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1.
Science ; 374(6575): eabf5787, 2021 Dec 24.
Artigo em Inglês | MEDLINE | ID: mdl-34941418

RESUMO

Body sizes of marine amniotes span six orders of magnitude, yet the factors that governed the evolution of this diversity are largely unknown. High primary production of modern oceans is considered a prerequisite for the emergence of cetacean giants, but that condition cannot explain gigantism in Triassic ichthyosaurs. We describe the new giant ichthyosaur Cymbospondylus youngorum sp. nov. with a 2-meter-long skull from the Middle Triassic Fossil Hill Fauna of Nevada, USA, underscoring rapid size evolution despite the absence of many modern primary producers. Surprisingly, the Fossil Hill Fauna rivaled the composition of modern marine mammal faunas in terms of size range, and energy-flux models suggest that Middle Triassic marine food webs were able to support several large-bodied ichthyosaurs at high trophic levels, shortly after ichthyosaur origins.


Assuntos
Evolução Biológica , Tamanho Corporal , Cetáceos/anatomia & histologia , Fósseis , Répteis/anatomia & histologia , Animais , Organismos Aquáticos , Cetáceos/fisiologia , Simulação por Computador , Dieta , Ecossistema , Cadeia Alimentar , Filogenia , Répteis/classificação , Répteis/fisiologia , Crânio/anatomia & histologia , Vertebrados/anatomia & histologia , Vertebrados/fisiologia
2.
J Evol Biol ; 34(5): 830-844, 2021 05.
Artigo em Inglês | MEDLINE | ID: mdl-33714223

RESUMO

Ecogeographical displacement of homoploid hybrid lineages from their parents is well documented and considered an important mechanism to achieve reproductive isolation. In this study, we investigated the origin of the flowering plant species Sempervivum tectorum in the Massif Central (France) through homoploid hybridization between lineages of the species from the Rhine Gorge area (Germany) and the Pyrenees (France). We used genotyping-by-sequencing genetic data as evidence for the hybrid origin of the Massif Central lineage, and WorldClim climatic data and soil pH and soil temperature data collected by us for ecological niche and species distribution modelling. We could show that the Massif Central lineage shows hybrid admixture and that the niche of this lineage is significantly different from those of the parental lineages. In comparison with the parental niches, different variables of the niche of the hybrid lineage are intermediate, parental-combined or extreme. The different niche of the Massif Central populations thus can plausibly be interpreted as hybridization-derived. Our species distribution modelling for the Last Glacial Maximum and Mid-Holocene showed that the potential distribution of the hybrid lineage at the likely time of its origin in the Quaternary possibly was parapatric in relation to the largely sympatric distributions of the parental lineages. We hypothesize that reproductive isolation of the hybrid lineage from the parental lineages resulted from the segregation of distribution ranges by a differential response of the three lineages to a warming climate.


Assuntos
Mudança Climática , Crassulaceae/genética , Hibridização Genética , Modelos Biológicos , Isolamento Reprodutivo , Adaptação Biológica , Ecossistema , Europa (Continente) , Filogeografia , Ploidias
3.
Ecol Evol ; 10(3): 1233-1251, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-32076510

RESUMO

While many morphological, physiological, and ecological characteristics of organisms scale with body size, some do not change under size transformation. They are called invariant. A recent study recommended five criteria for identifying invariant traits. These are based on that a trait exhibits a unimodal central tendency and varies over a limited range with body mass (type I), or that it does not vary systematically with body mass (type II). We methodologically improved these criteria and then applied them to life history traits of amphibians, Anura, Caudata (eleven traits), and reptiles (eight traits). The numbers of invariant traits identified by criteria differed across amphibian orders and between amphibians and reptiles. Reproductive output (maximum number of reproductive events per year), incubation time, length of larval period, and metamorphosis size were type I and II invariant across amphibians. In both amphibian orders, reproductive output and metamorphosis size were type I and II invariant. In Anura, incubation time and length of larval period and in Caudata, incubation time were further type II invariant. In reptiles, however, only number of clutches per year was invariant (type II). All these differences could reflect that in reptiles body size and in amphibians, Anura, and Caudata metamorphosis (neotenic species go not through it) and the trend toward independence of egg and larval development from water additionally constrained life history evolution. We further demonstrate that all invariance criteria worked for amphibian and reptilian life history traits, although we corroborated some known and identified new limitations to their application.

