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Simple Summary: The members of the order Odonata, commonly known as dragonflies and damselflies, play an essential role in freshwater ecosystems. However, identifying their rarity and conservation status is often difficult due to gaps between available data and existing knowledge. In this study, we employed the Rabinowitz rarity classification framework, using outputs from multispecies occupancy models that predict the occurrence of Odonata species in South Korea. We compared the results of these models with established information, such as geographic range, habitat preference, conservation status, and citizen science records. Our findings reveal that species with high need for conservation measures were typically identified as rare or data-deficient. However, notable discrepancies emerged, particularly for species traditionally regarded as common, often inhabiting lentic habitats. This highlights the necessity of standardized survey methods and improved access to data on legally protected species for accurate rarity assessments. Our study emphasizes the importance of enhancing survey protocols and data-sharing practices to provide more reliable species rarity evaluations and support effective conservation strategies for freshwater ecosystems. Accurate assessment of species rarity and conservation status requires an approach that integrates data-driven models with established ecological knowledge. In this study, we applied multispecies occupancy (MSO) and latent factor multispecies occupancy (LFMSO) models to estimate the occurrence of 133 Odonata species in South Korea. Using the model outputs, we implemented the Rabinowitz rarity framework to conduct data-based rarity assessments, which were then compared with known ecological information, including geographic ranges, habitat preferences, regional Red List statuses, and citizen science observations. Our findings reveal both alignments and discrepancies between these data-driven rarity assessments and traditional ecological knowledge. For example, species classified as near threatened (NT) or vulnerable (VU) on the regional Red List generally corresponded with high-rarity classifications based on the Rabinowitz framework. However, significant inconsistencies were identified, particularly for certain lentic Odonata species traditionally considered common. These results suggest that spatial biases in field surveys, combined with limited access to data on legally protected species, can impede accurate rarity assessments. These findings underscore the need for standardized survey protocols and improved data-sharing policies for sensitive species to reduce biases and enhance the reliability of rarity assessments. This is essential for effective conservation planning and biodiversity management in freshwater ecosystems. [ABSTRACT FROM AUTHOR]

Conservation of species requires the protection of the associated suitable habitat. However, it is usually not known how much habitat is required to detect a single rare species. This problem is important, and it is related directly to the success and optimization of conservation planning. However, to date, no statistical methods have been developed to address this problem adequately. In this study, from a statistical sampling theory, we propose an estimator to estimate the minimum area required to conserve one or more additional new rare species. The estimator is highly accurate, as demonstrated by numerical tests. Applying the estimator in a tropical forest plot showed that the additional habitat size required for discovering an additional individual of a previously unseen tropical tree species is about 3.86 ha with a SE of 1.10 ha. In conclusion, the proposed estimator may be applied to conservation planning by assisting conservation biologists and policymakers to balance urban‐related and conservation‐related land uses by estimating the minimum detection areas required for species. [ABSTRACT FROM AUTHOR]

Amphibians and reptiles are important ecological indicators of ecosystem status and play significant ecological roles. However, their populations are declining globally due to factors such as climate and land-use change. To effectively manage these species, it is crucial to study their distribution in protected areas. In this study, we provide new information on the distribution and ecology of amphibians and reptiles in the "Cilento, Vallo di Diano e Alburni" (CVDA) National Park in southern Italy. We used a comprehensive dataset consisting of 2465 records obtained from fieldwork, citizen science, and literature to evaluate species' rarity, habitat preferences and community assemblage. We investigated whether differences in species richness across different habitat types and elevations resulted from species selection of different environmental conditions. We quantified species probability of observation in different habitat types and estimated the significance of species-habitat associations. Species rarity was assessed by considering geographic range, population abundance, and habitat breadth. Collected data substantially improved knowledge of the distribution of numerous species compared to published data. Our findings are generally consistent with the species' ecological information available in Italy, but we also found some species' peculiar ecological aspects that are littleknown. The CVDA National Park emerges as an effective protected area that ensures good conservation status of the herpetofauna, also in the case of species showing population and range declines at the national scale. [ABSTRACT FROM AUTHOR]

Functional rarity (FR) — a feature combining a species' rarity with the distinctiveness of its traits — is a promising tool to better understand the ecological importance of rare species and consequently to protect functional diversity more efficiently. However, we lack a systematic understanding of FR on both the species level (which species are functionally rare and why) and the community level (how is FR associated with biodiversity and environmental conditions). Here, we quantify FR for 218 plant species from German hay meadows on a local, regional, and national scale by combining data from 6500 vegetation relevés and 15 ecologically relevant traits. We investigate the association between rarity and trait distinctiveness on different spatial scales via correlation measures and show which traits lead to low or high trait distinctiveness via distance‐based redundancy analysis. We test how species richness and FR are correlated, and use boosted regression trees to determine environmental conditions that are driving species richness and FR. On the local scale, only rare species showed high trait distinctiveness while on larger spatial scales rare and common species showed high trait distinctiveness. As infrequent trait attributes (e.g., legumes, low clonality) led to higher trait distinctiveness, we argue that functionally rare species are either specialists or transients. While specialists occupy a particular niche in hay meadows leading to lower rarity on larger spatial scales, transients display distinct but maladaptive traits resulting in high rarity across all spatial scales. More functionally rare species than expected by chance occurred in species‐poor communities indicating that they prefer environmental conditions differing from characteristic conditions of species‐rich hay meadows. Finally, we argue that functionally rare species are not necessarily relevant for nature conservation because many were transients from surrounding habitats. However, FR can facilitate our understanding of why species are rare in a habitat and under which conditions these species occur. [ABSTRACT FROM AUTHOR]

