The systematic position of Phaeocryptopus gaeumannii

Phaeocryptopus gaeumannii, causal agent of the Douglas-fir foliar disease Swiss needle cast, is the only known pathogenic species of the genus. Current classifications place Phaeocryptopus in the Venturiaceae (Pleosporales), typified by the apple-scab pathogen Venturia inaequalis. All core members of this family have hyphomycetous anamorphs. We sought to confirm these relationships by means of phylogenetic analyses of the small (SSU) and large (LSU) subunits and internal transcribed spacer (ITS) region of nuclear ribosomal gene sequences (nrDNA). Analyses indicated that both the genus Phaeocryptopus and the family Venturiaceae, as currently defined, are unnatural groups. Phaeocryptopus nudus, type of the genus, is aligned in the Dothioraceae (Dothideales) and P. gaeumannii in the Mycosphaerellaceae (Capnodiales) near species of Mycosphaerella and Rasutoria. Core representatives of Venturiaceae formed an unambiguous clade but ordinal placement was unresolved. The family apparently is not included in the Pleosporales, Dothideales, Myriangiales or Capnodiales. Coelomycetous Rhizosphaera form-species are accepted generally as anamorphic states of Phaeocryptopus, however the relationship never has been established conclusively. Species of Rhizosphaera are closely related to P. nudus but not to P. gaeumannii, supporting an anamorph-teleomorph connection between Rhizosphaera and Phaeocryptopus and providing further evidence that P. gaeumanii is not congeneric with P. nudus.     

The histopathology of Phaeocryptopus gaeumannii on Douglas-fir needles

Germinating ascospores of Phaeocryptopus gaeumannii produce suprastomatal appressoria from which penetration pegs enter needles. Initial infection occurs between late May and early Jul and coincides with budbreak and shoot elongation. Colonization within needles is exclusively intercellular and increases continuously during Jul-May. No intracellular hyphae or haustoria were observed, but hyphae closely appressed to mesophyll and palisade cell walls are abundant by 3-5 mo after initial infection. Pseudothecial primordia begin to form in epistomatal chambers Oct-Apr, 4-9 mo after initial infection. Pseudothecial primordia developing in the epistomatal chamber are connected to the endophytic thallus by specialized cells in the substomatal chamber that have thickened apical walls and resemble phialides but are not involved in asexual reproduction. The apical wall thickenings instead appear to function as reinforcement against the turgor pressure of the guard cells, allowing cytoplasmic continuity to be maintained between the developing pseudothecium and vegetative hyphae within the needle. Concurrent with the formation of pseudothecial primorida, epiphytic hyphae emerge from the periphery of developing pseudothecia, grow across the needle surface, form numerous anastomoses and reenter the needle by producing appressoria above unoccupied stomata. Epiphytic hyphae and their associated appressoria gradually become more abundant during Oct-Jan.     

Polymorphic microsatellite markers for the Douglas‐fir pathogen Phaeocryptopus gaeumannii,causal agent of Swiss Needle Cast disease

Ten polymorphic microsatellite markers were isolated from Phaeocryptopus gaeumannii, causal agent of the Douglas‐fir foliage disease Swiss Needle Cast. The primer sets were tested on 60 isolates that had, with more conservative markers, previously segregated into three reproductively isolated lineages comprising nine genotypes. The microsatellite data yielded 46 multilocus genotypes that segregated into three groups identical to the three lineages previously recovered. Microsatellite genotypic diversity ranged from 0.85 to 0.99 within lineages and was lowest where both pathogen and host are exotic.     

