoides, Pastinaca sativa. In four populations of each species we analysed the extent to which allele and genotype frequencies vary in consecutive life history stages including the summer seed bank, which has been overlooked up to now. We compared the winter seed bank (i.e., seeds collected before the spring germination peak), seedlings, rosettes, the summer seed bank (i.e., seeds collected after the spring germination peak) and fruiting plants. We found that: (1) All three species partitioned most of their genetic diversity within life history stages and less among stages within populations and among populations. (2) All genetic diversity parameters, except for allele frequencies, were similar among all life history stages across all populations in different species. (3) There were differences in allele frequencies among life history stages at all localities in Amaranthus retroflexus and at three localities in both Carduus acanthoides and Pastinaca sativa. (4) Allele frequencies did not differ between the winter and summer seed bank in most Carduus acanthoides and Pastinaca sativa populations, but there was a marked difference in Amaranthus retroflexus. In conclusion, we have shown that the summer seed bank is not genetically depleted by spring germination and that a majority of genetic diversity remains in the soil through summer. We suggest that seed banks in the species investigated play an important role by maintaining genetic diversity sufficient for recovery rather than by accumulating new genetic diversity at each locality.     

Age and growth of diadromous <Emphasis Type="Italic">Galaxias maculatus</Emphasis> (Jenyns, 1842) in southernmost South America (54° S) including contribution of age classes to reproduction

The population of Galaxias maculatus studied here, Arroyo Negro (54° S), is located at the southern extreme of the species distribution. This is the first work on growth and other life history traits of a Fueguian diadromous population based on otoliths study. This species is part of the native fish fauna of Patagonia. Furthermore, studies on the growth and reproduction of G. maculatus in South America mostly refer to freshwater populations of Andean-Patagonian lakes and rivers (about 41° S). Size cohorts were studied; age and growth parameters were estimated, the latter using the VBGM. Four size cohorts were established, and 3+ was determined as maximum age class. No differences were found in growth curves between males and females. The 1+ age class was by far not only the most numerous in the population but also the most represented in the reproductive population. The relation between mean TL and latitude was positive (r?=?0.62) for South American populations; however, further studies are needed to determine whether it is this population’s life strategy, the local adaptation of a peripheral population or countergradient growth. The results are interpreted in the context of the information available for other populations, and provide important information about the plasticity in life history traits of this species.     

Influence of Environment and Mitochondrial Heritage on the Ecological Characteristics of Fish in a Hybrid Zone

Background

Ecological characteristics (growth, morphology, reproduction) arise from the interaction between environmental factors and genetics. Genetic analysis of individuals'' life history traits might be used to improve our understanding of mechanisms that form and maintain a hybrid zone.

Methodology/Principal Findings

A fish hybrid zone was used to characterize the process of natural selection. Data were collected during two reproductive periods (2001 and 2002) and 1117 individuals (nase, Chondrostama nasus nasus, sofie C. toxostoma toxostoma and hybrids) were sampled. Reproductive dates of the two parental species overlapped at sympatric sites. The nase had an earlier reproductive period than the sofie; males had longer reproductive periods for both species. Hybridisation between female nase and male sofie was the most likely. Hybrids had a reproductive period similar to the inherited parental mitochondrial type. Growth and reproductive information from different environments has been synthesised following a bayesian approach of the von Bertalanffy model. Hybrid life history traits appear to link with maternal heritage. Hybrid size from the age of two and size at first maturity appeared to be closer to the size of the maternal origin species (nase or sofie).Median growth rates for hybrids were similar and intermediate between those of the parental species. We observed variable life history traits for hybrids and pure forms in the different parts of the hybrid zone. Geometrical analysis of the hybrid fish shape gave evidence of two main morphologies with a link to maternal heritage.

Conclusions/Significance

Selective mating seemed to be the underlying process which, with mitochondrial heritage, could explain the evolution of the studied hybrid zone. More generally, we showed the importance of studies on hybrid zones and specifically the study of individuals'' ecological characteristics, to improve our understanding of speciation.     

