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Phylogenetic metrics are essential tools used in the study of ecology, evolution and conservation. Phylogenetic diversity (PD) in particular is one of the most prominent measures of biodiversity and is based on the idea that biological features accumulate along the edges of phylogenetic trees that are summed. We argue that PD and many other phylogenetic biodiversity metrics fail to capture an essential process that we term attrition. Attrition is the gradual loss of features through causes other than extinction. Here we introduce "EvoHeritage", a generalization of PD that is founded on the joint processes of accumulation and attrition of features. We argue that while PD measures evolutionary history, EvoHeritage is required to capture a more pertinent subset of evolutionary history including only components that have survived attrition. We show that EvoHeritage is not the same as PD on a tree with scaled edges; instead, accumulation and attrition interact in a more complex non-monophyletic way that cannot be captured by edge lengths alone. This leads us to speculate that the one-dimensional edge lengths of classic trees may be insufficiently flexible to capture the nuances of evolutionary processes. We derive a measure of EvoHeritage and show that it elegantly reproduces species richness and PD at opposite ends of a continuum based on the intensity of attrition. We demonstrate the utility of EvoHeritage in ecology as a predictor of community productivity compared with species richness and PD. We also show how EvoHeritage can quantify living fossils and resolve their associated controversy. We suggest how the existing calculus of PD-based metrics and other phylogenetic biodiversity metrics can and should be recast in terms of EvoHeritage accumulation and attrition.
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Biodiversidade , Filogenia , Evolução Biológica , Classificação/métodos , Modelos BiológicosRESUMO
Research on human language converges on a view in which a grammatical "subject" is the most saliently encoded entity in mental representation. However, subjecthood is not a syntactically uniform phenomenon. Notably, many languages encode morphological distinctions between subjects of transitive verbs (i.e., verbs that require an object) and subjects of intransitive verbs. We ask how this typological pattern manifests in a language like English (which does not morphologically signal it) by examining the "distinctiveness" of transitive versus intransitive subjects in memory during online sentence processing. We conducted a self-paced reading experiment that tested for "attraction" effects (Dillon et al., Journal of Memory and Language, 69(2), 85-103, 2013; Wagers et al., Journal of Memory and Language, 61, 206-237, 2009) in the processing of subject-verb number agreement. We find that transitive subjects trigger attraction effects, but that these effects are mitigated for intransitive subject attractors (independently of the number of other noun phrases present in the intervening clause). We interpret this as indicating that transitive subjects are less distinctive and therefore less representationally salient than intransitive subjects: This is because a transitive subject must compete with another clause-mate core argument (i.e., a direct object), which draws on resources from the same pool of memory resources. On the other hand, an intransitive subject minimally only competes with a non-core argument (i.e., an oblique noun phrase); this consumes fewer memory resources, leaving the subject to enjoy greater spoils.
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Idioma , Leitura , HumanosRESUMO
Several studies observed that a worse destination memory (i.e., capacity to remember to whom we said something) occurs when personal facts are shared, which was explained based on the internal attentional focus - the attentional focus is on the information and not on the recipient of the information. So, with two experiments, we aimed to mitigate the negative influence of the internal attentional focus on destination memory. Since it was previously observed that sharing information with distinctive faces leads to a better destination memory, in Experiment 1, participants (N = 30) were asked to transmit personal facts to distinctive and undistinctive faces. No differences were observed. To increase the attentional focus on the recipient of the information, in Experiment 2, participants (N = 30) were also asked to evaluate the distinctiveness of the recipients' faces. A better destination memory was not observed in Experiment 2 compared with Experiment 1. This leads us to conclude that asking participants to evaluate the faces did not promote a better destination memory when personal facts were shared. Nevertheless, by asking to evaluate the faces, the attentional focus was on the faces, where distinctive faces attracted more attention and led to a better destination memory.