Identification of reproductively isolated lineages of Amur grayling (Thymallus grubii Dybowski 1869): concordance between phenotypic and genetic variation

We analysed variation at maternally (mitochondrial DNA control region sequences) and bi-parentally (10 microsatellites) inherited genetic markers, as well as across 12 meristic characters in 7 populations of Amur grayling, Thymallus grubii, from eastern Siberia. All three data sets were concordant in supporting the existence of three diagnosable, reciprocally monophyletic, and most probably reproductively isolated, lineages of grayling within the Amur drainage. There was a significant correlation between genetic and phenotypic divergence, both within and among lineages. Two phenotypically distinct forms (with and without an orange spot on the posterior portion of the dorsal fin), found in sympatry in the lower Amur, most likely result from secondary contact, as they demonstrate 4.6% sequence divergence at the mitochondrial DNA control region. This divergence, together with the existence of at least one nearby population of orange spot grayling outside the Amur drainage (0.8% divergence) underscore the palaeo-hydrological complexity of the system, which presumably promoted genetic divergence in a shifting allopatric framework throughout the Pleistocene. Grayling from the upper Amur, corresponding to the type locality for the species, formed a sister group (1.4-1.6% divergent) to the orange spot lineage perhaps diverging in the early Pleistocene (1.4-1.6 Ma).     

Colour forms of Amazonian cichlid fish represent reproductively isolated species

Laboratory mate choice experiments have confirmed species status for cichlid fish in the African Great Lakes that differ in colour and little else. Colour differences between allopatric populations of the South American cichlid genus Apistogramma are known for many species, yet the status of such populations has not been previously tested. Analysis of the genetic relationships and mate choice characteristics of populations previously described as Apistogramma caetei from eastern Amazonia indicates genetic differentiation into at least three allopatric lineages, which also show strong prezygotic isolation through female mate choice, confirming them as Biological species. If future studies confirm that this result is indicative of a general trend, the species richness of the South American cichlid fishes may presently be seriously underestimated.     

Sympatric wolf and coyote populations of the western Great Lakes region are reproductively isolated

Interpretation of the genetic composition and taxonomic history of wolves in the western Great Lakes region (WGLR) of the United States has long been debated and has become more important to their conservation given the recent changes in their status under the Endangered Species Act. Currently, the two competing hypotheses on WGLR wolves are that they resulted from hybridization between (i) grey wolves (Canis lupus) and western coyotes (C. latrans) or (ii) between grey wolves and eastern wolves (C. lycaon). We performed a genetic analysis of sympatric wolves and coyotes from the region to assess the degree of reproductive isolation between them and to clarify the taxonomic status of WGLR wolves. Based on data from maternal, paternal and bi‐parental genetic markers, we demonstrate a clear genetic distinction between sympatric wolves and coyotes and conclude that they are reproductively isolated and that wolf–coyote hybridization in the WGLR is uncommon. The data reject the hypothesis that wolves in the WGLR derive from hybridization between grey wolves and western coyotes, and we conclude that the extant WGLR wolf population is derived from hybridization between grey wolves and eastern wolves. Grey‐eastern wolf hybrids (C. lupus × lycaon) comprise a substantial population that extends across Michigan, Wisconsin, Minnesota and western Ontario. These findings have important implications for the conservation and management of wolves in North America, specifically concerning the overestimation of grey wolf numbers in the United States and the need to address policies for hybrids.     

The population genetic approach delineates the species boundary of reproductively isolated corymbose acroporid corals

In this study, we used a population genetic approach with microsatellite markers to attempt to clarify the species boundary of Acropora corals. Species in this taxon are usually difficult to distinguish with the usual molecular phylogenetic approach. We used Acropora sp. 1 and Acropora digitifera as the target species to shed light on the species boundary of Acropora at the population level. These species are morphologically and ecologically similar but are reproductively isolated by differences of a few months in their spawning seasons. We could not distinguish these species using a phylogenetic analysis of the mitochondrial control region, as previously reported in other Acropora species. In contrast, a population genetic approach clearly distinguished these species both sympatrically and allopatrically. Our results suggest that recent speciation and shared ancestral polymorphisms could partly explain the para- and polyphyly of several Acropora species.     

