Search

Aim: Habitat diversity has been linked to the diversity and structure of island communities, however, little is known about patterns and processes within habitats. Here we aim to determine the contributions of habitat type and inferred dispersal frequency to the differences in taxonomic structure between assemblages in the same island habitat. Location: The Macaronesian archipelagos (Azores, Madeira, the Canary Islands and Cabo Verde). Taxon: Spiders (Araneae). Methods: We established forest and dry habitat sites (each with five plots) on two islands per archipelago. We collected spiders using standardised sampling protocols. We tested the differences in beta diversity separately for each habitat and for each inferred category of ballooning (an aerial dispersal strategy) frequency across geographic scales through nested non-parametric permutational multivariate analyses of variance. We then tested whether ballooning and habitat influenced heterogeneity in species composition (dispersion in beta diversity) in the two habitat types. We analysed the effects of habitat and ballooning on species abundance distribution (SAD) and rarity by fitting Gambin models and evaluating the contribution of ballooning categories to SAD. Results: Communities of the same archipelago and habitat were taxonomically more similar, and beta diversity increased with geographic scale, being greater in dry habitats. There was greater species replacement among assemblages in dry habitats than in forests, with greater differences for rare ballooners. There were no differences in SAD between habitats although dry habitat sites seemed to harbour more species with low abundances (rare species) than forests. Main conclusions: Habitat type does not only condition the differences between spider assemblages of the same habitat but also the scale at which they occur. These differences may be determined by the heterogeneity in the physical structure of each habitat as well as how much this structure facilitates aerial dispersal (ballooning), and should be considered in theories/hypotheses on island community assembly as well as in conservation strategies. [ABSTRACT FROM AUTHOR]

The Yuanjiang dry-hot valley features hot and dry climate, low vegetation and soil degradation. It had lush vegetation in the past, but has become degraded in recent decades. Understanding the interrelationship between species and the habitat is necessary to explain this change. In this study, a link between fern and fern allies – a group that is hypersensitive to environmental factors and their circumstances is constructed. Intensive transects and plots were designed to be proxies for extant fern and fern allies, and their habitats. Fifty years of meteorological records of precipitation and temperature along altitude and river running direction (latitudinal) were employed. Alpha and beta diversity are used to access diversity. Species_estimated, Singletons, Uniques, ACE, ICE, and Chao2, which associate to abundance and rarity, are subscribed to the correlation between fern and fern allies, and their ecosystem. Eight species, Selaginella pseudopaleifera, Aleuritopteris squamosa, Adiantum malesianum, Pteris vittata, Davallia trichomanoides, Sinephropteris delavayi, Selaginella jugorum, and Lygodium japonicum are used as indicators of a typical xeric and sun-drying habitat. The results indicate (1) accompanied by dramatically shrinking habitats, fern and fern allies are in very low diversity and abundance, whereas the rarity is relatively high; (2) for fern and fern allies, environmental factors are positive when altitude goes up; and (3) eight indicator species are latitudinally correlated with fern and fern allies along the river running direction. [ABSTRACT FROM AUTHOR]

Spatial rarity is often used to predict extinction risk, but rarity can also occur temporally. Perhaps more relevant in the context of global change is whether a species is core to a community (persistent) or transient (intermittently present), with transient species often susceptible to human activities that reduce niche space. Using 5–12 yr of data on 1,447 plant species from 49 grasslands on five continents, we show that local abundance and species persistence under ambient conditions are both effective predictors of local extinction risk following experimental exclusion of grazers or addition of nutrients; persistence was a more powerful predictor than local abundance. While perturbations increased the risk of exclusion for low persistence and abundance species, transient but abundant species were also highly likely to be excluded from a perturbed plot relative to ambient conditions. Moreover, low persistence and low abundance species that were not excluded from perturbed plots tended to have a modest increase in abundance following perturbance. Last, even core species with high abundances had large decreases in persistence and increased losses in perturbed plots, threatening the long‐term stability of these grasslands. Our results demonstrate that expanding the concept of rarity to include temporal dynamics, in addition to local abundance, more effectively predicts extinction risk in response to environmental change than either rarity axis predicts alone. [ABSTRACT FROM AUTHOR]

Copyright of Biotropica is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Measuring commonness and rarity is pivotal to ecology and conservation. Zeta diversity, the average number of species shared by multiple sets of assemblages, and Dark diversity, the number of species that could occur in an assemblage but are missing, have been recently proposed to capture two aspects of the commonness‐rarity spectrum. Despite a shared focus on commonness and rarity, thus far, Zeta and Dark diversities have been assessed separately. Here, we review these two frameworks and suggest their integration into a unified paradigm of the "rarity facets of biodiversity." This can be achieved by partitioning Alpha and Beta diversities into five components (the Zeta, Eta, Theta, Iota, and Kappa rarity facets) defined based on the commonness and rarity of species. Each facet is assessed in traditional and multiassemblage fashions to bridge conceptual differences between Dark diversity and Zeta diversity. We discuss applications of the rarity facets including comparing the taxonomic, functional, and phylogenetic diversity of rare and common species, or measuring species' prevalence in different facets as a metric of species rarity. The rarity facets integrate two emergent paradigms in biodiversity science to better understand the ecology of commonness and rarity, an important endeavor in a time of widespread changes in biodiversity across the Earth. [ABSTRACT FROM AUTHOR]

Copyright of Bankarstvo Magazine is the property of Association of Serbian Banks and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract Climate change is expected to alter the distributions of species around the world, but estimates of species’ outcomes vary widely among competing climate scenarios. Where should conservation resources be directed to maximize expected conservation benefits given future climate uncertainty? Here, we explore this question by quantifying variation in fish species’ distributions across future climate scenarios in the Red River basin south‐central United States. We modeled historical and future stream fish distributions using a suite of environmental covariates derived from high‐resolution hydrologic and climatic modeling of the basin. We quantified variation in outcomes for individual species across climate scenarios and across space, and identified hotspots of species loss by summing changes in probability of occurrence across species. Under all climate scenarios, we find that the distribution of most fish species in the Red River Basin will contract by 2050. However, the variability across climate scenarios was more than 10 times higher for some species than for others. Despite this uncertainty in outcomes for individual species, hotspots of species loss tended to occur in the same portions of the basin across all climate scenarios. We also find that the most common species are projected to experience the greatest range contractions, underscoring the need for directing conservation resources toward both common and rare species. Our results suggest that while it may be difficult to predict which species will be most impacted by climate change, it may nevertheless be possible to identify spatial priorities for climate mitigation actions that are robust to future climate uncertainty. These findings are likely to be generalizable to other ecosystems around the world where future climate conditions follow prevailing historical patterns of key environmental covariates.