Effects of restoration management on peatlands formerly used for intensive agriculture are rarely evaluated or discussed over larger spatial and temporal scales. Here, restoration of the Drentsche Aa brook valley was evaluated at the landscape level. Detailed vegetation maps were used with 1982 serving as the baseline, 1994 representing vegetation before rewetting, and 2015 after rewetting. Based on the mapping typology and phytosociological records, 15 main vegetation types were distinguished. Species richness and Shannon index values were calculated as plant diversity indicators, and the number of rare species was used as a rarity indicator. Basic landscape metrics were evaluated as measures of spatial heterogeneity. Results after restoration measures showed extensive vegetation type conversions clearly pointed to lower nutrient levels, and an increase in marsh vegetation at the cost of wet meadows. Significantly higher landscape heterogeneity was achieved, while biodiversity indicators showed small differences over time due to a mixture of positive and negative changes at different locations. This study shows that long‐term restoration management on agricultural peatlands can be successful at landscape level. Our experience highlights the importance of continuity in management given the prolonged influence by intensive agriculture, both from former land uses and from the surrounding valley flanks. [ABSTRACT FROM AUTHOR]

Questions: Ecologists collecting field samples of biological data have a keen interest in addressing the following question: how many rare species are there in as‐yet unsurveyed additional samples? Depending on the size of a targeted additional sample, statistical models for estimating the number of rare species have not been systematically established and compared. Location: Global. Methods: For fairly comparing and predicting rare‐species richness at the same sample‐size baseline, we systematically developed and compared four estimators for rarefaction and extrapolation of rare‐species richness with a given specific abundance. These four estimators included a uniformly minimum variance unbiased (UMVUE), Bayesian‐weighted, Chao‐derived unweighted and naïve estimator. Results: After extensive numerical tests, for conducting rarefaction of rare‐species richness (i.e., when additional sample size was not larger than the original one) it is recommended to implement UMVUE, as it has zero bias and coverage percentage closest to 0.95. However, the performance of Bayesian‐weighted and Chao‐derived estimators is also satisfactory. By contrast, for conducting extrapolation of rare‐species richness (i.e., when the additional sample size is larger than the original one), the Bayesian‐weighted estimator is recommended, as it has the best performance among the four estimators (here UMVUE is inapplicable). Conclusions: There was no absolute winner, as the different estimators have their own merits and are recommended under different settings. When conducting rarefaction of rare‐species richness, UMVUE, which has the highest accuracy, is recommended. By contrast, when conducting extrapolation of rare‐species richness, the Bayesian‐weighted estimator is recommended, as it has the overall best performance. To facilitate the potential application in the comparison and prediction of rare‐species diversity using rarefaction and extrapolation techniques, an R package (fRSE) has been developed; it is freely distributed at the following URL: https://github.com/ecomol/fRSE. [ABSTRACT FROM AUTHOR]

We conducted a survey on the Alpine fauna of one of the largest Natural Park of the Italian Alps (Stelvio National Park) in the framework of a broad ecological monitoring of Alpine biodiversity. A two-years standardized sampling employing pitfall traps along a 1200 m altitudinal gradient led to the discovery of two interesting inquiline social parasite ants of the genus Myrmica: M. myrmicoxena Forel, 1895 and M. microrubra Seifert, 1993. Myrmica myrmicoxena, which is classified as Vulnerable according to the IUCN Red List, was so far known from only three sites across a narrow geographic range between Italy and Switzerland. Our data support the previous hypothesis over its ecology and host association. Myrmica microrubra is considered an incipient species of high evolutionary interest, sometimes regarded as an intraspecific form of M. rubra. While having a wide distribution in Europe, its presence in Italy was hitherto known only from a single site, and our record extends its altitudinal distribution limit in Europe upwards by about 600 m.

The majority of species in many communities are rare, and it is an enduring challenge to understand the mechanism of species rarity and commonness in local communities. The niche partitioning hypotheses posit that common species occupy wide and core positions, while rare species occupy narrow and outlying niche positions. We test these hypotheses here, simultaneously considering both an environmental and a functional perspective on niches.We examined how niches correlate with species abundance in environmental and functional space by quantifying relationships between species abundance and niche width and niche position. Environmental niches were defined as the section of an environmental gradient where each species occurred, and functional niches using species traits were thought to be related to resource acquisition. Hypotheses were tested using a dataset including functional traits collected from 4,302 individual trees of 423 species and environmental data in one subtropical and one tropical forest in China.Consistent with the niche partitioning hypotheses, rare species in our two study systems tended to occupy the edges of the functional and environmental niche space. This likely allows rare species to avoid competition from dominant species. However, rare species tended to have a similar or larger niche width than common species in functional space, which contrasts with their narrower niche width in environmental space.Synthesis. Our results support the prediction that rare species occupy outlying niches to avoid competition with common species. We found inconsistent evidence, though, about the niche width of rare species. Rare species may be less constrained in functional space, and persist by dint of their functional lability and ability to use a variety of resources. Our work supports previously hypothesized mechanisms underlying local species abundance patterns, but highlights new idiosyncrasies when considering environmental niche or functional space alone. A free Plain Language Summary can be found within the Supporting Information of this article. [ABSTRACT FROM AUTHOR]

Aims: The effect of biogeographical processes on the spatial turnover component of beta‐diversity over large spatial extents remains scarcely understood. Here, we aim at disentangling the roles of environmental and historical factors on plant taxonomic and phylogenetic turnover, while controlling for the effects of species richness and rarity. Location: European beech (Fagus sylvatica) forests in Europe. Methods: We aggregated plant species occurrences from vegetation plots in spatial grid cells of 0.25º × 0.25º to calculate the spatial turnover component of taxonomic (TBDturn) and phylogenetic (PBDturn) beta‐diversity for each cell. We also calculated the deviation of PBDturn given TBDturn (PBDdev‐turn), which measures the importance of phylogenetic turnover after factoring out taxonomic turnover. Beta‐diversity was calculated for each grid cell as the mean pairwise dissimilarity between the focal cell and all other cells. We used structural equation modeling (SEM) to examine the relationships between environmental (climate, soil pH, and distance from the geographical distribution limit of beech) and historical (distance from beech glacial refugia) predictors and beta‐diversity metrics. Results: We found a geographically consistent variation in taxonomic and phylogenetic turnover. Overall, TBDturn and PBDturn increased significantly toward more extreme climatic conditions, on more acidic soils, and toward the margins of beech distribution. The effects of environmental variables and the distance from glacial refugia on beta‐diversity metrics were mediated by species richness and rarity. Phylogenetic turnover was low in relation to taxonomic turnover (i.e., high PBDdev‐turn) in areas closer to glacial refugia. Conclusions: Continental‐scale patterns of beta‐diversity in European beech forests are the result of complementary ecological and evolutionary processes. In general, beech forests are taxonomically and phylogenetically more distinct in climatically marginal areas of their European range. However, the spatial variation of beta‐diversity in European beech forest flora is still strongly characterized by the distribution of groups of closely related species that evolved or survived in glacial refugia. [ABSTRACT FROM AUTHOR]

