bluuebunny/crossref_metadata_2025 huggingface dataset:
Direct and Indirect Effects of Nectar Robbing on the Pollinating Behavior of Patagona gigas (Trochilidae)1
Authors: González‐Gómez Paulina L. , Valdivia Carlos E.
Published: November 2005

In central Chile, nectar robbing of Puya coerulea (Bromeliaceae) flowers by the austral blackbird, Curaeus curaeus, had a direct impact on the plant via removal of floral resources and, in some cases, damage or even destruction of flowers. These robbing visits also likely had an indirect impact on plant fitness due to the decreased rate of legitimate visits by the hummingbird Patagona gigas to inflorescences with many robbed flowers. The proportion of flowers within an inflorescence visited by P. gigas was inversely proportional to the ratio of robbed flowers.
Spatial and Temporal Distribution of Northern Waterthrushes Among Nonbreeding Habitats in Southwestern Puerto Rico1
Authors: Hunt Pamela D. , Reitsma Leonard , Burson Sherman L. , Steele Benjamin B.
Published: November 2005

We surveyed nonbreeding Northern Waterthrushes (Seiurus noveboracensis) in several coastal habitats in southwestern Puerto Rico, West Indies. Waterthrush abundance was highest (mean = 2.2/point) in well‐developed mangrove habitats characterized by large trees and standing water, and lowest (mean = 0.1/point) in dry coastal scrub and savannah. Within the latter habitats, waterthrushes were more common in moist microhabitats such as temporary ponds and dry washes. Abundance in most habitats declined between October and January, probably a result of the presence of transients during the October surveys, Between January and March, abundance in mature red mangrove (Rhizophora mangle) forests increased dramatically, suggesting that this habitat provides a refuge for birds at the end of the dry season and prior to northward migration. In conjunction with other data demonstrating the use of coastal red mangroves as nocturnal roosting sites, these results suggest that mangroves are the most important nonbreeding habitat for this species. Conservation of this globally threatened habitat may thus be important for the long‐term stability of waterthrush populations.
GCRT J1745—3009: a precessing radio pulsar?
Authors: Zhu W. W. , Xu R. X.
Published: November 2005

A unique transient bursting radio source, GCRT J1745—3009, has been discovered near the direction of the Galactic Centre. The explanation of this phenomenon is still an open question, although some efforts to understand its nature have been made. This Letter shows that most of the observed features can be reproduced by our proposed precessing pulsar model. It is found that the precession angle of the pulsar should be larger (≳15°) than that of previously known precessing pulsars, which have a precession angle ≲10°, if the beam width of the pulsar is larger than 10°. The pulsar could be a nulling (or even extremely nulling) radio pulsars to account for the transient nature of the source. This model can be confirmed if a pulsar is detected at the position of the source. The pulsar could hardly be a normal neutron star (but could probably be a solid quark star) if the spin period of the pulsar is detected to be ≳10 ms in the future.
Vascular Neurology: A New Neurologic Subspecialty in the United States
Authors: Adams Harold P. , Juul Dorthea , Scheiber Stephen
Published: November 2005

The American Board of Psychiatry and Neurology (ABPN) has established a certification process for the subspecialty of vascular neurology. In addition, the Accreditation Council for Graduate Medical Education has approved residencies (fellowships) in vascular neurology in the United States. These steps are in response to the growth of a special body of knowledge related to the diagnosis and treatment of patients with cerebrovascular disease. The certificate in vascular neurology recognizes those ABPN-certified neurologists or child neurologists who have demonstrated proficiency in the management of patients with vascular diseases of the central nervous system. This may have implications for similar initiatives in other countries
Management of Patients with Symptomatic Intracranial Atherosclerosis
Authors: Leung Thomas W. , Kwon Sun U. , Wong Ka Sing
Published: November 2005

Intracranial atherosclerosis is a common cause of stroke, accounting for about 50% of ischaemic stroke in Asia and 8% in North America. Many prospective studies have confirmed that intracranial stenosis is an independent predictor for poor outcomes such as recurrent vascular event and death, despite the use of antiplatelet agents. The annual event rate is about 15% per year. The dismal outcome prompts the study of more aggressive treatment strategies, including warfarin and endovascular intervention. We have reviewed the published literature for the treatment of symptomatic intracranial stenosis. The Warfarin–Aspirin Symptomatic Intracranial Disease (WASID) trial and Warfarin–Aspirin Recurrent Stroke Study (WARSS) studies failed to show that oral anticoagulation was better than aspirin in IAS. Initial encouraging results were found in the use of dual antiplatelet therapy in arresting the progression of stenosis. The results of the endovascular studies are mixed: there are more encouraging results with recent advances of technology in stent design, but a randomized controlled study is still lacking. Although there is still no established therapy for IAS, the results of ongoing randomized clinical trials to study dual antiplatelet agents and the use of endovascular intervention may soon provide clinicians with more evidence to better manage patients with this condition.
Habitat management by aboriginals promotes high spider diversity on an Asian tropical island
Authors: Tsai Zon‐Ing , Huang Pao‐Shen , Tso I‐Min
Published: November 2005

