Stocking may increase mitochondrial DNA diversity but fails to halt the decline of endangered Atlantic salmon populations

Over the last 50 years, Spanish Atlantic salmon (Salmo salar) populations have been in decline. In order to bolster these populations, rivers were stocked with fish of northern European origin during the period 1974-1996, probably also introducing the furunculosis-inducing pathogen, Aeromonas salmonicida. Here we assess the relative importance of processes influencing mitochondrial (mt)DNA variability in these populations from 1948 to 2002. Genetic material collected over this period from four rivers in northern Spain (Cantabria) was used to detect variability at the mtDNA ND1 gene. Before stocking, a single haplotype was found at high frequency (0.980). Following stocking, haplotype diversity (h) increased in all rivers (mean h before stocking was 0.041, and 0.245 afterwards). These increases were due principally to the dramatic increase in frequency of a previously very low frequency haplotype, reported at higher frequencies in northern European populations proximate to those used to stock Cantabrian rivers. Genetic structuring increased after stocking: among-river differentiation was low before stocking (1950s/1960s Phi(ST) = -0.00296-0.00284), increasing considerably at the height of stocking (1980s Phi(ST) = 0.18932) and decreasing post-stocking (1990s/2002 Phi(ST) = 0.04934-0.03852). Gene flow from stocked fish therefore seems to have had a substantial role in increasing mtDNA variability. Additionally, we found significant differentiation between individuals that had probably died from infectious disease and apparently healthy, angled fish, suggesting a possible role for pathogen-driven selection of mtDNA variation. Our results suggest that stocking with non-native fish may increase genetic diversity in the short term, but may not reverse population declines.

Diversity, phylogeny and distribution of bean rhizobia in salt-affected soils of North-West Morocco

Different molecular methods: BOX-PCR fingerprinting, R-FLP-PCR and sequencing of the 16S rDNA as well as the symbiotic genes nodC and nifH, were used to study the genetic diversity within a collection of nodulating bean rhizobia isolated from five soils of North-West Morocco. BOX fingerprints analysis of 241 isolates revealed 19 different BOX profiles. According to the PFLP-PCR and sequencing of 16S rDNA carried out on 45 representative isolates, 5 genotypes were obtained corresponding to the species Rhizobium etli, R. tropici, R. gallicum, R. leguminosarum and Sinorhizobium meliloti. The most abundant species were R. etli and R. tropici (61% and 24%, respectively). A high intraspecific diversity was observed among the R. etli isolates, while the R. tropici group was homogeneous. Most of the rhizobia studied belong to species known to nodulate common bean, while 2 species were unconventional microsymbionts: R. leguminosarum biovar viciae and S. meliloti. Our results, especially the nodulation promiscuity of common bean and the relation between the predominance of some species of rhizobia in particular soils and the salt content of these soils, indicate that there is a real need for a better understanding of the distribution of common bean rhizobia species in the soils of Morocco before any inoculation attempt.

The distribution of species diversity across a flora's component lineages: dating the Cape's 'relicts'

The Cape Floristic Region is exceptionally species-rich both for its area and latitude, and this diversity is highly unevenly distributed among genera. The modern flora is hypothesized to result largely from recent (post-Oligocene) speciation, and it has long been speculated that particular species-poor lineages pre-date this burst of speciation. Here, we employ molecular phylogenetic data in combination with fossil calibrations to estimate the minimum duration of Cape occupation by 14 unrelated putative relicts. Estimates vary widely between lineages (7-101 Myr ago), and when compared with the estimated timing of onset of the modern flora's radiation, it is clear that many, but possibly not all, of these lineages pre-date its establishment. Statistical comparisons of diversities with lineage age show that low species diversity of many of the putative relicts results from a lower rate of diversification than in dated Cape radiations. In other putative relicts, however, we cannot reject the possibility that they diversify at the same underlying rate as the radiations, but have been present in the Cape for insufficient time to accumulate higher diversity. Although the extremes in diversity of currently dated Cape lineages fall outside expectations under a underlying diversification rate, sampling of all Cape lineages would be required to reject this null hypothesis.

Low genetic diversity in a marine nature reserve: re-evaluating diversity criteria in reserve design

Little consideration has been given to the genetic composition of populations associated with marine reserves, as reserve designation is generally to protect specific species, communities or habitats. Nevertheless, it is important to conserve genetic diversity since it provides the raw material for the maintenance of species diversity over longer, evolutionary time-scales and may also confer the basis for adaptation to environmental change. Many current marine reserves are small in size and isolated to some degree (e.g. sea loughs and offshore islands). While such features enable easier management, they may have important implications for the genetic structure of protected populations, the ability of populations to recover from local catastrophes and the potential for marine reserves to act as sources of propagules for surrounding areas. Here, we present a case study demonstrating genetic differentiation, isolation, inbreeding and reduced genetic diversity in populations of the dogwhelk Nucella lapillus in Lough Hyne Marine Nature Reserve (an isolated sea lough in southern Ireland), compared with populations on the local adjacent open coast and populations in England, Wales and France. Our study demonstrates that this sea lough is isolated from open coast populations, and highlights that there may be long-term genetic consequences of selecting reserves on the basis of isolation and ease of protection.