Rarity is an important aspect of biodiversity often neglected in ecological studies. Species abundance distributions (SADs) are useful tools to describe patterns of commonness–rarity in ecological communities. Most studies assume field observations of species relative abundances are approximately equal to their true relative abundances, thus dismissing the potential for, and importance of unseen rare species. Here, we adopted the approach proposed by Chao et al. (Ecol, 96:1189–1201, 2015) to estimate the number and abundance of unseen species, and thus the true SADs, for tree species in 48 forest sites in Minas Gerais state, Brazil (4 rainforests, 35 semideciduous forests, and 9 deciduous forests). Also, we assessed the correlations between both unseen and rare species and sampling protocol and environment characteristics (climate, terrain, terrain heterogeneity). We found estimated true SADs invariably had higher species richness values than observed in the surveys, due to the increase in rare species. We estimate that up to 55.6% of tree species per site were unseen (8.5–55.6%), with an average of 26.6%. The estimated percentage of rare species per site was between 31.9% and 72.8%, with an average of 57.78%. We found rarity to be most strongly correlated with the percentage of unidentified trees, local terrain conditions and heterogeneity at site-level. Semideciduous forest and rainforest had similar higher percentages of unseen species (c. 27.2%) when compared to deciduous forests, probably due to the relatively higher local heterogeneity of these forests, which may provide more niches for rare species. Future studies should consider estimating true species abundances to better assess biodiversity. [ABSTRACT FROM AUTHOR]

Species distribution models (SDMs) are widely used in ecology and conservation. However, their performance is known to be affected by a variety of factors related to species occurrence characteristics. In this study, we used a virtual species approach to overcome the difficulties associated with testing of combined effects of those factors on performance of presence-only SDMs when using real data. We focused on the individual and combined roles of factors related to response variable (i.e. sample size, sampling bias, environmental filtering, species prevalence, and species response to environmental gradients). Results suggest that environmental filtering is not necessarily helpful and should not be performed blindly, without evidence of bias in species occurrences. The more gradual the species response to environmental gradients is, the greater is the model sensitivity to an inappropriate use of environmental filtering, although this sensitivity decreases with higher species prevalence. Results show that SDMs are affected to the greatest degree by the species response to environmental gradients, species prevalence, and sample size. Models' accuracy decreased with sample size below 300 presences. Furthermore, a high level of interactions among individual factors was observed. Ignoring the combined effects of factors may lead to misleading outcomes and conclusions. [ABSTRACT FROM AUTHOR]

Knowledge of species distribution is crucial for their protection, and this was our motivation to identify hotspots of the Habitats Directive (HD) species in the Carpathians. As a data source we used reports and species distribution maps submitted by the EU Member States according to the Habitats Directive Article 17 in 2019. The highest HD species richness areas are in the south-eastern part of the Western Carpathians and in the south-west outcrops of the Carpathians at the SK/AT and CZ/AT borders. The south-eastern part of the Western Carpathians is important for all studied species groups, specific patterns of distribution exhibit fish (distribution along big rivers), amphibians (high diversity also in the outer Western Carpathians and Transylvanian Basin) and partially plant species (besides SE Western Carpathians, quite high diversity also in other parts of the Western Carpathians). We analysed the relation between species richness, proportion of species groups, and concentration of rare species. Mammals are the dominant taxonomical group, especially in species-poor grid cells. The proportion of invertebrates increases with increased species richness. The widespread species prevail in species-poor grid cells and their proportion decreases with increasing species richness. We also identified areas with low Natura 2000 coverage, but with high biodiversity or a high number of rare species. These areas have high potential to improve protection of the HD species by designating new Natura 2000 sites or enlarging existing ones. [Display omitted] • Habitats Directive Article 17 data for analyse hotspots of HD species in Carpathians • SE part of the Western Carpathians is a hotspot of the Habitats Directive species. • Valuable areas with low Natura 2000 coverage were identified. • Analyse of species richness, species groups, and concentration of rare species [ABSTRACT FROM AUTHOR]

The analysis of species distribution and functional diversity (FD) in natural gradients of aridity and temperature at high altitudes could provide indication of future changes in plant communities as both are responsive to environment and strongly influence ecosystem functioning and stability. We established eleven altitudinal transects in high altitude region of western Himalaya, six of which represented north aspect and the rest represented south aspect. In each transect, vegetation was sampled randomly at every 200 m elevation to estimate species rarity, niche width and different FD indices [community-weighted mean traits (CWM), functional richness (FRic), functional divergence (FDiv), functional dispersion (FDis) and functional specificity (FSpe)]. These indices indicate resource utilization, competition for resources, optimal plant strategies, and presence of functionally specialist species. We found a total of 418 plant species, most of which were having narrow niche and distribution. Proportion of species with narrow niche was high at higher elevations, 36.5% species were rare with 17% of them being endemic to Himalaya. At south aspect, lower values of CWM plant height along with lower FRic, FDiv, FDis, and FSpe were recorded. Further, CWM plant height, FRic, FDiv, FDis and FSpe significantly decreased with increasing elevation. Influence of gradients of aridity (aspect) and decreasing temperature (elevation) on species distribution and FD suggest that functioning of high altitude communities is very likely to be affected in future. Our findings therefore emphasize that the plant communities present at higher elevations are more vulnerable under climate change. [ABSTRACT FROM AUTHOR]