Orchid Island, 92 km off the southeast coast of Taiwan, has the northernmost tropical forests in East Asia. We assessed effects of habitat management by Orchid Island inhabitants, the Yami people, on spider diversity by comparing assemblages collected from the ground to canopy among four habitats (natural forest, cultivated woodland, second growth forest and grasslands) that receive different degrees of disturbance. Species and guild composition did not differ among replicates of habitat but differed significantly among habitats. Variation in spider diversity was inversely correlated with vegetation density. Cultivated woodland subjected to an intermediate level of disturbances had a lower understory vegetation density than natural forest, but higher spider diversity. Neither insect abundance nor biomass varied significantly among habitats suggesting little room for effects of prey availability on spider diversity. It appears that the Yami people maintain high spider diversity on Orchid Island by generating novel habitat types with different vegetation structures and disturbance regimes.
Microsporogenesis inAmelanchier alnifolia: sporogenous cells, microsporocytes, and tetrads
Authors: Sumner Michael J. , Remphrey William R.
Published: November 2005

As part of an overall program aimed at increasing our knowledge of the male reproductive system of Amelanchier alnifolia Nutt., this study documents structural and developmental changes that occur in the sporogenous cells, microsporocytes, and tetrads of microspores during microsporogenesis using general cytochemical techniques in conjunction with bright field, fluorescence, and transmission electron microscopy. The sporogenous cells are thin walled and stain positively for β-1,4-glucans, pectic acids, and cellulose, but not callose. At the microsporocyte and tetrad stages of microsporogenesis, thick walls develop and stain positively for β-1,4-glucans (hemicelluloses but not cellulose), pectic acids, and callose. Thus, the eventual release of maturing microspores from the tetrads requires the digestion of all three of these carbohydrate wall materials. Postmeiotic cytokinesis is of the simultaneous type and is initiated when Golgi vesicles aggregate simultaneously into a network of cylindrical tubules in both central and peripheral cell locations of the coenocytic tetrad. Eventually, this network fuses to form the new cell walls within the microspore tetrad.
Genetic diversity and population structure of boreal white spruce (Picea glauca) in pristine conifer-dominated and mixedwood forest stands
Authors: Rajora Om P. , Mann Ishminder K. , Shi Yong-Zhong
Published: November 2005

White spruce ( Picea glauca (Moench) Voss) is a characteristic primary species of the Canadian boreal forest region, where it occurs in conifer-dominated and mixedwood forest types. Genetic diversity and population structure of white spruce may differ between the conifer-dominated and mixedwood forest types owing to the inherent differences in stand structure and dynamics. The objective of our study was to determine genetic diversity and population structure of pristine white spruce stands as they occur in conifer-dominated and mixedwood forest types at the EMEND (Ecosystem Management Emulating Natural Disturbance) study sites in northern Alberta. Nuclear microsatellite DNA markers were used to examine genetic diversity and population structure of 16 pristine natural old-growth (≥100 years) white spruce stands (subpopulations) of fire origin; 8 from conifer-dominated and 8 from neighboring mixedwood forest types. High levels of genetic diversity were observed, as expected. The genetic diversity and genetic constitution of white spruce were similar between the conifer-dominated and mixedwood forest types. Most of the genetic variation resided within subpopulations, with only about 2% genetic differentiation detected among 16 subpopulations as well as among 8 subpopulations within the same forest type. The mean genetic distances among subpopulations within and between the forest types were similar. Our study suggests that white spruce genetic resources are similar in the conifer-dominated and mixedwood forest types located in the EMEND study area in northern Alberta, and it provides the benchmarks for determining and monitoring the genetic diversity impacts of forest harvesting and forest fires.
Spatial genetic and clonal structure inMaianthemum dilatatumas defined by AFLP markers
Authors: Wilson Amy S.G. , van der Kamp Bart J. , Ritland Carol
Published: November 2005

Amplified fragment length polymorphisms (AFLPs) were used to investigate the clonal and spatial genetic structure of Maianthemum dilatatum (A. Wood) Nels. & J.F. Macbr. (Convallariaceae), a clonal rhizomatous herb, which can form large patches of continuous cover. Within a subpopulation covering approximately 3 ha, all patches (n = 21) were mapped and sampled. Within these patches, 116 ramets were sampled and assigned to 74 putative genets. Small patches appeared to be single genets while larger patches were genetically heterogeneous and only moderately differentiated (ΦST= 0.291, p = 0.001). Less intense sampling in other populations produced similar results in that single genet populations were not found. Evidence of genet natality was present with the detection of five yearlings within a single season. Spatial autocorrelation measures detected spatial genetic structure attributable to both clonal growth and gene flow processes. It was concluded that within M. dilatatum populations, clonality is a significant factor, but the spatial structuring of genetic variation suggests that both low levels of restricted gene flow and repeated recruitment of genets occur.
Conidial morphology, virulence, molecular characterization, and host–parasite interactions of selected Alternaria panax isolates on American ginseng
Authors: Quayyum H.A. , Dobinson K.F. , Traquair J.A.
Published: November 2005

