Search

Understanding species coexistence requires information about how species interact and partition their ecological niche. Niches of closely related species tend to be quite similar and thereby, when syntopic, overlap can result in competition when shared resources are limiting. Brocket deer of tropical forests are ecologically similar species due to convergence or relatedness. As a group, what little is known about their ecology suggests spatial and temporal niche separation while dietary differences among species remain largely unknown. The possibility of competition has been suggested, as it is rare for more than two species to co‐occur. If competition is important, then it may limit syntopy of more species and its importance should increase with relatedness between species. Based on analyses of faecal samples, camera traps, and stable isotopes and multidimensional analysis of niche space, we test spatial, temporal and dietary niche differences and compare niche breadth in two syntopic species pairs: Mazama rufa with M. nana (both of subtribe Odocoileina) and M. jucunda (Odocoileina) with Subulo gouazoubira (Blastocerina). In 2007–2008 and 2017–2019, 240 faecal samples and 375 records were collected in the Brazilian Atlantic Forest. Spatial partitioning among both species pairs was found, with S. gouazoubira and M. nana having greater niche breadth, which may permit or facilitate coexistence. Odocoileina tend to be nocturnal, while Blastocerina tend to be diurnal, which suggests that phylogeny may influence species coexistence. Furthermore, the species tended to overlap with respect to diet. These results suggest interference competition avoidance by niche partitioning at the level of habitat and time, allowing coexistence. Thereby, despite the morphological similarities, brocket deer species of evolutionarily convergent subtribes preserve differences in ecological niche dimensions that facilitate the coexistence of their populations. [ABSTRACT FROM AUTHOR]

Understanding how fecal glucocorticoid (GC) concentration is associated with reproduction in wild animals allows us to associate physiological stress with the costs of reproduction. Glucocorticoids are among the main stress-related hormones, and their secretion is strongly associated with reproductive seasonality. Using non-invasive methods (thereby avoiding causing stress), we used fecal GC metabolites (FGC) to test the hypothesis that the reproductive phase (mating, non-mating, gestation, and lactation) influences stress levels of the seasonally reproductive Pampas Deer (Ozotoceros bezoarticus). Furthermore, we compared FGC between sexes and between males of different antler statuses (velvet, hard, cast). During 1 year, in the Pantanal of Brazil, we collected 621 fresh fecal samples (327 from females, 294 from males) from which we estimated FGC using enzyme immunoassay (EIA). FGC concentrations varied by reproductive phase and antler status. Agonistic and courtship interactions associated with mating (i.e., fights between males, attempts to mount females), suggest that they influence FGC concentrations most strongly in both sexes. Females also had greater FGC concentrations during lactation, suggesting that this phase and parental care are also associated with increased physiological stress. In males, the association of FGC concentrations with antler status may be, in part, associated with photoperiod and testosterone secretion, both of which can trigger reproductive and agonistic behaviors. Finally, reproductive synchrony of the sexes causes similar FGC over time and suggests that environmental factors contribute as well. We show that non-invasive monitoring of glucocorticoid metabolites levels is an effective tool for detecting changes in the physiological stress response in Pampas Deer, suggesting that this tool will be useful for detecting changes in physiological stress caused by human disturbance, such as cattle ranching in Pantanal and similar disturbances elsewhere. [ABSTRACT FROM AUTHOR]

We propose an experimental activity in order to develop a mathematical model that relates step length and walking speed of human beings. We employ two well-known physics teaching softwares, namely, Tracker to carry out the video analysis and LibreOffice/Calc to obtain graphs, trend lines and equations. The predictions of our model are compared with those of similar models present in the literature. This activity is simple, practical and viable in the most diverse school circumstances, and it has been applied on several occasions in high school lectures at our institute. We have found that it can be, in many ways, useful in physics teaching.

We study a sample of 936 early-type galaxies located in 48 low- z regular galaxy clusters with M 200 ≥ 1014 M⊙ at z < 0.1. We examine variations in the Kormendy relation (KR) according to their location in the projected phase space (PPS) of the clusters. We have used a combination of Bayesian statistical methods to identify possible differences between the fitted relations. Our results indicate that the overall KR is better fitted when we take into account the information about PPS regions. We also find that objects with time since infall ≥6.5 Gyr have a significant statistical difference of the KR coefficients relative to objects that are more recent in the cluster environment. We show that giant central ellipticals are responsible for tilting the KR towards smaller slopes. These galaxies present a late growth probably due to cumulative preprocessing during infall, plus cannibalism and accretion of smaller stripped objects near the centre of the clusters. [ABSTRACT FROM AUTHOR]

The structural, electronic, and optical properties of homogeneous and inhomogeneous Ca 1 − x Mg x O alloys are studied with the density functional theory (DFT) under the assumption of polymorphism. Large supercells (2 × 2 × 2 and above) with different lattice symmetries and varying Mg molar fraction x were constructed, representing distinct solid phases that may coexist in micro/nanodomains of inhomogeneous alloys. We demonstrate that these polymorphs exhibit rich phenomenology like similar formation enthalpies for a given concentration x , but different electronic and optical properties. For example, Ca 0.5 Mg 0.5 O may have crystallites with four possible lattice symmetries using a 2 × 2 × 2 supercell for its description, with bandgaps varying between 3.26 eV (direct) and 4.46 eV (indirect). The DFT-simulated X-ray diffraction shows that polymorphism causes broadening and shift of the diffraction peaks. We also performed a detailed calculation of the bandgaps, optical absorption, and dielectric constants as a function of x for each polymorph, and they exhibit a structured bandgap behavior with maxima and minima in the 0.0 < x < 1.0 range, which is in marked contrast to Vegard's law rule of mixtures. We also report a direct-to-indirect bandgap transition occurring between 0.072 ≤ x ≤ 0.1094 for the F M 3 ¯ M symmetry. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the effect of genotype–environment interaction (GEI) on the yearling weight of Simmental cattle raised in Brazil, including the sex dimorphism in reaction norm models. The environmental gradient (EG) was formed using the average weight at 365 days of the contemporary groups. Two approaches were adopted in this study to evaluate reaction norms for weight at 365 days: a single-trait model and a multitrait model in which the data for males and females were separated and considered different traits for the analysis of sexual dimorphism. The genetic parameters were estimated using the Bayesian inference and Gibbs sampling. Analysis of the trend of the heritability estimates obtained with the single-trait model along the EG revealed a value of about 0.33 (EG: −21) in the worst environments, which decreased in the intermediate environments and reached a value of 0.24 in EG: −8, with a subsequent increase of the estimates up to 0.51 in EG: +23. Using the multitrait model, similar trends were observed for the heritability estimates, which ranged from 0.25 to 0.54 for males and from 0.23 to 0.50 for females. The results show that the weight of Simmental cattle raised in the tropics is influenced by GEI and greater genetic progress could be obtained by selecting better environments. However, no significant differences in the response to most environmental changes were observed between sexes and there is only evidence of genetic heteroscedasticity in environments with lower production levels. [ABSTRACT FROM AUTHOR]