In natural ecological communities, most species are rare and thus susceptible to extinction. Consequently, the prediction and identification of rare species are of enormous value for conservation purposes. How many newly found species will be rare in the next field survey? We took a Bayesian viewpoint and used observed species abundance information in an ecological sample to develop an accurate way to estimate the number of new rare species (e.g., singletons, doubletons, and tripletons) in an additional unknown sample. A similar method has been developed for incidence‐based data sets. Five seminumerical tests (3 abundance cases and 2 incidence cases) showed that our proposed Bayesian‐weight estimator accurately predicted the number of new rare species with low relative bias and low relative root mean squared error and, accordingly, high accuracy. Finally, we applied the proposed estimator to 6 conservation‐directed empirical data sets (3 abundance cases and 3 incidence cases) and found the prediction of new rare species was quite accurate; the 95% CI covered the true observed value very well in most cases. Our estimator performed similarly to or better than an unweighted estimator derived from Chao et al. and performed consistently better than the naïve unweighted estimator. We recommend our Bayesian‐weight estimator for conservation applications, although the unweighted estimator of Chao et al. may be better under some circumstances. We provide an R package RSE (rare species estimation) at https://github.com/ecomol/RSE for implementation of the estimators. Article impact statement: A novel Bayesian‐weighted estimator can accurately predict number of newly found rare species in additional ecological samples. [ABSTRACT FROM AUTHOR]

Abstract Based on an updated checklist of the benthic caridean shrimp fauna of the Eastern Tropical Pacific (ETP), we analyzed their large-scale species richness distribution patterns using a grid approximation. Caridean fauna is composed of 183 species belonging to 67 genera and 18 families. Alpheidae, Palaemonidae and Thoridae contributed largely to species richness. Alpheus and Synalpheus were the most diverse genera. Most species (24%) have a narrow distribution inhabiting a single grid, and as many as 135 are restricted to < 5 grids. Mexico has the largest richness (130) besides Ecuador (98) and Panama (75). Richness among grids varies largely; overall, it is larger around Galapagos and Panama, Colombia, Costa Rica and the Gulf of California. There was a meaningful correlation between a proxy of sampling intensity and richness, suggesting that along with habitat heterogeneity or large-scale evolutionary processes currently invoked as richness drivers, the pattern can also be related to differences in research efforts. Exponential fitting and Chao2 index suggest that the caridean faunal inventory from the ETP is still far from being complete. Overall, the results call for a more thoughtful and systematic sampling scheme in order to get information from poorly sampled environments and areas in the ETP.

We reviewed the local current status and summarized the suspected causes of rarity, and presumed major threats to the 84 rarest bird speciesin the state of Rio de Janeiro, southeastern Brazil. We have focused on the bird species that have not been recently recorded or have fewer than 10records in the last five decades in the state of Rio de Janeiro. Of these, 24 species are considered globally threatened or near threatened, and at least about 30 species are actually common or abundant elsewhere in their distribution. More than half of these species are forest birds inhabiting mainlylowland forests, but less than one-fifth of these species are endemic to the Atlantic Forest. The trophic guilds with the highest numbers of species were omnivores and insectivores. The main habitats used by the rarest bird species were wetlands, lowland forest canopy, secondary forest canopy and secondary forest edge. Bird species using two or more habitats were more represented among rare species than those using only a single habitat. Ninespecies were considered locally extinct, 11 probably Extinct, 27 Critically Endangered and 13 considered Data Deficient in Rio de Janeiro which are of increased conservation concern in the region. Although included among the rarest birds found in the state of Rio de Janeiro, 24 species were not classified as locally threatened because they are naturally rare migrants or vagrants in the region, without evidence of significant population sizereduction in the state in recent decades. Fifteen species had their conservation status considered threatened in the state for the first time. Forty-four species had their local conservation status uplisted, while only five species were downlisted. The major causes of rarity and threats to these species in the region are habitat loss and hunting/trapping, but nearly one-third of them have unknown causes of rarity.

Communities comprising alien species with different residence times are natural experiments allowing the assessment of drivers of community assembly over time. Stochastic processes (such as dispersal and fluctuating environments) should be the dominant factors structuring communities of exotic species with short residence times. In contrast, communities should become more similar, or systematically diverge, if they contain exotics with increasing resident times, due to the increasing importance of deterministic processes (such as environmental filtering). We use zeta diversity (the number of species shared by multiple assemblages) to explore the relationship between the turnover of native species and two categories of alien species with different residence times (archaeophytes [introduced between 4000 BC and 1500 AD] and neophytes [introduced after 1500 AD]) in a network of nature reserves in central Europe. By considering multiple assemblages simultaneously, zeta diversity allows us to determine the contribution of rare and widespread species to turnover. Specifically, we explore the relative effects of assembly processes representing isolation by distance, environmental filtering, and environmental stochasticity (fluctuating environments) on zeta diversity using Multi‐Site Generalized Dissimilarity Modelling (MS‐GDM). Four clusters of results emerged. First, stochastic processes for structuring plant assemblages decreased in importance with increasing residence time. Environmental stochasticity only affected species composition for neophytes, offering possibilities to predict the spread debt of recent invasions. Second, native species turnover was well explained by environmental filtering and isolation by distance, although these factors did not explain the turnover of archaeophytes and neophytes. Third, native and alien species compositions were only correlated for rare species, whereas turnover in widespread alien species was surprisingly unrelated to the composition of widespread native species. Site‐specific approaches would therefore be more appropriate for the monitoring and management of rare alien species, whereas species‐specific approaches would suit widespread species. Finally, the size difference of nature reserves influences not only native species richness, but also their richness‐independent turnover. A network of reserves must therefore be designed and managed using a variety of approaches to enhance native diversity, while controlling alien species with different residence times and degrees of commonness. [ABSTRACT FROM AUTHOR]