4.
Ecol Evol ; 8(11): 5480-5494, 2018 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-29938067

RESUMO

Allometric relationships linking species characteristics to body size or mass (scaling) are important in biology. However, studies on the scaling of life history traits in the reptiles (the nonavian Reptilia) are rather scarce, especially for the clades Crocodilia, Testudines, and Rhynchocephalia (single extant species, the tuatara). Previous studies on the scaling of reptilian life history traits indicated that they differ from those seen in the other amniotes (mammals and birds), but so far most comparative studies used small species samples and also not phylogenetically informed analyses. Here, we analyzed the scaling of nine life history traits with adult body mass for crocodiles (n = 22), squamates (n = 294), turtles (n = 52), and reptiles (n = 369). We used for the first time a phylogenetically informed approach for crocodiles, turtles, and the whole group of reptiles. We explored differences in scaling relationships between the reptilian clades Crocodilia, Squamata, and Testudines as well as differences between reptiles, mammals, and birds. Finally, we applied our scaling relationships, in order to gain new insights into the degree of the exceptionality of the tuatara's life history within reptiles. We observed for none of the life history traits studied any difference in their scaling with body mass between squamates, crocodiles, and turtles, except for clutch size and egg weight showing small differences between these groups. Compared to birds and mammals, scaling relationships of reptiles were similar for time-related traits, but they differed for reproductive traits. The tuatara's life history is more similar to that of a similar-sized turtle or crocodile than to a squamate.

5.
PLoS One ; 13(2): e0184756, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29489816

RESUMO

In his 2016 paper, Myhrvold criticized ours from 2014 on maximum growth rates (Gmax, maximum gain in body mass observed within a time unit throughout an individual's ontogeny) and thermoregulation strategies (ectothermy, endothermy) of 17 dinosaurs. In our paper, we showed that Gmax values of similar-sized extant ectothermic and endothermic vertebrates overlap. This strongly questions a correct assignment of a thermoregulation strategy to a dinosaur only based on its Gmax and (adult) body mass (M). Contrary, Gmax separated similar-sized extant reptiles and birds (Sauropsida) and Gmax values of our studied dinosaurs were similar to those seen in extant similar-sized (if necessary scaled-up) fast growing ectothermic reptiles. Myhrvold examined two hypotheses (H1 and H2) regarding our study. However, we did neither infer dinosaurian thermoregulation strategies from group-wide averages (H1) nor were our results based on that Gmax and metabolic rate (MR) are related (H2). In order to assess whether single dinosaurian Gmax values fit to those of extant endotherms (birds) or of ectotherms (reptiles), we already used a method suggested by Myhrvold to avoid H1, and we only discussed pros and cons of a relation between Gmax and MR and did not apply it (H2). We appreciate Myhrvold's efforts in eliminating the correlation between Gmax and M in order to statistically improve vertebrate scaling regressions on maximum gain in body mass. However, we show here that his mass-specific maximum growth rate (kC) replacing Gmax (= MkC) does not model the expected higher mass gain in larger than in smaller species for any set of species. We also comment on, why we considered extant reptiles and birds as reference models for extinct dinosaurs and why we used phylogenetically-informed regression analysis throughout our study. Finally, we question several arguments given in Myhrvold in order to support his results.


Assuntos
Dinossauros , Répteis , Animais , Aves , Análise de Regressão
6.
J Theor Biol ; 444: 83-92, 2018 05 07.
Artigo em Inglês | MEDLINE | ID: mdl-29452173

