Segregation Hypothesis Research Articles

Ecological niche segregation between sympatrically breeding blue petrels and thin-billed prions

Ecological niche theory predicts coexisting species will segregate spatially, temporally or trophically to limit competition. Few studies have investigated niche segregation in multiple dimensions during the breeding season in sympatric, morphologically similar seabird species. Moreover, these studies showed discrepancies between theoretical predictions and observations. We tested the hypothesis of niche segregation during breeding between 2 sympatric small-sized seabirds, the blue petrel Halobaena caerulea and the thin-billed prion Pachyptila belcheri, by quantifying foraging niche and trophic differences. Combining at-sea GPS and isotopic (stable carbon and nitrogen) data, we assessed spatial, foraging habitat and trophic segregation. We found strong latitudinal and longitudinal segregation between species during incubation. Mean maximum distance from the colony during foraging trips was ~2330 and ~1300 km for blue petrels and thin-billed prions, respectively. Foraging habitat segregation varied during incubation, with blue petrels foraging close to the ice edge and prions foraging in oceanic areas far from ice. Although sample size was low, there was also some evidence for spatial and habitat segregation during chick-rearing, with prions foraging in areas with negative sea surface height anomalies. Trophic segregation was revealed by differences in stable isotopes, with blue petrels feeding on higher trophic level prey than prions (mean plasma δ15N : 9.6 ± 0.4 and 9.0 ± 0.3‰, respectively). Spatial distribution and diet are the primary segregation mechanisms, and patterns of segregation may result from competitive exclusion rather than niche specialization. Spatial and trophic segregation may have evolved to minimize competition, allowing co-existence of these 2 abundant sympatric breeding species.

Root foraging strategies and niche segregation of three mediterranean shrub species

Shrubs are usually adapted to stressful environments in which soil resources are limited, and thus, roots are fundamental for their biological success. However, root measures are challenging to collect, especially in field conditions and at the individual level. For this study, we collected data on the three‐dimensional distribution of fine root biomass of twenty‐three individuals belonging to three shrub species in a mediterranean shrubland in central Spain: gum rockrose Cistus ladanifer, rosemary Salvia rosmarinus, and hairy‐fruited broom Cytisus striatus. Our goal was to determine the soil‐foraging strategies adopted by the plants. We hypothesized that plants would show stabilizing niche differences explaining the high plant biodiversity characteristic of mediterranean shrublands and that they would follow the game theory model's prediction of exploitative segregation of roots behaving territorially but also over‐proliferating roots close to their stem and engaging in a root tragedy of the commons. We found that two‐thirds to three‐fourths of the biomass was belowground, and the system's productivity was roughly 500–600 g C m−2 year−1. Only rosemary plants competed with neighbors following the exploitative segregation predictions. Broom plants had the shallowest and most widespread root systems but significantly reduced their root range toward competing neighbors. Gum rockrose presented deep, narrow root systems avoiding extensive overlap with neighbors but did not appear to respond to competitive pressure levels. Shrubs appeared to stratify their roots at different soil depths, supporting the niche segregation hypothesis.

Diet variability of snappers (Teleostei: Lutjanidae) in a bay-to-reef ecosystem of the Mexican Caribbean

Fishes use environmental resources differently. Snapper ontogenic movements among coastal habitats lead to diverse diets. We investigated the diets of seven snapper species (Lutjanus apodus, L. analis, L. griseus, L. jocu, L. mahogoni, L. synagris, and Ocyurus chrysurus) in three interconnected coastal environments in the western Caribbean: Río Huach channel, Chetumal/Corozal bay, and the adjacent Xcalak reef lagoon. These three encompass all habitats used by the seven species in the study area. Snapper diets were mostly composed of fish and crustaceans, but dominance of either group varied among the studied habitats; for example, fish were the main prey for L. apodus from the reef lagoon zone, but second in the bay. Snappers are piscivorous-invertivorous mesopredators; the species that relied the most on fishes were L. griseus and L. jocu, whereas O. chrysurus preferred crustaceans. Stomach content results revealed a high degree of dietary overlap among species. Our findings suggested a tradeoff in relative weight between fish and crustaceans as the main food source of snappers at these connected areas, supporting the hypothesis of niche segregation. Our results can be used as a baseline to further our understanding of the ecology and differences in resource use by snapper species in an area undergoing important anthropogenic changes.

