Different Measures Of Diversity Research Articles

When is a word in good company for learning?

Although identifying the referents of single words is often cited as a key challenge for getting word learning off the ground, it overlooks the fact that young learners consistently encounter words in the context of other words. How does this company help or hinder word learning? Prior investigations into early word learning from children's real-world language input have yielded conflicting results, with some influential findings suggesting an advantage for words that keep a diverse company of other words, and others suggesting the opposite. Here, we sought to triangulate the source of this conflict, comparing different measures of diversity and approaches to controlling for correlated effects of word frequency across multiple languages. The results were striking: while different diversity measures on their own yielded conflicting results, once nonlinear relationships with word frequency were controlled, we found convergent evidence that contextual consistency supports early word learning. RESEARCH HIGHLIGHTS: The words children learn occur in a sea of other words. The company words keep ranges from highly variable to highly consistent and circumscribed. Prior findings conflict over whether variability versus consistency helps early word learning. Accounting for correlated effects of word frequency resolved the conflict across multiple languages. Results reveal convergent evidence that consistency helps early word learning.

Taxonomic, functional, and phylogenetic diversity of lizard assemblages across habitats and seasons in a Brazilian Cerrado area

AbstractOne of the core issues in community ecology is the understanding of mechanisms that determine community structure. In this study, we examine how two structurally distinct habitats (campo sujo – a grassy savanna habitat with low shrubby cover – and seasonal semi‐deciduous forest) and distinct hydrological seasons (dry and rainy) influence the taxonomic, functional and phylogenetic diversity of lizard assemblages in a savanna area in the Brazilian Cerrado. We used pitfall traps to sample lizards from May 2000 to February 2002. To quantify spatio‐temporal changes in the lizard assemblages, we used parameters of taxonomic (species richness – SR), functional (functional diversity – SES.FD, functional redundancy – FR and functional dispersion – FDis), and phylogenetic diversity (phylogenetic species richness – PSR and phylogenetic species variability – PSV). We also estimate functional and phylogenetic structure of the assemblages in each habitat during dry and rainy seasons. We recorded 182 lizards distributed among 14 species. Species composition differed among habitat types, but did not differ seasonally within habitats. SES.FD, FDis, and FR also differed among habitat types but not among seasons, with SES.FD and FDis being greater in seasonal semi‐deciduous forest, while FR was greater in campo sujo. SR, PSR, and PSV were not influenced by the factors analysed. The lizard assemblage of campo sujo was functionally clustered in the dry season and phylogenetically clustered in the rainy season. These results demonstrate that differences among habitat types and seasons are important in shaping the taxonomic, functional, phylogenetic diversity and structure of lizard assemblages in the savanna area studied. Our study also demonstrates the importance of using different measures of diversity to obtain a better understanding on the mechanisms that influence the lizard assemblages in a highly seasonal environment.

Linguistic diversity and conservation opportunities at UNESCO World Heritage Sites in Africa.

Africa contains much of Earth's biological and cultural-linguistic diversity, but conserving this diversity is enormously challenging amid widespread poverty, expanding development, social unrest, and rapidly growing human population. We examined UNESCO (United Nations Educational, Scientific and Cultural Organization) Natural World Heritage Sites (WHSs) on continental Africa and nearby islands-48 protected areas containing globally important natural or combined natural and cultural resources-to gauge the potential for enlisting Indigenous peoples in their conservation. We used geographic information system technology to identify instances where Natural WHSs co-occur with Indigenous languages, a key indicator of cultural diversity. And, we compared the geographic ranges for 4 taxa and selected freshwater species with occurrence of all Indigenous languages within Natural WHSs and subsections of WHSs covered by the geographic extent of Indigenous languages to measure the correlation between linguistic and biological diversity. Results indicated that 147 languages shared at least part of their geographic extent with Natural WHSs. Instances of co-occurrence where a WHS, a language, or both were endangered marked localities particularly deserving conservation attention. We examined co-occurrence of all languages and all species, all languages and endangered species, and endangered languages and endangered species and found a correlation between linguistic and biological diversity that may indicate fundamental links between these very different measures of diversity. Considering only endangered species or endangered languages and species reduced that correlation, although considerable co-occurrence persisted. Shared governance of government-designated reserves is applicable for natural WHSs because it capitalizes on the apparent connection between culture and nature. Natural WHSs in Africa containing speakers of Indigenous languages present opportunities to conserve both nature and culture in highly visible settings where maintaining natural systems may rely on functioning Indigenous cultural systems and vice versa.