The fungus Alternaria panax Whetzel causes leaf and stem blight of American ginseng ( Panax quinquefolius L.). Six isolates of A. panax, collected from widely separated ginseng-growing areas in North America, were characterized on the basis of their colony and conidial morphology, molecular characteristics, and virulence. Colony morphology on standard media and conidial morphology based on light microscopy showed some variation with geographic locality: Wisconsin isolates were slightly different from Ontario and British Columbia isolates. Isolates from each locality were equally virulent on American ginseng. Ginseng phytotoxin was present in the conidial germination fluid of all isolates. Sequences of the β-tubulin gene from all six isolates were identical as were the sequences of the internal transcribed spacer (ITS) region of the rDNA gene. The ITS1 and ITS2 gene sequences of the six isolates were also identical to those of American and Korean isolates of A. panax deposited in GenBank. Cellulase and pectinase were detected by agar biodiffusion assays of a representative isolate. Germination of conidia of this isolate on ginseng leaflets began within 2 h of application to leaf surfaces, and over 80% of conidia germinated within 12 h of application. Conidia produced one to several germ tubes that grew in all directions over the leaflet surface. The germ tubes formed terminal appressoria over stomatal openings, epidermal cells, and epidermal cell junctions. The frequency of direct penetration into ginseng leaflets was greater than penetration through stomata. Both retraction of plasma membrane and disruption of chloroplast membranes were observed 12 h after leaflet inoculation. At 24 h after inoculation, hyphae were present in both intercellular spaces and inside mesophyll cells. Severe disruption of plasma membrane, chloroplasts, and mitochondria was observed between 24 and 48 h after inoculation.
Seed rain and seedling establishment of the dioecious treeNeolitsea sericea(Lauraceae): effects of tree sex and density on invasion into a conifer plantation in central Japan
Authors: Arai Nobumasa , Kamitani Tomohiko
Published: November 2005

We studied the effects of differences in parent sex and density on seed rain and seedling and (or) sapling recruitment in a dioecious tree species (Neolitsea sericea (Bl.) Koidz.) with bird-dispersed seeds. We established four microhabitats: male or female trees inside or outside a single patch. The density of bird-disseminated seeds was significantly higher beneath females and inside the patch than beneath males and single trees outside the patch; this led to higher density of emerged seedlings inside the patch. The survival rate of germinated seedlings was also higher inside the patch than below single trees. In contrast, the survival rate of saplings was highest beneath males outside the patch, although very few seeds are dispersed beneath single males. Seedling and sapling recruitment beneath females and inside the patch will be accelerated owing to higher density of dispersed seeds, high seedling survival, and greater sapling density. In contrast, recruitment beneath males will be very slow. However, microhabitats beneath males are probably more suitable for seedling and sapling recruitment than microhabitats beneath females, since the survival rate of saplings was higher beneath males. Parental sex-biased seed rain and seedling and (or) sapling recruitment in dioecious plants may explain the regeneration pattern at a local scale.
Cumulative effects of mortality factors on reproductive output in two co-occurring Quercus species: which mortality factors most strongly reduce reproductive potential?
Authors: Fukumoto Hiroshi , Kajimura Hisashi
Published: November 2005

We examined the factors that limit the potential reproductive output by two co-occurring deciduous oaks, Quercus variabilis Blume and Quercus serrata Thunb. ex Murray, studied over two growing seasons. We assessed the relative importance of each factor that could affect reproductive potential during the pre-dispersal phase on the basis of both the magnitude of the reproductive loss and the variation in such losses. Five factors (abortion of pistillate flowers, abortion of acorns, predation by an immature acorn-feeding guild of insects, predation by a mature acorn-feeding guild of insects, and degeneration of acorns) reduced the reproductive potential of Q. variabilis during the pre-dispersal phase. Of these factors, insect predation by the immature acorn-feeding guild and by the mature acorn-feeding guild made the greatest contribution to the variation among plants in total reproductive losses, even though they did not always cause the largest overall reproductive losses. For Q. serrata, the same five factors plus predation by a guild of insects that feeds on pistillate flowers affected reproductive potential during the pre-dispersal phase. Of these factors, abortion of pistillate flowers was responsible for the majority of the reproductive losses and made the largest contribution to the variation among plants in overall reproductive losses.
Corticolous species of Protoparmelia (lichenized Ascomycotina) in North America
Authors: Brodo Irwin M. , Aptroot André
Published: November 2005

Protoparmelia hypotremella van Herk, Spier & V. Wirth is reported here as an addition to the North American lichen flora. Fertile material of P. hypotremella was found for the first time, and it is described in detail. The hyaline hair-like appendages on both polar ends of the ascospores, characteristic of the genus, are illustrated for the first time. The species is then compared with Protoparmelia ochrococca , known from western North America, and Protoparmelia oleagina , still known only from Europe. A key to the corticolous species of Protoparmelia is provided.
A field study of seed dispersal and seedling performance in the invasive exotic vine Vincetoxicum rossicum
Authors: Ladd David , Cappuccino Naomi
Published: November 2005