Contributions of Ni-content and irradiation temperature to the kinetic of solute cluster formation and consequences on the hardening of VVER materials

The study of solute clusters induced by neutron irradiation is fundamental to the understanding of the embrittlement phenomena of Reactor Pressure Vessel (RPV) steels. In this paper, the influence of Ni-content and irradiation temperature on these cluster formation are investigated using atom probe tomography.VVER 1000-BM (base metal) and 1000-W (weld) steels were chosen for their high Ni content of 1.2 and 1.7 at%, respectively. They were irradiated up to doses of 0.28 dpa at two temperatures (265 and 300 °C). The irradiations were performed at SCK CEN in the BR2 reactor.After irradiation, Mn, Ni and Si rich clusters were observed. A careful study of their composition indicates that these clusters actually contain iron. Moreover, the evolution of Fe cluster concentration with the dose indicates a constant supply of solutes throughout the irradiation thanks to the flux coupling. With increasing dose, both the cluster size and number density increase.The effect of temperature has to be dissociated from that of Ni content. Both of them result in an increase of the cluster number density at a given dose. The irradiation temperature has a more pronounced effect than chemical composition (mainly Ni effect). This can be explained by the fact that more matrix damage is produced at lower irradiation temperature. The influence of Ni on cluster number density is significantly higher at the lower temperature. All these observations support the hypothesis of radiation-induced segregation, even if a thermodynamic contribution to solute clustering cannot be excluded, in particular in the higher Ni steel irradiated at low temperature.In all cases, the yield strength increases proportionally to the volume fraction of radiation-induced defects (√(Vf)).

Geographic and temporal variations in strandings of beaked whales (Ziphiidae) on the coasts of the UK and the Republic of Ireland from 1800-2002

This study analyses published records of beaked whale strandings from the coasts of the UK and the Republic of Ireland between 1800 and 2002. Strandings of northern bottlenose whales (Hyperoodon ampullatus) were lowest in April and highest in September. The number of strandings between months differed significantly from an even spread over all months of the year, with more strandings between July and October. Most strandings in late summer and autumn occurred on North Sea coasts and their stomach contents included the squid Gonatus fabricii, which is found only in more northern waters. This suggests that these whales may be migrating southward at this time of year. Most strandings of Sowerby’s beaked whales (Mesoplodon bidens) also occurred in late summer and autumn, although this was not significant. Strandings of Cuvier’s beaked whales (Ziphius cavirostris) occurred almost exclusively on the Atlantic coasts of the UK and in Ireland. There were significantly more Cuvier’s beaked whale strandings than expected in January and February and in June and July. A Cuvier’s beaked whale which stranded in northern Scotland in February contained similar prey to two whales stranded in north-western Spain at the same time of year, suggesting this animal could have been feeding in more southern waters prior to stranding. Seasonal patterns of strandings of northern bottlenose and Cuvier’s beaked whales were significantly different with more of the former stranding in August to October and more of the latter from November to July. This is consistent with a hypothesis of temporal segregation between the two species to reduce potential competition for prey.

Minorities and property values: Evidence from residential buildings in Israel

This study estimates, for the first time, individuals valuation of living in a building with a member of a minority, by exploiting unique restricted data on about a third of Israel’s neighborhoods. We rely on the hedonic approach and use a difference-in-differences identification strategy, comparing nearby buildings that experienced either early or late entry of minorities. We find that house prices declined by 2–3% after the first move-in of Israelis of Ethiopian origin or ultra-Orthodox Jews. Our analysis shows that New-immigrants only significantly affect prices during a massive migration wave (-10%) and indicate that Israeli Arabs do not affect prices. Results are not driven by (a) the socio-demographic profile of the minorities who enter, (b) the difference between their profile and the existing residents profile, (c) buyers and sellers profiles after the first minority entrance or (d) neighborhood characteristics. The findings support the hypothesis of segregation due to discrimination.