The causes of species rarity are of critical concern because of the high extinction risk associated with rarity. Studies examining individual rare species have limited generality, whereas trait-based approaches offer a means to identify functional causes of rarity that can be applied to communities with disparate species pools. Differences in functional traits between rare and common species may be indicative of the functional causes of species rarity and may therefore be useful in crafting species conservation strategies. However, there is a conspicuous lack of studies comparing the functional traits of rare species and co-occurring common species. We measured 18 important functional traits for 19 rare and 134 common understory plant species from North Carolina's Sandhills region and compared their trait distributions to determine whether there are significant functional differences that may explain species rarity. Flowering, fire, and tissue-chemistry traits differed significantly between rare and common, co-occurring species. Differences in specific traits suggest that fire suppression has driven rarity in this system and that changes to the timing and severity of prescribed fire may improve conservation success. Our method provides a useful tool to prioritize conservation efforts in other systems based on the likelihood that rare species are functionally capable of persisting. [ABSTRACT FROM AUTHOR]

Managing and restoring tallgrass prairie ecosystem is an important form of pollinator conservation in the Midwestern United States. Prairie reconstruction has been found to enhance native bee diversity and abundance, but it is less clear if prairie reconstruction conserves species thought to be at-risk. We reanalyze a previously published dataset on the bee communities of reconstructed and remnant prairie in the US state of Minnesota to investigate how the abundance of at-risk species respond to local factors, such as floral diversity and prairie type (reconstructed or remnant), and landscape factors, in the form of surrounding agricultural production. We defined at-risk species in two ways. For bumble bees, we used the IUCN red list of bumble bees for North America. As other species in the bee community have not been systematically evaluated, we used an independent data set to calculate a community-level measure of rarity as a proxy for species risk. We calculated community rarity metrics using a Species Weighted Mean (SWM) approach, with species level rarity (relative abundance and site occurrence) derived from a regional dataset comprised of over 30,000 specimens from across the US state of Minnesota. We found that the declining bumble bee Bombus fervidus had higher abundances in remnant rather than reconstructed prairies. Floral richness was associated with rarer bee communities (lower SWM values) across remnant and reconstructed prairies. We show that planting and managing prairies for floral diversity promotes bee communities with rarer species, but that remnants better support some at-risk species such as Bombus fervidus. [ABSTRACT FROM AUTHOR]

Human activities may generate geometrical landscape (i.e. composed of rectilinear and repetitive landscape units) structures that can significantly influence the spatial distribution of birds. While bird distribution in various landscape types has been extensively studied, the role played by landscape configuration and composition in different facets of bird diversity remains unclear. Here, these two main components of landscape characteristics (i.e. configuration and composition) are disentangled and their relative influence on three different facets of bird assemblages: taxonomic and functional characteristics, and the presence of rare species, is tested. We chose four large coastal salinas of Western France as a relevant model of geometrical and human-dominated landscapes where each landscape unit can be easily identified and mapped. The landscape characteristics of these sites were mapped and quantified. Then, terrestrial breeding birds were sampled in 172 point-counts using a standardized protocol. 69 diurnal terrestrial bird species were detected and considered in analyses (waterbirds and owls excluded). Landscape composition was found to have a higher influence on bird communities than landscape configuration, which fits with the 'landscape composition hypothesis'. More specifically, the most 'extreme' landscapes - those with low terrestrial surface areas, low landscape richness and diversity, low cohesion, and very patchy landscapes with complex geometrical shapes - host the lowest bird taxonomic abundance, richness and diversity and functional richness, but are characterized by the presence of rare species (mainly wetland specialist species, e.g. Reed Bunting Emberiza schoeniclus and species with restricted ranges e.g. Bluethroat Luscinia svecica namnetum). Our results suggest that conservation plans in such geometrical and human-dominated habitats should not only focus on one aspect of landscape characteristics or one aspect of biological diversity but also consider the adverse effects of landscape characteristics on these different facets. [ABSTRACT FROM AUTHOR]

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Undersampling is commonplace in biodiversity surveys of species-rich tropical assemblages in which rare taxa abound, with possible repercussions for our ability to implement surveys and monitoring programmes in a cost-effective way., We investigated the consequences of information loss due to species undersampling (missing subsets of species from the full species pool) in tropical bat surveys for the emerging patterns of species richness ( SR) and compositional variation across sites., For 27 bat assemblage data sets from across the tropics, we used correlations between original data sets and subsets with different numbers of species deleted either at random, or according to their rarity in the assemblage, to assess to what extent patterns in SR and composition in data subsets are congruent with those in the initial data set. We then examined to what degree high sample representativeness ( r ≥ 0·8) was influenced by biogeographic region, sampling method, sampling effort or structural assemblage characteristics., For SR, correlations between random subsets and original data sets were strong ( r ≥ 0·8) with moderate (ca. 20%) species loss. Bias associated with information loss was greater for species composition; on average ca. 90% of species in random subsets had to be retained to adequately capture among-site variation. For nonrandom subsets, removing only the rarest species (on average c. 10% of the full data set) yielded strong correlations ( r > 0·95) for both SR and composition. Eliminating greater proportions of rare species resulted in weaker correlations and large variation in the magnitude of observed correlations among data sets., Species subsets that comprised ca. 85% of the original set can be considered reliable surrogates, capable of adequately revealing patterns of SR and temporal or spatial turnover in many tropical bat assemblages. Our analyses thus demonstrate the potential as well as limitations for reducing survey effort and streamlining sampling protocols, and consequently for increasing the cost-effectiveness in tropical bat surveys or monitoring programmes. The dependence of the performance of species subsets on structural assemblage characteristics (total assemblage abundance, proportion of rare species), however, underscores the importance of adaptive monitoring schemes and of establishing surrogate performance on a site by site basis based on pilot surveys. [ABSTRACT FROM AUTHOR]