The exotic vine Vincetoxicum rossicum (Kleopow) Barbar. (Asclepiadaceae) is a major natural-areas pest throughout the Great Lakes Basin. Colonization of new areas by this herbaceous perennial occurs by comose wind-dispersed seeds. Previous experiments suggested a trade-off between seed dispersability and seed quality: smaller seeds dispersed farther but were less likely to emerge and seedlings were smaller when grown in competition with turf grasses in the greenhouse. We examined dispersability by trapping seeds at distances of 0–60 m from a seed source, and we assessed seedling performance by sowing seeds of known weight in an old field. Smaller seeds travelled significantly farther than larger seeds; however, the relationship between weight and distance dispersed was weak (r2 = 0.043). Large seeds were significantly more likely to emerge, and the seedlings survive and grow taller; however, the relationships between seed size and these performance variables were also weak (r2 ≤ 0.02). The dispersability–quality tradeoff is unlikely to play an important role in V. rossicum spread at the local scale, as even large seeds are competent dispersers and even seedlings from small seeds are capable of becoming established. Seedlings from polyembryonic seeds were more likely to successfully establish than seeds from which a single seedling emerged. The high seedling emergence (50% for seeds planted above ground; 72% for those buried to a depth of 1 cm) and survivorship (71%–100%, depending on embryony) are likely to contribute to the success of this species.
Opportunities for geitonogamy in the clonal herb Maianthemum dilatatum
Authors: Wilson Amy S.G. , van der Kamp Bart J. , Ritland Carol
Published: November 2005

Clonal plant species have a diverse range of morphologies, which influences the spatial proximity of clonemates, which may affect the rate of geitonogamy. This study measured fine-scale clonal structure, pollinator behaviour, and impacts of geitonogamy on seed set in Maianthemum dilatatum (A. Wood) Nels. & J.F. Macbr., a herb with a spreading clonal morphology. Despite having a dispersive habit, on average more than 75% of the 10 nearest flowering neighbours of a ramet were clonemates of that ramet. Pollinators foraged preferentially among near-neighbours, but during bouts, visitors typically visited only two floral ramets, effectively lowering the expected contribution to geitonogamy based on flight distances alone. Experimental hand pollinations, pollinator exclusion, and emasculation treatments provided evidence that geitonogamy attributable to pollen from neighbouring ramets may reduce seed set in natural populations through a mechanism of self-interference. Even in a dispersive clonal plant species such as M. dilatatum, clonemate-level geitonogamy is a likely factor constraining female reproductive success.
Effects of severe dwarf mistletoe infection on the ectomycorrhizal community of aPinus contortastand in Yellowstone Park
Authors: Cullings Ken , Raleigh Chris , Vogler Detlev R.
Published: November 2005

Molecular methods were used to test the hypothesis that severe infection by dwarf mistletoe ( Arceuthobium , a carbon-sink parasite) affects the ectomycorrhizal (EM) communities of its host, lodgepole pine. Results indicate significantly lower EM fungal species richness (2 ± 0.2 SE species per core in uninfected and 1 ± 0.2 species per core in infected blocks; P < 0.005), Shannon–Wiener diversity indices (1.1 in uninfected and 0.6 in infected; P < 0.05), and also differences in species EM fungal composition; uninfected blocks are dominated by a species of Cortinarius while the infected stand is dominated by species of Russula , and Piloderma (26%). By contrast, dwarf mistletoe infection has no apparent effect on evenness (0.65 in controls and 0.47 in infected; 0.05 < P < 0.1), or on EM infection levels (35 ± 7 EM tips per core in uninfected and 21 ± 5 in infected; P > 0.1). Thus, dwarf mistletoe infection may select for EM fungal species that impose a lower carbon demand on the host, or that possess carbon-degrading abilities to augment carbon lost to the parasite, enabling the trees in infected blocks to maintain relatively high EM infection levels. Our results indicate that effects of dwarf mistletoe infection occur not just in the crown of infected but extend into the soil as well, and hence may have much greater implications for ecosystem function than previously thought.
The anatomy ofAskeptosaurus italicusfrom the Middle Triassic of Monte San Giorgio and the interrelationships of thalattosaurs (Reptilia, Diapsida)
Authors: Müller Johannes
Published: November 2005

The anatomy of the thalattosauriform reptile Askeptosaurus italicus from the Middle Triassic of Monte San Giorgio is redescribed. Important anatomical features are the plesiomorphic braincase, the unique fronto-lacrimal contact, the absence of a previously described thyroid fenestra, and significant intraspecific variation in the carpus. An analysis of thalattosaur ingroup relationships reveals that Endennasaurus and the monophyletic Askeptosaurus and Anshunsaurus are the sister group to all other thalattosaurs, whereas the Monte San Giorgio taxa Clarazia and Hescheleria form the sister clade of Thalattosaurus, and the Chinese Xinpusaurus and the Californian Nectosaurus form a monophyletic group. The analysis supports the biogeographic interpretation of trans-Pacific relationships and a re-invasion of Tethyan areas.
Unusual tetrapod teeth from the Upper Triassic Chinle Formation, Arizona, USA
Authors: Irmis Randall B , Parker William G
Published: November 2005

Two teeth collected from the Upper Triasssic Chinle Formation of northeastern Arizona are described here and named Kraterokheirodon colberti gen. et sp. nov. These teeth are novel in having an occlusal ridge with six cusps and a posterior shelf lacking dentine. Evidence for thecodont implantation of the root suggests amniote affinities for these teeth. They do not match any teeth known for basal vertebrates or basal tetrapods. Although the teeth display some affinities with "traversodont" cynodonts, there are significant differences that preclude a referral to this group. These teeth most probably represent an unknown tetrapod clade and document the presence of a large amniote previously unknown from Late Triassic terrestrial faunas.
Paleoproterozoic reworking of an Archean thrust fault in the Hearne domain, Western Churchill Province: UPb geochronological constraints
Authors: MacLachlan K , Davis W J , Relf C
Published: November 2005

