Sex-specific covariance between metabolic rate, behaviour and morphology in the ground beetle Carabus hortensis

Background Individuals within the same species often differ in their metabolic rates, which may covary with behavioural traits (such as exploration), that are consistent across time and/or contexts, and morphological traits. Yet, despite the frequent occurrence of sexual dimorphisms in morphology and behaviour, few studies have assessed whether and how sexes differ in metabolic trait covariances. Methods We investigated sex-specific relationships among resting or active metabolic rate (RMR and AMR, respectively) with exploratory behaviour, measured independently of metabolic rate in a novel environment, body size and body mass, in Carabus hortensis ground beetles. Results RMR, AMR and exploratory behaviour were repeatable among individuals across time, except for male RMR which was unrepeatable. Female RMR neither correlated with exploratory behaviour nor body size/body mass. In contrast, AMR was correlated with both body size and exploratory behaviour. Males with larger body sizes had higher AMR, whereas females with larger body sizes had lower AMR. Both male and female AMR were significantly related to exploratory behaviour, though the relationships between AMR and exploration were body mass-dependent in males and temperature-dependent in females. Discussion Differences between sexes exist in the covariances between metabolic rate, body size and exploratory behaviour. This suggests that selection acts differently on males and females to produce these trait covariances with potentially important consequences for individual fitness.

Atmospheric and snow nitrate isotope systematics at Summit, Greenland: the reality of the post-depositional effect

The effect of post–depositional processing on the preservation of snow nitrate isotopes at Summit, Greenland remains a subject of debate which hinders the interpretations of ice–core nitrate concentrations and isotope records. Here we present the first year–round observations of atmospheric aerosol nitrate and its isotopic compositions at Summit, and compare them with published surface snow and snowpack observations. The atmospheric δ15N(NO3–) remained negative throughout the year, ranging from –3.1 ‰ to –47.9 ‰ with a mean of (–14.8 ± 7.3) ‰, and displayed no apparent seasonality that is different from the distinct seasonal δ15N(NO3–) variations observed in snowpack. The spring average aerosol δ15N(NO3–) was (–17.9 ± 8.3) ‰, significantly depleted compared to snowpack spring average of (4.6 ± 2.1) ‰, with surface snow δ15N(NO3–) of (–6.8 ± 0.5) ‰ that is in between. The differences in aerosol, surface snow and snowpack δ15N(NO3–) are best explained by the photo-driven post–depositional processing of snow nitrate, with potential contributions from fractionation during nitrate deposition. In contrast to δ15N(NO3–), the atmospheric Δ17O(NO3–) was of similar seasonal pattern and magnitude of change to that in snowpack, suggesting little to no changes in Δ17O(NO3–) from photolysis, consistent with previous modeling results. The atmospheric δ18O(NO3–) varied similarly as atmospheric Δ17O(NO3–), with summer low and winter high values. However, the difference between atmospheric and snow δ18O(NO3–) was larger than that of Δ17O(NO3–), and the linear relationships between δ18O/Δ17O(NO3–) were different for atmospheric and snowpack samples. This suggests the oxygen isotopes are also affected before preservation in the snow at Summit, but the degree of change for δ18O(NO3–) is larger than that of Δ17O(NO3–) given that photolysis is a mass-dependent process.

The Chirality of Isotopomers of Glycine Compared using Next-Generation QTAIM

The effect of the presence of a deuterium (D) or tritium (T) isotope bonded to the alpha carbon of glycine is determined without the need to apply external forces e.g. electric fields or using normal mode analysis. Isotopic effects were accounted for using the mass-dependent diagonal Born-Oppenheimer energy correction (DBOC) at the CCSD level of theory. We calculated the stress tensor trajectories of the dominant C-N bond within next generation quantum theory of atoms in molecules (NG-QTAIM). S-character chirality was discovered using the stress tensor trajectories, instead of the Cahn–Ingold–Prelog (CIP) rules, for ordinary glycine. The S-character chirality was preserved after the substitution of the H on the alpha carbon for a D isotope but transformed to R-character chirality after replacement with the T isotope. This reversal of the chirality depending on the presence of a single D or T isotope bound to the alpha carbon adds to the debate on the nature of the extraterrestrial origins of chirality in simple amino acids. We demonstrate that NG-QTAIM is a promising tool for understanding isotopic induced electronic charge density changes, useful in analysis of infrared (IR) or circular dichroism (CD) spectra explaining changes in mode couplings and bands intensities or sign.