Community structure of tenebrionid beetles in the Ulan Buh Desert (Inner Mongolia, China) (Coleoptera: Tenebrionidae)

Tenebrionids are a conspicuous faunal component of Central Asian deserts, but little is known about their community ecology. We investigated how tenebrionid community structure varied along a vegetational gradient in the Ulan Buh Desert (Gobi Desert). Sampling was done with pitfall traps in three sites with different vegetation cover. Species abundance distributions were fitted by the geometric series model, which expresses the “niche pre-emption” hypothesis. Community structure was investigated using different measures of diversity (number of species, Margaleff richness and Shannon-Weaner index), dominance (Simpson and Berger-Parker indexes) and evenness (Pielou’s index). The observed tenebrionid species richness was similar to that known from other Gobi Desert sites. The three investigated sites have similar species-abundance patterns, but the most dominant species varied among them. This suggests that the local environment operates a filtering action on the same basic fauna, allowing different species to dominate under different conditions. Overall, the highest total abundance was observed in the true desert site, however this site had a community structure similar to that observed in the site with more vegetation. By contrast, the investigated site with intermediate conditions showed a higher diversity and evenness, and a lower dominance. Thus, intermediate conditions of plant cover favour tenebrionid diversity, whereas a dense cover or a very sparse cover increases the dominance.

Variation in different measures of diversity during primary succession on a tropical coastal dune

ABSTRACTBackground: The understanding of the processes that govern community assembly during ecological succession helps determine the ecological attributes in restoration and monitoring programmes.Aims: The aim of this long-term study of primary succession was to analyse changes in species richness, diversity, taxonomic distinctness and functional types to understand community assembly processes.Methods: For 25 years, species turnover was monitored in 150 permanent plots in a dune system on the coast of the Gulf of Mexico.Results: Earliest successional states had low species diversity and richness, a high unevenness in the taxonomic tree structure, and a lower number of functional groups, with psammophytes being dominant. Richness and diversity increased in a humped-back shape with intermediate states reaching the highest values. Succession generated taxonomic trees that became less uneven and more diverse, and the diversity of functional groups increased.Conclusions: The processes underlying community assembly are complex during succession: sand movement acts as an environmental filter affecting the dominant functional groups, and species interactions probably change from facilitation to competition. The understanding of the combined processes affecting the different measures of diversity over time can improve the effectiveness of restoration and conservation practice in dune systems.

Reduction of avian diversity in created versus natural and restored wetlands

Natural wetland ecosystems continue to suffer widespread destruction and degradation. Many recent studies argue that artificial or restored wetlands compensate for wetland loss and are valuable for waterbird conservation. However, detailed comparisons of the value of natural, artificial and restored wetlands are lacking. Our aim was to assess if the restoration or creation of wetlands can fully compensate for the loss of natural wetlands for waterbirds. We compared the waterbird communities in a set of 20 natural, restored and artificial wetlands, all of which are considered important for waterbirds and are located within the same protected area (Doñana Natural Space, south‐west Spain). We used different measures of diversity, including phylogenetic relatedness, and the proportion of threatened species at national, European and international levels. We found that artificial wetlands have consistently lower value than restored and natural wetlands, with little difference between the latter two. Natural wetlands are essential for conserving diversity across the tree of life and for threatened species, but restored wetlands can be of similar value and can assure maintenance of key ecological processes. Thus, when economic costs per unit area are similar, resources for wetland conservation are better invested in restoration projects than in wetland creation, and caution is required when suggesting that artificial wetlands compensate for the loss of natural wetlands.