Age, growth, maturity, and mortality of the Alaska skate, Bathyraja parmifera, in the eastern Bering Sea

The Alaska skate, Bathyraja parmifera, is the most abundant species of skate on the eastern Bering Sea shelf, accounting for over 90% of total skate biomass. However, little is known regarding the life history of this species despite its common occurrence as bycatch in several Bering Sea fisheries. This is the first study to focus on the age and growth of B. parmifera. From 2003 to 2005, more than one thousand specimens were collected by fisheries observers and on scientific groundfish surveys. Annual banding patterns in more than 500 thin sections of vertebral centra were examined for age determination. Caudal thorns were tested as a potentially non-lethal ageing structure. Annual band pair deposition was verified through edge and marginal increment analyses. A three-parameter von Bertalanffy growth function and a Gompertz growth function were fit to observed length-at-age data. Both models provided significant fits, although the Gompertz function best described the overall pattern of growth in both males and females, based upon statistical criteria and parameter estimates. Age and size at 50% maturity were 9 years and 92 cm TL for males and 10 years and 93 cm TL for females. The maximum observed ages for males and females were 15 years and 17 years, respectively. Estimates of natural mortality (M) ranged from 0.14 to 0.28, and were based on published relationships between M and longevity, age at maturity, and the von Bertalanffy growth coefficient. Due to these life history characteristics and a lack of long-term species-specific stock data, a conservative management approach would be appropriate for B. parmifera.     

Does Reproductive Investment Decrease Telomere Length in Menidia menidia?

Given finite resources, intense investment in one life history trait is expected to reduce investment in others. Although telomere length appears to be strongly tied to age in many taxa, telomere maintenance requires energy. We therefore hypothesize that telomere maintenance may trade off against other life history characters. We used natural variation in laboratory populations of Atlantic silversides (Menidia menidia) to study the relationship between growth, fecundity, life expectancy, and relative telomere length. In keeping with several other studies on fishes, we found no clear dependence of telomere length on age. However, we did find that more fecund fish tended to have both reduced life expectancy and shorter telomeres. This result is consistent with the hypothesis that there is a trade-off between telomere maintenance and reproductive output.     

Contrasting life history strategies of sympatric Arctic charr morphs, Salvelinus alpinus

In polymorphic populations morphs usually diverge in morphology, ecology and life history, which is most likely driven by adaptations to different environments or resources. Sympatric morphs may develop differences in several life history traits to be able to maximize fitness in alternative niches and habitats. Here, the contrasting life history traits of three sympatric Arctic charr (Salvelinus alpinus (L.)) morphs in a deep and oligotrophic lake in sub-arctic Norway are addressed. The charr morphs differ in spawning habitat and trophic niche. One is a littoral spawning morph that feeds on benthic invertebrates and zooplankton in the littoral and pelagic zones (referred to as the LO-morph), and two other are profundal spawning morphs that either utilize profundal soft bottom benthos as food resource (the PB-morph) or are piscivorous (the PP-morph). The LO-morph typically had intermediate life-history traits relative to the two profundal morphs that had highly contrasting life history traits, especially in growth and age and size of maturity. The PB-morph matured at a young age (～3 years) and at a small body size (～8.5 cm), thereby increasing their fitness by investing in reproduction early in life, which results in a short generation time and decreased probability of being predated before first reproduction. The PP-morph on the other hand, matured at an old age (～9.2 years) and a large body size (～26 cm), thereby increasing their fitness by investing in somatic growth to enhance initial fecundity, and also to reach a large body size profitable for piscivory. The different trade-off regime between the PP- and PB-morphs seems to be caused by adaptation to alternative trophic niches, and appears to be an important factor for the co-occurrence of the two sister-morphs in the profundal zone.     