RESUMO

Ectothermic and endothermic vertebrates differ not only in their source of body temperature (environment vs. metabolism), but also in growth patterns, in timing of sexual maturation within life, and energy intake functions. Here, we present a mathematical model applicable to ectothermic and endothermic vertebrates. It is designed to test whether differences in the timing of sexual maturation within an animal's life (age at which sexual maturity is reached vs. longevity) together with its ontogenetic gain in body mass (growth curve) can predict the energy intake throughout the animal's life (food intake curve) and can explain differences in energy partitioning (between growth, reproduction, heat production and maintenance, with the latter subsuming any other additional task requiring energy) between ectothermic and endothermic vertebrates. With our model we calculated from the growth curves and ages at which species reached sexual maturity energy intake functions and energy partitioning for five ectothermic and seven endothermic vertebrate species. We show that our model produces energy intake patterns and distributions as observed in ectothermic and endothermic species. Our results comply consistently with some empirical studies that in endothermic species, like birds and mammals, energy is used for heat production instead of growth, and with a hypothesis on the evolution of endothermy in amniotes published by us before. Our model offers an explanation on known differences in absolute energy intake between ectothermic fish and reptiles and endothermic birds and mammals. From a mathematical perspective, the model comes in two equivalent formulations, a differential and an integral one. It is derived from a discrete level approach, and it is shown to be well-posed and to attain a unique solution for (almost) every parameter set. Numerically, the integral formulation of the model is considered as an inverse problem with unknown parameters that are estimated using a series of empirical data.


Assuntos
Ingestão de Energia/fisiologia , Modelos Teóricos , Termogênese/fisiologia , Animais , Índice de Massa Corporal , Temperatura Corporal , Crescimento/fisiologia , Maturidade Sexual/fisiologia , Vertebrados
7.
Naturwissenschaften ; 104(11-12): 90, 2017 Oct 11.
Artigo em Inglês | MEDLINE | ID: mdl-29022052

RESUMO

Endothermy and its evolution are still an unresolved issue. Here, we present a model which transforms an ectothermic amniote (ancestor) into a derived amniote (descendant) showing many characteristics seen in extant endothermic birds and mammals. Consistent with the fossil record within the ancestral lineages of birds and mammals, the model assumes that mutations in genes which get active during ontogeny and affect body growth resulted in a reduced asymptotic body size and an early growth stop of the descendant. We show that such a postulated early growth stop in the descendant simultaneously increases the growth rate and metabolic rate, and also changes six life history traits (offspring mass, annual clutch/litter mass, number of offspring per year, age and mass at which sexual maturity is reached, age at which the individual is fully grown) of the descendant compared to a similar-sized ancestor. All these changes coincide with known differences between recent ectothermic and endothermic amniotes. We also elaborate many other differences and similarities in biological characteristics supporting the early growth stop. An early stop in growth during ontogeny thus could have played a key role in the evolution of endothermy within the reptilia and therapsids. It generated variability in characteristics of ancestral ectotherms, which was subject to natural selection in the past and resulted in many adaptations linked to endothermy in today's birds and mammals.


Assuntos
Evolução Biológica , Regulação da Temperatura Corporal/genética , Crescimento e Desenvolvimento/fisiologia , Modelos Biológicos , Adaptação Fisiológica/genética , Animais , Tamanho Corporal , Fósseis , Crescimento e Desenvolvimento/genética
8.
Ecol Evol ; 6(23): 8352-8365, 2016 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-28031788

RESUMO

Whether basal metabolic rate-body mass scaling relationships have a single exponent is highly discussed, and also the correct statistical model to establish relationships. Here, we aimed (1) to identify statistically best scaling models for 17 mammalian orders, Marsupialia, Eutheria and all mammals, and (2) thereby to prove whether correcting for differences in species' body temperature and their shared evolutionary history improves models and their biological interpretability. We used the large dataset from Sieg et al. (The American Naturalist174, 2009, 720) providing species' body mass (BM), basal metabolic rate (BMR) and body temperature (T). We applied different statistical approaches to identify the best scaling model for each taxon: ordinary least squares regression analysis (OLS) and phylogenetically informed analysis (PGLS), both without and with controlling for T. Under each approach, we tested linear equations (log-log-transformed data) estimating scaling exponents and normalization constants, and such with a variable normalization constant and a fixed exponent of either ⅔ or ¾, and also a curvature. Only under temperature correction, an additional variable coefficient modeled the influence of T on BMR. Except for Pholidata and Carnivora, in all taxa studied linear models were clearly supported over a curvature by AICc. They indicated no single exponent at the level of orders or at higher taxonomic levels. The majority of all best models corrected for phylogeny, whereas only half of them included T. When correcting for T, the mathematically expected correlation between the exponent (b) and the normalization constant (a) in the standard scaling model y = a xb was removed, but the normalization constant and temperature coefficient still correlated strongly. In six taxa, T and BM correlated positively or negatively. All this hampers a disentangling of the effect of BM, T and other factors on BMR, and an interpretation of linear BMR-BM scaling relationships in the mammalian taxa studied.