Frequencies of lateral morphs in different age classes of the flounder Platichthys flesus (Pleuronectidae) from the White Sea

In the populations of the European flounder Platichthys flesus (Linnaeus, 1758), the proportions of left- and right-sided individuals vary widely, and possible causes of this variation remain little explored. The hypothesis of ecological segregation of phenotypical morphs in the European flounder relies primarily on observations of certain differences in morphology and foraging performance between the left- and right-sided individuals. The flounders of different sex and size/age, however, can differ in the character of biotic associations with the environment and other hydrobionts. We have examined the interaction of size/age and sex of the fish with the probability of encountering left-sided individuals in 4 populations of the European flounder from the White Sea basin. The results of the study have shown that the proportion of the reversed individuals did not differ among the flounders of various size and age in all the populations studied. The proportion of the left- and right-sided morphs in different size-age classes in all investigated populations did not depend on the sex of the fish. Revealed interpopulation diversity of phenotypic composition of flounder from the White Sea is not connected with the size/age and sex structure of compared samples.

Gender and Economic Downturn. The Focus on Women and the Pandemic Crisis

Abstract The goal of the paper is to consider whether women are vulnerable or protected on the labour market during the pandemic crisis, seeking answers in the wider context of previous downturns and economic theory. In times of crisis, female employment is likely to be more susceptible to cuts, for several reasons explained i.a. by the flexible buffers hypothesis or sex segregation hypothesis. Since the pandemic crisis is still unfolding, many of its effects are still unknown but it can be expected that the COVID-19 crisis may have an unequal impact on women and men. Additional challenges in this crisis can be found in the home. Gender effects vary across EU countries, however, it is essential to develop at both the European and national level effective policy responses leading to gender balance in various dimensions (including paid and unpaid work).

First Locality Record of Melanistic Oncilla (Leopardus tigrinus) in Monteverde, Costa Rica

The persistence of the coat color polymorphism melanism has been reported for several tropical felids, but its evolutionary advantages remain an active area of research. Few publications have explored melanism in the elusive species, oncilla (Leopardus tigrinus) within the Neotropical part of their range in Costa Rica. Herein, I present the first record of a melanistic oncilla within the montane cloud forest of Monteverde, Costa Rica. Recent studies have found support for theories (e.g. Temporal Segregation Hypothesis and Gloger’s Rule) explaining the ecological advantages driving melanism in oncilla and tropical felid populations. However, it is unclear what is driving melanism in this Monteverde oncilla population due to the singular observation. Further research investigating whether melanism is occurring at a higher frequency in other individuals in the region is critical to better understanding the occurrence of melanism in local populations of this cryptic species. The montane cloud forest in Monteverde provides critical habitat to this vulnerable species within the small Neotropical part of their range. Melanistic individuals may be particularly threatened by land-use change and increasing human pressure if theories for the evolutionary advantages and ecological conditions motivating melanism are supported.

Neighbourhood-based evidence of tree diversity promotion by beech in an old-growth deciduousconiferous mixed forest (Eastern Carpathians)