A través de este documento, el Comité de Rarezas de Euskadi (CRE) recopila la homologación de citas de aves raras en 2020 en el territorio de Euskadi (Comunidad Autónoma Vasca). Este Comité, creado al amparo del Comité Ornitológico de Euskadi (COE), ejerce su actividad para recopilar, estudiar y publicar todas las citas de especies o subespecies cuya presencia en Euskadi es accidental o irregular. A lo largo de 2020 se evaluaron un total de 136 citas, además de otras 2 citas pendientes de 2019. De todas ellas, 70 fueron homologadas, 5 se asignaron a categoría D, 3 a categoría E, 48 fueron rechazadas (no homologadas) y 10 quedaron pendientes de evaluación. Por otro lado, dado el alto número de citas registradas durante los últimos años, se elimina de la lista de aves raras, desde el 1 de enero de 2021, el elanio común Elanus caeruleus. Asimismo, dado el escaso número de citas registradas durante los últimos años, se incorpora a la lista, desde el 1 de enero de 2021, el porrón pardo Aythya nyroca.

Nodular fasciitis (NF) and proliferative fasciitis (PF) are benign, reactive mesenchymal neoplasms that can mimic malignancies due to their rapid growth and histological characteristics. NF typically affects the subcutaneous tissue, occasionally involving muscles and fascia, predominantly in young adults, and appears frequently in the upper extremities, trunk, and head/neck. PF, a pseudosarcomatous lesion, primarily occurs in the subcutaneous tissue of adults aged 40-70 years and is uncommon in younger populations. This article presents two pediatric cases of NF and PF in unusual locations: a six-year-old girl with a vulvar NF and a 10-year-old girl with a gluteal PF. Both cases demonstrated rapid growth and distinct histological features, confirmed by immunohistochemical analyses and fluorescence in situ hybridization (FISH). These cases underscore the importance of accurate histological recognition to avoid misdiagnosis and ensure appropriate treatment, highlighting the rarity of such occurrences in children and the need for awareness among clinicians and pathologists., Competing Interests: Human subjects: Consent was obtained or waived by all participants in this study. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work., (Copyright © 2024, Bagaloni et al.)

The Colombian weasel, Neogale felipei (Izor & de la Torre, 1978), is one of the most enigmatic and threatened carnivores in South America, with only six confirmed records in the Andes of Ecuador and Colombia. During a long-term trail camera survey conducted at Mesenia-Paramillo Natural Reserve, we recorded the northernmost occurrence of the species, which extends its distribution by approximately 120 km to the north from the nearest previously known locality in Colombia. We also provide some comments on its natural history. [ABSTRACT FROM AUTHOR]

Background: Among sarcomas, which are rare cancers, many types are exceedingly rare; however, a definition of ultra‐rare cancers has not been established. The problem of ultra‐rare sarcomas is particularly relevant because they represent unique diseases, and their rarity poses major challenges for diagnosis, understanding disease biology, generating clinical evidence to support new drug development, and achieving formal authorization for novel therapies. Methods: The Connective Tissue Oncology Society promoted a consensus effort in November 2019 to establish how to define ultra‐rare sarcomas through expert consensus and epidemiologic data and to work out a comprehensive list of these diseases. The list of ultra‐rare sarcomas was based on the 2020 World Health Organization classification, The incidence rates were estimated using the Information Network on Rare Cancers (RARECARENet) database and NETSARC (the French Sarcoma Network's clinical‐pathologic registry). Incidence rates were further validated in collaboration with the Asian cancer registries of Japan, Korea, and Taiwan. Results: It was agreed that the best criterion for a definition of ultra‐rare sarcomas would be incidence. Ultra‐rare sarcomas were defined as those with an incidence of approximately ≤1 per 1,000,000, to include those entities whose rarity renders them extremely difficult to conduct well powered, prospective clinical studies. On the basis of this threshold, a list of ultra‐rare sarcomas was defined, which comprised 56 soft tissue sarcoma types and 21 bone sarcoma types. conclusions: Altogether, the incidence of ultra‐rare sarcomas accounts for roughly 20% of all soft tissue and bone sarcomas. This confirms that the challenges inherent in ultra‐rare sarcomas affect large numbers of patients. The list of ultra‐rare sarcomas, defined as those sarcomas with an incidence ≤1 per 1,000,000, comprises 56 soft tissue sarcoma and 21 bone sarcoma types. The incidence of ultra‐rare sarcomas accounts for roughly 20% of all soft tissue and bone sarcomas, confirming that challenges inherent to ultra‐rare sarcomas affect large numbers of patients. [ABSTRACT FROM AUTHOR]

Based on the analysis of both historical and recent collections, this paper reports an annotated list of taxa which are new to the lichen biota of Italy or of its administrative regions. Specimens were identified using a dissecting and a compound microscope; routine chemical spot tests and standardized thin-layer chromatography (TLC or HPTLC). The list includes 225 records of 153 taxa. Twenty taxa are new to Italy, the others are new to one or more administrative regions, with 15 second records and 5 third records for Italy. Some of the species belong to recently-described taxa, others are poorly known, sterile or ephemeral lichens which were largely overlooked in Italy. Several species are actually rare, either because of the rarity of their habitats (e.g. old-growth forests), or because in Italy they are at the margins of their bioclimatic distribution. The picture of the lichen biota of Italy has now new pixels, but its grain is still coarse. Further analysis of historical collections, increased efforts in the exploration of some areas, and the taxonomic revision of critical groups are still necessary to provide more complete distributional data for new biogeographic hypotheses, taxonomic and ecological research, and biodiversity conservation. [ABSTRACT FROM AUTHOR]