9.
Environ Entomol ; 45(4): 829-40, 2016 08.
Artigo em Inglês | MEDLINE | ID: mdl-27271947

RESUMO

In Germany, the thermophilic European mantid (Mantis religiosa L.) is endangered. Here, we study habitat requirements during its life, and discuss the applicability of the two conservation measures grazing and mowing to this insect species. At two study sites in south-western Germany, which were each subject to one of these measures, we recorded structural and climatic conditions within different microhabitats. We also conducted capture-mark-recapture studies for adult M. religiosa, and mapped adult roosting, oothecae deposition, egg hatching, and imaginal molting in microhabitats over two vegetation periods. In order to assess microhabitat preference of M. religiosa during its life, and identify climatic conditions driving preferences, we applied the Lille habitat preference index and conducted logistic regression analysis for life phases. Our results suggest that temperature is important for egg and nymph development. For egg deposition, females preferred solid substrates with high heat-storing capacities, as those attenuate the negative influence of cold weather periods on egg development. Being ambush predators, males and females preferred roosting sites with sufficient shelter and high prey abundance. Contrary to our expectation, the conservation measures reduced adult population sizes, and presumably reproduction rates. We thus suggest that mowing during the adult phase should reduce vegetation height to a moderate level to keep prey abundance high. Mowing with a clearing saw or grazing over a short period in small fenced areas should be preferred over prolonged grazing, as grazers collaterally stamp down the vegetation. Grazers indirectly reduce prey availability by deteriorating prevailing microclimatic conditions.


Assuntos
Conservação dos Recursos Naturais , Ecossistema , Mantódeos/fisiologia , Comportamento Predatório , Animais , Espécies em Perigo de Extinção , Feminino , Alemanha , Masculino , Mantódeos/crescimento & desenvolvimento , Ninfa/crescimento & desenvolvimento , Ninfa/fisiologia , Óvulo/crescimento & desenvolvimento , Óvulo/fisiologia , Densidade Demográfica
10.
Ecol Evol ; 6(10): 3146-53, 2016 May.
Artigo em Inglês | MEDLINE | ID: mdl-27096075

RESUMO

Most large mammals have constantly been exposed to anthropogenic influence over decades or even centuries. Because of their long generation times and lack of sampling material, inferences of past population genetic dynamics, including anthropogenic impacts, have only relied on the analysis of the structure of extant populations. Here, we investigate for the first time the change in the genetic constitution of a natural red deer population over two centuries, using up to 200-year-old antlers (30 generations) stored in trophy collections. To the best of our knowledge, this is the oldest DNA source ever used for microsatellite population genetic analyses. We demonstrate that government policy and hunting laws may have strong impacts on populations that can lead to unexpectedly rapid changes in the genetic constitution of a large mammal population. A high ancestral individual polymorphism seen in an outbreeding population (1813-1861) was strongly reduced in descendants (1923-1940) during the mid-19th and early 20th century by genetic bottlenecks. Today (2011), individual polymorphism and variance among individuals is increasing in a constant-sized (managed) population. Differentiation was high among periods (F ST > ***); consequently, assignment tests assigned individuals to their own period with >85% probability. In contrast to the high variance observed at nuclear microsatellite loci, mtDNA (D-loop) was monomorphic through time, suggesting that male immigration dominates the genetic evolution in this population.

11.
Mar Pollut Bull ; 102(1): 134-41, 2016 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-26621577

RESUMO

Plastic ingestion by marine biota has been reported for a variety of different taxa. In this study, we investigated 290 gastrointestinal tracts of demersal (cod, dab and flounder) and pelagic fish species (herring and mackerel) from the North and Baltic Sea for the occurrence of plastic ingestion. In 5.5% of all investigated fishes, plastic particles were detected, with 74% of all particles being in the microplastic (<5mm) size range. The polymer types of all found particles were analysed by means of Fourier transform infrared (FT-IR) spectroscopy. Almost 40% of the particles consisted of polyethylene (PE). In 3.4% of the demersal and 10.7% of the pelagic individuals, plastic ingestion was recorded, showing a significantly higher ingestion frequency in the pelagic feeders. The condition factor K was calculated to test differences in the fitness status between individuals with and without ingested plastic, but no direct effect was detected.