A molecular phylogeny of the pheasants and partridges suggests that these lineages are not monophyletic

Cytochrome b and D-loop nucleotide sequences were used to study patterns of molecular evolution and phylogenetic relationships between the pheasants and the partridges, which are thought to form two closely related monophyletic galliform lineages. Our analyses used 34 complete cytochrome b and 22 partial D-loop sequences from the hypervariable domain I of the D-loop, representing 20 pheasant species (15 genera) and 12 partridge species (5 genera). We performed parsimony, maximum likelihood, and distance analyses to resolve these phylogenetic relationships. In this data set, transversion analyses gave results similar to those of global analyses. All of our molecular phylogenetic analyses indicated that the pheasants and partridges arose through a rapid radiation, making it difficult to establish higher level relationships. However, we were able to establish six major lineages containing pheasant and partridge taxa, including one lineage containing both pheasants and partridges (Gallus, Bambusicola and Francolinus). This result, supported by maximum likelihood tests, indicated that the pheasants and partridges do not form independent monophyletic lineages.     

Population niche structure

Summary The response of twenty maternal families of the annual Abutilon theophrasti to two resource gradients, nutrient and light, was investigated. The structure of the population niche for both biomass and reproductive output was found to be quite different on the two gradients. On the light gradient there was a great diversity of responses among the families while on the nutrient gradient the families responded in a similar manner. On both gradients the plants showed a significant genotype/environment interaction. Three strategies for the production of seed variation have been proposed-all offspring are adapted to the same restricted environment, each offspring of an individual is adapted to a particular environment somewhat different thant that of its siblings, and all the offspring are able to grow in a wide range of environments. We found evidence for all three of these strategies amongst the families. The range of responses seen amongst families (of the same species) in this study was as broad as that found in previous studies among species of the old field annual community to which Abutilon theophrasti belongs. This has significant implications to the nature of competitive interactions and to the evolution of differential resource use in plant populations.     

Population structure and mitochondrial DNA variation in sedentary Neotropical birds isolated by forest fragmentation

The current worldwide concern about tropical deforestation raises questions about the sustainability of avian populations in isolated forest fragments. One of the most important issues concerns the sizes of forest fragments necessary to maintain populations and the genetic variation within them. We address this by: (1) using mtDNA sequence variation to infer aspects of the population structure of four species of understory birds from four sites in southern Costa Rican rainforest; and (2) determining whether forest fragmentation that has occurred in the last 50 years has had an effect on the amount of within-population variation for the species in question. High levels of between-population differentiation (D_xy) were found over a relatively small geographic scale (<130 km) for white-breasted wood-wren (Henicorhina leucosticta), bicolored antbird (Gymnopithys leucaspis), and gray-headed tanager (Eucometis penicillata), suggesting that these species are highly sedentary and exhibit strong female philopatry. No mtDNA variation was found in Plain Antvireo (Dysithamnus mentalis). In all three of the polymorphic species there was a significant decrease in mtDNA nucleotide diversity in populations isolated by forest fragmentation as compared to populations in contiguous primary forest. Even in relatively large (250–1000 ha) forest reserves, sedentary avian species have lost roughly half (range 43–85) of the nucleotide diversity in mtDNA over a relatively short period of time. Our results indicate that sedentary avian species in forest fragments isolated by clearing have undergone severe reductions in effective population size due to population bottlenecks perpetuated by prolonged isolation and potential edge effects.     

Incongruence between morphological and mitochondrial-DNA characters suggests hybrid origins of parthenogenetic weevil lineages (Genus aramigus)

An expanded matrix of morphological characters for the genus Aramigus (Coleoptera: Curculionidae), which includes numerous polyploid parthenogenetic lineages, was compared and combined with a published matrix of mitochondrial DNA (mtDNA) characters. The matrix of morphological characters provides little resolution of the A. tessellatus and A. uruguayensis species complexes but does resolve previously unresolved relationships among other morphologically defined species (A. globoculus + A. intermedius, A. curtulus + A. planioculus). The morphological and mtDNA characters are significantly incongruent (0.435 < or = IM < or = 0.463; IMF = 0.0735), according to the tests of Farris et al. (P = 0.010) and Templeton (P < 0.005), probably because of hybrid origins of polyploid parthenogenetic lineages. For the few sexual lineages included in both matrices, morphology and mtDNA provide congruent estimates of phylogeny. In spite of recent injunctions against combining data sets that are incongruent because of differing histories, the results of the combined analyses were used to select one of the most-parsimonious mtDNA trees as the best estimate of maternal-lineage genealogy and to reconstruct the evolution of parthenogenesis under the assumption that transitions from sexuality to parthenogenesis are irreversible. Where cytogenetically justified, as in weevils, the irreversibility assumption is useful for producing conservative estimates of the age of parthenogenetic lineages in spite of potential sampling bias against sexuals.     

