Estimating the Diets of Animals Using Stable Isotopes and a Comprehensive Bayesian Mixing Model

Using stable isotope mixing models (SIMMs) as a tool to investigate the foraging ecology of animals is gaining popularity among researchers. As a result, statistical methods are rapidly evolving and numerous models have been produced to estimate the diets of animals—each with their benefits and their limitations. Deciding which SIMM to use is contingent on factors such as the consumer of interest, its food sources, sample size, the familiarity a user has with a particular framework for statistical analysis, or the level of inference the researcher desires to make (e.g., population- or individual-level). In this paper, we provide a review of commonly used SIMM models and describe a comprehensive SIMM that includes all features commonly used in SIMM analysis and two new features. We used data collected in Yosemite National Park to demonstrate IsotopeR's ability to estimate dietary parameters. We then examined the importance of each feature in the model and compared our results to inferences from commonly used SIMMs. IsotopeR's user interface (in R) will provide researchers a user-friendly tool for SIMM analysis. The model is also applicable for use in paleontology, archaeology, and forensic studies as well as estimating pollution inputs

Is That Me or My Twin? Lack of Self-Face Recognition Advantage in Identical Twins

Despite the increasing interest in twin studies and the stunning amount of research on face recognition, the ability of adult identical twins to discriminate their own faces from those of their co-twins has been scarcely investigated. One’s own face is the most distinctive feature of the bodily self, and people typically show a clear advantage in recognizing their own face even more than other very familiar identities. Given the very high level of resemblance of their faces, monozygotic twins represent a unique model for exploring self-face processing. Herein we examined the ability of monozygotic twins to distinguish their own face from the face of their co-twin and of a highly familiar individual. Results show that twins equally recognize their own face and their twin’s face. This lack of self-face advantage was negatively predicted by how much they felt physically similar to their co-twin and by their anxious or avoidant attachment style. We speculate that in monozygotic twins, the visual representation of the self-face overlaps with that of the co-twin. Thus, to distinguish the self from the co-twin, monozygotic twins have to rely much more than control participants on the multisensory integration processes upon which the sense of bodily self is based. Moreover, in keeping with the notion that attachment style influences perception of self and significant others, we propose that the observed self/co-twin confusion may depend upon insecure attachment

Lymphocytes and Macrophages Are Infected by Theileria equi, but T Cells and B Cells Are Not Required to Establish Infection In Vivo

Theileria equi has a biphasic life cycle in horses, with a period of intraleukocyte development followed by patent erythrocytic parasitemia that causes acute and sometimes fatal hemolytic disease. Unlike Theileria spp . that infect cattle ( Theileria parva and Theileria annulata ), the intraleukocyte stage (schizont) of Theileria equi does not cause uncontrolled host cell proliferation or other significant pathology. Nevertheless, schizont-infected leukocytes are of interest because of their potential to alter host cell function and because immune responses directed against this stage could halt infection and prevent disease. Based on cellular morphology, Theileria equi has been reported to infect lymphocytes in vivo and in vitro , but the specific phenotype of schizont-infected cells has yet to be defined. To resolve this knowledge gap in Theileria equi pathogenesis, peripheral blood mononuclear cells were infected in vitro and the phenotype of infected cells determined using flow cytometry and immunofluorescence microscopy. These experiments demonstrated that the host cell range of Theileria equi was broader than initially reported and included B lymphocytes, T lymphocytes and monocyte/macrophages. To determine if B and T lymphocytes were required to establish infection in vivo , horses affected with severe combined immunodeficiency (SCID), which lack functional B and T lymphocytes, were inoculated with Theileria equi sporozoites. SCID horses developed patent erythrocytic parasitemia, indicating that B and T lymphocytes are not necessary to complete the Theileria equi life cycle in vivo . These findings suggest that the factors mediating Theileria equi leukocyte invasion and intracytoplasmic differentiation are common to several leukocyte subsets and are less restricted than for Theileria annulata and Theileria parva . These data will greatly facilitate future investigation into the relationships between Theileria equi leukocyte tropism and pathogenesis, breed susceptibility, and strain virulence

Does the Dark Triad manifest similarly in men and women?: Measurement invariance of the Dirty Dozen across sex

The Dark Triad is a constellation of three socially undesirable personality traits: narcissism, psychopathy, and Machiavellianism. Previous research has shown that men tend to score higher than women on Dark Triad scales, but the validity of these results is questionable as there is no evidence that the scales used exhibit measurement invariance across sex in the adult population. Here, we report four studies assessing the measurement invariance across sex of a recently developed, concise measure of the Dark Triad, namely Jonason and Webster's (2010) Dirty Dozen (DD). As no validated Italian version of the DD was available, we developed an Italian version and assessed its psychometric properties. Studies 1 to 3 revealed that the Italian DD had adequate psychometric properties, and replicated the three-factor structure and the nomological network of the original version. Study 4 provided evidence of the measurement invariance of the DD across sex, such that men scored higher than women with respect to psychopathy, Machiavellianism, and, to a lesser extent, narcissism. These findings indicate that the DD can be used to provide reliable assessments of sex differences in Dark Triad traits. Furthermore, the results of sex comparisons are consistent with a biosocial approach to social role theory that assumes that being agentic rather than communal is considered desirable for men and undesirable for women

Did Narcissism Evolve?

This chapter, like each chapter in the edited book, focuses on narcissism (arrogance, exploitativeness, self-admiration, etc.). My goal is to entertain and evaluate the possibility that narcissism evolved. It is important to point out that, by way of background, just because something is morally suspect does not mean that it didn’t evolve; indeed, bad things can evolve. But despite narcissism being heritable, there is no direct evidence that narcissism is caused by specific genes, indicating that the evolutionary mechanisms are unknown. Through which pathways—such as mating pathways—does narcissism get passed onto the next generation? Narcissism appears to be positively correlated with short-term mating (e.g., promiscuity), suggesting that narcissism gets pushed into subsequent generations via promiscuous activity. The idea that narcissism evolved via short-term mating, however, is currently questionable, mainly because narcissists are not physically attractive at the unadorned level; in theory, narcissists should be attractive at the unadorned level because short-term mating situations select for raw attractiveness. All told, the prospect of narcissism having evolved is in a precarious position as of this writing. Several gaps in the literature lead to a call for more molecular genetic research and collaborative, large-scale behavioral research