Assuntos
Ingestão de Alimentos , Monitoramento Ambiental , Peixes , Plásticos/análise , Poluentes Químicos da Água/análise , Animais , Humanos , Mar do Norte , Polietileno/análise , Polímeros , Espectroscopia de Infravermelho com Transformada de Fourier
12.
R Soc Open Sci ; 2(7): 140440, 2015 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-26587259

RESUMO

Placodontia is a clade of durophagous, near shore marine reptiles from Triassic sediments of modern-day Europe, Middle East and China. Although much is known about their primary anatomy and palaeoecology, relatively little has been published regarding their life history, i.e. ageing, maturation and growth. Here, growth records derived from long bone histological data of placodont individuals are described and modelled to assess placodont growth and life-history strategies. Growth modelling methods are used to confirm traits documented in the growth record (age at onset of sexual maturity, age when asymptotic length was achieved, age at death, maximum longevity) and also to estimate undocumented traits. Based on these growth models, generalized estimates of these traits are established for each taxon. Overall differences in bone tissue types and resulting growth curves indicate different growth patterns and life-history strategies between different taxa of Placodontia. Psephoderma and Paraplacodus grew with lamellar-zonal bone tissue type and show growth patterns as seen in modern reptiles. Placodontia indet. aff. Cyamodus and some Placodontia indet. show a unique combination of fibrolamellar bone tissue regularly stratified by growth marks, a pattern absent in modern sauropsids. The bone tissue type of Placodontia indet. aff. Cyamodus and Placodontia indet. indicates a significantly increased basal metabolic rate when compared with modern reptiles. Double lines of arrested growth, non-annual rest lines in annuli, and subcycles that stratify zones suggest high dependence of placodont growth on endogenous and exogenous factors. Histological and modelled differences within taxa point to high individual developmental plasticity but sexual dimorphism in growth patterns and the presence of different taxa in the sample cannot be ruled out.

13.
PLoS One ; 10(9): e0138785, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26393343

RESUMO

The eggshell is an important physiological structure for the embryo. It enables gas exchange, physical protection and is a calcium reserve. Most squamates (lizards, snakes, worm lizards) lay parchment-shelled eggs, whereas only some gekkotan species, a subgroup of lizards, have strongly calcified eggshells. In viviparous (live-bearing) squamates the eggshell is reduced or completely missing (hereafter "shell-less"). Recent studies showed that life-history strategies of gekkotan species differ between species with parchment- and rigid-shelled eggshells. Here we test if the three different eggshell types found in the squamates are also associated with different life-history strategies. We first investigated the influence of the phylogeny on the trait "eggshell type" and on six life-history traits of 32 squamate species. Phylogenetic principal component analysis (pPCA) was then conducted to identify an association between life-history strategies and eggshell types. Finally, we also considered adult weight in the pPCA to examine its potential effect on this association. Eggshell types in squamates show a strong phylogenetic signal at a low taxonomical level. Four out of the six life-history traits showed also a phylogenetic signal (birth size, clutch size, clutches per year and age at female maturity), while two had none (incubation time, maximum longevity). The pPCA suggested an association of life-history strategies and eggshell types, which disappeared when adult weight was included in the analysis. We conclude that the variability seen in eggshell types of squamates is weakly influenced by phylogeny. Eggshell types correlate with different life-history strategies, and mainly reflect differences in adult weights of species.