The nature, timing and control of Archean crustal architecture on the distribution of Proterozoic reworking in Western Churchill Province are investigated in the Yathkyed Lake area, central Nunavut. The Tyrrell shear zone (TSZ) marks the boundary between the northwestern and central Hearne subdomains, respectively, in the hanging wall and footwall. Metamorphism and deformation in the hanging wall are ca. 2.662.50 Ga. Two episodes of metamorphism are recorded in a foliated granodiorite in the footwall, at 1818+52 and 1827 ± 5.6 Ma. The latter age is interpreted as the time of amphibolite-facies metamorphism and deformation in the footwall. A crosscutting dyke provides a minimum age of 1818 ± 2 Ma for this metamorphism and deformation. The TSZ is dominated by dextral oblique-slip shear fabrics. A suite of leucogranite dykes provide a maximum age of 1816 ± 2 Ma for dextral shearing. Dextral deformation is bracketed between 1815 ± 2 and 1811 ± 1 Ma, the ages of two other granitoid dykes. In an area of low dextral strain, there are proto-sheath folds related to Neoarchean thrusting. Paleoproterozoic transtensional shearing in the TSZ was localized along a preexisting late Archean thrust fault. The prior existence of this structure resulted in localization of penetrative Paleoproterozoic deformation in its footwall. This domain of high-grade Proterozoic deformation was uplifted in a regional, antiformal, metamorphic culmination, in part, by dextral-normal shearing along the TSZ. Penetrative basement deformation at depth played a role in transmitting farfield stresses related to the Trans-Hudson Orogen into its hinterland.
Anatomy of the Early Cretaceous bird Eoenantiornis buhleri (Aves: Enantiornithes) from China
Authors: Zhou Zhonghe , Chiappe Luis M , Zhang Fucheng
Published: November 2005

A detailed description of the anatomy, in particular of the skull, of Eoenantiornis is provided. This description reveals many morphological characters previously unknown for enantiornithine birds, such as presence of a distinct facet for the intramandibular articulation between the dentary and postdentary bones. Eoenantiornis documents an intermediate stage in the abbreviation of the alular digit among Ornithothoraces, which paralleled a similar transformation within Ornithuromorpha. Our analysis also indicates that Eoenantiornis belongs to the Euenantiornithes.
A new genus of rhizodontid (Sarcopterygii, Tetrapodomorpha) from the Lower Carboniferous Horton Bluff Formation of Nova Scotia, and the evolution of the lower jaws in this group
Authors: Brazeau Martin D
Published: November 2005

Letognathus gen. nov. is described from the Lower Carboniferous (Tournaisian) Horton Bluff Formation. Included in this genus is the species Letognathus hardingi (Dawson 1868), which was originally assigned toRhizodus and later toStrepsodus, but it is distinct from these genera in tooth morphology and the presence of several more primitive rhizodontid characters. By contrast with these latter more derived genera, the parasymphysial plate contacts the first coronoid; the first coronoid bears a row of lingually deflected teeth, the tooth striations occur around the entire circumference of the crown and are much finer and less regular than those ofStrepsodus, and marginal tooth row reaches anteriorly to the dentary symphysis. Phylogenetic analysis indicates that rhizodontid jaws primitively bear symphysial tusks; slender recumbent teeth; an anterior projection of the dentary over the anteromesial depression for the median symphysial plate and shows the highly derived jaws ofStrepsodus andRhizodus evolved within the Rhizodontida, rather than as primitive characters for the group. This new jaw material supports earlier models of mandibular kinesis and shows that the coronoid fangs were oriented such as to facilitate kinesis. Rhizodontid jaw evolution seems to be marked by parallelisms with tristichopterids and early tetrapods.
Accretion-related metamorphism of the Metchosin Igneous Complex, southern Vancouver Island, British Columbia
Authors: Timpa Sean , Gillis Kathryn M , Canil Dante
Published: November 2005

The metamorphic history of the volcanic sequence of the Metchosin Igneous Complex (MIC), an Eocene ophiolite exposed on southern Vancouver Island, British Columbia, Canada, was studied to examine the roles of seafloor and accretion-related processes. Metamorphic facies in the volcanics vary from prehniteactinolite assemblages in the east to greenschist and amphibolite assemblages in the west. In the east, metamorphism is typified by chlorite ± prehnite ± epidote ± actinolite assemblages that fill vesicles and replace interstitial material; plagioclase is variably albitized, and clinopyroxene is relatively fresh. In the west, the common groundmass assemblage is amphibole + epidote ± chlorite. These assemblages and chlorite geothermometry show a regional eastwest gradient of ∼510 °C/km that is oblique to the volcanic stratigraphy. The regional metamorphic facies distribution for the MIC volcanics is not consistent with seafloor hydrothermal metamorphism documented for ocean crust from mid-ocean ridges, ocean islands, or island arcs. We speculate that underthrusting of the MIC beneath the Pacific Rim Terrane led to the regional metamorphism of the MIC, and that the change in metamorphic grade from east to west results from regional tilting of the complex, perhaps by orographic effects, during or after accretion.
Mississippian volcanic assemblage conformably overlying Cordilleran miogeoclinal strata, Turnagain River area, northern British Columbia, is not part of an accreted terrane
Authors: Erdmer Philippe , Mihalynuk Mitchell G , Gabrielse Hubert , Heaman Larry M , Creaser Robert A
Published: November 2005