Neighbourhood models are useful tools for understanding the role of positive and negative interactions in maintaining the tree species diversity in mixed forests. Under such a presumption, we aimed at testing several hypotheses concerning the mechanisms of autogenic species coexistence in an old-growth, beech-fir-spruce stand, which is part of the Slătioara forest reserve (Eastern Carpathians). Univariate/bivariate spatial point pattern analyses, the individual tree species-area relationship, the species mingling analysis and generalised linear mixed models of neighbour interference were applied on data concerning the position and allometry of all saplings and trees occurring within a 0.24 ha plot. The monospecific distribution of either beech or spruce saplings did not support the spatial segregation hypothesis. There was no evidence of conspecific negative distance dependence, as no spatial segregation was detected between the saplings and trees of any species. Within 4 m-neighbourhood, the beech saplings appeared as diversity accumulators, which might be indicative of indirect facilitation (e.g., herd protection hypothesis). At tree stage, none of the three species showed either accumulator or repeller patterns in their neighbourhood with respect to sapling species richness. Signals of positive and negative interspecific association were found in tree-sized beech (at scales of 10 to 20 m) and spruce (at scales of 4 to 17 m), respectively. The former, highly interspersed pattern is in accordance with the hypothesis of positive complementary effects, whereas the latter, poorly intermingled pattern is probably linked to the unexpected, positive neighbouring effect of spruce trees on the stem growth of their conspecific saplings. Such self-favouring process might be due to a facilitative below-ground mechanism. Conversely, the beech saplings were suppressed through interference from the neighbouring conspecific trees. The beech appears to be the key promoter of tree species coexistence in the study forest stand, in contrast to the low interspersion of spruce in the overstorey leading to lower local tree diversity.

Neighbourhood-based evidence of tree diversity promotion by beech in an old-growth deciduous-coniferous mixed forest (Eastern Carpathians)

Neighbourhood models are useful tools for understanding the role of positive and negative interactions in maintaining the tree species diversity in mixed forests. Under such a presumption, we aimed at testing several hypotheses concerning the mechanisms of autogenic species coexistence in an old-growth, beech-fir-spruce stand, which is part of the Slatioara forest reserve (eastern Carpathians). Univariate/bivariate spatial point pattern analyses, the individual tree species-area relationship, the species mingling analysis and generalised linear mixed models of neighbour interference were applied on data concerning the position and allometry of all saplings and trees occurring within a 0.24 ha plot. The monospecific distribution of either beech or spruce saplings did not support the spatial segregation hypothesis. There was no evidence of conspecific negative distance dependence, as no spatial segregation was detected between the saplings and trees of any species. Within 4 m-neighbourhood, the beech saplings appeared as diversity accumulators, which might be indicative of indirect facilitation (e.g., herd protection hypothesis). At tree stage, none of the three species showed either accumulator or repeller patterns in their neighbourhood with respect to sapling species richness. Signals of positive and negative interspecific association were found in tree-sized beech (at scales of 10 to 20 m) and spruce (at scales of 4 to 17 m), respectively. The former, highly interspersed pattern is in accordance with the hypothesis of positive complementary effects, whereas the latter, poorly intermingled pattern is probably linked to the unexpected, positive neighbouring effect of spruce trees on the stem growth of their conspecific saplings. Such self-favouring process might be due to a facilitative below-ground mechanism. Conversely, the beech saplings were suppressed through interference from the neighbouring conspecific trees. The beech appears to be the key promoter of tree species coexistence in the study forest stand, in contrast to the low interspersion of spruce in the overstorey leading to lower local tree diversity.

Reproductive Phenology of Five Species of Terrestrial Frogs (Genus Eleutherodactylus) from Cuba

We studied the reproductive phenology of five endemic Eleutherodactylus species that coexist in a mountain rainforest in Cuba and estimated their sex ratios at immature and mature stages. We tested the hypothesis that in Neotropical humid sites, reproductive activity in sympatric species will vary in the time of occurrence so that there is no complete temporal overlap. We also investigated whether the length of the breeding season was associated to relative testes size as a proxy for male–male competition. We inferred reproductive phenology from seasonal variation in the number of sexually active individuals, their gonad developmental stage, and male vocal activity from January 2003 to March 2004. Our data do not support the hypothesis of temporal segregation in reproduction for this assemblage because we found a prolonged reproductive pattern in the five species, but there was decreased breeding intensity in the cooler months (November–February). This deduction is supported by a drop in the weight of the ovaries and the number of vitellogenic follicles, absence of mature females or reduction of their abundance, and disappearance of male vocal activity in the winter. We found differences in relative testes size among species, which were not related to differences in the length of the breeding season, but rather to interspecific differences in sex ratio.