Floristic diversity was evaluated in twelve tropical dry forest fragments of seven municipalities in southern Tolima (Colombia) in the strategic Tatacoa ecoregion and its area of influence in the upper Magdalena. A network of 12 plots of 50 × 50 m (0.25 ha), one in each fragment, was established, registering all individuals with dbh greater than 5 cm. 121 morphospecies were found grouped into 41 families. The richness ranged from 15 to 34 species per plot, allowing a classification of vegetation cover in different categories of diversity indices such as richness and uniformity. We determined the estimated richness, whose maximum values varied between 44 and 46 species. The plots with the highest number of unique species reached values between 9 and 11, while higher values of unitary abundantly unique species were between 3 and 5. The relative abundance model that best described the studied forests was the logarithmic series; however, with early succession plots the geometric series considerably improved fit. Log-normal and Broken Stick models tended to yield intermediate fits. Furthermore, the beta diversity relationships for these forests exceeded 50% similarity. The results permit a prioritization of these forests based on plant diversity and rarity in ters of their potential for future conservation and restoration of tropical dry forest of the upper Magdalena. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to examine links between the diversity measures (Patil and Taillie 1982) and the disparity measures (Lindsay 1994), quantities apparently developed for somewhat different purposes. We demonstrate that numerous diversity measures satisfying all the desirable criteria mentioned by Patil and Taillie can be defined by the generating functions of certain disparities and the associated residual adjustment functions. This provides the statistician and the ecologist a wide class of flexible indices for the statistical measurement of diversity. [ABSTRACT FROM AUTHOR]

Abstract: This large-scale, landscape-level study aims to assess tree species diversity, stem density and stand structure of six major tropical hill forests of southern Eastern Ghats, India, namely, Bodamalai (BM), Chitteri (CH), Kalrayan (KA), Kolli hills (KO), Pachaimalai (PM) and Shervarayan hills (SH). The Eastern Ghats of India is relatively under-studied compared with the Western Ghats biodiversity hotspot. The entire stretch of southern Eastern Ghats was divided into smaller grids of 6.25km×6.25km, totaling to 120 grids. Within each grid, a belt transect of 0.5ha (5m×1000m) area was laid and all trees ≥30cm girth at breast height (gbh) were enumerated. A total of 272 tree species (≥30cm gbh) that belonged to 181 genera and 62 families were recorded in the total 60ha area inventoried. Diversity indices such as Shannon, Simpson and Fisher''s alpha indices were 2.44, 0.03 and 42.1, respectively, for the whole 60ha area. One way ANOVA revealed that the species richness varied significantly across the six sites (F (5,823) =4.854, p <0.0002). Also, the contribution of tree species to total species richness classified by three plant types viz. evergreen, brevi-deciduous and deciduous species varied significantly across the sites (One way ANOVA: F (2,15) =10.05, p <0.002). Similarity indices such as Jaccard and Sørensen showed that sites CH and KA are more similar in terms of species composition. The total stand density and basal area for the total 60ha area were 27,412 stems (457stemsha−1) and 1012.12m2 (16.9m2 ha−1), respectively. The stand density and basal area for the six sites ranged from 290 (in site BM) to 527stemsha−1 (in site KA) and from 5.6 (in site BM) to 24.4m2 ha−1 (in site KO), respectively. Stand density and basal area of tree species varied significantly across the six hill complexes (F (5,823) =4.85, p <0.0002 and F (5,823) =2.71, p <0.02, respectively). A positive correlation was obtained between stand density and species richness in sites PM (r s =0.65, p <0.05) and SH (r s =0.67, p <0.05), but not in other sites. The predominant tree species in the tropical forests of southern Eastern Ghats include Albizia amara, Euphorbia antiquorum, Canthium dicoccum var. dicoccum, Memecylon edule, Chloroxylon swietenia and Nothopegia heyneana. Taxonomically, Euphorbiaceae constituted the most diverse family with 25 species. Whereas, by tree abundance the Mimosaceae with 4126 stems enumerated from the 60ha area formed the dominant family. Bray–Curtis cluster analysis, based on tree species composition and abundance revealed that the low-diverse site BM formed a separate entity from other hill complexes. This large-scale tree diversity inventory provides a baseline data for a variety of investigations and is expected to be useful for effective forest management and biodiversity conservation of southern Eastern Ghats region. [Copyright &y& Elsevier]

The moss Ptychomitrium serratum (C. Müll. Hal. ex Schimp.) Besch., is native to Mexico and parts of western Texas and southern New Mexico, and it is a rare adventive in the area from East Texas and Louisiana to Missouri, Tennessee, South Carolina, and northward to locations near the coast in New York State and Massachusetts. In the adventive part of this calcicole’s range, all collections are from the past 50 years. Concrete, mortar, and rarely asphalt shingle are its only known substrata in this region, which contrasts sharply with its common occurrence on limestone in the native portion of its range. These observations indicate recent, perhaps on-going, immigration into the eastern United States and dispersal from established populations in this region. This monoicous moss commonly produces spores, which are its primary means of spread. Given the low density occurrences in the adventive portion of the range of P. serratum, dispersal may be generally northeastward from Mexico – Texas – New Mexico, following northeastward storm tracks in the southern and eastern United States. The apparently recent spread of this moss does not show obvious reliance on any direct human activity. On retrouve la mousse Psychomitrium serratum (C. Müll. Hal. ex Schimp.) Besch., au Mexique et dans des régions de l'ouest du Texas et du sud du Nouveau-Mexique; elle constitue une adventice rare dans l'est du Texas, en Louisiane, au Missouri, au Tennessee et en Caroline du Sud, incluant des localités près de la côte de l'état de New York et du Massachusetts. Dans la région adventive de l'aire de cette mousse calcicole, toutes les collections se limitent aux 50 dernières années. Dans ces régions, son habitat se limite au ciment, au mortier et plus rarement aux bardeaux d'asphalte, ce qui contraste fortement avec son habitat commun sur la pierre à chaux dans la portion indigène de son aire. Ces observations indiquent une immigration récente, peut-être toujours en cours, vers les états de l'est des tats-Unis, avec une dispersion à partir des populations établies dans ces régions. Cette mousse monoïque produit d'abondantes spores, lesquelles constituent son principal moyen de dispersion. Compte tenu de la faible présence dans la portion adventive de l'aire du P. serratum, la dispersion pourrait se faire dans une direction nord-est, suivant les poussées des tempêtes allant du sud vers l'est des tats-Unis. La distribution apparente récente de cette mousse ne semble indiquer aucune relation directe avec l'activité humaine. [ABSTRACT FROM AUTHOR]