Deterministic diversity changes in freshwater phytoplankton in the Yunnan–Guizhou Plateau lakes in China

Diversity measures reflect different aspects of a community, which are determined by different ecological processes. However, information is still limited on the ecological processes that are represented by different measures of species diversity. In this study, the primary driving factors for richness and diversity indices were tested. The possible ecological processes represented by each index were analyzed. First, the type of ecological process that governed the phytoplankton community in the Yunnan–Guizhou Plateau lakes, either deterministic or stochastic, was identified by Caswell's neutral model. The results indicate that a deterministic process governs the phytoplankton community. Second, the driving factors of richness and diversity indices were screened with mixed models. The results suggest that the variation of phytoplankton richness in different lakes or sites was primarily related to bottom-up factors. The variations in evenness and other measures based on the relative abundance were driven by both top-down and bottom-up factors, such as zooplankton biomass, and pH and mean light, respectively. Finally, although the different measures of diversity may respond to specific bottom-up or top-down processes, the responses to the two processes were not independent of each other. These findings will increase our understanding of the relationships between ecological processes and diversity measures for freshwater phytoplankton.

Marine protected areas are insufficient to conserve global marine plant diversity

AbstractAimMarine plants are only incidentally included in conservation efforts for marine biodiversity. Here, for the first time, we apply phylogenetic methods to marine macrophytes (mangroves and seagrass species) to test for gaps in the current conservation network by identifying global diversity hotspots for these plant groups, and assess the degree to which hotspots are represented within the current network of marine protected areas (MPAs).LocationGlobal.MethodsWe calculated five metrics of marine plant diversity: phylogenetic diversity, species richness, species endemism, phylogenetic endemism and ‘evolutionary distinctiveness and global endangerment’ (EDGE).ResultsOverall, the diversity of marine plants was poorly represented by current MPAs. Different measures of diversity showed spatial mismatch, demonstrating how strategies that maximize one diversity measure may be inefficient at protecting other facets of marine plant biodiversity. However, complementarity analyses revealed that complete representation can be achieved very efficiently with few additional locations.Main conclusionsOur study highlights the need for an integrative approach to conserve both the species diversity and phylogenetic diversity of marine plants. While MPAs are a valuable instrument for conserving marine biodiversity, we now face the challenge of increasing coverage to protect other branches of the marine tree of life.

A Combination of Species Evenness and Functional Diversity Is the Best Predictor of Disease Risk in Multihost Communities.

Although accumulated evidence has shown that biodiversity can play an important role in disease transmission and prevalence, it remains unclear how different measures of diversity based on taxonomy or function perform in predicting disease risk. In this article, we assess the relative ability of species richness, Shannon's evenness index, single functional traits, and several functional diversity metrics and their interactions to predict disease risk in both nonequilibrium and equilibrium communities simulated by a multihost epidemiological model. On the basis of generalized linear models and Akaike's information criterion, we found that Shannon's evenness index outperforms species richness as a single variable in explaining variation in disease risk, while the best combination consists of Shannon's evenness index and functional diversity. This study is, to our knowledge, the first to demonstrate the important role played by species evenness and functional diversity in accounting for variation in disease risk in multihost communities.

Innovation and role of corruption and diversity

Research has established that various socioeconomic and institutional factors affect the rate of country-level innovation. However, little attention has been given to the effects of corruption and cultural diversity on innovation in cross-country analyses. It is widely accepted that innovation is a major engine of national economic growth, and policy makers and business leaders have recognized the need to create environments that foster innovative activities. This study builds on previous research using the Global Innovation Index ( GII, 2009 ) to empirically explore the impact of corruption and its interactive relationship with economic development, in addition to the effect of three different measures of diversity on country-level innovation. The results of this analysis suggest that corruption significantly harms innovation activities across countries, but the effect is mitigated in wealthier countries. As expected, ethnic diversity weakens innovation activities; however, religious diversity, which can be a proxy for tolerance, is found to positively contribute to innovation.