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This article primarily focuses on the localization and extraction of multiple moving objects in images taken from a moving camera platform, such as image sequences captured by drones. The positions of moving objects in the images are influenced by both the camera's motion and the movement of the objects themselves, while the background position in the images is related to the camera's motion. The main objective of this article was to extract all moving objects from the background in an image. We first constructed a motion feature space containing motion distance and direction, to map the trajectories of feature points. Subsequently, we employed a clustering algorithm based on trajectory distinctiveness to differentiate between moving objects and the background, as well as feature points corresponding to different moving objects. The pixels between the feature points were then designated as source points. Within local regions, complete moving objects were segmented by identifying these pixels. We validated the algorithm on some sequences in the Video Verification of Identity (VIVID) program database and compared it with relevant algorithms. The experimental results demonstrated that, in the test sequences when the feature point trajectories exceed 10 frames, there was a significant difference in the feature space between the feature points on the moving objects and those on the background. Correctly classified frames with feature points accounted for 67% of the total frames.The positions of the moving objects in the images were accurately localized, with an average IOU value of 0.76 and an average contour accuracy of 0.57. This indicated that our algorithm effectively localized and segmented the moving objects in images captured by moving cameras.
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The alarming decline of amphibians, sometimes marked by sudden extinctions, underlines the urgent need for increased conservation efforts. Conservationists recognize that more action, particularly the setting of national targets, is needed to ensure the future persistence and recovery of species and habitats. Protecting habitats that harbor evolutionarily diverse species preserves divergent genetic information within ecosystems. Türkiye holds 36 amphibian species at the intersection of two continents, creating three biodiversity hotspots and phylogenetic transitional areas. In this study, we aimed to determine the hotspot regions and to evaluate the effectiveness of the protected areas in Türkiye in preserving amphibian populations. First, we estimated four community indexes (species richness and three evolutionary distinctiveness measures) for amphibian communities in Türkiye divided into 371 grid cells with a ca 50 × 50 km size. Then, the spatial extent of protected areas is evaluated from two perspectives: current (has a protection status) and candidate protected areas (Key Biodiversity Areas, not protected) coverage in those grid cells. Finally, these two approaches' effectiveness in protecting areas was assessed by modeling four diversity metrics using GLS models. Current protected areas protect about 6% of the total amphibian distribution in Türkiye, while Key Biodiversity Areas would cover 30% if declared protected areas. We estimated that the coastal areas of Türkiye are identified as hotspots based on the four measured amphibian community indexes. Our study also highlights that Key Biodiversity Areas (KBAs) can contribute to conserving high levels of amphibian richness and evolutionary distinctiveness of species across Türkiye. However, existing protected areas (PAs) networks were insufficient to protect amphibians.
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Our understanding of the community assembly processes acting on non-indigenous species (NIS), as well as the relationship with native species is limited, especially in marine ecosystems. To overcome this knowledge gap we here develop a trait-based approach based on the functional distinctiveness metric to assess niche overlap between NIS and native species, using high-resolution data on benthic invertebrate communities in the Baltic Sea. Our results show that NIS retain a certain degree of similarity with native species, but display one or a few singular unique traits (e.g., bioturbation ability). Furthermore, we demonstrate that community assembly processes, including both environmental filtering and limiting similarity affect NIS establishment, but that their effects may be highly context dependent, as illustrated by pronounced spatial patterns in distinctiveness. Finally, our trait-based approach provides a generic framework applicable to other areas and organisms, to better understand and address biological invasions.
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Ecossistema , Invertebrados , Animais , Invertebrados/genética , FenótipoRESUMO
Current models of island biogeography treat endemic and non-endemic species as if they were functionally equivalent, focussing primarily on species richness. Thus, the functional composition of island biotas in relation to island biogeographical variables remains largely unknown. Using plant trait data (plant height, leaf area and flower length) for 895 native species in the Canary Islands, we related functional trait distinctiveness and climate rarity for endemic and non-endemic species and island ages. Endemics showed a link to climatically rare conditions that is consistent with island geological change through time. However, functional trait distinctiveness did not differ between endemics and non-endemics and remained constant with island age. Thus, there is no obvious link between trait distinctiveness and occupancy of rare climates, at least for the traits measured here, suggesting that treating endemic and non-endemic species as functionally equivalent in island biogeography is not fundamentally wrong.