Abstract: Although traditional agricultural land use maintains biodiversity, recent land-use changes involving abandonment or use intensification have rapidly reduced the biodiversity of agricultural landscapes. Organisms living in agricultural landscapes are likely to respond differently to these changes, with some species declining rapidly and others remaining unchanged. However, few studies have focused on this interspecific difference in susceptibility to land abandonment and intensification in agricultural landscapes. We hypothesize that rarer herb species are more susceptible to both abandonment and intensification than are common herbs due to habitat preferences in the semi-natural grasslands of agricultural landscapes. To test this hypothesis, we examined the distributions of two pairs of congeneric grasslands species on abandoned and consolidated (production-intensified) paddy fields to assess differences in vulnerability to paddy abandonment and consolidation between the rarer and the more common species in an agricultural landscape. We found that higher, steeper fields farther from roads in the upper areas of paddy terraces were more frequently abandoned in our study area. The two rarer species had significantly more overlap with the distribution of fields at risk of abandonment than did the two more common congeneric species. In addition, the two rarer species were significantly less widely distributed in consolidated fields. Thus, both land abandonment and intensification appear to asymmetrically decrease habitats of rarer species. In light of our findings, we also discuss biodiversity conservation in agricultural landscapes with changing land use. [Copyright &y& Elsevier]

The establishment of a network of reserves is of fundamental importance to the loss of biodiversity. Seven different area selection methods for the establishment of a reserve network were applied in the present study: (a) 5% cut-off value of the grid cells with the highest species richness or conservation value, (b) complementarity analysis using as criteria species richness or conservation value or rarest species richness, and (c) mixed complementarity analysis using as criteria species richness or conservation value. These methods were applied in the orchid taxa of east Macedonia. The conservation values of taxa were estimated on the basis of regional rarity, broad-scale rarity, and species specialization. The spatial overlap between the resulting networks and the Natura 2000 network of the study area was assessed. Furthermore, the efficiency of the latter network to protect the orchid taxa of the study area was examined. Our results suggest that: (a) a multiscale estimation of rarity is necessary for the unbiased estimation of species conservation values; (b) species specialization adds valuable ecological information to the assessment of taxa conservation values; (c) complementarity and mixed complementarity analyses on species richness or conservation value safeguard all the taxa of the region; (d) complementarity analysis on the basis of the richness of the rarest species safeguards all the rarest taxa, but not the total number of the remaining taxa; (e) the 5% cut-off value on species richness or conservation value fails to protect all the taxa of the region, including a large number of the rarest taxa; and (f) the Natura 2000 network, despite its large coverage in the study area, fails to safeguard all the taxa, including some of the rarest. [ABSTRACT FROM AUTHOR]

Initiatives that establish species rarity as an indicator of conservation priority might be biased if they disregard important evolutionary and adaptive processes taking place in lower diversity communities and ecotones. Conservation policies regarding the Atlantic forest strongly emphasize the core formation (i.e. the rainforest stricto sensu) rather than the marginal habitats (e.g. restingas, swamps, and high altitude campos) and species that are rare/endemic. To discuss this issue I revisit a hypothesis I have forwarded in 2002 that postulates that plant colonization of habitats marginal to the Atlantic rain forests of the State of Rio de Janeiro was largely related to terrestrial nurse plants that originally, in the rainforest habitat, were canopy plants such as epiphytes or hemi-epiphytes. Adaptations to water and nutrient restrictions, typical of life in the canopy, granted success to such plants upon migration to sandy, swampy or rocky substrates in neighbouring areas. Many such species, then, behaved as nurse plants and favoured colonization of these more extreme habitats by a number of other rainforest species. I now review recent evidence that corroborate this hypothesis, while examining the nature of such nurse plants. In all marginal habitats, nurse plants are often highly abundant locally and have high ecophysiological vigour, while both widespread and endemic species are found among them. Thus, nursing effect, local abundance, and ecophysiological performance are not related to species geographic distribution or to their spectrum of habitat preference. Paradoxically, several abundant nurse plant species have low Darwinian fitness. These studies provoke two reflections. First, the Atlantic forest sensu lato, i.e. the core formation plus the peripheral ones, should be treated collectively as a biodiversity hotspot, rather than the core rainforest formation alone. Second, widespread or common species play important functional roles in such marginal habitats and, despite their ubiquity, ecologically they might be less fit than rare/endemic ones at the local level due, for instance, to current constraints to sexual reproduction. Thus, they should also be targeted as conservation priorities. [Copyright &y& Elsevier]

A promising shortcut for quantifying species patterns is to use genera and families as surrogates of species. At large spatial scales, concurrence between patterns of richness, rarity, and composition of species and higher taxa is generally high. Only a few researchers, however, have examined this relationship at the local scale, which is frequently the relevant scale in land-use conflicts. We investigated the reliability of the higher-taxon approach in assessing patterns of species richness, rarity, and composition at the local scale. We studied diversity patterns of three commonly used surrogate taxa: vascular plants, ground-dwelling beetles, and moths. We conducted year-round field surveys for these taxa in the Jerusalem Mountains and the Judean foothills, Israel. Richness and composition of species were highly correlated with richness and composition of genera for all taxa. At the family level, correlations with richness and composition of species were much lower. Excluding monotypic genera and families did not affect these relations. Rarity representation based on higher taxa varied considerably depending on the taxon, and rarity scale and was weaker compared with richness and composition representation. Cumulative richness curves of species and genera showed similar patterns, leveling off at equivalent sampling efforts. Genus-level assessments were a reliable surrogate for local patterns of species richness, rarity, and composition, but family-level assessments performed poorly. The advantage of using coarse taxonomic scales in local diversity surveys is that it may decrease identification time and the need for experts, but it will not reduce sampling effort. [ABSTRACT FROM AUTHOR]