Three-locus analysis in conjunction with strain crosses confirms the existence of reproductively isolated populations in Paramecium jenningsi

Paramecium jenningsi (Diller & Earl, 1958) was formerly considered to be a species with only one syngen (genetic species) based on an inter-strain cross of two strains, cytological analysis, and an investigation of esterases and acid phosphatases. However, the existence of syngens within the species was later suggested by genetic studies, i.e. classical strain crosses of new strains and molecular PCR-based analyses (RAPD, RFLP), as well as by sequencing the H4 gene fragment. This issue still needs to be clarified by the application of molecular markers, genetic tests and cytological preparations. In the present study, we tested 12 strains of P. jenningsi originating from Asia, North America and Africa. Trees reconstructed on the basis of three genome fragments (ITS1-5.8S-ITS2-5’LSU, COI and CytB) show that P. jenningsi is divided into two distinct clusters (PJ1, PJ3) and one branch (PJ2) which correspond to reproductively isolated groups revealed by strain crosses. A study based both on strain crosses and a three-locus comparison gives the opportunity for a more complete identification of the reproductively isolated populations of P. jenningsi and other ciliate species.     

Hepatic lineages isolated from developing rat liver show different ways of maturation

Immunocytochemical analysis revealed that different hepatic cell types exist during liver development: (i). cells co-expressing the stem-cell marker Thy1 and the hepatic lineage marker CK-18 and (ii). cells only expressing CK-18 (hepatoblasts). In this study we separated the different hepatic cells and analyzed gene-expression and phenotype. Fetal rat livers were digested by collagenase solution. OX43- and OX44-positive hematopoietic cells were depleted and Thy1-positive cells were enriched using Magnetic cell sorting. The different cell compartments were analyzed by RT-PCR and immunocytochemistry for Thy1, CK-18, AFP, and albumin. Hepatoblasts expressed albumin at all times and AFP in the early stages. Thy1-enriched cells expressed CK-18 at all times, albumin in the early, and AFP in the late stages. Thy1-positive cells from fetal livers express liver specific genes. The data suggest that Thy1-positive hepatic cells develop towards hepatic stem cells, and hepatoblasts develop towards mature hepatocytes of the adult liver.     

Population structure and eigenanalysis

Current methods for inferring population structure from genetic data do not provide formal significance tests for population differentiation. We discuss an approach to studying population structure (principal components analysis) that was first applied to genetic data by Cavalli-Sforza and colleagues. We place the method on a solid statistical footing, using results from modern statistics to develop formal significance tests. We also uncover a general “phase change” phenomenon about the ability to detect structure in genetic data, which emerges from the statistical theory we use, and has an important implication for the ability to discover structure in genetic data: for a fixed but large dataset size, divergence between two populations (as measured, for example, by a statistic like F_ST) below a threshold is essentially undetectable, but a little above threshold, detection will be easy. This means that we can predict the dataset size needed to detect structure.     

Population structure of eastern Sicily

A sample of 465 persons from Eastern Sicily was studied for 11 red-cell enzymes, namely GLO, GPT, EsD, PGP, PGD, Dia, AcP, PGM, SOD, CAI and CAII. The allele frequencies were compared with those of other Italian populations and showed that the island is homogeneous with the mainland for these systems. The rate of heterozygosity was studied as a function of interparental distance; although high (0.77) the correlation did not reach significance.     

Population structure of Francisella tularensis

We have sequenced fragments of five metabolic housekeeping genes and two genes encoding outer membrane proteins from 81 isolates of Francisella tularensis, representing all four subspecies. Phylogenetic clustering of gene sequences from F. tularensis subsp. tularensis and F. tularensis subsp. holarctica aligned well with subspecies affiliations. In contrast, F. tularensis subsp. novicida and F. tularensis subsp. mediasiatica were indicated to be phylogenetically incoherent taxa. Incongruent gene trees and mosaic structures of housekeeping genes provided evidence for genetic recombination in F. tularensis.     