Population structure and ontogenetic habitat use of Micropogonias furnieri in the Southwestern Atlantic Ocean inferred by otolith chemistry

The whitemouth croaker Micropogonias furnieri is a demersal sciaenid fish widely distributed in Atlantic coasts and estuaries from Mexico to Argentina. In the South Atlantic (33°- 41 °S), there are two stocks: Río de la Plata (RDP) and El Rincón (ER), respectively. Studies based on genetic, age and size structure data suggested that RDP stock would be composed of two different populations, one estuarine-dependent (estuarine type) and the other with oceanic spawning sites (oceanic type). The hypothesis of segregation between the estuarine and oceanic types, and between these and the ER stock was tested by using the otolith chemistry in the edge (adult stage) and core (early stage) of fish. Li/Ca, Na/Ca, Mn/Ca, Cu/Ca, Ba/Ca, and Pb/Ca ratios were determined by LA-ICP-MS. Several ratios were significantly different between sampling sites for edge and core (p < 0.05). For edge, PERMANOVA showed significant differences (p < 0.05) between all sampling sites, while the quadratic discriminant analyses showed a mean jackknifed classification of 83 % (87 % for Uruguay, 76 % for RDP, and 86 % for ER). This supports the hypothesis of differentiation of the RDP stock into oceanic and estuarine-dependent groups. The non-metric multidimensional scaling and cluster analysis based on the core chemistry suggested that there would be at least two large chemical signatures in the early stage. The elemental ratio time series showed a potential endogenous effect on the incorporation of various elements (e.g. Ba, Mn, Li) in the early stages, while Sr/Ca time series suggested a general migratory behavior between estuarine and marine habitats throughout ontogeny.

Global connectedness of local NGOs: do different types of funding create barriers for cooperation?

How does international financial aid affect the cooperative behavior of local non-governmental organizations (NGOs)? Can NGOs, while turning global, preserve peer connections with local actors and be engaged in local issues? The civil society literature contains competing perspectives on and reports of how international financial aid may restructure local civic networks. Some scholars argue that international support comes at the expense of local integration as inclusion in global networks takes local NGOs out of the local context, while others find evidence that organizations do not have to face “a forced choice”, and may well be integrated both globally and locally. Drawing on this scholarship, we examine two hypotheses on how transnational funding influences cooperation patterns among NGOs. The hierarchy argument states that public entities tend to cooperate with internationally funded NGOs as external contact signals quality and trustworthiness. The segregation argument, on the contrary, suggests financial homophily according to which organizations are more likely to choose peers similar in sources of funding. To test these hypotheses, we apply Exponential Random Graph Models to the data on cooperation among 221 Kazakhstani NGOs. Results support the segregation hypothesis implying that NGOs are likely to have a bias towards similarly funded peers.

Sex‐specific migratory behaviors in a temperate ungulate

AbstractSexual segregation has been intensely studied across diverse ecosystems and taxa, but studies are often limited to periods when animals occupy distinct seasonal ranges. Some avian and marine studies have revealed that habitat segregation, when sexes differ spatially or temporally in use of the physical landscape, is common during the migratory period and characterized by sex‐specific differences in migratory behaviors. Recent research highlights the importance of understanding movement patterns in the context of the full annual life cycle and highlights the need to extend relevant theories of sexual segregation to the migratory period. We tested predictions from two leading hypotheses of sexual segregation, the forage‐selection hypothesis (FSH) and the reproductive strategy hypothesis (RSH) as applied to the migratory period. We collected global positioning system (GPS) location data for male and female mule deer (Odocoileus hemionus) in south‐central Wyoming and northwest Colorado and tested the main predictions of the FSH and RSH. Both sexes showed high fidelity to their migratory routes, but route fidelity was more variable in males. Males also started spring migrations earlier, ended spring and autumn migrations later, and spent 22% more time on stopover sites during spring migrations. Consequently, males took twice as long in spring and 44% longer in autumn to complete migration. Our results revealed clear sex‐specific migratory behaviors and supported predictions of the RSH that male foraging behaviors optimize body condition for the autumn rut, and females prioritize foraging while balancing reproductive constraints. Specifically, males timed their movements with spring green‐up as optimally as females, and the timing of male migrations and use of stopovers suggested that males prioritized time in areas of high‐quality forage. This refutes predictions of the FSH during the migratory period that males should consistently choose habitats with abundant, low‐quality forage. Our findings provide an important contribution to sexual segregation theory by extending relevant theories to understand male and female movements during the migratory period.

