bluuebunny/crossref_metadata_2025_split huggingface dataset:
The relative influence of natural selection and geography on gene flow in guppies
Authors: CRISPO ERIKA , BENTZEN PAUL , REZNICK DAVID N. , KINNISON MICHAEL T. , HENDRY ANDREW P. 
Published: December 2005

AbstractTwo general processes may influence gene flow among populations. One involves divergent selection, wherein the maladaptation of immigrants and hybrids impedes gene flow between ecological environments (i.e. ecological speciation). The other involves geographic features that limit dispersal. We determined the relative influence of these two processes in natural populations of Trinidadian guppies (Poecilia reticulata). If selection is important, gene flow should be reduced between different selective environments. If geography is important, gene flow should be impeded by geographic distance and physical barriers. We examined how genetic divergence, long‐term gene flow, and contemporary dispersal within a watershed were influenced by waterfalls, geographic distance, predation, and habitat features. We found that waterfalls and geographic distance increased genetic divergence and reduced dispersal and long‐term gene flow. Differences in predation or habitat features did not influence genetic divergence or gene flow. In contrast, differences in predation did appear to reduce contemporary dispersal. We suggest that the standard predictions of ecological speciation may be heavily nuanced by the mating behaviour and life history strategies of guppies.
Hybrid origin and differentiation of two tetraploidAchilleaspecies in East Asia: molecular, morphological and ecogeographical evidence
Authors: GUO Y.‐P. , VOGL C. , VAN LOO M. , EHRENDORFER F. 
Published: December 2005

AbstractAchillea(Asteraceae‐Anthemideae) offers classical models for speciation by hybridization and polyploidy. Here, we test the suspected allotetraploid origin of two species,Achillea alpinaandAchillea wilsonianabetween phylogenetically distinct lineages in East Asia. A total of 421 AFLP bands from 169 individuals and 19 populations of five 2x‐ and two 4x‐species were obtained. The data set was analysed with a newly developed model that accounts for polyploidy and assumes lack of recombination between the parental chromosome sets (i.e. disomic inheritance).A.alpinaandA.wilsonianathen appear to be allotetraploids betweenAchillea acuminata‐2x (sect.Ptarmica) andAchillea asiatica‐2x (sect.Achillea). The two 4x‐species share 44% and 48% of their AFLP bands withA.acuminata‐2x, and 39% and 38% withA.asiatica‐2x, respectively. Eight plastid haplotypes (A–H) were detected by polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP) analyses.A.alpina‐4x andA. wilsoniana‐4x share haplotype F only withA. asiatica‐2x. This is consistent with the hybrid origin(s) involving the latter as the maternal ancestor. This result corroborates our previous DNA sequence data, whereA. alpina‐4x andA. wilsoniana‐4x are also placed close toA. asiatica‐2x. Morphology, ecology, and amplified fragment length polymorphism (AFLP) profiles of the two 2x‐species are distinct, whereas the two 4x‐species, grouped asA.alpinaaggregate,form a nearly continuous link between them. Considering all evidence, this 4x‐aggregate is regarded as the product of a hybridization between genetically distant 2x‐ancestors limited to China and adjacent areas: oneA.acuminata‐like, and the otherA. asiatica‐like. The allopolyploidA.alpinaagg. exhibits considerable morphological variation and ecological flexibility, and has expanded throughout eastern Asia and to northern North America, far beyond the ranges of their presumed 2x‐ancestors.
Matching the origin of an invasive weed for selection of a herbivore haplotype for a biological control programme
Authors: GOOLSBY JOHN A. , DE BARRO PAUL J. , MAKINSON JEFFREY R. , PEMBERTON ROBERT W. , HARTLEY DIANA M. , FROHLICH DONALD R. 
Published: December 2005

