What is the extent of prokaryotic diversity?

The extent of microbial diversity is an intrinsically fascinating subject of profound practical importance. The term 'diversity' may allude to the number of taxa or species richness as well as their relative abundance. There is uncertainty about both, primarily because sample sizes are too small. Non-parametric diversity estimators make gross underestimates if used with small sample sizes on unevenly distributed communities. One can make richness estimates over many scales using small samples by assuming a species/taxa-abundance distribution. However, no one knows what the underlying taxa-abundance distributions are for bacterial communities. Latterly, diversity has been estimated by fitting data from gene clone libraries and extrapolating from this to taxa-abundance curves to estimate richness. However, since sample sizes are small, we cannot be sure that such samples are representative of the community from which they were drawn. It is however possible to formulate, and calibrate, models that predict the diversity of local communities and of samples drawn from that local community. The calibration of such models suggests that migration rates are small and decrease as the community gets larger. The preliminary predictions of the model are qualitatively consistent with the patterns seen in clone libraries in 'real life'. The validation of this model is also confounded by small sample sizes. However, if such models were properly validated, they could form invaluable tools for the prediction of microbial diversity and a basis for the systematic exploration of microbial diversity on the planet.     

High β diversity in the flora of Californian serpentine 'islands'

Identification of global biodiversity hotspots is a leading conservationpriority ( Hotspots.Conservation International, Washington, DC; Precious Heritage: The Statusof Biodiversity in the United States. Oxford University Press, Oxford, UK), but weknow little about the nature and structure of such hotspots. Botanical richnessin one recently identified hotspot, the California Floristic Province, has longbeen attributed by evolutionists to edaphic and climatic heterogeneity. Here we demonstrate that the flora restricted (endemic) toserpentine soil, the state's most botanically distinctive substrate, showsunusually high ' diversity' – i.e., spatial variation inspecies composition – among regions, although ''diversity within any given region is low. Conservation of an endemic-rich florarequires a network of sites to capture this among-region or spatial component ofdiversity.     

Microbial diversity and the “lower-limit” problem of biodiversity

Science is now studying biodiversity on a massive scale. These studies are occurring not just at the scale of larger plants and animals, but also at the scale of minute entities such as bacteria and viruses. This expansion has led to the development of a specific sub-field of “microbial diversity”. In this paper, I investigate how microbial diversity faces two of the classical issues encountered by the concept of “biodiversity”: the issues of defining the units of biodiversity and of choosing a mathematical measure of diversity. I also show that the extension of the scope of biodiversity to microbial entities such as viruses and many other not-clearly-alive entities raises yet another foundational issue: that of defining a “lower-limit” of biodiversity.     

More diversity,less tolerance? The effect of type of cultural diversity on the erosion of tolerance in Swiss municipalities

Immigration and the ways in which host societies receive newcomers pose challenges for modern civil societies. This article contributes to the ongoing discussion about how ethnic diversity influences tolerance towards immigrants. Compared to previous studies, we analyse tolerance as a sequential concept in order to uncover the effects of contextual diversity on attitudes towards immigrants and the granting of certain rights to this group. Moreover, we distinguish different shares of ethnic groups based on their ethnic and cultural origins both on the independent and dependent variable. The analysis relies on a subnational survey of sixty municipalities in Switzerland, revealing that only certain ethnic groups are seen as an economic and cultural threat.     

What generates the diversity of Wolbachia—arthropod interactions?

Wolbachia are strictly endocellular, vertically transmitted bacteria associated with insects and crustaceans. This group of parasites modify their hosts' reproduction so as to increase their own fitness. This paper reviews the variability of these parasitic alterations and their consequences for host biology and populations. Wolbachia induce cytoplasmic incompatibility (a characteristic apparently specific to Wolbachia) in several insects and one isopod crustacean; parthenogenesis (thelytoky) in haplo-diploid insects; feminization in various isopods. The consequences of these phenomena on speciation, population dynamics and genetic polymorphism are discussed. The variability of the mechanisms of host sex determination is one important factor responsible for the diversity of Wolbachia-host interactions. However, parasite characteristics, such as the capacity to disturb host mitosis, and the ability to be horizontally transferred between hosts, also appear to play a role in this diversity.     