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Clima , Plantas , Fenótipo , Folhas de Planta , Espanha , IlhasRESUMO
Trees are vital to the survival of numerous species and to forest ecosystem functioning. However, the current distribution, vulnerability to extinction, and conservation priorities of globally endangered trees are not well known. We mapped the global distribution of 1686 tree species listed as endangered on the International Union for the Conservation of Nature Red List and identified conservation priority for them based on species richness, life-history traits, evolutionary distinctiveness, future climate change, and intensity of human activities. We also evaluated the impacts of various threats to these endangered tree species and evaluated the effectiveness of their protection based on the percentage of the species' range inside protected areas. The worldwide distribution of endangered trees, from the tropics through temperate zones, was uneven. Most endangered tree species were not protected in their native ranges, and only 153 species were fully protected. Hotspots of tree diversity occurred primarily in the tropics, and 79.06% of these were highly vulnerable to threats. We identified 253 areas of high priority for the conservation of endangered trees that are highly threatened and insufficiently protected. In particular, 43.42% of unprotected tree species in priority areas lacked recommended conservation measures or had no associated conservation plan. The priority conservation areas and unprotected trees we identified serve as a guideline for future management underpinning the post-2020 global biodiversity framework.
Prioridades de conservación para los árboles amenazados que enfrentan múltiples amenazas en todo el mundo Resumen Los árboles son vitales para la supervivencia de numerosas especies y para el funcionamiento de los ecosistemas forestales. Sin embargo, no se conoce muy bien la distribución actual, vulnerabilidad a la extinción y prioridades de conservación de los árboles amenazados a nivel mundial. Mapeamos la distribución global de 1686 especies de árboles catalogadas como en peligro por la Lista Roja de la Unión Internacional para la Conservación de la Naturaleza e identificamos su prioridad de conservación con base en la riqueza de especies, características de historia de vida, singularidad evolutiva, cambio climático futuro e intensidad de las actividades humanas. También evaluamos el impacto de varias amenazas sobre estas especies y analizamos la efectividad de su protección con base en el porcentaje de la distribución de la especie ubicado dentro de un área protegida. La distribución mundial de árboles en peligro, desde los trópicos y hasta las zonas templadas, fue desigual. La mayoría de las especies no estaban protegidas dentro de su distribución nativa y sólo 153 especies contaban con protección completa. Los puntos calientes de diversidad de árboles se ubicaron principalmente en los trópicos, y el 79.06% de estos tenían una vulnerabilidad alta ante las amenazas. Identificamos 253 áreas de gran prioridad para la conservación de los árboles en peligro que están amenazados y con poca protección. En particular, el 43.42% de las áreas sin protección dentro de las áreas prioritarias no contaban con las medidas recomendadas de conservación o no tenían asociado un plan de conservación. Las áreas prioritarias de conservación y los árboles sin protección que identificamos son una pauta para futuros manejos que apuntalan el marco de trabajo post-2020 para la biodiversidad.
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Ecossistema , Árvores , Animais , Humanos , Conservação dos Recursos Naturais , Espécies em Perigo de Extinção , BiodiversidadeRESUMO
In the midst of the sixth mass extinction, limited resources are forcing conservationists to prioritize which species and places will receive conservation action. Evolutionary distinctiveness measures the isolation of a species on its phylogenetic tree. Combining a species' evolutionary distinctiveness with its globally endangered status creates an EDGE score. We use EDGE scores to prioritize the places and species that should be managed to conserve bird evolutionary history. We analyzed all birds in all countries and important bird areas. We examined parrots, raptors, and seabirds in depth because these groups are especially threatened and relatively speciose. The three focal groups had greater median threatened evolutionary history than other taxa, making them important for conserving bird evolutionary history. Australia, Brazil, Indonesia, Madagascar, New Zealand, and the Philippines were especially critical countries for bird conservation because they had the most threatened evolutionary history for endemic birds and are important for parrots, raptors, and seabirds. Increased enforcement of international agreements for the conservation of parrots, raptors, and seabirds is needed because these agreements protect hundreds of millions of years of threatened bird evolutionary history. Decisive action is required to conserve the evolutionary history of birds into the Anthropocene.
En medio de la sexta extinción masiva, los recursos limitados están obligando a los conservacionistas a priorizar cuáles especies y lugares recibirán acciones de conservación. La peculiaridad evolutiva mide el aislamiento de una especie con respecto a su árbol filogenético. La combinación entre la peculiaridad evolutiva de una especie y su estado de conservación mundial genera un puntaje EDGE. Usamos estos puntajes para priorizar los lugares y especies que se deben gestionar para conservar la historia evolutiva ornitológica. Analizamos todas las especies de aves en todos los países y áreas de importancia ornitológica. Estudiamos a profundidad a los psitácidos, rapaces, y aves marinas por el nivel de amenaza que enfrentan estos grupos y porque cuentan con muchas especies. Estos tres grupos tuvieron una mayor mediana de historia evolutiva amenazada que los demás taxones, por lo que son de suma importancia para la conservación de la historia evolutiva ornitológica. Australia, Brasil, Indonesia, Madagascar, Nueva Zelanda y las Filipinas fueron países particularmente críticos para la conservación de las aves pues cuentan con la mayor historia evolutiva amenazada de aves endémicas y son localidades importantes para nuestros tres grupos focales. Se requiere de un incremento en la aplicación de los acuerdos internaciones para la conservación de los psitácidos, rapaces y aves marinas ya que estos acuerdos protegen cientos de millones de años de historia evolutiva ornitológica. Se necesitan acciones decisivas para conservar la historia evolutiva de las aves en el Antropoceno.