1. Anthropogenic land‐use change alters the ecological communities in a landscape's remaining natural habitat. These matrix effects are understudied in rare species, which comprise a majority of biodiversity, contribute to ecosystem services, and are particularly vulnerable to population declines. 2. This study used bee species survey data from New Jersey forest fragments, in conjunction with an independent museum data set, to identify rare bee species and developed regularised regularised regression models of matrix effects on their richness and abundance. 3. By using a regularised modelling approach, this study explains 44.43% of variation in rare bee species richness between forest fragments and 27.27% of variation in their abundance (average adjusted R2). 4. The present study's results identified specific subcategories of urban land use in the surrounding 1000 m of forest fragments that explained patterns in rare bee species richness and abundance, providing insights into how to select forest fragments to conserve rare bees. Low priority should be given to fragments in close proximity to high‐ and medium‐density housing, which likely harms rare bees by increasing impervious surface cover. Low priority should also be given to fragments near golf courses and athletic fields; this study speculates that these land uses harm rare bees through mowing and pesticide application. Finally, high priority should be given to fragments composed of a larger proportion of mature forest, which likely provides a greater diversity of native floral resources. Altogether, this study's model results reveal the importance of matrix habitats for the biodiversity of rare species in forest fragments. [ABSTRACT FROM AUTHOR]

Although amateur birding makes important contributions towards conservation and the tourism industry, the precise motivations driving birders have not been extensively investigated. The aims of this study were to analyse birders' highlights for birding trips within southern Africa and to establish whether local and foreign birders preferred to see rare or morphologically unusual birds, as opposed to common or morphologically indistinct birds. Morphological traits included: average body size, colour and unusual features; rarity-related traits included: maximum abundance, and range. A total of 673 terrestrial birds were included, and morphological and rarity-related traits were recorded for each species. Birding trip reports for long (two to four weeks) trips across southern Africa that included full sightings lists and highlights were used to indicate which species qualified as highlights (morphologically unusual, rare or both). Both among local and foreign birders, large-bodied birds were the main highlights, with the other characteristics not retrieved as significant. This contradicts the expectation that local birders would be more interested in rarity; however, this result could be explained by the fact that only long birding trips were considered, whereas rarity may more often be sought by specialized local birders on shorter, targeted trips. [ABSTRACT FROM AUTHOR]

Preserving biodiversity and its many components is a priority of conservation science and how to efficiently allocate resources to preserve healthy populations of as many species, habitats, and ecosystems as possible. We used the U.S. Geological Survey (USGS) Gap Analysis Project (GAP) species models released in 2018, which identify predicted habitats for terrestrial vertebrates in the conterminous United States, to illustrate hotspots of biodiversity for the major taxonomic groups. This collection represents the first complete compilation of terrestrial vertebrate species models for the conterminous United States (U.S. Geological Survey (USGS), 2018a). We used the species models but not the available subspecies models; this resulted in the inclusion of 282 amphibian models, 621 bird models, 365 mammal models, and 322 reptiles in our analysis. We also used population trend information and made spatial queries to characterize species in three dimensions: geographic range (small or large), habitat breadth (narrow or wide), and population trend (decreasing vs stable or increasing). This characterization allowed us to divide the species into eight groups (A-H) with similar characteristics. Group A species (large geographic range, wide habitat breadth, and stable or increasing population trend) are species that are common now with no indication of becoming rare. Species B-H have theoretical or known characteristics that could lead them to become rare with the H species exhibiting small geographic range, narrow habitat breadth, and decreasing population trend. Finally, we evaluated the prevalence of mapped habitat on protected lands for each species, exploring the patterns of representation in the rare species groups by ecoregion. The species we identified with population and habitat use characteristics that potentially predispose them to being or becoming rare represented a large percentage of each taxon. Potentially rare species were widely distributed among ecoregions. Of the 20 ecoregions in the country, 14 have a greater number of rare species than the national average for at least one taxon. Protection of the habitat for the majority of these rare species is below that recommended (17% of available habitat) by the Convention on Biological Diversity (CBD). The Everglades ecoregion was the only ecoregion that protected more than half of its rare or potentially rare species.

The soil seed bank (SSB) plays an important role in determining future community composition and health of forests. The extent to which abiotic conditions alter the abundance and diversity of the future forest composition via modulating the regenerative capacity of the SSB and their relationship with each other is not fully understood. We studied how elevation and abiotic conditions (canopy openness, slope, aspect, soil pH, and a natural gradient of these soil nutrients: total nitrogen [N], total carbon [C], C:N ratio, available phosphorus [P], available potassium [K], calcium [Ca], iron [Fe], magnesium [Mg], manganese [Mn], and sulfur [S]) affect community characteristics, calculated as: (1) seedling abundance, (2) species richness, (3) Shannon-Weiner diversity index, (4) Simpson index, (5) Chao 2 richness estimator, (6) number of species represented by only one individual, and (7) number of species that occur only in one plot. We used soils sampled in 13 1-ha plots along an altitudinal gradient from 400 to 1850 m above sea level. We determined both direct and indirect causal relationships between abiotic factors and SSB community characteristics using linear mixed models and structural equation modeling. Increased elevation and canopy openness resulted in lower species richness and diversity as well as fewer rare species. However, greater canopy openness resulted in higher abundance. Abundance and richness of the SSB were lower in steeper slopes, but this negative effect appeared to be along an indirect pathway through soil pH and nutrients such as soil Mn and S. Soil P had a significant negative relationship with SSB characteristics for all indices evaluated here, except for SSB abundance, which was positively affected by increased soil pH. Our results highlight the role of abiotic factors in forest regeneration and resilience through their influence on the soil seed bank community. This study is one of the very first to provide data on the SSB along a wide elevational range in subtropical forests, and can be the basis to assess the regeneration potential and health of the study region.

Tropical short, steep coastal streams are typically dominated by diadromous species, especially amphidromous fishes, crustaceans, and molluscs. We undertook a study to determine the distribution of fishes along the stream continuum and determine if substantial natural instream barriers influenced assemblage composition.We surveyed fish assemblages in three short, steep coastal streams in the Australian Wet Tropics by snorkelling and performing single pass counts in each 100‐m section along the entire main channel from the high‐tide mark to the source (or near source: until fish were no longer recorded). A primary focus was mapping the distribution and relative abundance of sicydiine gobies, and we also estimated freshwater crustacean numbers (Caridea: Palaemonidae and Atyidae).In total, 2,837 individual fish of 25 species were recorded upstream of the high‐tide mark across the three streams and the first records of an additional sicydiine goby (Smilosicyopus leprurus) were obtained from continental Australia. Consistent with findings from tropical Pacific island streams, we observed a shift in fish assemblage composition along the elevation gradient and in relation to major instream barriers (e.g. waterfalls >5 m, and high flow chutes across smooth bedrock surfaces). Species richness of diurnal predatory fishes was greatest in the lower course of streams and absent upstream of major instream barriers.Diurnal predatory fishes were, in some instances, found upstream of barriers. Specifically, large adult (>200 mm total length) Kuhlia rupestris (diurnal predators) accessed reaches above challenging sequences of cascades combined with small waterfalls. In contrast, all sizes of that species, adult Kuhlia marginata (>150 mm total length) and a diversity of other diurnal predatory fishes occupied the lower course of streams including upstream of gentle cascade sequences or isolated small waterfalls.Where abundances of diurnal predatory fishes were high, freshwater carideans were rarely observed. Peak densities of carideans were observed upstream of major barriers, with moderate densities in the upper mid‐course in the presence of few Kuhlia spp.The current study demonstrates the value of complete single‐pass surveys of fish assemblages in tropical short, steep coastal streams by revealing the highly localised occupation of particular reaches by rare fishes. It also points towards the importance of stream‐specific characteristics, namely the position of waterfalls in dictating diadromous predator distribution with consequences for community structure, thereby aligning with the Riverine Discontinuum Concept. [ABSTRACT FROM AUTHOR]