AbstractThe Florida Everglades have been invaded by an exotic weed fern, Lygodium microphyllum. Across its native distribution in the Old World tropics from Africa to Australasia it was found to have multiple location‐specific haplotypes. Within this distribution, the climbing fern is attacked by a phytophagous mite, Floracarus perrepae, also with multiple haplotypes. The genetic relationship between mite and fern haplotypes was matched by an overarching geographical relationship between the two. Further, mites that occur in the same location as a particular fern haplotype were better able to utilize the fern than mites from more distant locations. From a biological control context, we are able to show that the weed fern in the Everglades most likely originated in northern Queensland, Australia/Papua New Guinea and that the mite from northern Queensland offers the greatest prospect for control.
Beringian origins and cryptic speciation events in the fly agaric (Amanita muscaria)
Authors: GEML J. , LAURSEN G. A. , O'NEILL K. , NUSBAUM H. C. , TAYLOR D. L. 
Published: December 2005

Abstract Amanita muscaria sensu lato has a wide geographic distribution, occurring in Europe, Asia, Africa, Australia, New Zealand, and North, Central and South America. Previous phylogenetic work by others indicates three geographic clades (i.e. ‘Eurasian’, ‘Eurasian‐alpine’ and ‘North American’ groups) within A. muscaria. However, the historical dispersal patterns of A. muscaria remained unclear. In our project, we collected specimens from arctic, boreal and humid temperate regions in Alaska, and generated DNA sequence data from the protein‐coding beta‐tubulin gene and the internal transcribed spacer (ITS) and large subunit (LSU) regions of the ribosomal DNA repeat. Homologous sequences from additional A. muscaria isolates were downloaded from GenBank. We conducted phylogenetic and nested clade analyses (NCA) to reveal the phylogeographic history of the species complex. Although phylogenetic analyses confirmed the existence of the three above‐mentioned clades, representatives of all three groups were found to occur sympatrically in Alaska, suggesting that they represent cryptic phylogenetic species with partially overlapping geographic distributions rather than being allopatric populations. All phylogenetic species share at least two morphological varieties with other species, suggesting ancestral polymorphism in pileus and wart colour pre‐dating their speciations. The ancestral population of A. muscaria likely evolved in the Siberian–Beringian region and underwent fragmentation as inferred from NCA and the coalescent analyses. The data suggest that these populations later evolved into species, expanded their range in North America and Eurasia. In addition to range expansions, populations of all three species remained in Beringia and adapted to the cooling climate.
Circumnutation of rice coleoptiles: its relationships with gravitropism and absence in lazy mutants
Authors: YOSHIHARA TAKESHI , IINO MORITOSHI 
Published: December 2005

ABSTRACTAlthough circumnutation occurs widely in higher plants, its mechanism is little understood. The idea that circumnutation is based on gravitropism has long been investigated, but the reported results have been controversial. We used dark‐grown coleoptiles of rice (Oryza sativa L.) to re‐investigate this issue. The following results supported the existence of a close relationship between gravitropism and circumnutation: (1) circumnutation disappears on a horizontal clinostat; (2) circumnutation is interrupted by a gravitropic response and re‐initiated at a definable phase after gravitropic curvature; (3) circumnutation can be re‐established by submergence and a brief gravitropic stimulation in the coleoptiles that have stopped nutating in response to red light; and (4) lazy mutants show no circumnutation. In spite of these results, however, there were cases in which gravitropism and circumnutation could be separated. Firstly, the non‐circumnutating lazy coleoptile showed nearly a wild‐type level of gravitropic responsiveness in its upper half, although this part was an active site of both gravitropism and circumnutation in wild‐type coleoptiles. Secondly, coleoptiles could nutate without overshooting the vertical when developing phototropic curvature. It is concluded that gravitropism influences, but it is not directly involved in the process of circumnutation. It is further suggested that a gravity signal, shared with gravitropism, contributes to the maintenance of circumnutation.
Effects of chronic ozone exposure on gene expression in Arabidopsis thaliana ecotypes and in Thellungiella halophila
Authors: LI PINGHUA , MANE SHRINIVASRAO P. , SIOSON ALLAN A. , ROBINET CECILIA VASQUEZ , HEATH LENWOOD S. , BOHNERT HANS J. , GRENE RUTH. 
Published: December 2005

