bluuebunny/crossref_metadata_2025_split huggingface dataset:
Competition between young exotic invasive and native dominant plant species: implications for invasions within riparian areas
Authors: Bottollier‐Curtet Marion , Planty‐Tabacchi Anne‐Marie , Tabacchi Eric 
Published: January 2013

AbstractQuestionsThe high competitiveness of exotic invasive species has often been demonstrated, but usually with respect to native species known to have low competitive ability. Considering five exotic and five native riparian species with close characteristics regarding competitive ability, habitat and growth form, we addressed the following questions: (i) do the selected invasive plants produce more biomass than the selected native dominants under competitive pressure; and (ii) are the selected invasive species better competitors than the selected native dominants?LocationCommon garden experiment at the Henri Gaussen Botanical Garden, Toulouse, France.MethodsWe selected five native dominant species and five exotic invasive species co‐occurring along a riparian successional gradient of the middle Garonne River (SW France). Young plants of each species were planted in pots in ten intra‐ and 17 inter‐specific combinations in conditions of high water and nutrient availability. To simulate the effects of hydrological disturbance during earlier growth stages, a partial cutting of plants was applied 6 weeks after planting. We measured above‐ground and below‐ground biomass of individuals of each species after 6 mo of growth.ResultsThere were large disparities among species performances, regardless of whether the species were exotic or native. The exotic species produced more above‐ground and below‐ground biomass than the natives species for 73% of the selected species pairs. The exotic species had higher competitive ability than the native species, mainly related to the high competitive effect of I. glandulifera. The two species with the highest biomass production and competitive ability were invasive exotics, whereas the two species with the lowest were dominant natives.ConclusionsOur results predict that competition among young individuals could play a major role for the invasion success of the studied exotic species in European riparian areas.
Vegetation–environment relationships in alpine mires of the West Carpathians and the Alps
Authors: Sekulová Lucia , Hájek Michal , Syrovátka Vít 
Published: January 2013

AbstractQuestionsHow do two distant mountain ranges differ in their vegetation–environment relationships, overall species composition and its variability and species richness of vascular plants and bryophytes in alpine fens and bogs? Is the floristic difference consistent along the acidity–alkalinity gradient?LocationWest Carpathians (Poland, Slovakia) and Swiss Alps.MethodsVascular plant and bryophyte species compositions and environmental characteristics were sampled along the large acidity–alkalinity gradient within the alpine belts. PERMANOVA was used for testing floristic differences between the regions, DCA for the patterns description, CCA for testing the vegetation–environment relationships and linear models for testing the local species richness determinants. Compositional β‐diversity (rate of compositional turnover) and regional species pool were compared using PERMDISP and sample‐based rarefaction curves.ResultsMost floristic variation was explained by water pH in both regions. Macroclimate was the second most important gradient in the Alps, correlating with the second DCA axis delimiting the moderately poor brown‐moss fens from the Sphagnum bogs. The species composition differed significantly between the regions in all three pH classes, expect for bryophytes in the middle pH class. Bryophytes exhibited higher similarities between the regions, except in acidic mires. Vascular plant composition differed most in the middle pH class. The local species richness was predominantly determined by pH, except for bryophytes in the Alps. As compared to bryophytes, vascular plant local species richness was affected by more factors and showed a clear linear response to pH. Within the particular pH classes, there were few differences in local species richness, compositional β‐diversity and regional species pool between the two mountain ranges.ConclusionsThe pattern in inter‐regional floristic dissimilarities differs between bryophytes and vascular plants, probably because of better dispersal ability of bryophytes, and different causes of these dissimilarities: lower mass effect at extreme ends of the acidity–alkalinity gradient in the case of vascular plants and higher compositional β‐diversity of acidic mires in the case of bryophytes. Contrary to previously explored alpine springs of the same regions, local species richness and composition were determined rather by pH than mineral richness, and all patterns were more consistent between the regions and the taxonomic groups.
Effect of propagule pressure on recovery of aCalifornia grassland after an extreme disturbance
Authors: Larios Loralee , Aicher Rebecca J. , Suding Katharine N. 
Published: January 2013