A Paleozoic volcanic assemblage exposed in northern British Columbia, near the Turnagain River, previously considered to be part of an accreted terrane, was reported to be in depositional contact with a part of the Cordilleran miogeocline. This paper presents an integrated field, UPb geochronology, SmNd isotopic, and geochemical study across the basal contact of the volcanic assemblage. Strongly evolved εNd(T) values, between 13 and 21, from samples of lower Paleozoic sedimentary rocks exposed below the volcanic rocks, and correlated with Atan  Kechika  Road River  Earn strata of the miogeocline farther east, support a North American miogeoclinal affinity, consistent with previously established regional stratigraphic and structural relationships. Nd isotopic data from the volcanic assemblage contrast significantly with data from the sedimentary rocks and record a mantle source (εNd(T) values between +4.0 and +7.0), consistent with a magmatic arc or back arc; negative Nb anomalies are similarly compatible with either arc- or back-arc-related magmatism. A concordant 339.7 ± 0.6 Ma UPb zircon date was obtained from the volcanic assemblage. The mixed gradational contact between the miogeoclinal and volcanic rocks is marked by interlayering of finely laminated grey and green phyllites on the scale of centimetres, with no evidence of a tectonic contact. Bedding at the contact is folded into tight outcrop-scale folds that are intruded by an Early Jurassic (187.5 ± 2.9 Ma) granodiorite. On the basis of all available evidence, the contact is interpreted as a facies transition. The Mississippian volcanic assemblage may link the miogeocline with the early development of an Angayucham  Slide Mountain basin.
Geology and juxtaposition history of the Yukon-Tanana, Slide Mountain, and Cassiar terranes in the Glenlyon area of central Yukon
Authors: Colpron Maurice , Gladwin Kaesy , Johnston Stephen T , Mortensen James K , Gehrels George E
Published: November 2005

In central Yukon, the pericratonic YukonTanana terrane (YT) is juxtaposed with the Cassiar terrane (CT, parautochthonous North America) along the Tummel fault zone (TFZ), a 34 km wide, northwest-trending belt comprising imbricate fault slices of Slide Mountain terrane (SM, greenstone, chert, serpentinite) and synorogenic clastic rocks. Northeast of the TFZ, the CT comprises Paleozoic metapelitic rocks, marble, and amphibolite of continental margin affinity. To the southwest, the YT consists of a pre-Late Devonian metasedimentary complex overlain and intruded by Mississippian clastic, volcanic, and plutonic successions of continental arc affinity. In the TFZ, Middle to Late Permian ocean-floor basalt of the SM shows evidence of crustal contamination, suggesting deposition at the edge of a marginal ocean basin. Deformation features in the TFZ include early ductile fabrics overprinted by younger brittle structures. Triassic synorogenic clastic rocks in the TFZ, and at the base of a klippen above the YT, suggest that terrane imbrication began shortly after the Early Triassic. 40Ar/39Ar mica ages from the region suggest cooling of the YT, SM, and part of CT below 300 °C by Early Jurassic time. Pervasive brittle structures in the Ragged Lake klippe, which roots into the TFZ, indicate brittle thrusting of the SM over the CT in post-Triassic time. Early Cretaceous plutons intrude the CT (Glenlyon Batholith) and the TFZ (leucogabbro) and impose a contact aureole that extends westward into the YT. Steep brittle structures that deformed the TFZ also affect, in part, the Glenlyon Batholith but do not significantly offset its contact aureole. Consequently, little displacement can have occurred along the TFZ after Early Cretaceous time.
Early Silurian (Wenlockian) δ13C profiles from the Cape Phillips Formation, Arctic Canada and their relation to biotic events
Authors: Noble Paula J , Zimmerman Matthew K , Holmden Chris , Lenz Alfred C
Published: November 2005

Geochemical data from the Cape Phillips Formation, Arctic Canada, are examined in association with three Silurian biotic crises in the graptolite community; the early Wenlockian Ireviken, mid Wenlockian Cyrtograptus lundgreni, and end Wenlockian Colonograptus ludensis extinction events. Positive δ13Corg excursions are associated with the Ireviken and C. lundgreni events, but not the Co. ludensis Event. The Ireviken and C. lundgreni excursions are recognized worldwide and are herein interpreted to be the result of carbonate weathering in response to eustatic sea-level drop. The C. lundgreni excursion is of greater magnitude in the more proximal basin margin section at Abbott River, Cornwallis Island, and is explained by the amplification of a more strongly positive δ13C signature in shallower parts of an epeiric basin during increased exposure and weathering of the carbonate shelf. Excursion C5, within the C. praedeubeli  C. deubeli Zone, is also of regional significance, as it occurs in both the Abbott River section and Twilight Creek section on Bathurst Island, and is also recognized in Estonia, Poland, and England. Excursion C6 is recognized in the Gorstian Stage, yet its regional significance remains equivocal. There is a reasonable general agreement between the shape of the δ13Corg and δ13Ccarb curves, yet the δ13Ccarb curve is largely a record of detrital carbonate derived from the shelf. The δ13Corg curve represents extraction of dissolved inorganic carbon by plankton and thus is more indicative of ambient paleoceanographic conditions. These data are valuable in that they provide a detailed secular marine δ13C curve for the Wenlockian of Arctic Canada from relatively unaltered sections of varying facies whose ages are well constrained by graptolite biostratigraphy.
An individual-based modeling approach to spawning-potential per-recruit models: an application to blue crab (Callinectes sapidus) in Chesapeake Bay
Authors: Bunnell David B , Miller Thomas J
Published: November 2005