Genotypic and phenotypic diversity of a baculovirus population within an individual insect host

It is becoming increasingly apparent that many pathogen populations, including those of insects, show high levels of genotypic variation. Baculoviruses are known to be highly variable, with isolates collected from the same species in different geographical locations frequently showing genetic variation and differences in their biology. More recent Studies at smaller scales have also shown that virus DNA profiles from individual larvae can show polymorphisms within and between populations of the same species. Here, we investigate the genotypic and phenotypic variation of an insect baculovirus infection within a single insect host. Twenty four genotypically distinct nucleopolyhedrovirus (NPV) variants were isolated from an individual pine beauty moth, Panolis flammea, caterpillar by in vivo cloning techniques. No variant appeared to be dominant in the population. The Pafl NPV variants have been mapped using three restriction endonucleases and shown to contain three hypervariable regions containing insertions of 70-750 bp. Comparison of seven of these variants in an alternative host, Mamestra brassicae, demonstrated that the variants differed significantly in both pathogenicity and speed of kill. The generation and maintenance of pathogen heterogeneity are discussed. (c) 2005 Elsevier Inc. All rights reserved.

Diversity and systematics of the Malacosporea (Myxozoa)

Myxozoans belonging to the recently described class Malacosporea parasitize freshwater bryozoans during at least part of their life cycle. There are at present only two species described in this class: Buddenbrockia plumatellae and Tetracapsuloides bryosalmonae. The former can exist as vermiform and sac-like stages in bryozoan hosts. The latter, in addition to forming sac-like stages in bryozoans, is the causative agent of salmonid proliferative kidney disease (PKD). We undertook molecular and ultrastructural investigations of new malacosporean material to further resolve malacosporean diversity and systematics. Phylogenetic analyses of 18S rDNA sequences provided evidence for two new putative species belonging to the genus Buddenbrockia, revealing a two-fold increase in the diversity of malacosporeans known to date. One new malacosporean is a vermiform parasite infecting the bryozoan Fredericella sultana and the other occurs as sac-like stages in the rare bryozoan, Lophopus crystallinus. Both bryozoans represent new hosts for the genus Buddenbrockia. Our results have established that the malacosporean which infected F. sultana was not a vermiform stage of T. bryosalmonae, although it was collected from a site endemic for PKD. Ultrastructural investigation of new material of B. plumatellae revealed the presence of numerous external tubes associated with developing polar capsules, confirming that the absence of external tubes should no longer be considered as a character of the class Malacosporea.

Bryophyte diversity and community structure on thatched roofs of the Holnicote Estate, Somerset, U.K.

We investigated patterns of bryophyte species richness and community structure, and their relation to roof variables, on thatched roofs of the Holnicote Estate, South Somerset. Thirty-two bryophyte species were recorded from 28 sampled roofs, including the globally rare and endangered thatch moss, Leptodontium gemmascens. Multiple regression analyses revealed that thatch age has a highly significant positive effect on the number of species present, accounting for nearly half the observed variation in species richness after removal of outliers. Aspect has a slight and marginally significant effect on species diversity (accounting for an additional 6% of variation), with north-facing samples having slightly more species. Age also has a significant impact on total bryophyte cover after removal of outlying observations. TWINSPAN analysis of bryophyte cover data suggests the existence of at least five discrete communities. Simple Discriminant Analyses indicate that these communities occupy different ecological subspaces as defined by the measured roof variables, with pitch, aspect and thatch age emerging as especially significant attributes. Contingency Analysis indicates that some communities are disfavoured by water reed as compared to wheat straw. The findings are significant for understanding the structure of bryophyte communities, for evaluating the effect of bryophyte cover on thatch performance, and for conservation of thatch communities, especially those harbouring rare species.

Inter-simple sequence repeat and aggressiveness analyses revealed high genetic diversity, recombination and long-range dispersal in Fusarium culmorum

Inter-simple sequence repeat (ISSR) analysis and aggressiveness assays were used to investigate genetic variability within a global collection of Fusarium culmorum isolates. A set of four ISSR primers were tested, of which three primers amplified a total of 37 bands out of which 30 (81%) were polymorphic. The intraspecific diversity was high, ranging from four to 28 different ISSR genotypes for F. culmorum depending on the primer. The combined analysis of ISSR data revealed 59 different genotypes clustered into seven distinct clades amongst 75 isolates of F. culmorum examined. All the isolates were assayed to test their aggressiveness on a winter wheat cv. 'Armada'. A significant quantitative variation for aggressiveness was found among the isolates. The ISSR and aggressiveness variation existed on a macro- as well as micro-geographical scale. The data suggested a long-range dispersal of F. culmorum and indicated that this fungus may have been introduced into Canada from Europe. In addition to the high level of intraspecific diversity observed in F. culmorum, the index of multilocus association calculated using ISSR data indicated that reproduction in F. culmorum cannot be exclusively clonal and recombination is likely to occur.