Assuntos
Evolução Biológica , Casca de Ovo/química , Casca de Ovo/fisiologia , Répteis/fisiologia , Animais , Feminino , Filogenia , Análise de Componente Principal , Répteis/classificação , Répteis/genética , Especificidade da Espécie
14.
Mol Biol Rep ; 42(6): 1059-67, 2015 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-25424838

RESUMO

Strong anthropogenic impact has caused 28 of the currently recognized 55 species of deer (Cervidae) to be listed on the IUCN Red List. Particular threats to vulnerable species include habitat deterioration and hybridization with alien, introduced species. The scarcity of many species has severely hampered genetic analyses of their populations, including the detection of loci for cross-species amplification. Because deer antlers are shed and re-grown annually, antlers offer the possibility for non-invasive genetic sampling of large individual numbers, and may provide material for reference genotyping from historical samples stored in zoos, museums and trophy collections of rare and extinct species/populations. In this paper, we report cross-species amplification of 19 nuclear microsatellite loci and the amplification of 16S mtDNA for barcoding from nearly a third of all deer species worldwide based on high quality DNA extracted from antler bone up to 40 years old. Phylogenetic analysis based on mtDNA of seventeen species and five subspecies corroborate previously published phylogenetic data, thus confirming the specific resolution of the DNA extraction methodology.


Assuntos
Chifres de Veado/metabolismo , DNA Mitocondrial/genética , Cervos/genética , Variação Genética , Repetições de Microssatélites/genética , Animais , Código de Barras de DNA Taxonômico/métodos , Cervos/classificação , Genótipo , Masculino , Filogenia , Reação em Cadeia da Polimerase , RNA Ribossômico 16S/classificação , RNA Ribossômico 16S/genética , Especificidade da Espécie
15.
Genetica ; 143(1): 11-20, 2015 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-25500950

RESUMO

Past and recent climatic changes induced shifts in species ranges. Mantis religiosa has also expanded its range across Germany within the past decades. To determine the ancestry of German M. religiosa we sequenced four mitochondrial genes (COI, COII, Cyt b, ND4) of European M. religiosa populations. We found an east, central and west European lineage of M. religiosa. These distinct lineages are consistent with genetic isolation by distance during glacial periods, and the re-colonization of northern parts of Europe by species from different refugia. Within Germany, we found haplotypes clustering to the central and west European lineage suggesting that M. religiosa immigrated from two directions into Germany. Mismatch distributions, and negative Tajima's D and Fu's Fs values indicate a current range expansion of the central and west European lineage. We hypothesise that ongoing global warming which increases the availability of thermally favourable areas in Germany for M. religiosa adds to its current range expansion. In conclusion, M. religiosa colonized Germany via two directions: west German populations descended from French populations and east German populations from Czech populations.


Assuntos
DNA Mitocondrial , Mantódeos/classificação , Mantódeos/genética , Migração Animal , Animais , Meio Ambiente , Europa (Continente) , Variação Genética , Genética Populacional , Geografia , Alemanha , Filogenia , Filogeografia , Análise Espacial
16.
Biomed Res Int ; 2014: 795481, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24883328

RESUMO

Revealing long-term effects of contaminants on the genetic structure of organisms inhabiting polluted environments should encompass analyses at the population, molecular, and cellular level. Following this concept, we studied the genetic constitution of zebra mussel populations from a polluted (Dp) and reference sites (Cl) at the river Drava, Croatia, and applied microsatellite and DNA damage analyses (Comet assay, micronucleus test (MNT)). Additionally, mussels from both populations were exposed to polluted wastewater in the laboratory for three days, and DNA damage was analyzed to evaluate acclimatization and genetic adaptation of the investigated populations to the polluted environment. The two populations differed in their genetic constitution. Microsatellite analysis suggested that Dp had undergone a genetic bottleneck. Comet assay did not indicate any difference in DNA damage between the two populations, but MNT revealed that Dp had an increased percentage of micronuclei in hemocytes in comparison to Cl. The laboratory experiment revealed that Dp had a lower percentage of tail DNA and a higher percentage of micronuclei than Cl. These differences between populations were possibly caused by an overall decreased fitness of Dp due to genetic drift and by an enhanced DNA repair mechanism due to acclimatization to pollution in the source habitat.