Due to expanding global trade and movement of people, new plant species are establishing in exotic ranges at increasing rates while the number of native species facing extinction from multiple threats grows. Yet, how species losses and gains globally may, together, be linked to traits and macroevolutionary processes is poorly understood. Here, we show that, adjusting for diversification rate and clade age, the proportion of threatened species across flowering plant families is negatively related to the proportion of naturalised species per family. Moreover, naturalisation is positively associated with range size, short generation time, autonomous seed production and interspecific hybridisation, but negatively with age and diversification, whereas threat is negatively associated with range size and hybridisation, and positively with biotic pollination, age and diversification rate. That we find such a pronounced signature of naturalisation and threat across plant families suggests that both trait syndromes have coexisted over deep evolutionary time and counter to intuition, that neither strategy is necessarily superior to the other over long evolutionary timespans. [ABSTRACT FROM AUTHOR]

The current paper sheds light on The Speech Act Theory and its role in constructing argumentation by applying it on a selected set of anecdotes (rarities) of the book entitled Al-Bukhalāʾ (The Misers) written by Al-Jāḥiz. In fact, the present research has two main objectives : the first is to test the cognitive explanatory competence of the theory in hand, and the second is to know the method of employing linguistic structures in convincing certain arguments. To fulfil the above aims, the research edopted for a pragmatic method starting from the analysis of the linguistic structures to reach the pragmatic level, which is most of the time is extra-linguistic inguistic in nature. The main finding that we come through this investigation is that there is an intimate relationship between the linguistic structure of the anecdote and its impact degrees on the receiver. And this is a relationship that takes place under the effect of the pragmatic level with all its components. [ABSTRACT FROM AUTHOR]

Aim: Detection of rare species is limited by their intrinsic nature and by the constraints associated with traditional field surveys. Remote sensing (RS) provides a powerful alternative to traditional detection methods through the increasing availability of RS products. Here, we assess the capacity of RS at high and medium resolution to detect rare plants with direct and indirect approaches, and how the performance of RS can be influenced by the characteristics of species. Methods: An extensive literature review was conducted to synthesize the use of RS to detect or predict rare plant occurrence at high and medium resolution (<30 m and 30–300 m, respectively). The concept of "rarity" was based on Rabinowitz's rare species classification. The literature review was performed in Scopus for the period 1990–2020. Results: While direct detection is often limited, it is possible with high and very high spatial resolution data for rare plants with distinctive traits. RS is also able to capture biophysical conditions driving rare plant distributions, which can indirectly provide accurate predictions for them. Both approaches have the potential to discover new populations of rare plants. RS can also feed SAMs of rare plants, which combined with SDMs can provide a valuable approach for rare plant detection. While direct detection is limited by the space occupied by a species within its habitat and its morphological, phenological and physiological characteristics, the predictive performance of RS‐based SDMs (indirect detection) can be influenced by habitat size, habitat specificity and phenological features of rare plants. Similarly, model predictive performance can be influenced by the rarity form of the target species according to the rarity classification criteria. Main conclusions. With this synthesis, the strong potential of RS for the purposes of detection and prediction of rare plant has been highlighted, with practical applications for conservation and management. [ABSTRACT FROM AUTHOR]

The generality and drivers of rarity, defined along the axes of geographic range, population size and habitat specificity, have received considerable scientific attention for well over a century. Yet, studies that examine rarity holistically among these three attributes are limited, especially among invertebrate and marine taxa. The perceived paradox of deep‐sea species, with often low population size but large geographic ranges, remains poorly resolved and understood. Here I assess seven forms of rarity and their drivers in deep‐sea bivalves across the Atlantic Ocean. Rarity appears to be a common trait among deep‐sea bivalves, with nearly 85% of the species exhibiting some form of rarity. Bivalves also showed a strong bimodal pattern of very common and very rare species. Geographic range, population size and habitat specificity were all heavily right skewed. Taxonomic superfamilies, body size, energy availability, temperature, depth and latitude, all significantly predicted geographic range, population size and habitat specificity. In a few cases, these patterns were counter to theoretical expectations. The drivers of rarity appear to be predictable from knowledge of the intrinsic biological and extrinsic environmental context of the species. These findings have major implications for deep‐sea conversation, especially as anthropogenic threats are increasing. [ABSTRACT FROM AUTHOR]

Premise: Rarity is a complex and central concept in ecology and conservation biology. Yet, it is still poorly understood why some species are rare and others common. Here, we aimed to understand the drivers of species rarity patterns in woody plant communities. Methods: We analyzed the local abundance and landscape frequency of 121 woody plant species across 238 plots on American Samoa and Hawaiian islands. We first assessed whether taxonomy, life form (shrub, small tree, large tree), and dispersal syndrome (dispersed by animals or by other means) are associated with the rarity of species. We then analyzed phylogenetic patterns in plant rarity and tested whether rarity patterns are associated with species evolutionary distinctiveness and the number of species within genera and families. Results: Large trees were less abundant but more frequent than shrub species. Animal‐dispersed species tended to be less abundant than species dispersed by other means, while species frequency was not associated with dispersal syndromes. Relative frequency in Hawai′i exhibited a more robust phylogenetic signal than did abundance. Both evolutionary distinctiveness and taxa species richness were significantly associated with the frequency of shrub species in Hawai′i. Conclusions: Life form appears consistently associated with the rarity of species. High diversification rate is probably a key factor explaining landscape‐scale rarity of native species on isolated archipelagos like Hawai′i. At the landscape scale, rarity appears to be inversely associated with evolutionary distinctiveness, but at the local scale, species abundance may be not associated with evolutionary distinctiveness. [ABSTRACT FROM AUTHOR]