Structure and diversity of the T-cell receptor α chain in the Mexican axolotl

 Polymerase chain reaction was used to isolate cDNA clones encoding putative T-cell receptor (TCR) α chains in an amphibian, the Mexican axolotl (Ambystoma mexicanum). Five TCRα-V chain-encoding segments were identified, each belonging to a separate family. The best identity scores for these axolotl TCRα-V segments were all provided by sequences belonging to the human TCRα-V1 family and the mouse TCRα-V3 and TCRα-V8 families. A total of 14 different TCRA-J segments were identified from 44 TCRA-V/TCRA-J regions sequenced, suggesting that a large repertoire of TCRA-J segments is a characteristic of most vertebrates. The structure of the axolotl CDR3 α chain loop is in good agreement with that of mammals, including a majority of small hydrophobic residues at position 92 and of charged, hydrophilic, or polar residues at positions 93 and 94, which are highly variable and correspond to the TCRA-V/J junction. This suggests that some positions of the axolotl CDR3 α chain loop are positively selected during T-cell differentiation, particularly around residue 93 that could be selected for its ability to makes contacts with major histocompatibility complex-associated antigenic peptides, as in mammals. The axolotl Cα domain had the typical structure of mammalian and avian Cα domains, including the charged residues in the TM segment that are thought to interact with other proteins in the membrane, as well as most of the residues forming the conserved antigen receptor transmembrane motif. Received: 12 June 1996 / Revised: 11 September 1996     

Whither the diversity bargain?

In Natasha Warikoo’s account, the “diversity bargain” is widespread among white elite American college students. This bargain is tentative support for preferences for underrepresented minorities in college admissions, conditioned on the admitted minority students providing white students with multicultural experiences that signal elite cosmopolitanism. This essay reviews three possible explanations for the pervasiveness of the diversity bargain: campus experiences with the benefits of diversity; socialization into expectations that elites give lip service to the benefits of diversity; and Warikoo’s methodological and analytical choices.     

A ‘fast-food approach’ to the standardization of quadratic diversity

Abstract

Intuitively, a community composed of ecologically dissimilar taxa is more diverse than a community composed of more similar taxa. However, since traditional diversity indices such as Shannon's entropy or Simpson's diversity are computed solely from the relative abundances of a given species assemblage, they cannot account for ecological differences between species. There have been recent developments regarding the use of quadratic entropy, a diversity index that incorporates both species relative abundances and a measure of the pairwise ecological differences between species. In this paper we firstly show that under some specific circumstances quadratic entropy can be additively decomposed into α- β- and γ-diversities, a property that renders it a desirable measure of diversity in the ecological practice. Next, we suggest a quick and simple method for obtaining a standardized version of quadratic entropy that may allow an easier interpretation of the resulting diversity values.     

The molecular diversity of α-gliadin genes in the tribe Triticeae

Many of the unique properties of wheat flour are derived from seed storage proteins such as the α-gliadins. In this study these α-gliadin genes from diploid Triticeae species were systemically characterized, and divided into 3 classes according to the distinct organization of their protein domains. Our analyses indicated that these α-gliadins varied in the number of cysteine residues they contained. Most of the α-gliadin genes were grouped according to their genomic origins within the phylogenetic tree. As expected, sequence alignments suggested that the repetitive domain and the two polyglutamine regions were responsible for length variations of α-gliadins as were the insertion/deletion of structural domains within the three different classes (I, II, and III) of α-gliadins. A screening of celiac disease toxic epitopes indicated that the α-gliadins of the class II, derived from the Ns genome, contain no epitope, and that some other genomes contain much fewer epitopes than the A, S(B) and D genomes of wheat. Our results suggest that the observed genetic differences in α-gliadins of Triticeae might indicate their use as a fertile ground for the breeding of less CD-toxic wheat varieties.     

Will we ever understand? The undescribable diversity of the prokaryotes

This communication will summarize recent estimations on prokaryotic cell numbers, technical aspects of the exploration of the hidden diversity of the as-yet-uncultured prokaryotes and their function in the environment, recognition of novel major lines of descent, elucidation of novel metabolic pathways and attempts to improve the definition of the taxon species. These are some of recent highlights that will reflect only incompletely recent advances of microbiologist and other aspects of diversity at the genomic level, including the tremendous influence of whole genome sequences on the development of DNA macro- and microarrays for rapid identification of genes and specimen, the annotation of gene sequences to gene function by proteomics and the recognition of the extent of lateral gene transfer in the evolution of the genome, hence of contemporary organisms. As an example of modern trends in systematics three new families will be described for recently described genera, namely Thermoleophilaceae, Solirubrobacteraceae and Conexibacteraceae, which are phylogenetically positioned among environmental clone sequences at the root of the class Actinobacteria.     