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Conservação dos Recursos Naturais , Espécies em Perigo de Extinção , Animais , Filogenia , Biodiversidade , Aves/genéticaRESUMO
Inattentional blindness is the failure to notice an unexpected object in plain sight when attention is otherwise engaged. We investigated what determines observers' attentional set in a dynamic-counting inattentional blindness paradigm, when task instructions and visual distinctiveness of task-relevant objects were either congruent or in opposition. In seven experiments, observers counted bounces by task-relevant objects, with the instruction either to count-by-shape (squares, diamonds, crosses) or count-by-colour (blue, purple). To manipulate visual distinctiveness, we varied the extent to which task-relevant and task-irrelevant objects looked different on two dimensions: shape and colour. When colour better distinguished task-relevant from task-irrelevant objects, observers-even if instructed count-by-shape-reported an unexpected object that matched the colour of task-relevant objects. Crucially, when instructed count-by-colour, but shape better distinguished task-relevant from task-irrelevant objects, observers reported an unexpected object that matched the shape of task-relevant objects. We conclude that observers set their attention to promote efficient task performance.
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Transtornos Mentais , Percepção Visual , Humanos , Cognição , Cegueira , Análise e Desempenho de TarefasRESUMO
An illusion of distinctiveness for faces is described that manifests as a positive association between perceived familiarity and perceived distinctiveness. This association seems partly rooted in intrinsic facial characteristics but is boosted by actual exposure to faces. Such illusion could impede research on familiar faces where distinctiveness is manipulated or controlled and researchers will need to find ways around it.
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Ilusões , Humanos , Face , Reconhecimento PsicológicoRESUMO
It has been proposed that representations emerge from a single memory system organized along a continuum of specificity. This continuum is assumed to reflect a scale between the simulation of overlapping and specific features of the traces, which depends on trace distinctiveness. More specifically, higher trace distinctiveness facilitates the simulation of trace-specific features, which increase the discriminability of traces and lead to the emergence of a more specific representation. In two experiments, participants were asked to identify match (low task discrimination demand) or mismatch (high task discrimination demand) associations between actions and characters that were visually either highly or lowly distinctive. The results of Experiment 1 show that in the high-distinctiveness context, performance was better when identifying a mismatch rather than a match, while the opposite was true in the low-distinctiveness context. The results of Experiment 2 show that using a dynamic visual noise to interfere with the participants' ability to simulate the features of the characters also reduced the benefit of the high-distinctiveness context for the mismatch trials (Experiment 2a and 2b) and increased the benefit of the low-distinctiveness context for the match trials (Experiment 2b). Taken together, these results suggest that the simulation of trace-specific features underlies the emergence of specific representations, which can be beneficial when the discrimination demand of the task is high and detrimental when this demand is low. Memory might therefore be viewed as a scale of simulation between overlapping and specific trace features.
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Memória , HumanosRESUMO
We tested the validity of two alternative accounts of the Attentional Boost Effect (ABE) - the finding that words associated with to-be-responded targets are recognized better than words associated with to-be-ignored distractors. The distinctiveness hypothesis assumes that, during recognition, participants probe their memories for distinctive information confirming that a word was studied (e.g., "I remember having pressed the spacebar, so I must have studied the word"). This strategy cannot be used in a between-subjects condition in which participants cannot appreciate the differences between target - and distractor-paired words. In agreement, Experiments 1A and 1B found that the ABE was significant in a within-subjects design, whereas it was eliminated in a between-subjects design. On the other hand, the performance anticipation hypothesis assumes that, during the study phase, participants anticipate the need of responding to a subset of target-paired words: this would create a persistent performance anticipation that would prevent them from effectively encoding distractor-paired words. In contrast with this account, we found that, when blocks of five distractor trials were regularly alternated with blocks of five target trials in Experiment 2, recognition accuracy decreased linearly in both conditions. Overall, these results suggest that distinctiveness, but not performance anticipation, might underlie the ABE.