Most species in ecological communities are rare, whereas only a few are common. This distributional paradox has intrigued ecologists for decades but the interpretation of species abundance distributions remains elusive.We present Fuzzy Quantification of Common and Rare Species in Ecological Communities (FuzzyQ) as an R package. FuzzyQ shifts the focus from the prevailing species‐categorization approach to develop a quantitative framework that seeks to place each species along a rarity‐commonness gradient. Given a community surveyed over a number of sites, quadrats, or any other convenient sampling unit, FuzzyQ uses a fuzzy clustering algorithm that estimates a probability for each species to be common or rare based on abundance–occupancy information. Such a probability can be interpreted as a commonness index ranging from 0 to 1. FuzzyQ also provides community‐level metrics about the coherence of the allocation of species into the common and rare clusters that are informative of the nature of the community under study.The functionality of FuzzyQ is shown with two real datasets. We demonstrate how FuzzyQ can effectively be used to monitor and model spatiotemporal changes in species commonness, and assess the impact of species introductions on ecological communities. We also show that the approach works satisfactorily with a wide range of communities varying in species richness, dispersion and abundance currencies.FuzzyQ produces ecological indicators easy to measure and interpret that can give both clear, actionable insights into the nature of ecological communities and provides a powerful way to monitor environmental change on ecosystems. Comparison among communities is greatly facilitated by the fact that the method is relatively independent of the number of sites or sampling units considered. Thus, we consider FuzzyQ as a potentially valuable analytical tool in community ecology and conservation biology. [ABSTRACT FROM AUTHOR]

Quantifying the abundance of species is essential to ecology, evolution, and conservation. The distribution of species abundances is fundamental to numerous longstanding questions in ecology, yet the empirical pattern at the global scale remains unresolved, with a few species' abundance well known but most poorly characterized. In large part because of heterogeneous data, few methods exist that can scale up to all species across the globe. Here, we integrate data from a suite of well-studied species with a global dataset of bird occurrences throughout the world--for 9,700 species (~92% of all extant species)--and use missing data theory to estimate speciesspecific abundances with associated uncertainty. We find strong evidence that the distribution of species abundances is log left skewed: there are many rare species and comparatively few common species. By aggregating the species-level estimates, we find that there are ~50 billion individual birds in the world at present. The global-scale abundance estimates that we provide will allow for a line of inquiry into the structure of abundance across biogeographic realms and feeding guilds as well as the consequences of life history (e.g., body size, range size) on population dynamics. Importantly, our method is repeatable and scalable: as data quantity and quality increase, our accuracy in tracking temporal changes in global biodiversity will increase. Moreover, we provide the methodological blueprint for quantifying species-specific abundance, along with uncertainty, for any organism in the world. [ABSTRACT FROM AUTHOR]

Class rarity is a frequent challenge in cybersecurity. Rarity occurs when the positive (attack) class only has a small number of instances for machine learning classifiers to train upon, thus making it difficult for the classifiers to discriminate and learn from the positive class. To investigate rarity, we examine three individual web attacks in big data from the CSE-CIC-IDS2018 dataset: "Brute Force-Web", "Brute Force-XSS", and "SQL Injection". These three individual web attacks are also severely imbalanced, and so we evaluate whether random undersampling (RUS) treatments can improve the classification performance for these three individual web attacks. The following eight different levels of RUS ratios are evaluated: no sampling, 999:1, 99:1, 95:5, 9:1, 3:1, 65:35, and 1:1. For measuring classification performance, Area Under the Receiver Operating Characteristic Curve (AUC) metrics are obtained for the following seven different classifiers: Random Forest (RF), CatBoost (CB), LightGBM (LGB), XGBoost (XGB), Decision Tree (DT), Naive Bayes (NB), and Logistic Regression (LR) (with the first four learners being ensemble learners and for comparison, the last three being single learners). We find that applying random undersampling does improve overall classification performance with the AUC metric in a statistically significant manner. Ensemble learners achieve the top AUC scores after massive undersampling is applied, but the ensemble learners break down and have poor performance (worse than NB and DT) when no sampling is applied to our unique and harsh experimental conditions of severe class imbalance and rarity. [ABSTRACT FROM AUTHOR]

The Anthropocene affects how we manage the environment in many ways, perhaps most importantly by undermining how past conditions act as baselines for future expectations. In a period when historical analogues become less meaningful, we need to forge new practices and methods of environmental monitoring and management, including how to categorize, manage, and analyze the deluge of environmental data. In particular, we need practices to detect emerging hazards, changing baselines, and amplified risk. Some current data practices, however, especially the designation and dismissal of outliers, might mislead efforts to better adapt to new environmental conditions. In this article we ask these questions: What are the politics of determining what counts as "abnormal" and is worthy of exclusion in an era of the ever-changing "normal"? What do data exclusions, often in the form of outliers, do to our ability to understand and regulate in the Anthropocene? We identify a recursive process of distortion at play where constructing categories of abnormal–normal allows for the exclusion of "outliers" from data sets, which ultimately produces a false rarity and hides environmental changes. To illustrate this, we draw on a handful of examples in regulatory science and management, including the Exceptional Event Rule of the Clean Air Act, beach erosion models for nourishment projects, and the undetected ozone hole. We conclude with a call for attention to the construction of "normal" and "abnormal" events, systems, data, and natures in the Anthropocene. [ABSTRACT FROM AUTHOR]

Conservation biology must set geographic conservation priorities not only based on the compositional or structural but also on the functional dimensions of biodiversity. However, assessing functional diversity is challenging at the regional scale. We propose the use of satellite-derived Ecosystem Functional Types (EFTs), defined here as patches of land surface that share similar primary production dynamics, to incorporate such aspects of ecosystem functional diversity into the selection of protected areas. We applied the EFT approach to the Baja California Peninsula, Mexico, to characterize the regional heterogeneity of primary production dynamics in terms of EFTs; to set conservation priorities based on EFT richness and rarity; and to explore whether such EFT-based conservation priorities were consistent with and/or complementary to previous assessments focused on biodiversity composition and structure. EFTs were identified based on three ecosystem functional attributes derived from seasonal dynamics of the Enhanced Vegetation Index: the annual mean (proxy of primary production), the seasonal coefficient of variation (descriptor of seasonality), and the date of maximum (indicator of phenology). EFT-based priorities identified 26% of the peninsula as being of extreme or high priority and reinforced the value of the ecosystem functional diversity of areas already prioritized by traditional conservation assessments. In addition, our study revealed that biodiversity composition- and structure-based assessments had not identified the full range of important areas for EFT diversity and tended to better capture areas of high EFT rarity than those of high EFT richness. Our EFT-based assessment demonstrates how remotely sensed regional heterogeneity in ecosystem functions could reinforce and complement traditional conservation priority setting. [ABSTRACT FROM AUTHOR]