Altering the rhythm of target and background talkers differentially affects speech understanding.

Three experiments investigated listeners' ability to use speech rhythm to attend selectively to a single target talker presented in multi-talker babble (Experiments 1 and 2) and in speech-shaped noise (Experiment 3). Participants listened to spoken sentences of the form "Ready [Call sign] go to [Color] [Number] now" and reported the Color and Number spoken by a target talker (cued by the Call sign "Baron"). Experiment 1 altered the natural rhythm of the target talker and background talkers for two-talker and six-talker backgrounds. Experiment 2 considered parametric rhythm alterations over a wider range, altering the rhythm of either the target or the background talkers. Experiments 1 and 2 revealed that altering the rhythm of the target talker, while keeping the rhythm of the background intact, reduced listeners' ability to report the Color and Number spoken by the target talker. Conversely, altering the rhythm of the background talkers, while keeping the target rhythm intact, improved listeners ability to report the Color and Number spoken by the target talker. Experiment 3, which embedded the target talker in speech-shaped noise rather than multi-talker babble, similarly reduced recognition of the target sentence with increased alteration of the target rhythm. This pattern of results favors a dynamic-attending theory-based selective-entrainment hypothesis over a disparity-based segregation hypothesis and an increased salience hypothesis.

Integrated 3D Tomography and Computational Modeling to Study Forces in Metaphase Spindles

Chromosome segregation during mitosis and meiosis are fundamental processes of life. During its course a bipolar spindle assembles and initially aligns the chromosomes on a metaphase plate before they are segregated to the two arising daughter cells during anaphase. The different cellular components of mitotic and meiotic spindles: microtubules, chromosomes, motor proteins and also membranes, such as the cell cortex or nuclear envelope, must interact with each other during spindle assembly, chromosome alignment and segregation.While we have achieved a very good understanding of signaling cascades and checkpoints that monitor and control mitosis, we are lacking an understanding on how the nano‐scale components of a spindle physically interact and generate the forces needed to faithfully align and segregate chromosomes. We have very little knowledge about the mechanics of spindles. In order to overcome the current limitations, we are generating a holistic description of mitotic and meiotic spindles in C. elegans embryos and mouse oocytes. This ambitious task will be achieved by a combination of 3D electron tomography, light microscopy and computational simulations. 3D tomography provides unprecedented detailed information about every individual microtubule within the spindle. We can measure the length, position and interactions of single microtubules with subcellular targets. In addition, we have developed tools to analyze the curvature of microtubules. Curvature originates from forces experienced by the microtubule and provides a read out of spindle intrinsic forces. The source of those forces can be determined by a combined approach of mutant analysis and computational simulations. To complement the static tomography data, we perform state‐of‐the‐art light microscopy. In conjunction with the light and electron microscopy we develop hypothesis and mechanical models of chromosome congression, alignment and segregation and test those in computational simulations and by selective depletion of proteins. We are using this approach to develop a (near) true‐to‐life model of microtubule, chromosome and membrane interactions and forces during mitosis.3D reconstruction of a meiotic metaphase spindle in the C. elegans embryoThis reconstruction is generated using 3D electron tomography of high‐pressure frozen samples and subsequent image processing and segmentation. The resolution of 2.3nm provides single microtubule resolution.Figure 1

Natural Selection of Melanism in Costa Rican Jaguar and Oncilla: A Test of Gloger’s Rule and the Temporal Segregation Hypothesis