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Atenção , Memória , Humanos , Reconhecimento Psicológico , Rememoração MentalRESUMO
In this paper, we reflect on what inclusion can mean to the global Health Professions Education (HPE) community, the impact of lack of inclusion, and offer suggestions on how to be inclusive. To illustrate the impact of inclusion, we offer perspectives from the lens of a medical student, junior doctor, educators, and educational leaders. The viewpoints offered in this communication can be useful to broaden and nurture inclusive pedagogy and scholarship. Furthermore, since the aim of HPE is high quality patient care and social advocacy, emphasising inclusion in HPE could enhance inclusion in patient care.
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Bolsas de Estudo , Estudantes de Medicina , Humanos , Ocupações em SaúdeRESUMO
Identity distinctiveness, continuity, and coherence are all components of adolescents' identity development, but their longitudinal relations have rarely been examined. Data were analyzed on these three constructs collected over three years from 349 Dutch adolescents (Mage = 14.7, SDage = 0.7, 215 [61.6%] girls and 133 [38.1%] boys). A cross-lagged panel model of the three constructs showed that stability was relatively high for distinctiveness and continuity, whereas coherence was less stable. Distinctiveness and continuity were correlated positively within time, but cross-lagged associations were mostly not significant: Only distinctiveness and coherence negatively predicted each other across waves. Results suggest that distinctiveness, continuity, and coherence may be interrelated, but may not drive the development of each other.
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Comportamento do Adolescente , Desenvolvimento do Adolescente , Masculino , Feminino , Humanos , Adolescente , Estudos Longitudinais , Psicologia do AdolescenteRESUMO
The aim of this two-wave study is to investigate whether burnout, work engagement and workaholism can be empirically distinguished in one model and whether this model shows structural stability over a period of 2 years (i.e. whether the distinguishability between the constructs holds across time). The study was conducted among 118 judges in the Netherlands who completed questionnaires measuring burnout, work engagement and workaholism. The results showed that these are relatively distinguishable constructs, despite a considerable overlap of professional efficacy loading on work engagement (instead of burnout; as hypothesized), absorption loading on workaholism (in addition to work engagement; as hypothesized) and exhaustion loading on workaholism (in addition to burnout), which represents a new finding. These extra loadings led to model modifications, which were found at both time points. As hypothesized, this model appeared to be stable over time. Nevertheless, further clarification and conceptualization of these constructs are undoubtedly needed.
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The distinctiveness of neural information representation is crucial for successful memory performance but declines with advancing age. Computational models implicate age-related neural dedifferentiation on the level of item representations, but previous studies mostly focused on age differences of categorical information representation in higher-order visual regions. In an age-comparative fMRI study, we combined univariate analyses and whole-brain searchlight pattern similarity analyses to elucidate age differences in neural distinctiveness at both category and item levels and their relation to memory. Thirty-five younger (18-27 years old) and 32 older (67-75 years old) women and men incidentally encoded images of faces and houses, followed by an old/new recognition memory task. During encoding, age-related neural dedifferentiation was shown as reduced category-selective processing in ventral visual cortex and impoverished item specificity in occipital regions. Importantly, successful subsequent memory performance built on high item stability, that is, high representational similarity between initial and repeated presentation of an item, which was greater in younger than older adults. Overall, we found that differences in representational distinctiveness coexist across representational levels and contribute to interindividual and intraindividual variability in memory success, with item specificity being the strongest contributor. Our results close an important gap in the literature, showing that older adults' neural representation of item-specific information in addition to categorical information is reduced compared with younger adults.SIGNIFICANCE STATEMENT A long-standing hypothesis links age-related cognitive decline to a loss of neural specificity. While previous evidence supports the notion of age-related neural dedifferentiation of category-level information in ventral visual cortex, whether or not age differences exist at the item level was a matter of debate. Here, we observed age group differences at both levels as well as associations between both categorical distinctiveness and item specificity to memory performance, with item specificity being the strongest contributor. Importantly, age differences in occipital item specificity were largely due to reduced item stability across repetitions in older adults. Our results suggest that age differences in neural representations can be observed across the entire cortical hierarchy and are not limited to category-level information.