The distribution of the rare Karst Snowfly, Allocapnia cunninghami Ross & Ricker, 1971, was assessed during winters of 2019 and 2020. This species has been assigned a NatureServe ranking of G1 (= Critically Imperiled) and was recently included in a Center for Biological Diversity petition to the U.S. Fish and Wildlife Service as potentially threatened or endangered. Sampling for adult A. cunninghami occurred in 45 unique localities in central Kentucky and middle Tennessee, USA, mainly within the known historical range of this species. This species was found in winters of 2019 and 2020 in very low numbers compared to regional Allocapnia and the winter-emergent fauna in general. Allocapnia cunninghami was collected at only five unique localities and comprised only 1.1% and 1.0% of all Allocapnia and the total winter-emergent fauna individuals collected, respectively. By comparison, the widespread species A. rickeri Frison, 1942 was collected from 41 of 45 unique localities and comprised 70% of all individual adults collected. Despite the difficulties of interpreting historical locality data from 1964 to 1966, A. cunninghami appears to now be present in fewer stream sites and distributed more patchily compared to ca. 55 years ago. A confounding biological factor for A. cunninghami is that Allocapnia adults in general have poor dispersal capacity, making natural colonization and potential recolonization events substantially more problematic for what appears to be a rare species in slow decline within an already small native geographic range. Implications for insect conservation: By including positive collection data from 1999–2012, increasing the number of known contemporaneous sites to nine, predictive distributional models can now be generated to allow for more focused searching for previously undetected populations and potentially expand the known geographic range of this rare species. [ABSTRACT FROM AUTHOR]

Inflammatory myofibroblastic tumor is a rare group of neoplasms showing a mixture of spindle-shaped myofibroblasts or fibroblasts and a variable amount of inflammatory cells (eosinophils, plasma cells, and lymphocytes). They are not usually included in the differential diagnosis of nodules and masses because of their rarity, therefore, remaining an underdiagnosed entity. We report one such rare case in a 3-year-old female.

The Southwest Australian Floristic Region (SWAFR) supports an exceptional number of threatened and data-deficient flora. In this study, we: (i) collated statistics on the number, listing criteria and tenure of occurrence of threatened and data-deficient flora; (ii) conducted spatial and biogeographic analyses to address questions concerning patterns of diversity of threatened and data-deficient flora relative to the whole flora and evolutionary and threat drivers; and (iii) examined whether threatened and data-deficient flora richness is evenly distributed across plant lineages. We found that although threatened and data-deficient flora occurred across the breadth of the SWAFR, high richness was concentrated in a limited number of locations, which were not always strongly aligned with areas of higher land transformation. Data-deficient flora demonstrated different spatial patterns of occurrence to threatened flora. Approximately 70% of the populations of threatened and data-deficient flora occurred outside of lands managed primarily for conservation. Both evolutionary history and contemporary threats contribute to the current status and distribution of diversity of the threatened and data-deficient flora, with evolutionary history playing a significant role in predisposing a portion of the flora to having population traits that result in those flora meeting IUCN Red List criteria, along with ecological traits that predispose some to specific novel threats. An understanding of the distribution of species and threats, flora traits, and how these traits mediate susceptibility to threats, offers one potential way forward for an initial assessment of which of the 1819 data-deficient flora may be most at risk of extinction.

The study deals with the floristic diversity assessment and vegetation composition analysis in various forest types from Hosur Forest division situated in Eastern Ghats of Southern India, in the state of Tamil Nadu. The study recorded 468 species of plants belonging to 283 genera and 91 families, including Angiosperms (464 species), Pteridophytes (3 species) and Bryophytes (1 species). Of the total, 94 species are trees, 12 are lianas, 70 are shrubs, 34 species are climbers, 194 species are herbs, sedges 7, grasses 21, ferns 3 and 1 species of moss. The five most abundant families in Hosur Forest Division were Fabaceae (45 spp.), Poaceae (34 spp.), Acanthaceae (30 spp.), Euphorbiaceae (28 spp.) and Rubiaceae (25 spp.). The quantitative features such as density and important value index (IVI) varied greatly among forest and in different forest types. In the present study, the diversity index of shrubs and herbs were found to be higher than that of trees. The maximum species diversity was recorded in Southern dry mixed deciduous forest (SDMDF) followed by Southern Thorn Forest (STF) and Southern Thorn Scrub (STS). The species diversity (H) was recorded the highest for SDMDF (5.61) followed by STF (5.18) and the lowest for STS (5.12). The presence of large number of higher girth class tree species and low number of sapling and seedling indicates that the present forests investigated are old and exhibiting low regeneration.

Three metrics of species diversity – species richness, the Shannon index and the Simpson index – are still widely used in ecology, despite decades of valid critiques leveled against them. Developing a robust diversity metric has been challenging because, unlike many variables ecologists measure, the diversity of a community often cannot be estimated in an unbiased way based on a random sample from that community. Over the past decade, ecologists have begun to incorporate two important tools for estimating diversity: coverage and Hill diversity. Coverage is a method for equalizing samples that is, on theoretical grounds, preferable to other commonly used methods such as equal‐effort sampling, or rarefying datasets to equal sample size. Hill diversity comprises a spectrum of diversity metrics and is based on three key insights. First, species richness and variants of the Shannon and Simpson indices are all special cases of one general equation. Second, richness, Shannon and Simpson can be expressed on the same scale and in units of species. Third, there is no way to eliminate the effect of relative abundance from estimates of any of these diversity metrics, including species richness. Rather, a researcher must choose the relative sensitivity of the metric towards rare and common species, a concept which we describe as 'leverage.' In this paper we explain coverage and Hill diversity, provide guidelines for how to use them together to measure species diversity, and demonstrate their use with examples from our own data. We show why researchers will obtain more robust results when they estimate the Hill diversity of equal‐coverage samples, rather than using other methods such as equal‐effort sampling or traditional sample rarefaction. [ABSTRACT FROM AUTHOR]