Assuntos
Dano ao DNA/genética , Dreissena/genética , Monitoramento Ambiental , Poluentes Químicos da Água , Animais , Croácia , Dano ao DNA/efeitos dos fármacos , Dreissena/efeitos dos fármacos , Água Doce , Testes para Micronúcleos
17.
PLoS One ; 9(2): e88834, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24586409

RESUMO

We tested if growth rates of recent taxa are unequivocally separated between endotherms and ectotherms, and compared these to dinosaurian growth rates. We therefore performed linear regression analyses on the log-transformed maximum growth rate against log-transformed body mass at maximum growth for extant altricial birds, precocial birds, eutherians, marsupials, reptiles, fishes and dinosaurs. Regression models of precocial birds (and fishes) strongly differed from Case's study (1978), which is often used to compare dinosaurian growth rates to those of extant vertebrates. For all taxonomic groups, the slope of 0.75 expected from the Metabolic Theory of Ecology was statistically supported. To compare growth rates between taxonomic groups we therefore used regressions with this fixed slope and group-specific intercepts. On average, maximum growth rates of ectotherms were about 10 (reptiles) to 20 (fishes) times (in comparison to mammals) or even 45 (reptiles) to 100 (fishes) times (in comparison to birds) lower than in endotherms. While on average all taxa were clearly separated from each other, individual growth rates overlapped between several taxa and even between endotherms and ectotherms. Dinosaurs had growth rates intermediate between similar sized/scaled-up reptiles and mammals, but a much lower rate than scaled-up birds. All dinosaurian growth rates were within the range of extant reptiles and mammals, and were lower than those of birds. Under the assumption that growth rate and metabolic rate are indeed linked, our results suggest two alternative interpretations. Compared to other sauropsids, the growth rates of studied dinosaurs clearly indicate that they had an ectothermic rather than an endothermic metabolic rate. Compared to other vertebrate growth rates, the overall high variability in growth rates of extant groups and the high overlap between individual growth rates of endothermic and ectothermic extant species make it impossible to rule out either of the two thermoregulation strategies for studied dinosaurs.


Assuntos
Dinossauros/crescimento & desenvolvimento , Dinossauros/fisiologia , Animais , Evolução Biológica , Aves/crescimento & desenvolvimento , Aves/fisiologia , Índice de Massa Corporal , Ecologia , Peixes/crescimento & desenvolvimento , Peixes/fisiologia , Fósseis , Marsupiais/crescimento & desenvolvimento , Marsupiais/fisiologia , Répteis/crescimento & desenvolvimento , Répteis/fisiologia
18.
PLoS One ; 8(10): e74317, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-24204568

RESUMO

To estimate the body temperature (BT) of seven dinosaurs Gillooly, Alleen, and Charnov (2006) used an equation that predicts BT from the body mass and maximum growth rate (MGR) with the latter preserved in ontogenetic growth trajectories (BT-equation). The results of these authors evidence inertial homeothermy in Dinosauria and suggest that, due to overheating, the maximum body size in Dinosauria was ultimately limited by BT. In this paper, I revisit this hypothesis of Gillooly, Alleen, and Charnov (2006). I first studied whether BTs derived from the BT-equation of today's crocodiles, birds and mammals are consistent with core temperatures of animals. Second, I applied the BT-equation to a larger number of dinosaurs than Gillooly, Alleen, and Charnov (2006) did. In particular, I estimated BT of Archaeopteryx (from two MGRs), ornithischians (two), theropods (three), prosauropods (three), and sauropods (nine). For extant species, the BT value estimated from the BT-equation was a poor estimate of an animal's core temperature. For birds, BT was always strongly overestimated and for crocodiles underestimated; for mammals the accuracy of BT was moderate. I argue that taxon-specific differences in the scaling of MGR (intercept and exponent of the regression line, log-log-transformed) and in the parameterization of the Arrhenius model both used in the BT-equation as well as ecological and evolutionary adaptations of species cause these inaccuracies. Irrespective of the found inaccuracy of BTs estimated from the BT-equation and contrary to the results of Gillooly, Alleen, and Charnov (2006) I found no increase in BT with increasing body mass across all dinosaurs (Sauropodomorpha, Sauropoda) studied. This observation questions that, due to overheating, the maximum size in Dinosauria was ultimately limited by BT. However, the general high inaccuracy of dinosaurian BTs derived from the BT-equation makes a reliable test of whether body size in dinosaurs was ultimately limited by overheating impossible.