ABSTRACT Arabidopsis thaliana (At) ecotypes Columbia‐0 (Col‐0), Wassilewskija (WS), Cape Verde Islands (Cvi‐0) and a relative, Thellungiella halophila (Th), were exposed to 20–25% over ambient ozone [O3] in a free air concentration enrichment (FACE) experiment (http://www.soyFACE.uiuc.edu), mirroring increases expected in the near future. Col‐0 and WS accelerated development and developed lesions within 10 d under increased ozone, while Cvi‐0 and Th grew slowly. RNAs were used in microarray hybridizations (Col‐0‐based 26 000 elements, 70‐mer oligonucleotides). A two‐step analysis of variance (anova) model, including comparison with values obtained under [O3], was used for analyses. WS showed the greatest number of changes in gene expression in response to ozone. Th showed the least changes, suggesting that its expression state at [O3] was sufficient for resistance at increased ozone. Patterns observed in ambient air controls for Cvi‐0 and Col‐0 were most similar, while Th showed the greatest number of differences compared with the other controls. Compared with Col‐0, however, Cvi‐0 showed higher levels of expression of chaperones, receptor kinase‐like and photosynthesis‐related genes in ambient air. Cvi‐0 exhibited ozone‐mediated changes in a pathway involving AtSR, a homologue of the mammalian NFκB family of redox‐sensitive transcription factors, changes in chaperones, WRKY and C2H2 proteins and antioxidants. WS displayed ozone‐mediated decreases in the expression of two AtSR/NFκB family members, C2‐domain proteins and genes associated with cell wall growth and changes in the expression of marker genes for programmed cell death (PCD), among them RCD1, a key regulator in this pathway. Microarray data were verified by reverse transcriptase (RT)‐PCR. We relate O3‐response diversity across the four lines to different responses among signaling and transcriptional response networks and differences in gene expression at [O3] levels.
Cysteines 449 and 459 modulate the reduction–oxidation conformational changes of ribulose 1·5‐bisphosphate carboxylase/oxygenase and the translocation of the enzyme to membranes during stress
Authors: MARÍN‐NAVARRO JULIA , MORENO JOAQUÍN 
Published: December 2005

ABSTRACTThe role of cysteines 449 (Cys449) and 459 (Cys459) from the large subunit (LS) of ribulose 1·5‐bisphosphate carboxylase/oxygenase (Rubisco) in the reduction–oxidation (redox) regulation of the enzyme was assessed by site‐directed mutagenesis of these residues and chloroplast transformation of Chlamydomonas reinhardtii. In vitro studies indicated that mutations C449S, C459S or C449S/C459S do not affect the activity and proteolytic susceptibility of the enzyme in the reduced state. However, when oxidized, the mutant enzymes differed from the wild type (WT), showing an increased resistance to inactivation and, in the case of the double mutant (DM), an altered structural conformation as reflected by the kinetics of proteolysis with subtilisin. The response of the DM strain to saline stress revealed that the absence of Cys449 and Cys459 intensifies Rubisco degradation and the covalent disulfide and non‐disulfide polymerization of the enzyme in vivo. Saline stress also induced Rubisco translocation to a membrane (M) fraction that contained only covalently polymerized enzyme. Rubisco mobilization to this M fraction was enhanced also in the DM strain. Altogether, these results indicate that Cys449 and Cys459 participate in the modulation of the conformational changes promoted by oxidative modifications retarding processes related to the catabolism of the enzyme in vivo.
Relationships of disease and leaf area variables with yield in the Alternaria helianthi–sunflower pathosystem
Authors: Leite R. M. V. B. C. , Amorim L. , Bergamin Filho A. 
Published: December 2005