• Key message: Sampling needs differ by forest type for timber inventory and structural complexity metrics. We demonstrate in a typical mixed Eastern Hardwoods forest that optimal sampling of timber inventory metrics and spatially explicit structure indices may be achieved in one large plot plus a cruise for large diameter trees, but accurately capturing inventory metrics may not be possible with sparse large-scale sampling. • Context: Managing forest stand structures for multiple objectives require accurate and precise estimates of structural features that may be best estimated at different scales. • Aims: We document minimum necessary plot sizes for structural metrics and spatially explicit indices to characterize structure in a mature North American Eastern hardwoods forest. • Methods: Metrics and indices (Index of Aggregation, Diameter Differentiation Index, Dissimilarity Coefficient, Structural Complexity Index) were calculated within 0.05–1.75-ha plots for 1000 iterations of random placement in two 2.0-ha macroplots. Estimation adequacy required (1) precision (varied < 10% among plots) and (2) accuracy (within 10% of the 2.0-ha value at 5th and 95th percentiles). • Results: Minimum single plot sizes to achieve estimation adequacy were 0.25–0.75 ha for spatially explicit indices and 0.5–2 ha for stand metrics. A minimum of five 0.10-ha subplots would be needed for most indices and 6–25 for most metrics, but an untenable 375+ for the density of large diameter trees. • Conclusion: Estimation adequacy for structural complexity requires no greater sampling intensity than for timber metrics, except for density of large trees. A single large plot may be most cost-effective. National inventories in Eastern hardwoods may not estimate structural complexity well due to inadequate sampling intensity. [ABSTRACT FROM AUTHOR]

The Vampyressa melissa species complex comprises three rare bat species poorly represented in museum collections. Vampyressa melissa and V. sinchi are restricted to the eastern slope of the Andes, while V. elisabethae only is known from Panama, in Central America. The species complex has received recent attention in terms of systematic reviews, which concluded in the description of two species: one from Panama (V. elisabethae) and one from Colombia (V. sinchi). Vampyressa melissa recently was reported from the eastern slopes of the Cordillera Oriental of Colombia, in the department of Casanare. However, morphological and genetic (Cytochrome b) comparisons showed that these specimens belong to an undescribed species of the genus. The new species is the smallest member of the V. melissa complex and has a unique set of morphological characters compared to other Vampyressa species. Molecular evidence shows that the new species is sister to V. melissa (sensu stricto) from Colombia and Peru, albeit with high genetic divergence (7.9%). Nevertheless, Cytochrome b sequences of V. elisabethae and V. sinchi still are unknown. This new species increases to six the number of species in the genus. Vampyressa melissa , V. sinchi , and the new species, exhibit restricted distributions in the eastern slopes of the Andean Cordillera, in specific altitudinal ranges. Because of geographic constraints, their biological rarity, and the high deforestation rates in their distributional area, we suggest that these three species must be considered as taxa threatened with extinction. [ABSTRACT FROM AUTHOR]

The aim of the present study was to predict future changes in biodiversity attributes (richness, rarity, heterogeneity, evenness, functional diversity and taxonomic diversity) of freshwater fish species in river basins around the world, under different climate scenarios. To do this, we use a new methodological approach implemented within the ModestR software (NOO3D) which allows estimating simple species distribution predictions for future climatic scenarios. Data from 16,825 freshwater fish species were used, representing a total of 1,464,232 occurrence records. WorldClim 1.4 variables representing average climate variables for the 1960-1990 period, together with elevation measurements, were used as predictors in these distribution models, as well as in the selection of the most important variables that account for species distribution changes in two scenarios (Representative Concentration Pathways 4.5 and 6.0). The predictions produced suggest the extinction of almost half of current freshwater fish species in the coming decades, with a pronounced decline in tropical regions and a greater extinction likelihood for species with smaller body size and/or limited geographical ranges. [ABSTRACT FROM AUTHOR]

First observation of a Tyrrhenian endemic (Leucojum aestivum subsp. pulchellum, Amaryllidaceae) on the African continent (Algeria). -- This work highlights a plant of proven ecological and heritage importance. It is Leucojum aestivum subsp. pulchellum (Salisb.) Briq., a very rare and localized tyrrhenian endemic taxon from western Numidia (northeastern Algeria). Given its distribution and population characteristics and threats on the only observation locality in North Africa, the taxon deserves appropriate protection measures. [ABSTRACT FROM AUTHOR]

Inland sand areas scattered across the North American eastern deciduous forest and western tallgrass prairie ecotone are known for supporting pyrogenic early-successional vegetation and specially adapted terrestrial faunas. Many of these globally and regionally rare systems contain functionally connected wetland networks ("wetscapes") potentially important for aquatic insects. Sampling adults, nymphs, and exuviae in a remnant sand prairie-savanna wetscape in Illinois, USA, I assessed odonate species diversity (alpha, gamma, beta), distributions (spatial, temporal, abundance), and rarity status. In one field season (12 sites, 12 visits) I found more than a third of Illinois odonate species and close to half of the state's lentic breeding odonates, including a new state record (Erythemis vesiculosa). Richness averaged 25.8 species per site, reducing to 12.4 species with removal of nonbreeding occurrences. Three sites including a shrub swamp, beaver pond, and forested vernal depressions complex made significant contributions to beta diversity, dependent on general versus breeding occurrences. Majorities of Anisoptera species (70%) and Zygoptera species (53%) bred at three or fewer sites. Eight species flew during all or most of the study period (late May to early Oc-tober) whereas 14 species were detected on a single survey. Status classification derived from the observed spatial, temporal, and abundance distributions resulted in 24 common or very common species, 20 uncommon or rare species, and 10 vagrants across the wetscape. These context-specific classifications may be combined with diversity and breeding patterns and other information in wetscape prioritization schemes. [ABSTRACT FROM AUTHOR]

Landscapes, whose characters are the result of the action and interaction of natural and/or human factors, are dynamic. Proper understanding of today's landscapes is only possible through the knowledge of their historical dimension, in other words, changes that have occurred in timeslices or time-depth. Historic Landscape Characterization (HLC) is an approach to the management and understanding the present historic environment as a product of past changes and as the basis for future change. HLC was applied to Kazdağı National Park which has very important ecosystems in terms of the future of Turkey especially Asia and Europe. In this research, Kazdağı National Park Historic Landscape Character Types were mapped and relevant attributes were assigned them in 127 years of time depth with ArcGIS 10.1 software. HLC which was completed on the computer has been confirmed by field study and 'Direction of change', 'Rarity', 'Vulnerability' analysis was carried out. Finally, the relevant assessments were made in order to contribute protection, management and planning of National Park. [ABSTRACT FROM AUTHOR]

