1,055 research outputs found
Geographical and temporal body size variation in a reptile: roles of sex, ecology, phylogeny and ecology structured in phylogeny.
Geographical body size variation has long interested evolutionary biologists, and a range of mechanisms have been proposed to explain the observed patterns. It is considered to be more puzzling in ectotherms than in endotherms, and integrative approaches are necessary for testing non-exclusive alternative mechanisms. Using lacertid lizards as a model, we adopted an integrative approach, testing different hypotheses for both sexes while incorporating temporal, spatial, and phylogenetic autocorrelation at the individual level. We used data on the Spanish Sand Racer species group from a field survey to disentangle different sources of body size variation through environmental and individual genetic data, while accounting for temporal and spatial autocorrelation. A variation partitioning method was applied to separate independent and shared components of ecology and phylogeny, and estimated their significance. Then, we fed-back our models by controlling for relevant independent components. The pattern was consistent with the geographical Bergmann's cline and the experimental temperature-size rule: adults were larger at lower temperatures (and/or higher elevations). This result was confirmed with additional multi-year independent data-set derived from the literature. Variation partitioning showed no sex differences in phylogenetic inertia but showed sex differences in the independent component of ecology; primarily due to growth differences. Interestingly, only after controlling for independent components did primary productivity also emerge as an important predictor explaining size variation in both sexes. This study highlights the importance of integrating individual-based genetic information, relevant ecological parameters, and temporal and spatial autocorrelation in sex-specific models to detect potentially important hidden effects. Our individual-based approach devoted to extract and control for independent components was useful to reveal hidden effects linked with alternative non-exclusive hypothesis, such as those of primary productivity. Also, including measurement date allowed disentangling and controlling for short-term temporal autocorrelation reflecting sex-specific growth plasticity
How to generate pentagonal symmetry using Turing systems
We explore numerically the formation of Turing patterns in a confined circular domain with small aspect ratio. Our results show that stable fivefold patterns are formed over a well defined range of disk sizes, offering a possible mechanism for inducing the fivefold symmetry observed in early development of regular echinoids. Using this pattern as a seed, more complex biological structures can be mimicked, such as the pigmentation pattern of sea urchins and the plate arrangements of the calyxes of primitive camerate crinoids
Non-linear effects on Turing patterns: time oscillations and chaos.
We show that a model reaction-diffusion system with two species in a monostable regime and over a large region of parameter space, produces Turing patterns coexisting with a limit cycle which cannot be discerned from the linear analysis. As a consequence, Turing patterns oscillate in time, a phenomenon which is expected to occur only in a three morphogen system. When varying a single parameter, a series of bifurcations lead to period doubling, quasi-periodic and chaotic oscillations without modifying the underlying Turing pattern. A Ruelle-Takens-Newhouse route to chaos is identified. We also examined the Turing conditions for obtaining a diffusion driven instability and discovered that the patterns obtained are not necessarily stationary for certain values of the diffusion coefficients. All this results demonstrates the limitations of the linear analysis for reaction-diffusion systems
Coubertin and the artistic competitions in the Modern Olympic Games
El objetivo de este trabajo es analizar la importancia que tenía para
Coubertin la inclusión de concursos artísticos en el programa oficial de los
Juegos Olímpicos modernos. Se estudiará cómo, cuándo y por qué surgió la idea
en Coubertin de unir de manera armoniosa las artes y las letras a los Juegos
Olímpicos, como ya ocurriera en la antigua Olimpia. En los Juegos Olímpicos de
Estocolmo de 1912, se celebraron por primera vez competiciones deportivas y
concursos artísticos, cumpliéndose el anhelo de Coubertin. Sin embargo,
después de siete citas olímpicas en las que se habían celebrado concursos
artísticos, el COI decidió suprimirlos en 1949, sustituyéndolos por “Olimpíadas
Culturales”, “exhibiciones” o “exposiciones”. La metodología de este estudio es
histórica y se fundamenta en fuentes primarias y secundarias. Como conclusión,
para Coubertin fueron tan importantes los concursos artísticos en los Juegos
Olímpicos modernos que tuvieron el mismo rango que las competiciones
deportivasThe aim of this essay is to analyse the importance that Coubertin gave to
including the artistic competitions in the official programme of the modern
Olympic Games. It will be studied how, when and why Coubertin's idea of
harmoniously joining arts and letters to the Olympic Games appeared, as it had
already happened in ancient Olympia. In the Olympic Games of Stockholm
1912, sport and artistic competitions were celebrated for the first time, fulfilling
thus Coubertin's longing. However, after seven Olympic events where artistic
competitions had been held, the IOC decided to eliminate them in 1949 and to
replace them for "Cultural Olympics", "exhibitions" or "expositions". The
methodology of this study is historical and based on primary and secondary
sources. In conclusion, to Coubertin the artistic competitions in the modern
Olympic Games were so important as to have the same status as the sport
competition
Microhabitat selection in the common lizard: implications of biotic interactions, age, sex, local processes, and model transferability among populations.
Modeling species' habitat requirements are crucial to assess impacts of global change, for conservation efforts and to test mechanisms driving species presence. While the influence of abiotic factors has been widely examined, the importance of biotic factors and biotic interactions, and the potential implications of local processes are not well understood. Testing their importance requires additional knowledge and analyses at local habitat scale. Here, we recorded the locations of species presence at the microhabitat scale and measured abiotic and biotic parameters in three different common lizard (Zootoca vivipara) populations using a standardized sampling protocol. Thereafter, space use models and cross-evaluations among populations were run to infer local processes and estimate the importance of biotic parameters, biotic interactions, sex, and age. Biotic parameters explained more variation than abiotic parameters, and intraspecific interactions significantly predicted the spatial distribution. Significant differences among populations in the relationship between abiotic parameters and lizard distribution, and the greater model transferability within populations than between populations are in line with effects predicted by local adaptation and/or phenotypic plasticity. These results underline the importance of including biotic parameters and biotic interactions in space use models at the population level. There were significant differences in space use between sexes, and between adults and yearlings, the latter showing no association with the measured parameters. Consequently, predictive habitat models at the population level taking into account different sexes and age classes are required to understand a specie's ecological requirements and to allow for precise conservation strategies. Our study therefore stresses that future predictive habitat models at the population level and their transferability should take these parameters into account
The sizes of disc galaxies in intermediate-redshift clusters
We examine how the location of star formation within disc galaxies depends on
environment at intermediate redshift. This is achieved by comparing
emission-line (r_em) and restframe B-band (r_B) scalelengths for matched
samples of 50 field and 19 cluster star-forming, disc galaxies, with 0.25 < z <
1.0 and M_B < -19.5 mag. We find that at a given r_B the majority of our
cluster galaxies have r_em smaller than those in the field, by 25 percent on
average. These results are compared with studies of local galaxies, which find
a very similar behaviour. From the relations of r_em and r_B versus B-band
absolute magnitude (M_B) we infer that the difference between the
intermediate-z cluster and field samples is mostly attributable to variation in
r_em at a given M_B, while the r_B versus M_B relation is similar for the two
samples.Comment: 5 pages, 5 figures, accepted for publication in MNRAS Letter
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