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Envelhecimento/fisiologia , Reconhecimento Visual de Modelos , Córtex Visual/fisiologia , Adolescente , Adulto , Idoso , Feminino , Humanos , Masculino , Neurônios/fisiologia , Reconhecimento Psicológico , Córtex Visual/citologia , Córtex Visual/crescimento & desenvolvimentoRESUMO
Despite evidence of a positive effect of functional diversity on ecosystem productivity, the importance of functionally distinct species (i.e. species that display an original combination of traits) is poorly understood. To investigate how distinct species affect ecosystem productivity, we used a forest-gap model to simulate realistic temperate forest successions along an environmental gradient and measured ecosystem productivity at the end of the successional trajectories. We performed 10 560 simulations with different sets and numbers of species, bearing either distinct or indistinct functional traits, and compared them to random assemblages, to mimic the consequences of a regional loss of species. Long-term ecosystem productivity dropped when distinct species were lost first from the regional pool of species, under the harshest environmental conditions. On the contrary, productivity was more dependent on ordinary species in milder environments. Our findings show that species functional distinctiveness, integrating multiple trait dimensions, can capture species-specific effects on ecosystem productivity. In a context of an environmentally changing world, they highlight the need to investigate the role of distinct species in sustaining ecosystem processes, particularly in extreme environmental conditions.
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Ecossistema , Árvores , Biodiversidade , Ambientes Extremos , FlorestasRESUMO
Existing global regionalization schemes for plants consider the compositional affinities among biotas, but these have not explicitly considered phylogenetic information. Here, we present for the first time, a phytogeographical delineation of the global vascular flora based on species-level evolutionary relationships. We analysed 8737 820 geographical occurrence records for vascular plants together with a time-calibrated phylogeny including 67 269 species. We constructed a global phylogenetic regionalization by estimating species composition and phylogenetic beta diversity among 200 km × 200 km grid cells across the world. We identified de novo 16 phytogeographical units that are deeply split into two clusters: Laurasian and Gondwanan. Our regionalization broadly matches previous schemes, but also highlights the separation of the Gondwanan biota into an Holotropical cluster and an Australian-Neozealandic-Patagonian cluster. In contrast, no clear split among Laurasian and Gondwanan biotas was retrieved when omitting phylogenetic information. The integration of phylogenetic and geographical information provides new insights into the delineation of phytogeographical areas and their historical relationships, enabling the identification of three large, clearly differentiated biotas, here referred to as kingdoms: Holarctic, Holotropical, and Austral. Our results provide further evidence for delineating transition zones and show a clear latitudinal pattern of increasing evolutionary distinctiveness towards the poles.
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Biota , Traqueófitas , Austrália , Evolução Biológica , FilogeniaRESUMO
OBJECTIVE: To determine whether distinctive prolonged-grief-disorder- (PGD) and depressive-symptom states emerge among family caregivers of cancer patients over their first 2 years of bereavement. This may extend cross-sectional evidence that PGD and major depressive disorder (MDD) symptoms can co-occur/occur independently and validate their construct distinctiveness. METHODS: In this secondary-analysis study, PGD symptoms and depressive symptoms were measured over 666 caregivers using 11 grief symptom items of the Prolonged Grief-13 scale and 16 items of the Center for Epidemiologic Studies-Depression scale, respectively. Distinct PGD/depressive-symptom states were identified by latent transition analysis with dichotomous indicators (presence/absence) of PGD or depressive symptoms. RESULTS: Four distinct PGD/depressive-symptom states emerged. The resilient and subthreshold depression-dominant states showed low and moderate probabilities of the presence of majority of depressive symptoms, respectively, with no PGD symptoms having a greater than moderate probability of presence. The depression-dominant state was marked by a high probability of the presence for 9 of 16 depressive symptoms, with moderate probabilities for almost all PGD symptoms. The PGD-depression comorbid state was characterized by a high probability of presence of all PGD symptoms and depressive symptoms, except for moderate probabilities of presence of two depressive symptoms. CONCLUSION: Our longitudinal identification of a predominantly depressive state but absence of a PGD-dominant state provides further evidence that PGD and MDD are related but distinct constructs that can occur independently or concurrently as the PGD-depression comorbid state. When PGD is suspected, bereaved individuals should be assessed for the potential comorbidity of MDD.