Orphan worms and, homeless parasites enhance bilaterian diversity

Microscopic endoparasites belonging to the Phylum Myxozoa provide a striking example of how much there is still to be learned about the diversity of the Metazoa. Recent research on myxozoans has provided new insights into evolution within the Bilateria, revealing unparalleled levels of morphological simplification associated with parasitism, a home for an orphan worm, and a hypothesis of the endosymbiotic origin(s) for extrusible intracellular organelles in myxozoans and cnidarians. In addition, discovery of the source of a devastating disease of salmonid fish has enabled researchers to identify two ancient clades within the Myxozoa, and has exposed new mysteries concerning myxozoan life-cycle evolution and evolutionary diversification. This plethora of new insights exemplifies the fundamental value of studying obscure organisms.

Morphological diversity of the genus Licuala (Palmae)

There are about 141 described species of Licuala. Structurally, the genus has very consistent vegetative and fertile characters. As the genus undergoes revision, it is becoming clear that it contains great morphological variation within the strict vegetative and reproductive character constraints found in the genus. This paper describes the variation found in the genus and its significance in taxon delimitation.

Dinuclear complexes of M-II thiocyanate (M = Ni and Cu) containing a tridentate Schiff-base ligand: synthesis, structural diversity and magnetic properties

A dinuclear Ni-II complex, [Ni-2(L)(2)(H2O)(NCS)(2)]center dot 3H(2)O (1) in which the metal atoms are bridged by one water molecule and two mu(2)-phenolate ions, and a thiocyanato-bridged dimeric Cull complex, [Cu(L)NCS](2) (2) [L = tridentate Schiff-base ligand, N-(3-aminopropyl)salicylaldimine, derived from 1:1 condensation of salicylaldehyde and 1,3-diaminopropane], have been synthesized and characterized by IR and UV/Vis spectroscopy, cyclic voltammetry and single-crystal X-ray diffraction studies. The structure of 1 consists of dinuclear units with crystallographic C-2 symmetry in which each Ni-II atom is in a distorted octahedral environment. The Ni-O distance and the Ni-O-Ni angle, through the bridged water molecule, are 2.240(11) angstrom and 82.5(5)degrees, respectively. The structure of 2 consists of dinuclear units bridged asymmetrically by di-mu(1,3)-NCS ions; each Cull ion is in a square-pyramidal environment with tau = 0.25. Variable-temperature magnetic susceptibility studies indicate the presence of dominant ferromagnetic exchange coupling in complex 1 with J = 3.1 cm(-1), whereas complex 2 exhibits weak antiferromagnetic coupling between the Cu-II centers with J = -1.7 cm(-1). ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Structural diversity in supramolecular architectures of Mn(II) through non-covalent interactions

Two mononuclear complexes of manganese(II), [Mn(OCN)(2)(phen)(2)] 1 and [Mn(NCO)(2)(bpy)(2)] 2 [1,10-phenanthroline (phen); 2,2'-bipyridine (bpy)], have been synthesized and characterized by single crystal X-ray analysis, infra-red spectroscopy and magnetic studies. The coordination structure of complex 2 is already reported. The cyanate anions are pendent in both the complexes. In 1, cyanate anion links manganese(II) through O-atom, whereas in 2 it coordinates through N-atom. The mononuclear fragments of 1 are built up to a supramolecular lamellar 3D architecture by pi-pi interactions only. On the other hand, mononuclear fragments of 2 are assembled to a 2D supramolecular brick-wall architecture by C-H-... pi interactions.

Developmental trends in lexical diversity.

This article discusses issues in measuring lexical diversity, before outlining an approach based on mathematical modelling that produces a measure, D, designed to address these problems. The procedure for obtaining values for D directly from transcripts using software (vocd) is introduced, and then applied to thirty-two children from the Bristol Study of Language Development (Wells 1985) at ten different ages. A significant developmental trend is shown for D and an indication is given of the average scores and ranges to be expected between the ages of 18 and 42 months and at 5 years for these L1 English speakers. The meaning attributable to further ranges of values for D is illustrated by analysing the lexical diversity of academic writing, and its wider application is demonstrated with examples from specific language impairment, morphological development, and foreign/second language learning.