Psychometric Properties of Measures of Team Diversity With Likert Data

Certain diversity among team members is beneficial to the growth of an organization. Multiple measures have been proposed to quantify diversity, although little is known about their psychometric properties. This article proposes several methods to evaluate the unidimensionality and reliability of three measures of diversity. To approximate the interval scale required by the measures of diversity, a transformation on the Likert-item scores is proposed. Ridge maximum likelihood is used to deal with the issue of small sample size, and methods for evaluating the significance of the difference of two reliability estimates with correlated samples are also developed. Results with a real data set on entrepreneurial teams indicate that different measures of diversity may correspond to significantly different estimates of reliability. Results also indicate that diversity measures obtained with the transformed data tend to be more unidimensional than their counterparts obtained from Likert data. However, diversity measures obtained from Likert data tend to yield greater reliability estimates. Among the three examined measures of diversity, the standard deviation is found to yield greater and more efficient reliability estimates than the others and is thus recommended.

Relationships between adaptive and neutral genetic diversity and ecological structure and functioning: a meta-analysis.

Understanding the effects of intraspecific genetic diversity on the structure and functioning of ecological communities is a fundamentally important part of evolutionary ecology and may also have conservation relevance in identifying the situations in which genetic diversity coincides with species-level diversity.Early studies within this field documented positive relationships between genetic diversity and ecological structure, but recent studies have challenged these findings. Conceptual synthesis has been hampered because studies have used different measures of intraspecific variation (phenotypically adaptive vs. neutral) and have considered different measures of ecological structure in different ecological and spatial contexts. The aim of this study is to strengthen conceptual understanding by providing an empirical synthesis quantifying the relationship between genetic diversity and ecological structure.Here, I present a meta-analysis of the relationship between genetic diversity within plant populations and the structure and functioning of associated ecological communities (including 423 effect sizes from 70 studies). I used Bayesian meta-analyses to examine (i) the strength and direction of this relationship, (ii) the extent to which phenotypically adaptive and neutral (molecular) measures of diversity differ in their association with ecological structure and (iii) variation in outcomes among different measures of ecological structure and in different ecological contexts.Effect sizes measuring the relationship between adaptive diversity (genotypic richness) and both community- and ecosystem-level ecological responses were small, but significantly positive. These associations were supported by genetic effects on species richness and productivity, respectively.There was no overall association between neutral genetic diversity and measures of ecological structure, but a positive correlation was observed under a limited set of demographic conditions. These results suggest that adaptive and neutral genetic diversity should not be treated as ecologically equivalent measures of intraspecific variation.Synthesis. This study advances the debate over whether relationships between genetic diversity and ecological structure are either simply positive or negative, by showing how the strength and direction of these relationships changes with different measures of diversity and in different ecological contexts. The results provide a solid foundation for assessing when and where an expanded synthesis between ecology and genetics will be most fruitful.

Non-congruence among hotspots based on three common diversity measures in Yunnan, south-west China

Background: Yunnan is one of the richest regions of the world in terms of plant diversity. As a result of increasing pressure from land use, it is in need of identifying priority areas for conservation. Aim: In this study, we aimed to identify hotspots for plant conservation based on different measures of diversity and to establish the degree of spatial congruence among the different measures of diversity. Methods: We compiled checklists of overall species richness, threatened species and plants endemic to Yunnan with the help of literature and experts. The values of these three measures were grid mapped and the highest 2.5% of all cells with respect to each of the three plant diversity measures were designated as hotspot cells. The grid maps were overlapped to examine the spatial congruence of three different types of hotspots. Diversity measures were related to climatic and geographical factors. Finally, a gap analysis was carried out to examine the relationship between the location of existing nature reserves and the identified hotspots. Results: The hotspots of endemic plants and those of overall species richness were mostly concentrated in north-west Yunnan, whereas those of threatened plants were mainly observed in south Yunnan. No congruence was observed across the three types of hotspots of plant diversity at the top 2.5% cut-off level. With the relaxation of the cut-off level, an increasing trend of congruence could be observed, indicated by a strong correlation between measures of diversity. No strong relationship was found between climatic and geographical factors, and values of diversity measures. The gap analysis showed that there were some nature reserves located within or in the proximity of each identified hotspot. Conclusions: We suggest that non-congruence across different types of hotspots highlights the importance of cut-off levels for hotspot selection for congruence across different types of hotspots. Different mechanisms may be responsible for the spatial patterns of species diversity of total richness, endemic plants, threatened plants and the hotspots of the three diversity measures. Climatic and geographical factors cannot satisfactorily explain spatial patterns of plant diversity over the whole study area because controlling factors differ in geographical dimensions. Conservation strategy should also be different for different parts of Yunnan. In north-west Yunnan (hotspots of overall richness and endemism), attention needs to be focused on the protection and maintenance of diverse habitats, whereas in south Yunnan (hotspots of threatened plants) conservation strategies should concentrate on the restoration of habitats and off-site conservation.