An individual-based modeling approach to estimate biological reference points for blue crabs (Callinectes sapidus) in Chesapeake Bay offered several advantages over conventional models: (i) known individual variation in size and growth rate could be incorporated, (ii) the underlying discontinuous growth pattern could be simulated, and (iii) the complexity of the fishery, where vulnerability is based on size, shell status (e.g., soft, hard), maturity, and sex could be accommodated. Across a range of natural mortality (M) scenarios (0.3751.2·year1), we determined the exploitation fraction (µ) and fishing mortality (F) that protected 20% of the spawning potential of an unfished population, the current target. As M increased, µ20% and F20% decreased. Assuming that M = 0.9·year1, our models estimated µ20% = 0.45, which is greater than field-based estimates of µ in 64% of the years since 1990. Hence, the commercial fishery has likely contributed to the recent population decline in Chesapeake Bay. Comparisons of our results with conventional per-recruit approaches indicated that incorporating the complexity of the fishery was the most important advantage in our individual-based modeling approach.
Genetic differentiation in walleye pollock (Theragra chalcogramma) in response to selection at the pantophysin (PanI) locus
Authors: Canino Michael F , O'Reilly Patrick T , Hauser Lorenz , Bentzen Paul
Published: November 2005

Samples of walleye pollock (Theragra chalcogramma) from the North Pacific Ocean and Bering Sea were screened for variation at the pantophysin (PanI) locus. Global genetic differentiation across samples (FST = 0.038) was considerably greater than reported in previous population studies using allozymes, mtDNA, or microsatellite loci and significantly greater than FSTdistributions of neutral loci simulated over a large range of locus heterozygosity. PanI allele frequencies varied over a broad latitudinal gradient and were correlated with estimated mean surface temperatures, resulting in the greatest levels of genetic divergence between the northern Bering Sea and the southernmost locations in the temperate Pacific Ocean (Puget Sound, Japan). The discordance between estimates of population differentiation estimated from PanI and other neutral marker classes, both in magnitude and in geographic patterns, could arise from temperature-mediated effects of natural selection over broad geographic scales. Our empirical results suggest that loci subject to directional selection may prove to be useful markers for stock identification in weakly structured marine fishes.
Population subdivision and genetic signatures of demographic changes in Arctic grayling (Thymallus arcticus) from an impounded watershed
Authors: Stamford M D , Taylor E B
Published: November 2005

We examined allelic variation at seven microsatellite loci in 11 samples of Arctic grayling (Thymallus arcticus) from the Peace River watershed, northeastern British Columbia, to (i) assess population subdivision and (ii) test for population size changes promoted by hydroelectric dam construction in the watershed. The number of alleles and expected heterozygosity per locus averaged 2.3 and 0.29, respectively. Overall Fst(θ) was 0.21 (P < 0.003), but there was no distinction between age classes (0+ and 3+) within two streams (θ = 0.01, P > 0.05). Seven percent of the microsatellite variation (P < 0.005) was attributable to differences between samples above and below a historical natural barrier to upstream fish migration, the Peace River Canyon (the site of hydroelectric developments since the 1960s). Strong isolation-by-distance among samples was resolved (Mantel r = 0.64, P < 0.01). Coalescent analyses suggested that current Arctic grayling population sizes are less than 1% of historical sizes and that this decline began relatively recently (i.e., <300 years ago) under an exponential model of population size change or earlier in the late Pleistocene under a linear model. Significant microsatellite divergence occurs among Peace River Arctic grayling populations previously characterized by low mtDNA divergence.
Recruitment of mackerel icefish (Champsocephalus gunnari) at South Georgia indicated by predator diets and its relationship with sea surface temperature
Authors: Hill Simeon L , Reid Keith , North Anthony W
Published: November 2005

The South Georgia population of mackerel icefish (Champsocephalus gunnari) is exploited by both a fishery and predators, including gentoo penguins (Pygoscelis papua). Because considerable uncertainty surrounds recent estimates of stock size, there is a need to consider novel approaches that may give insight into the population dynamics of this species. We derive two indices of recruitment based on the occurrence of mackerel icefish in gentoo penguin diets, one of which is scaled by a survey estimate of the density of Antarctic krill (Euphausia superba), an alternative prey species for gentoo penguins. The closure of the fishery for much of the 1990s allowed the relationship between environmental conditions and recruitment to be studied without the confounding effects of fishing mortality. The recruitment indices were positively correlated with sea surface temperature with a lag time equal to the age of the fish. These results suggest strong links between mesoscale environmental processes and the smaller scale interaction between gentoo penguins and their mackerel icefish prey.
Estimation of age composition from length data by posterior probabilities based on a previous growth curve: application to Sebastes schlegelii
Authors: Baba Katsuhisa , Sasaki Masayoshi , Mitsutani Noriyuki
Published: November 2005