The persistence of coat color polymorphisms—such as the coexistence of melanistic and “wild-type” coat color—is an ongoing evolutionary puzzle. We tested the predictions of Gloger’s rule and the Temporal Segregation hypothesis that propose that melanistic individuals will (a) occur more frequently in closed tropical forest versus open habitat due to camouflage and thermoregulation advantages and (b) be more active during brighter times of the circadian and lunar cycle because black pigmentation is cryptic under bright illumination. Based on 10 years of camera trap records of jaguar and oncilla from dense tropical forest in Costa Rica, we compared activity and relative abundance of non-melanistic wild-type morphs (rosetted or spotted) versus melanistic morphs. Twenty-five percent of jaguar records in dense forest were melanistic compared with the global average of 10% in both open and closed habitats; 32% of oncilla records were melanistic compared with 18% overall in Brazil. Overlap analysis indicated that melanistic jaguars were more active during daylight hours compared with non-melanistic jaguars, which were more nocturnal and crepuscular. Likewise, melanistic oncillas were significantly more diurnal than non-melanistic oncillas; melanistic oncillas were also more active during full moon, while non-melanistic oncillas were less active. These results imply that melanistic jaguar and oncilla enjoy the adaptive benefits of superior camouflage when inhabiting dense forest and accrue a fitness advantage when hunting during conditions of brighter illumination. If true, natural selection would ensure that melanistic individuals persist when dense forest is retained but may be threatened by deforestation and accelerating human presence.

Reduced Segregation Between Cognitive and Emotional Processes in Cannabis Dependence.

Addiction is characterized by an erosion of cognitive control toward drug taking that is accentuated by negative emotional states. Here we tested the hypothesis that enhanced interference on cognitive control reflects a loss of segregation between cognition and emotion in addiction. We analyzed Human Connectome Project data from 1206 young adults, including 89 with cannabis dependence (CD). Two composite factors, one for cognition and one for emotion, were derived using principal component (PC) analyses. Component scores for these PCs were significantly associated in the CD group, such that negative emotionality correlated with poor cognition. However, the corresponding component scores were uncorrelated in matched controls and nondependent recreational cannabis users (n = 87). In CD, but not controls or recreational users, functional magnetic resonance imaging activations to emotional stimuli (angry/fearful faces > shapes) correlated with activations to cognitive demand (working memory; 2-back > 0-back). Canonical correlation analyses linked individual differences in cognitive and emotional component scores with brain activations. In CD, there was substantial overlap between cognitive and emotional brain-behavior associations, but in controls, associations were more restricted to the cognitive domain. These findings support our hypothesis of impaired segregation between cognitive and emotional processes in CD that might contribute to poor cognitive control under conditions of increased emotional demand.

Female American black bears do not alter space use or movements to reduce infanticide risk.

Infanticide occurs in a variety of animal species and infanticide risk has large implications for the evolution of behavior. Further, the sex hypothesis of sexual segregation predicts that for species in which infanticide occurs, females with dependent young will avoid males to reduce risk of sexually-selected infanticide. Infanticide risk-avoidance behavior has been studied primarily in social species, but also occurs in some solitary species. We used generalized linear mixed models to determine if space use and movements of female American black bears (Ursus americanus) during the breeding season were consistent with the sex hypothesis of sexual segregation in the Upper Peninsula of Michigan, USA. Space use and movements of female black bears (n = 16) were not consistent with avoidance behavior to reduce sexually-selected infanticide risk. Females with cubs occupied core areas (mean = 4.64 km2, standard error [SE] = 1.28) and home ranges (mean = 19.46 km2, SE = 5.10) of similar size to females without cubs (core area [mean = 4.11 km2, SE = 0.59]; home range [mean = 16.07 km2, SE = 2.26]), and those core areas and home ranges were not in areas with lesser relative probability of male use. Additionally, females with cubs did not reduce movements during times of day when male movements were greatest. As female bears do avoid potentially infanticidal males in populations with greater levels of infanticide, female black bears may exhibit variation in avoidance behavior based on the occurrence of infanticide.