An international project, DIWPA-IBOY, took place for simultaneously observing biodiversity throughout the Western-Pacific and Asian regions in 2001–2003, as one of the core projects for International Biodiversity Observation Year, a crosscutting network activity of DIVERSITAS (an international programme of biodiversity science). DIWPA-IBOY provides extensive data on species diversity obtained by the standardized method. Under this project, 51,742 individuals of Lepidoptera and 11,633 of Coleoptera were collected by light traps from the Tomakomai Experimental Forest of Hokkaido University, one of the core DIWPA-IBOY sites, in the cool-temperate region of northern Japan. Based on these data, this study examined the relative abundance distribution (RAD) to evaluate the amount of rare species in the Lepidoptera and Coleoptera communities. The beta diversities between sampling seasons, forest strata, and trap sites were also assessed to evaluate the spatio-temporal variability of species composition in these communities. In the analysis of the RAD, the best-fit model was selected from the log-Normal, Zipf–Mandelbrot, and Zipf models differing in the tail length of the RAD, i.e., the proportion of rare species. To explore the beta diversity between samples, the abundance-based Jaccard index with an unseen species estimator was calculated, and then a hierarchical clustering analysis was conducted. As a result of RAD analysis, the Coleoptera community was regarded as containing a larger proportion of rare species than the Lepidoptera community. The seasonal compartmentalization of the community, deduced from the beta-diversity analysis, was finer in Lepidoptera (seven assemblages recognized) than in Coleoptera (three assemblages). The spatial (vertical and horizontal) compartmentalization was negligible in both communities. The coincidence of the larger proportion of rare species and the lower beta diversity between seasons in the Coleoptera community was explained by the longer life spans of beetles compared to moths, based on the assumption that the length of life span acts as a temporal agent for mass effect on the analogy of the migration rate as a spatial agent for mass effect. [ABSTRACT FROM AUTHOR]

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The article discusses the study on the lichen species in the Northwest Forest Plan area of the U.S. Evaluated is the assessment regarding the probability of the association of individual species with land allocation and forest stand age classifications. Mentioned is the inventory of epiphytic macrolichens in the area.

This paper puts forth the view that diversity is an average property of a community and identifies that property as species rarity. An intrinsic diversity ordering of communities is defined and is shown to be equivalent to stochastic ordering. Also, the sensitivity of an index to rare species is developed, culminating in a crossing-point theorem and a response theory to perturbations. Diversity decompositions, analogous to the analysis of variance, are discussed for two-way classifications and mixtures. The paper concludes with a brief survey of genetic diversity, linguistic diversity, industrial concentration, and income inequality. [ABSTRACT FROM AUTHOR]

• Three related rarity indices were developed based on hectad distribution data. • Indices were applied to vegetation plot data from Irish Annex I habitats. • Habitat rankings based on rarity differed markedly from those based on richness. • Concordance was poor between results for bryophytes and those for vascular plants. • Biodiversity assessments can be improved by incorporation of rarity indices. Species richness is widely used as a measure of biodiversity in quantifying the conservation value of sites or habitats and in researching ecological functioning, but it gives equal weighting to different species irrespective of their rarity. We developed a Rarity Co-efficient and related indices utilising plant species distribution records to investigate the significance of this limitation and applied these to quantitative vegetation plot data from Irish habitats of European importance. The conservation value of habitats and ecosystems differed markedly depending upon whether it was measured by species richness, species rarity or both richness and rarity. Application of abundance-weighting had noteworthy effects on index values at the community level; dominance of non-native or very common species reduced values, while abundance of rare species increased values. Index values varied along successional gradients occurring in coastal dune systems and saltmarsh. Almost no significant concordance was found between the rankings of habitats based on richness or rarity index values derived from vascular plant data and those based on index values derived from bryophyte data, therefore these taxonomic groups are poor surrogates for each other. Habitats were divided into three categories based on similar patterns in these rankings: (a) habitats with specialist vascular plants, (b) species-rich vascular plant habitats and (c) important bryophyte habitats. Habitat assessment criteria should reflect these broad differences in conservation value. Integration of rarity indices into site conservation value assessments is recommended. [ABSTRACT FROM AUTHOR]

The distribution of individuals of different species across different sampling units is typically non-random. This distributional non-independence can be interpreted and modelled as a correlated multivariate distribution. However, this correlation cannot be modelled using a totally independent and random distribution such as the Poisson distribution. In this study, we utilized the negative multinomial distribution to overcome the problem encountered by the commonly used Poisson distribution and used it to derive insight into the implications of field sampling for rare species' distributions. Mathematically, we derived, from the negative multinomial distribution and sampling theory, contrasting relationships between sampling area, and the proportions of locally rare and regionally rare species in ecological assemblages presenting multi-species correlated distribution. With the suggested model, we explored the cross-scale relationships between the spatial extent, the population threshold for defining the rarity of species, and the multi-species correlated distribution pattern using data from two 50-ha tropical forest plots in Barro Colorado Island (Panama) and Heishiding Provincial Reserve (Guangdong Province, China). Notably, unseen species (species with zero abundance in the studied local sample) positively contributed to the distributional non-independence of species in a local sample. We empirically confirmed these findings using the plot data. These findings can help predict rare species–area relationships at various spatial scales, potentially informing biodiversity conservation and development of optimal field sampling strategies. [ABSTRACT FROM AUTHOR]