Critical Stellar Central Densities Drive Galaxy Quenching in the Nearby Universe

We study the structural and environmental dependence of star formation on the plane of stellar mass versus central core density (Σ1 kpc) in the nearby universe. We study the central galaxies in the sparse environment and find a characteristic population-averaged Σ1 kpc ∼ 109–109.2 M ⊙ kpc−2, above which quenching is operating. This Σ 1 kpc crit only weakly depends on the stellar mass, suggesting that the mass quenching of the central galaxies is closely related to the processes that operate in the central region rather than over the entire galaxies. For satellites, at a given stellar mass, environment quenching appears to operate in a similar fashion as mass quenching in centrals, also starting from galaxies with high Σ1 kpc to low Σ1 kpc, and Σ 1 kpc crit becomes strongly mass-dependent, in particular in dense regions. This is because (1) more low-mass satellites are quenched by the environmental effects in denser regions and (2) at fixed stellar mass and environment, the environment-quenched satellites have, on average, larger Σ1 kpc, M 1 kpc/M ⋆, and Sérsic index n, and as well as smaller size. These results imply that either some dynamical processes change the structure of the satellites during quenching or the satellites with higher Σ1 kpc are more susceptible to environmental effects.

Stellar Rotation in the Gaia Era: Revised Open Clusters’ Sequences

The period versus mass diagrams (i.e., rotational sequences) of open clusters provide crucial constraints for angular momentum evolution studies. However, their memberships are often heavily contaminated by field stars, which could potentially bias the interpretations. In this paper, we use data from Gaia DR2 to reassess the memberships of seven open clusters with ground- and space-based rotational data, and present an updated view of stellar rotation as a function of mass and age. We use the Gaia astrometry to identify the cluster members in phase space, and the photometry to derive revised ages and place the stars on a consistent mass scale. Applying our membership analysis to the rotational sequences reveals that: (1) the contamination in clusters observed from the ground can reach up to ∼35%; (2) the overall fraction of rotational outliers decreases substantially when the field contaminants are removed, but some outliers persist; (3) there is a sharp upper edge in the rotation periods at young ages; (4) at young ages, stars in the 1.0–0.6M ⊙ range inhabit a global maximum of rotation periods, potentially providing an optimal window for habitable planets. Additionally, we see clear evidence for a strongly mass-dependent spin-down process. In the regime where rapid rotators are leaving the saturated domain, the rotational distributions broaden (in contradiction with popular models), which we interpret as evidence that the torque must be lower for rapid rotators than for intermediate ones. The cleaned rotational sequences from ground-based observations can be as constraining as those obtained from space.

Detection of the Mass-dependent Dual Type Transition of Galaxy Spins in IllustrisTNG Simulations

A numerical detection of the mass-dependent spin transition of the galaxies is presented. Analyzing a sample of the galaxies with stellar masses in the range of 109 < (M ⋆/M ⊙) ≤ 1011 from the IllustrisTNG300-1 simulations, we explore the alignment tendency between the galaxy baryon spins and the three eigenvectors of the linearly reconstructed tidal field as a function of M ⋆ and its evolution in the redshift range of 0 ≤ z ≤ 1.5. Detecting a significant signal of the occurrence of the mass-dependent transition of the galaxy spins, we show that the centrals differ from the satellites in their spin transition type. As M ⋆ increases beyond a certain threshold mass, the preferred directions of the central galaxy spins transit from the minor to the intermediate tidal eigenvectors (type two) at z = 0.5 and 1, while those of the satellites transit from the minor to the major tidal eigenvectors (type one) at z = 1 and 1.5. It is also shown that the mass range and type of the spin transition depend on the galaxy morphology, the degree of the alignments between the baryon and total spin vectors, and the environmental density. Meanwhile, the stellar spins of the galaxies are found to yield a weak signal of the T1 transitions at z = 0, whose strength and trend depend on the degree of the alignments between the stellar and baryon spins. The possible mechanisms responsible for the T1 and T2 spin transitions are discussed.