Three field experiments were carried out in 1997/1998, 1998/1999 and 1999/2000 to investigate the relationship between severity (S) of alternaria leaf spot, caused by Alternaria helianthi, area under disease progress curve (AUDPC), healthy leaf area index at any given day (HLAI), healthy leaf area duration (HAD), radiation intercepted by healthy leaf area at any given day (HRI), total healthy leaf area absorption (HAA), and yield components of sunflower sown on four dates. AUDPC showed a relationship with yield in two years, following the negative exponential model coefficient of determination (R2 = 0·79 and 0·60). The HAD–yield relationship was linear for each of three trials (0·73 < R2 < 0·83). Among the integral variables analysed, the HAA–yield relationship was the best, fitted by the exponential model (0·77 < R2 < 0·89). Single‐point models using disease severity, HLAI and HRI to estimate yield at various times during the crop season were tested. The slope of the severity–yield relationship was stable from the R1 (inflorescence visible) growth stage. The HLAI–yield relationship was stable between R1 and R6 (anthesis completed) and increased from the R7 (first phase of achene development) stage. The HRI–yield relationship was variable and not stable. The relationship between severity and yield in the R3 (second phase of inflorescence elongation) growth stage proved that plants with disease severity higher than 10% had yield lower than 500 kg ha−1, regardless of the sowing date. This value can be used as a damage threshold for the disease. Disease severity can be used as an independent variable in a sunflower–alternaria leaf spot management system and can be used to produce recommendations at the research level, such as genetic breeding for disease resistance or studies on sowing date.
Biological control of fusarium crown and root rot of tomato with antagonistic bacteria and integrated control when combined with the fungicide carbendazim
Authors: Omar I. , O'Neill T. M. , Rossall S. 
Published: December 2005

Two bacterial isolates, Bacillus megaterium (c96) and Burkholderia cepacia (c91), demonstrated to be antagonistic against Fusarium oxysporum f.sp. radicis‐lycopersici, the causal organism of fusarium crown and root rot of tomato, were evaluated as biocontrol agents alone and when integrated with the fungicide carbendazim. In an initial screening, these isolates reduced disease incidence by 75 and 88%, respectively. In vitro, both biocontrol agents were highly tolerant to the fungicide carbendazim, commonly used to control fusarium diseases. Carbendazim reduced disease symptoms by over 50% when used at > 50 µg mL−1, but had little effect at lower concentrations. Combination of the bacterial isolates and carbendazim gave significant (P ≤ 0·05) control of the disease when plants were artificially inoculated with the pathogen. Application of carbendazim at a low concentration (1 µg mL−1) in combination with B. cepacia c91 reduced disease symptoms by 46%, compared with a reduction of 20% obtained with the bacterium alone and no control with the chemical treatment alone. A combination of B. megaterium c96 with an increased application rate of 10 µg mL−1 carbendazim significantly reduced disease symptoms by 84% compared with inoculated controls and by 77% compared with carbendazim treatment alone. In this experiment, the integrated treatment also slightly outperformed application of 100 µg mL−1 carbendazim, and bacteria applied without fungicide also provided good disease control.
Assessing mango anthracnose using a new three‐dimensional image‐analysis technique to quantify lesions on fruit
Authors: Corkidi G. , Balderas‐Ruíz K. A. , Taboada B. , Serrano‐Carreón L. , Galindo E. 
Published: December 2005

An accurate image‐analysis method was developed to assess quantitatively the spot‐like lesions on fruits resulting from pathogen attack. The technique was applied to evaluation of the development and severity of anthracnose of mango fruit, caused by the fungus Colletotrichum gloeosporioides. In this method, a stepper motor rotates the mango fruit along its longitudinal axis while acquiring a sequence of 360 images of its total surface (one image for each degree). This set of images is used to create a pseudocylindrical ‘equal‐area’ projection of the fruit in a two‐dimensional map containing complete morphometrical and photometrical information of its surface. The lesion area can easily be evaluated from this map with image‐analysis procedures. Quantitative data (percentage of area affected) can be used to establish an assessment scale for the disease based on lesion spots measured, as well as for detailed laboratory studies of mango anthracnose development. The average error of the method is −0·1%, standard deviation 0·44 (r2 = 0·99), and it may be adapted for use with most commercial image analysers and for other diseases with spot‐like symptoms.
Trapping of sustained turbidity currents by intraslope minibasins
Authors: LAMB MICHAEL P. , TONIOLO HORACIO , PARKER GARY 
Published: December 2005