Killing me slowly: Harsh environment extends plant maximum life span

Life span (the age of death for individuals that survived the establishment phase) is a key trait in plant life history. Despite its importance for understanding plant–environment relationships, there are still numerous substantial knowledge gaps about variation in plant maximum life spans and the ecological processes underlying these patterns.Based on plant age data obtained by means of herbochronology, we analysed patterns of intraspecific plant maximum life span variation in three perennial species (Campanula scheuchzeri, Helianthemun nummularium and Lotus corniculatus) along environmental gradients of mean annual temperature, soil depth and soil nutrients. This variation was compared with predictions from the ‘death-by-starvation hypothesis’ proposed by Hans Molisch in 1938, an unjustly forgotten ‘extrinsic’ theory on plant life span variation.Our study suggests that plant age variation within populations responds sensitively to growing conditions. The most important finding is that mean annual temperature or environmental conditions related to it seems to be a driving factor for intraspecific variation in plant maximum life span in all species studied. Despite large within-population variation, individuals of C. scheuchzeri, L. corniculatus and H. nummularium generally had a longer life span under colder climates (uplands in our case). In addition, soil depth (as a proxy for habitat susceptibility to drought) was found to have a significant positive effect on the age values in the case of C. scheuchzeri.These findings, therefore, are in line with Molisch’s “death-by-starvation hypothesis”: extended maximum life span results from reduced production of sink tissues and slow vegetative growth. We conclude that the analysis of plant life span adjustments along gradients of environmental factors can considerably contribute to our understanding of how plants may cope with changing environmental conditions, e.g., due to global change.     

The Influence of Life History and Sexual Dimorphism on Entheseal Changes in Modern Humans and African Great Apes

Entheseal changes have been widely studied with regard to their correlation to biomechanical stress and their usefulness for biocultural reconstructions. However, anthropological and medical studies have demonstrated the marked influence of both age and sex on the development of these features. Studies of entheseal changes are mostly aimed in testing functional hypotheses and are mostly focused on modern humans, with few data available for non-human primates. The lack of comparative studies on the effect of age and sex on entheseal changes represent a gap in our understanding of the evolutionary basis of both development and degeneration of the human musculoskeletal system. The aim of the present work is to compare age trajectories and patterns of sexual dimorphism in entheseal changes between modern humans and African great apes. To this end we analyzed 23 postcranial entheses in a human contemporary identified skeletal collection (N = 484) and compared the results with those obtained from the analysis of Pan (N = 50) and Gorilla (N = 47) skeletal specimens. Results highlight taxon-specific age trajectories possibly linked to differences in life history schedules and phyletic relationships. Robusticity trajectories separate Pan and modern humans from Gorilla, whereas enthesopathic patterns are unique in modern humans and possibly linked to their extended potential lifespan. Comparisons between sexes evidence a decreasing dimorphism in robusticity from Gorilla, to modern humans to Pan, which is likely linked to the role played by size, lifespan and physical activity on robusticity development. The present study confirms previous hypotheses on the possible relevance of EC in the study of life history, pointing moreover to their usefulness in evolutionary studies.     

Life History and Demographic Drivers of Reservoir Competence for Three Tick-Borne Zoonotic Pathogens

Animal and plant species differ dramatically in their quality as hosts for multi-host pathogens, but the causes of this variation are poorly understood. A group of small mammals, including small rodents and shrews, are among the most competent natural reservoirs for three tick-borne zoonotic pathogens, Borrelia burgdorferi, Babesia microti, and Anaplasma phagocytophilum, in eastern North America. For a group of nine commonly-infected mammals spanning >2 orders of magnitude in body mass, we asked whether life history features or surrogates for (unknown) encounter rates with ticks, predicted reservoir competence for each pathogen. Life history features associated with a fast pace of life generally were positively correlated with reservoir competence. However, a model comparison approach revealed that host population density, as a proxy for encounter rates between hosts and pathogens, generally received more support than did life history features. The specific life history features and the importance of host population density differed somewhat between the different pathogens. We interpret these results as supporting two alternative but non-exclusive hypotheses for why ecologically widespread, synanthropic species are often the most competent reservoirs for multi-host pathogens. First, multi-host pathogens might adapt to those hosts they are most likely to experience, which are likely to be the most abundant and/or frequently bitten by tick vectors. Second, species with fast life histories might allocate less to certain immune defenses, which could increase their reservoir competence. Results suggest that of the host species that might potentially be exposed, those with comparatively high population densities, small bodies, and fast pace of life will often be keystone reservoirs that should be targeted for surveillance or management.     