Areas of high diversity for the world’s inland-breeding waterbirds

Waterbirds are a globally-distributed, species-rich group of birds that are critically dependent upon wetland habitats. They can be used as ecosystem sentinels for wetlands, which as well as providing ecosystem services and functions essential to humans, are important habitats for a wide range of plant and animal taxa. Here we carry out the first global analysis of inland-breeding waterbird distributions using data from 471 waterbird species in 28 families to identify global areas of high waterbird diversity. First we identify the primary area of high diversity for all inland-breeding waterbird species to be in Eastern Africa. For globally threatened inland-breeding waterbirds, the area of highest diversity is in Eastern China. Second, we show that the current network of protected areas provides poor coverage for threatened waterbirds in Eastern and Central Asia, and Northern India. In contrast, there is a higher protected area coverage in most of Europe and Brazil. Targeting the specific areas that have the highest numbers of species and the poorest coverage of protected areas is vital for both waterbird and wetland conservation.     

Navigating the multiple meanings of β diversity: a roadmap for the practicing ecologist

A recent increase in studies of β diversity has yielded a confusing array of concepts, measures and methods. Here, we provide a roadmap of the most widely used and ecologically relevant approaches for analysis through a series of mission statements. We distinguish two types of β diversity: directional turnover along a gradient vs. non-directional variation. Different measures emphasize different properties of ecological data. Such properties include the degree of emphasis on presence/absence vs. relative abundance information and the inclusion vs. exclusion of joint absences. Judicious use of multiple measures in concert can uncover the underlying nature of patterns in β diversity for a given dataset. A case study of Indonesian coral assemblages shows the utility of a multi-faceted approach. We advocate careful consideration of relevant questions, matched by appropriate analyses. The rigorous application of null models will also help to reveal potential processes driving observed patterns in β diversity.     

Importance of species diversity in the revegetation of Alberta’s northern fescue prairies

Restoration of grassland ecosystems is critical to the provision of ecosystem services, however, legacies of historic disturbances pose a challenge to grassland restoration. In the northern Great Plains of North America, continued fragmentation and disturbance of northern fescue prairies has prompted more stringent criteria to regulate the revegetation of native prairies disturbed by industrial activities. Here, we evaluate methods of revegetating northern fescue prairies, disturbed by energy development, and test the hypothesis that higher richness of species seeded within disturbed areas improves the structure, diversity, and composition of revegetated communities. Our results demonstrate that disturbed northern fescue prairies are able to recover their structural elements, including vegetative and ground cover and plant litter, irrespective of the number of species in the seed mixes, even though revegetated areas remained similar in all measures of community diversity. Despite this, revegetated areas remained compositionally different from adjacent native prairies, 7 years following seeding treatments. Based on our observations, the persistent differences in the species composition of disturbed and undisturbed prairies highlight that all efforts should be practiced to minimize the scale of disturbance of northern fescue prairies through energy development.     

A comparison of genetic diversity between the Galápagos Penguin and the Magellanic Penguin

The Galápagos Penguin (Spheniscusmendiculus) is a United States federallylisted endangered species with populations onthe Galápagos Islands of Fernandina andIsabela. Although the waters around theislands are normally productive, lowproductivity during El Niño years resultsin high adult penguin mortality and lowrecruitment in following years. We usedmicrosatellite markers developed for Spheniscus penguins to study the long termgenetic effects of serial bottleneck events inthe Galápagos Penguin, and compared thisvariation to that of its congener, theMagellanic penguin (Spheniscusmagellanicus). The observed heterozygosityfor the Galápagos Penguin was 3%,significantly lower than the 46%heterozygosity of the Magellanic Penguin. Thislow level of heterozygosity is directly relatedto its low effective population size. Whilethis population has survived long term,presumably without high levels of geneticvariation, we feel that the greater frequencyof El Niño events, coupled with increasedhuman impacts such as introduced disease, oildischarge, and competition with fisheries, mayput the species in particular danger ofextinction.     

Examining serological diversity of “cowpea” rhizobia by the ELISA technique

To appraise the usefulness of the enzyme-linked immunosorbent assay (ELISA) technique for examining the serological diversity of slow-growing rhizobia, twelve diverse strains from three countries were examined with four antisera. Eleven of the strains were from the cowpea miscellany, and the twelfth was a Rhizobium japonicum strain. Some cowpea strains showed no antigenic relatedness with each other while others were closely related, and some showed a greater affinity with the R. japonicum strain than with other cowpea strains. All of the strains showed antigenic homology to an isolate from a wild Arachis sp., while two strains isolated from adjacent plants of the same cultivar had little homology. These patterns ofrelatedness and diversity clearly demonstrated the utility of the ELISA method, and so it was used to examine 53 strains isolated from cowpeas grown at three West African locations, Maradi (Niger), Ibadan and Onne (Nigeria). Broad ranges of serological diversity were found in the rhizobia at each location, moreover each population had its own general characteristics. Maradi strains were highly reactive with the five antisera used, Onne strains less so, and Ibadan strains even less so. ELISA reactivity correlated with colony morphology but not with nodulation potential.