AbstractDepositional turbidity currents have filled many intraslope minibasins with sediment creating targets for petroleum exploration. The dynamics of sustained turbidity currents and their depositional characteristics are investigated in a scaled physical model of a minibasin. Each turbidity current deposited a downstream thinning wedge of sediment near the inlet. Farther downstream the turbidity current was ponded by a barrier. The ponded part of the turbidity current was separated from the sediment‐free water above by a relatively sharp, horizontal settling interface indicating highly Froude‐subcritical flow. The very slow moving flow within the ponded zone created conditions for the passive rainout of suspended sediment onto the bed. In the lower part of the ponded zone, the concentration and mean grain‐size of the sediment in suspension tended to be relatively uniform in both the vertical and streamwise directions. As a result, the deposit emplaced in the ponded zone showed only a weak tendency toward downstream fining and was passively draped over the bed in such a way that irregularities in the inerodible bed were accurately reflected. The discharge of suspended sediment overflowing the downstream end of the minibasin was significantly less than the inflow discharge, resulting in basin sediment trapping efficiencies >95%. A simple model is developed to predict the trapping of sediment within the basin based on the relative magnitudes of the input discharge of turbid water and the detrainment discharge of water across the settling interface. This model shows a limiting case in which an intraslope basin captures 100% of the sediment from a ponded turbidity current, even through a succession of sustained flow events, until sediment deposition raises the settling interface above the downstream lip of the minibasin. This same process defines one of the mechanisms for minibasin filling in nature, and, when this mechanism is operative, the trap efficiency of sediment can be expected to be high until the minibasin is substantially filled with sediment.
Formation of subglacial till under transient bed conditions: deposition, deformation, and basal decoupling under a Weichselian ice sheet lobe, central Poland
Authors: PIOTROWSKI J. A. , LARSEN N. K. , MENZIES J. , WYSOTA W. 
Published: December 2005

AbstractA multi‐proxy approach involving a study of sediment architecture, grain size, grain roundness and crushing index, petrographic and clay mineral composition, till fabric and till micromorphology was applied to infer processes of till formation and deformation under a Weichselian ice sheet at Kurzetnik, Poland. The succession consists of three superposed till units overlying outwash sediments deformed at the top. The textural characteristics of tills vary little throughout the till thickness, whereas structural appearance is diversified including massive and bedded regions. Indicators of intergranular bed deformation include overturned, attenuated folds, boudinage structures, a sediment‐mixing zone, grain crushing, microstructural lineations, grain stacking and high fabric strength. Lodgement proxies are grooved intra‐till surfaces, ploughing marks and consistently striated clast surfaces. Basal decoupling by pressurized meltwater is indicated by undisturbed sand stringers, sand‐filled meltwater scours under pebbles and partly armoured till pellets. It is suggested that the till experienced multiple transitions between lodgement, deformation and basal decoupling. Cumulative strain was high, but the depth of (time‐transgressive) deformation much lower (centimetre range) than the entire till thickness (ca 2 m) at any point in time, consistent with the deforming bed mosaic model. Throughout most of ice overriding, porewater pressure was high, in the vicinity of glacier floatation pressure indicating that the substratum, consisting of 11 m thick sand, was unable to drain subglacial meltwater sufficiently.
An evaluation of a GARP model as an approach to predicting the spatial distribution of non‐vagile invertebrate species
Authors: Stockman Amy K. , Beamer David A. , Bond Jason E. 
Published: December 2005

ABSTRACTOne of the primary goals of any systematic, taxonomic or biodiversity study is the characterization of species distributions. While museum collection data are important for ascertaining distributional ranges, they are often biased or incomplete. The Genetic Algorithm for Rule‐set Prediction (GARP) is an ecological niche modelling method based on a genetic algorithm that has been argued to provide an accurate assessment of the spatial distribution of organisms that have dispersal capabilities. The primary objective of this study is to evaluate the accuracy of a GARP model to predict the spatial distribution of a non‐invasive, non‐vagile invertebrate whose full distributional range was unknown. A GARP predictive model based on seven environmental parameters and 42 locations known from historical museum records for species of the trapdoor spider genus Promyrmekiaphila was produced and subsequently used as a guide for ground truthing the model. The GARP model was neither a significant nor an accurate predictor of spider localities and was outperformed by more simplistic BIOCLIM and GLM models. The isolated nature of Promyrmekiaphila populations mandates that environmental layers and their respective resolutions are carefully chosen for model production. Our results strongly indicate that, for modelling the spatial distribution of low vagility organisms, one should employ a modelling method whose results are more conducive to interpretation than models produced by a ‘black box’ algorithm such as GARP.