Population structure of ice-breeding seals

The development of population genetic structure in ice-breeding seal species is likely to be shaped by a combination of breeding habitat and life-history characteristics. Species that return to breed on predictable fast-ice locations are more likely to exhibit natal fidelity than pack-ice-breeding species, which in turn facilitates the development of genetic differentiation between subpopulations. Other aspects of life history such as geographically distinct vocalizations, female gregariousness, and the potential for polygynous breeding may also facilitate population structure. Based on these factors, we predicted that fast-ice-breeding seal species (the Weddell and ringed seal) would show elevated genetic differentiation compared to pack-ice-breeding species (the leopard, Ross, crabeater and bearded seals). We tested this prediction using microsatellite analysis to examine population structure of these six ice-breeding species. Our results did not support this prediction. While none of the Antarctic pack-ice species showed statistically significant population structure, the bearded seal of the Arctic pack ice showed strong differentiation between subpopulations. Again in contrast, the fast-ice-breeding Weddell seal of the Antarctic showed clear evidence for genetic differentiation while the ringed seal, breeding in similar habitat in the Arctic, did not. These results suggest that the development of population structure in ice-breeding phocid seals is a more complex outcome of the interplay of phylogenetic and ecological factors than can be predicted on the basis of breeding substrate and life-history characteristics.     

Population structure of pierid butterflies

Summary Mark-release-recapture techniques were used to study alfalfa pest populations of Colias philodice eriphyle. Two new methods for estimating relative catchability and residence rates were used to compare males to females. The results show that: (1) both sexes had limited dispersal, with mean individual ranges less than 100 m; (2) males were more abundant than females; (3) males and females had similar residence times; (4) males were more catchable than females in uncut fields, but not in cut fields. Explanations for the differences between the sexes are considered. Females may be less catchable in uncut fields because they spend less time in flight than males. Males may be more abundant than females because they develop faster, and may have lower pre-adult mortality. The differences between the sexes are discussed with respect to reproductive strategy. Comparisons with non-pest C.p. eriphyle show differences between pest and non-pest populations. Pest C.p. eriphyle were more sedentary. The residence times were similar for pest and non-pest populations, but pest C.p. eriphyle probably have longer reproductive life-spans. Mid-summer broods of the pest population were partially overlapping; the non-pest population has discrete broods. Pest population density varied less between years than non-pest population density. The differences between pest and non-pest C.p. eriphyle support the idea of ecological diversity among conspecific populations.     

The tertiary structure of full-length bovine adrenodoxin suggests functional dimers

The three-dimensional X-ray crystal structure of full-length oxidized bovine adrenodoxin (Adx) has been determined at 2.5 A resolution by molecular replacement using a structure of a truncated form as a starting model. Crystals of Adx belong to a primitive monoclinic space group P2(1) with four Adx molecules in an asymmetric unit. The unit cell dimensions are a = 59.44 A, b = 77.03 A, c = 59.68 A, and beta = 94.83 degrees. The structure has been refined to an R factor of 23.5%. Structures of the four molecules of full-length Adx (127 amino acids) in the asymmetric unit were compared with each other and also with that of the truncated Adx (4-108). The overall topology of full-length Adx remains the same as described earlier for the truncated protein. Differences that do occur are almost wholly confined to alternate side-chain conformations that reflect differing lattice contacts made by two proteins. Extensive interactions found between molecules 1 and 2 in the full-length Adx asymmetric unit may reflect the ability of Adx to form dimers in vivo and are consistent with hydrodynamic measurements which show that in solution there is an equilibrium between monomeric and dimeric forms of Adx. Dimerization of Adx could explain why the truncated form has greater affinity for the P450 redox partner than the full-length form. From these results it can be considered that the mechanism of electron transfer is not necessarily the same in different mitochondrial P450 systems.