Assuntos
Temperatura Corporal , Dinossauros/fisiologia , Algoritmos , Animais , Tamanho Corporal , Dinossauros/anatomia & histologia , Dinossauros/crescimento & desenvolvimento , Gráficos de Crescimento , Modelos Teóricos , Répteis
19.
PLoS One ; 8(8): e72862, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23991160

RESUMO

It has been hypothesized that a high reproductive output contributes to the unique gigantism in large dinosaur taxa. In order to infer more information on dinosaur reproduction, we established allometries between body mass and different reproductive traits (egg mass, clutch mass, annual clutch mass) for extant phylogenetic brackets (birds, crocodiles and tortoises) of extinct non-avian dinosaurs. Allometries were applied to nine non-avian dinosaur taxa (theropods, hadrosaurs, and sauropodomorphs) for which fossil estimates on relevant traits are currently available. We found that the reproductive traits of most dinosaurs conformed to similar-sized or scaled-up extant reptiles or birds. The reproductive traits of theropods, which are considered more bird-like, were indeed consistent with birds, while the traits of sauropodomorphs conformed better to reptiles. Reproductive traits of hadrosaurs corresponded to both reptiles and birds. Excluding Massospondyluscarinatus, all dinosaurs studied had an intermediary egg to body mass relationship to reptiles and birds. In contrast, dinosaur clutch masses fitted with either the masses predicted from allometries of birds (theropods) or to the masses of reptiles (all other taxa). Theropods studied had probably one clutch per year. For sauropodomorphs and hadrosaurs, more than one clutch per year was predicted. Contrary to current hypotheses, large dinosaurs did not have exceptionally high annual egg numbers (AEN). Independent of the extant model, the estimated dinosaur AEN did not exceed 850 eggs (75,000 kg sauropod) for any of the taxa studied. This estimated maximum is probably an overestimation due to unrealistic assumptions. According to most AEN estimations, the dinosaurs studied laid less than 200 eggs per year. Only some AEN estimates obtained for medium to large sized sauropods were higher (200-400 eggs). Our results provide new (testable) hypotheses, especially for reproductive traits that are insufficiently documented or lacking from the fossil record. This contributes to the understanding of their evolution.


Assuntos
Evolução Biológica , Dinossauros , Ecologia , Fósseis , Animais , Dinossauros/classificação , Filogenia
20.
PLoS One ; 8(6): e67012, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23840575

RESUMO

Information on aging, maturation, and growth is important for understanding life histories of organisms. In extinct dinosaurs, such information can be derived from the histological growth record preserved in the mid-shaft cortex of long bones. Here, we construct growth models to estimate ages at death, ages at sexual maturity, ages at which individuals were fully-grown, and maximum growth rates from the growth record preserved in long bones of six sauropod dinosaur individuals (one indeterminate mamenchisaurid, two Apatosaurus sp., two indeterminate diplodocids, and one Camarasaurus sp.) and one basal sauropodomorph dinosaur individual (Plateosaurus engelhardti). Using these estimates, we establish allometries between body mass and each of these traits and compare these to extant taxa. Growth models considered for each dinosaur individual were the von Bertalanffy model, the Gompertz model, and the logistic model (LGM), all of which have inherently fixed inflection points, and the Chapman-Richards model in which the point is not fixed. We use the arithmetic mean of the age at the inflection point and of the age at which 90% of asymptotic mass is reached to assess respectively the age at sexual maturity or the age at onset of reproduction, because unambiguous indicators of maturity in Sauropodomorpha are lacking. According to an AIC-based model selection process, the LGM was the best model for our sauropodomorph sample. Allometries established are consistent with literature data on other Sauropodomorpha. All Sauropodomorpha reached full size within a time span similar to scaled-up modern mammalian megaherbivores and had similar maximum growth rates to scaled-up modern megaherbivores and ratites, but growth rates of Sauropodomorpha were lower than of an average mammal. Sauropodomorph ages at death probably were lower than that of average scaled-up ratites and megaherbivores. Sauropodomorpha were older at maturation than scaled-up ratites and average mammals, but younger than scaled-up megaherbivores.


Assuntos
Envelhecimento/fisiologia , Osso e Ossos/anatomia & histologia , Dinossauros/anatomia & histologia , Dinossauros/crescimento & desenvolvimento , Animais , Evolução Biológica , Índice de Massa Corporal , Tamanho Corporal , Osso e Ossos/fisiologia , Fósseis , Modelos Biológicos , Filogenia , Reprodução
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