Plants vary widely in how common or rare they are, but whether commonness of species is associated with functional traits is still debated. This might partly be because commonness can be measured at different spatial scales, and because most studies focus solely on aboveground functional traits. We measured five root traits and seed mass on 241 central European grassland species, and extracted their specific leaf area, height, mycorrhizal status and bud‐bank size from databases. Then we tested if trait values are associated with commonness at seven spatial scales, ranging from abundance in 16‐m2 grassland plots, via regional and European‐wide occurrence frequencies, to worldwide naturalization success. At every spatial scale, commonness was associated with at least three traits. The traits explained the greatest proportions of variance for abundance in grassland plots (42%) and naturalization success (41%) and the least for occurrence frequencies in Europe and the Mediterranean (2%). Low root tissue density characterized common species at every scale, whereas other traits showed directional changes depending on the scale. We also found that many of the effects had significant non‐linear effects, in most cases with the highest commonness‐metric value at intermediate trait values. Across scales, belowground traits explained overall more variance in species commonness (19.4%) than aboveground traits (12.6%). The changes we found in the relationships between traits and commonness, when going from one spatial scale to another, could at least partly explain the maintenance of trait variation in nature. Most importantly, our study shows that within grasslands, belowground traits are at least as important as aboveground traits for species commonness. Therefore, belowground traits should be more frequently considered in studies on plant functional ecology. [ABSTRACT FROM AUTHOR]

Study region: The study is conducted over 30 meteorological sub-divisions of India. Study focus: The Multivariate Standardized Drought Index (MSDI) is employed to analyze the drought conditions caused by simultaneous precipitation and soil moisture deficiencies. The Severity-Duration-Frequency (SDF) relationships for the 30 sub-divisions are derived using copula-based conditional distribution for duration and severity; which are further used to prepare the country-wide drought atlas for different return periods. Subsequently, the developed atlas is used to assess the spatial extent and historical context of the impactful 2015 drought event. New hydrological insights for the region: This is the first study to present a country-wide drought atlas for India, considering concurrent deficits in precipitation and soil moisture, and using copula-based SDF relationships. In general, drought characteristics such as severity and duration are found to be significantly correlated, highlighting the importance of their joint modeling for probabilistic risk assessment of droughts in India. The drought atlas reveals regions that are severely affected by the drought variability. The drought atlas developed here shows that the impactful 2015 drought event was severely deficient both in terms of precipitation and soil moisture. In particular, West Uttar Pradesh, East Uttar Pradesh, Jharkhand, Marathwada, Telangana and North Interior Karnataka sub-divisions are found to be under a very rare drought (probability of exceedance less than 10 %).

Fungi are among the least known organisms on earth, with an estimated number of species between 1.5 and 10 million. This number is expected to be refined, especially with increasing knowledge about microfungi in undersampled habitats and increasing amounts of data derived from environmental DNA sequencing. A significant proportion of newly generated sequences fail to match with already named species, and thus represent what has been referred to as fungal "dark taxa". Due to the challenges associated with observing, identifying, and preserving sporophores, many macro- and microfungal species are only known from a single collection, specimen, isolate, and/or sequence-a singleton. Mycologists are consequently used to working with "rare" sequences and specimens. However, rarity and singleton phenomena lack consideration and valorization in fungal studies. In particular, the practice of publishing new fungal species names based on a single specimen remains a cause of debate. Here, we provide some elements of reflection on this issue in the light of the specificities of the fungal kingdom and global change context. If multiple independent sources of data support the existence of a new taxon, we encourage mycologists to proceed with formal description, irrespective of the number of specimens at hand. Although the description of singleton-based species may not be considered best practice, it does represent responsible science in the light of closing the Linnean biodiversity shortfall., (© 2024. The Author(s).)

Black ruff (Centrolophus niger) is a rare and poorly studied species found in both the Atlantic and Pacific Oceans and also in the Mediterranean Sea. It is sporadically caught south of Iceland during the annual International Ecosystem Summer Survey of the Nordic Seas. In total, 43 specimens were caught from 2009 to 2021, of which 41 specimens were caught during 2017-2021. All specimens, except one, were caught using a pelagic trawl (cod-end mesh-size: 50 mm) close to the surface (trawl depth: 0-35 m) with in situ temperature ranging from 9 to 13°C. The area south of Iceland is characterized by having warmer temperatures than other areas around the island, which might be indicative of a northern limit for the distribution of black ruff. The fish were primarily in the range of 29-46 cm with a few larger individuals up to 71 cm. Fourteen fish, caught in 2017 and 2021, were dissected to gather biological information on this species. These fish were all juveniles with no obvious sign of gonad development. Correlations between total length, fork length, and standard length are presented. Otoliths were thin and delicate with a length of ~13-16 mm, and otolith size (length, width, and area) was correlated with fish size. Much of the stomach content was at an advanced stage of digestion, but some contents could be identified and consisted of invertebrates, primarily of the orders Amphipoda and Calanoida with some unidentified fish also present., (© 2023 The Authors. Journal of Fish Biology published by John Wiley & Sons Ltd on behalf of Fisheries Society of the British Isles.)

Using data from a wide range of natural communities including the human microbiome, plants, fish, mushrooms, rodents, beetles, and trees, we show that universally just a few percent of the species account for most of the biomass. This is in line with the classical observation that the vast bulk of biodiversity is very rare. Attempts to find traits allowing the tiny fraction of abundant species to escape rarity have remained unsuccessful. Here, we argue that this might be explained by the fact that hyper-dominance can emerge through stochastic processes. We demonstrate that in neutrally competing groups of species, rarity tends to become a trap if environmental fluctuations result in gains and losses proportional to abundances. This counter-intuitive phenomenon arises because absolute change tends to zero for very small abundances, causing rarity to become a "sticky state", a pseudoattractor that can be revealed numerically in classical ball-in-cup landscapes. As a result, the vast majority of species spend most of their time in rarity leaving space for just a few others to dominate the neutral community. However, fates remain stochastic. Provided that there is some response diversity, roles occasionally shift as stochastic events or natural enemies bring an abundant species down allowing a rare species to rise to dominance. Microbial time series spanning thousands of generations support this prediction. Our results suggest that near-neutrality within niches may allow numerous rare species to persist in the wings of the dominant ones. Stand-ins may serve as insurance when former key species collapse., Competing Interests: Competing interests statement:In 2019, M.S. and J.M.L. were co-authors in a perspective paper.