Phenotypic plasticity in age and size at maturity and its effects on the integrated phenotypic expressions of life history traits of Cardamine flexuosa (Cruciferae)

We analyzed variation in phenotypic plasticity of life history traits between two Cardamine flexuosa populations based on differences in plasticity of age and size at maturity. C. flexuosa (Cruciferae) is a facultative, vernalization-sensitive, long-day annual, and its phenology and the phenotypic expressions of many life history traits are largely controlled by photoperiod and vernalization in natural populations. We used plants from two populations which differed in their responses to chilling and photoperiod treatments. The timing of developmental processes was changed by controlling temperature and photoperiod regimes in growth chambers. Plasticity in size at maturity was analyzed as changes in a growth trajectory using two parameters, age at maturity (Δt) and growth rate (k). Both traits showed plasticity, but differences between the populations were found mostly for Δt. Distinctive differences in size at maturity of individuals in the two populations were mainly due to different amounts of plasticity in Δt. Variations in plasticity of nine other life history traits and their associations to age and size at maturity were also analyzed. Variation for eight of the traits can be described, at least in part, as a function of age and size at maturity for both populations, and most of the variation in the total number of seeds was explained by age and size at maturity. Only age at maturity had any effect on changes in resource allocation. The nine life history traits were integrated through associated character expressions with age and size at maturity. Changes in the association between a trait and age and/or size at maturity were rather conservative compared to changes in the plasticity of a trait between the two populations. Associations with age and size at maturity are mostly explicable in terms of inherent relationships in the developmental processes, and they may limit the ecological range expansion and the adaptive evolution of plasticity in C. flexuosa. The negative correlation between reproductive allocation and age at maturity can be a cost of delaying maturation in C. flexuosa.     

Contrasting life histories in neighbouring populations of a large mammal

Background

A fundamental life history question is how individuals should allocate resources to reproduction optimally over time (reproductive allocation). The reproductive restraint hypothesis predicts that reproductive effort (RE; the allocation of resources to current reproduction) should peak at prime-age, whilst the terminal investment hypothesis predicts that individuals should continue to invest more resources in reproduction throughout life, owing to an ever-decreasing residual reproductive value. There is evidence supporting both hypotheses in the scientific literature.

Methodology/Principal Findings

We used an uncommonly large, 38 year dataset on Alpine chamois (Rupicapra rupicapra) shot at various times during the rutting period to test these two hypotheses. We assumed that body mass loss in rutting males was strongly related to RE and, using a process-based approach, modelled how male relative mass loss rates varied with age. For different regions of our study area, we provide evidence consistent with different hypotheses for reproductive allocation. In sites where RE declined in older age, this appears to be strongly linked to declining body condition in old males. In this species, terminal investment may only occur in areas with lower rates of body mass senescence.

Conclusions/Significance

Our results show that patterns of reproductive allocation may be more plastic than previously thought. It appears that there is a continuum from downturns in RE at old age to terminal investment that can be manifest, even across adjacent populations. Our work identifies uncertainty in the relationship between reproductive restraint and a lack of competitive ability in older life (driven by body mass senescence); both could explain a decline in RE in old age and may be hard to disentangle in empirical data. We discuss a number of environmental and anthropogenic factors which could influence reproductive life histories, underlining that life history patterns should not be generalised across different populations.     

Bone Histology Reveals a High Environmental and Metabolic Plasticity as a Successful Evolutionary Strategy in a Long-Lived Homeostatic Triassic Temnospondyl

Evolutionary stasis (long-term stability of morphology in an evolving lineage) is a pattern for which explanations are usually elusive. The Triassic tetrapod Gerrothorax pulcherrimus, a gill-bearing temnospondyl, survived for 35 million years in the Germanic Basin of Central Europe persisting throughout the dinosaur-dominated Late Triassic period. This evolutionary stasis coincides with the occurrence of this species in a wide range of habitats and environmental conditions. By the combination of palaeoecological and palaeohistological analyses, we found great ecological flexibility in G. pulcherrimus and present substantial evidence of developmental and metabolic plasticity despite the morphological stasis. We conclude that G. pulcherrimus could show the capacity to settle in water bodies too harsh or unpredictable for most other tetrapods. This would have been made possible by a unique life history strategy that involved a wide reaction norm, permitting adjustment to fluctuating conditions such as salinity and level of nutrients. Growth rate, duration of juvenile period, age at maturity, and life span were all subject to broad variation within specimens of G. pulcherrimus in one single lake and in between different lakes. In addition to providing a better understanding of fossil ecosystems, this study shows the potential of such a methodology to encourage palaeobiologists and evolutionary biologists to consider the mechanisms of variation in extant and fossil organisms by using a similar time-scope reference.