We developed a system to estimate the age composition of a fish population (Sebastes schlegelii) from length data by considering fish growth, length variation, proportion of age classes, and sexual dimorphism. Reasonable interpolations allowed age composition to be estimated when length data and agelength relationships were measured in different seasons. A growth curve was fitted to the mean length growth using a maximum likelihood method with an assumption of a normal distribution in length variation. Posterior probabilities were constructed with normal distributions according to Bayes’ theorem, and age composition and its confidence limits were reasonably estimated from the posterior probabilities and by bootstrap resampling. The influence of annual fluctuations of population properties was assessed by cross-validation, which was improved by updating the prior probabilities. While the new system was more robust than the agelength key for small numbers of aging data, it was impossible to improve the system by focusing on the length data alone because the correlation between the estimation error and the likelihood calculated from the length data alone was weak.
Two generations of outbreeding in coho salmon (Oncorhynchus kisutch): effects on size and growth
Authors: McClelland Erin K , Myers James M , Hard Jeffrey J , Park Linda K , Naish Kerry A
Published: November 2005

Outbreeding is a potential genetic risk in Pacific salmon (Oncorhynchus spp.) when aquaculture practices introduce nonnative domesticated fish to wild environments, making interbreeding with wild populations possible. In this study, F1 and F2 hybrid families of coho salmon (Oncorhynchus kisutch) were created using a captive freshwater aquaculture strain and a locally derived hatchery population that is integrated with naturally spawning fish. Intermediate growth was detected in F1 and F2 hybrids from crosses reared in captivity; both generations had mean weight and length values between those of the parent populations after their first year (p < 0.05). In the early life history stages, maternal effects increased alevin growth in progeny of hatchery dams relative to those of captive dams (p < 0.001). Aquaculture control families showed greater growth rates than hybrids in late summer of their 1st year and in the following spring (p < 0.05), while the hatchery controls had lower growth rates during the first summer (p < 0.05). Line cross analysis indicated that changes in additive and dominance interactions, but not unfavorable epistatic interactions, likely explain the differences in weight, length, and growth rate observed in hybrids of these stocks of coho salmon.
Invertebrates associated with residual ballast water and sediments of cargo-carrying ships entering the Great Lakes
Authors: Duggan Ian C , van Overdijk Colin DA , Bailey Sarah A , Jenkins Philip T , Limén Helene , MacIsaac Hugh J
Published: November 2005

Most ships entering the Great Lakes carry cargo and declare “no-ballast-on board” (NOBOB) status. Approximately 250 of these vessels annually load Great Lakes’ ballast water when they offload inbound cargo and then discharge this water (which has now mixed with residual water previously present in the tanks) when they load outbound cargo. This procedure potentially allows nonindigenous species present in ballast residuals to invade the Great Lakes. We collected residual sediment, water, and associated organisms from 38 NOBOB ships entering the Great Lakes. We recorded seven established Great Lakes’ nonindigenous species, including some discovered since ballast water exchange was implemented. Occurrences of species not yet invaded indicate that this vector provides further opportunity for invasion. Collectively, NOBOB vessels appear to constitute a greater risk than ballasted vessels, as they make up a greater proportion of the traffic entering the lakes (~90%), and they do not undergo ballast exchange. Invertebrates in residual water appear to have a greater opportunity for discharge than those in sediments, although most in the water fraction have already invaded this system. Invertebrate numbers in residual freshwater ballast could be dramatically lowered if these vessels flushed with open-ocean water prior to entering the Great Lakes.
Effects of crystal structure on the uptake of metals by lake trout (Salvelinus namaycush) otoliths
Authors: Melancon Sonia , Fryer Brian J , Ludsin Stuart A , Gagnon Joel E , Yang Zhaoping
Published: November 2005

This is the first study to report spectroscopic and elemental analysis of aragonite and vaterite growing simultaneously and separately in both the core and the edges of the same otolith. Our investigations focused on understanding differential trace metal uptake, including the influence of the metal itself (i.e., ionic radii), the crystalline structure, and the development state of the fish. Chemistry and crystal structure of sagittal otoliths from lake trout (Salvelinus namaycush) were studied using laser ablation combined with inductively coupled plasma mass spectrometry (LA-ICP-MS) and Raman spectroscopy, respectively. Analyses of the composition of vaterite and aragonite growing in the same growth ring show that smaller cations like Mg (0.86 Å) (1 Å = 0.1 nm) and Mn (0.81 Å) were more abundant in the vaterite hexagonal crystal structure, whereas larger cations such as Sr (1.32 Å) and Ba (1.49 Å) were preferentially incorporated in aragonite (orthorhombic). Similarly, the coprecipitation of aragonite and vaterite in cores and edges allowed us to demonstrate that the uptake rates (as determined by element-specific partition coefficients) for Sr and Ba were greater in aragonite than vaterite, whereas those of Mg and Mn were higher in vaterite than in aragonite.