Traditional Measures of Diversity and Sensitivity of Power Entropies

Objectives: We dealt with the traditional measures of diversity and their sample estimates. We also studied a way to compare sensitivity to changes of different measures of diversity. Methods: We proposed a new estimator of measures of diversity. We compared our estimator with three established estimators in a simulation study. We introduced a function called sensitivity to changes of a measure of diversity H and we described its basic characteristics. Results: The proposed estimator compares favorably to other well established estimators. The sensitivity to changes has a clear interpretation and is easy to compute. Conclusions: The sensitivity of measure of diversity to changes could be used to compare behavior of different measures of diversity and to select one or few that are the most suitable for a given problem.

Spatial congruency of benthic diatom, invertebrate, macrophyte, and fish assemblages in European streams

Understanding patterns in taxonomic congruency and the importance of environmental variables as drivers of these patterns is a prerequisite for analyzing changes in regional species pools. Here we evaluated the spatial correspondence of benthic diatoms, invertebrates, macrophytes, and fish assemblages in minimally disturbed lowland (n=38) and mountain (n=32) streams and, using constrained ordination and variance decomposition, determined how environmental and biological variables related to these patterns. Using different measures of diversity, abundance, and community composition, principal components analysis failed to reveal a single gradient in lowland and mountain streams. This was due to differences in the relationships between individual diversity measures and environmental variables characterizing habitat diversity (number of debris dams, silt and cobble substratum) in lowland streams, and catchment area and oxygen saturation in mountain streams. Despite the low spatial coherence of individual measures, integral multivariate analyses of community structure revealed coherent patterns between taxonomic groups. From 31.0% to 47.7% of the variance in diversity of fish, invertebrate, and macrophyte assemblages in mountain streams and from 11.9% to 33.7% of the variance in diversity in lowland streams were explained by one or more of the remaining three groups. Partial redundancy analyses showed that composition of other taxonomic groups was generally a better predictor of assemblage diversity than interactions with environmental variables, lending support to the importance of species interactions for spatial coherence. Finally, although we found little support for a single biodiversity gradient, correlations between fish diversity and macrophyte and invertebrate diversity in mountain streams and between macrophyte diversity and invertebrate and diatom diversity in lowland streams suggest that these two groups (i.e., fish in mountain and macrophytes in lowland streams) may function as surrogate indicators for the diversity of other taxonomic groups.

Genetic differentiation and diversity analysis of medicinal tree Syzygium cumini (Myrtaceae) from ecologically different regions of India

This study represents the agro-ecological zone wise surveys of molecular variation of important medicinal tree Syzygium cumini Linn. (Jamun) which is native to India. It is used world wide in treatment of diabetes. Despite of its diverse medicinal properties no molecular data is available about the pattern of variation in its natural range. Populations of S. cumini in India are located in different habitats which differ from each other with regard to ecological factors. In this study, random amplified polymorphic DNA (RAPD) markers were used to detect inter and intra levels of genetic variations of sixteen S. cumini genotypes collected from three major agro-ecological zones of India. A total of 220 amplification products were scored of which 87.50 % were polymorphic. The level of polymorphism ranged from 47.69 % to 74.87 % polymorphic bands per population and was correlated with population size. Different measures of diversity: Shannon's index of phenotypic diversity (I) = 0.451 ± 0.230; Nei's genetic diversity (h) = 0.300 ± 0.172; effective number of alleles per locus (Ne) = 1.51 ± 0.347; total species diversity (Hsp) = 0.315 ± 0.031 and within population diversity (Hpop) = 0.158 ± 0.104 showed high genetic diversity at species level. Coefficient of genetic differentiation (Gst =0.498; Nm = 0.503) revealed significant genetic differentiation among the populations. Most of the genetic variations are contained among the populations. The results of cluster analysis and principal component analysis (PCA) give only little evidence for an ecotypic differentiation of S. cumini populations. Present genetic structure of population suggests ex situ conservation in seed banks in which seeds from at least five populations need to collected and conserved. Secondly, our study provides practical information to herbal drugs manufactures who use Jamun as a raw material.

Valuing housing stock diversity

Purpose – This paper seeks to explore the roles that different measures of housing stock and socio‐economic diversity have on the value of residential homes in San Diego, California.Design/methodology/approach – This paper employs a hedonic pricing model to estimate the effects of different measures of diversity on housing prices based on a sample of approximately 6,500 houses in San Diego County, California. The measures of diversity can be classified broadly as either socio‐economic diversity (racial and ethnic diversity, variation in income, education, age, etc.) or diversity in housing stock (variability in housing and lot size, the age of structures, the mix or single family and multiple family, etc.).Findings – The results suggest that home prices increase with greater diversity in the size of homes in a neighborhood, but tend to decrease with higher levels of diversity in the age of homes. In addition, there is evidence that smaller than average houses on smaller than average lots command a premium...

Issues in the determination of the optimal portfolio of electricity supply options

In recent years a growing amount of attention has been focused on the need to develop a cost-effective portfolio of electricity supply options that provides society with a measure of protection from such factors as fuel price volatility and supply interruptions. A number of strategies, including portfolio theory, real options theory, and different measures of diversity have been suggested. In this paper we begin by first considering how we might characterize an optimal portfolio of supply options and identify a number of constraints that must be satisfied as part of the optimization process. We then review the strengths and limitations of each approach listed above. The results of our review lead us to conclude that, of the strategies we consider, using the concept of diversity to assess the viability of an electricity supply portfolio is most appropriate. We then provide an example of how a particular measure of diversity, the Shannon–Weiner Index, can be used to assess the diversity of the electricity supply portfolio in the state of Illinois, the region served by the Midwest Independent System Operator (MISO), and the continental United States.

Patterns and mechanisms responsible for the relationship between the diversity of litter macro-invertebrates and leaf degradation

Laboratory microcosms were used to determine how leaf degradation processes (C–CO2 release and leaf mass loss) are affected by the diversity of soil macro-invertebrate assemblages (comprising earthworms, woodlice and millipedes). The relationships were tested using different measures of diversity (number of species and trait dissimilarities). Net diversity effects and transgressive overyielding were calculated to disentangle the relative impacts of negative, neutral and positive species interactions on the relationships observed. Minimum trait dissimilarities were found to be correlated with leaf mass loss and, to a lesser extent, with C–CO2 release. This suggests that process rates increase as trait similarity in species assemblage decreases. Conversely, increasing the number of species resulted in the saturation of process rates after 1–2 species had been added to a microcosm. The process rates observed could mainly be explained by positive species interactions (40–50% of microcosms being process-dependent), followed by neutral interactions (20–40%) and selection effects or negative interactions (less than 20%). These results thus suggest that the effects of a soil macro-invertebrate assemblage on soil processes are more likely to be driven by complementarity or facilitation than by competition.

Different measures of biodiversity

In their analysis of global trends of diversity in marine plankton, Irigoien et al. find that taxonomic diversity of zooplankton (consumer) is a unimodal function of community biomass that is unrelated to phytoplankton (producer) diversity. Their results are unexpected because in terrestrial organisms primary-producer diversity is a good predictor of consumer diversity. I contend that this apparent uncoupling of producer and consumer diversity in marine plankton is likely to be an artefact due to the authors' use of different measures of diversity for producers and for consumers.