AbstractQuestionsHow is natural regeneration of a patchy landscape affected by within‐patch species interactions and among‐patch dispersal after an extreme disturbance? Do landscape dispersal processes facilitate the invasion of native‐dominated patches by exotic species in adjacent patches?LocationIrvine Ranch Natural Landmark,Irvine,California,USA.MethodsWe monitored plant community composition in paired grassland patches that were initially dominated by native or exotic grasses at eight sites. We followed recovery of native and exotic grassland species over time, starting in a record drought year prior to an intense fire, and then for 3 yr with more typical rainfall patterns after the fire. Additionally, we compared seed rain of native and exotic species across native and exotic patches, quantifying how seed rain influenced species abundance in the following year. Multivariate and regression analyses were used to assess the potential homogenization of the landscape.ResultsFollowing the extreme drought/fire disturbance, the exotic annual grasses quickly recovered in abundance in patches that they dominated prior to the disturbance. However, the native grass,Stipa pulchra, was not able to recover in the patches it once dominated. As the exotic grasses gradually increased in the native patches, the paired patch types became more similar in composition over time. Exotic grasses produced up to 28 times more seed than the native dominant grass,Stipa; even in the patches initially dominated byStipa, exotic seed rain was equivalent or greater than the native. Seed rain was positively correlated with the following year's abundance for both exotic and native species.ConclusionsAfter an extreme disturbance, recovery of native patches can be stalled by an influx of propagules from neighbouring exotic patches. This exotic seed rain can allow the invasion of areas once dominated by natives, thus inhibiting regeneration. The matrix surrounding remnant native stands can be a critical factor in determining whether an extreme disturbance enhances native diversity vs. increasing its susceptibility to invasion.
The spatial scaling of saprotrophic fungal beta diversity in decomposing leaves
Authors: Feinstein Larry M. , Blackwood Christopher B. 
Published: January 2013

AbstractAssembly of fungal communities remains poorly understood in part because of the daunting range of spatial scales that may be involved in this process. Here, we use individual leaves as a natural sampling unit, comprising spatially distinct habitat and/or resource patches with unique histories and suites of resources. Spatial patterns in fungal beta diversity were tested for consistency with the metacommunity paradigms of species sorting and neutral dynamics. Thirty senesced leaves were collected from the forest floor (O horizon) in replicate upland forest, riparian forest and vernal pool habitats. We quantified spatial distance between leaves, and fungal community composition was assayed by terminal restriction fragment length polymorphism. Significant distance‐decay relationships were detected at all but one upland site. This is the first study where changes in fungal community composition were quantified across discrete adjacent habitat patches, providing evidence that fungal distance decay is operational at a scale of centimetres. Although leaves of differing lignin contents were sampled from each site, leaf type was not consistently important in explaining variation in fungal community composition. However, depth of a leaf within the forest floor significantly influenced community composition at five of six sites. Environmental heterogeneity associated with depth could include moisture gradients, relative influence of soil or spore colonization, and impact of forest floor biotic community (i.e. collembola and earthworms). Because the influence of spatial distance and depth on fungal community composition could not be disentangled, both species‐sorting and neutral processes may be embedded within the distance‐decay relationships that we found.
Interannual variation in effective number of breeders and estimation of effective population size in long‐lived iteroparous lake sturgeon (Acipenser fulvescens)
Authors: Duong Thuy Yen , Scribner Kim T. , Forsythe Patrick S. , Crossman James A. , Baker Edward A. 
Published: January 2013

AbstractQuantifying interannual variation in effective adult breeding number (Nb) and relationships between Nb, effective population size (Ne), adult census size (N) and population demographic characteristics are important to predict genetic changes in populations of conservation concern. Such relationships are rarely available for long‐lived iteroparous species like lake sturgeon (Acipenser fulvescens). We estimated annual Nb and generational Ne using genotypes from 12 microsatellite loci for lake sturgeon adults (n = 796) captured during ten spawning seasons and offspring (n = 3925) collected during larval dispersal in a closed population over 8 years. Inbreeding and variance Nb estimated using mean and variance in individual reproductive success derived from genetically identified parentage and using linkage disequilibrium (LD) were similar within and among years (interannual range of Nb across estimators: 41–205). Variance in reproductive success and unequal sex ratios reduced Nb relative to N on average 36.8% and 16.3%, respectively. Interannual variation in Nb/N ratios (0.27–0.86) resulted from stable N and low standardized variance in reproductive success due to high proportions of adults breeding and the species' polygamous mating system, despite a 40‐fold difference in annual larval production across years (437–16 417). Results indicated environmental conditions and features of the species' reproductive ecology interact to affect demographic parameters and Nb/N. Estimates of Ne based on three single‐sample estimators, including LD, approximate Bayesian computation and sibship assignment, were similar to annual estimates of Nb. Findings have important implications concerning applications of genetic monitoring in conservation planning for lake sturgeon and other species with similar life histories and mating systems.
Rangewide landscape genetics of an endemic Pacific northwestern salamander
Authors: Trumbo Daryl R. , Spear Stephen F. , Baumsteiger Jason , Storfer Andrew 
Published: January 2013

AbstractA species' genetic structure often varies in response to ecological and landscape processes that differ throughout the species' geographic range, yet landscape genetics studies are rarely spatially replicated. The Cope's giant salamander (Dicamptodon copei) is a neotenic, dispersal‐limited amphibian with a restricted geographic range in the Pacific northwestern USA. We investigated which landscape factors affect D. copei gene flow in three regions spanning the species' range, which vary in climate, landcover and degree of anthropogenic disturbance. Least cost paths and Circuitscape resistance analyses revealed that gene flow patterns vary across the species' range, with unique combinations of landscape variables affecting gene flow in different regions. Populations in the northern coastal portions of the range had relatively high gene flow, largely facilitated by stream and river networks. Near the southeastern edge of the species' range, gene flow was more restricted overall, with relatively less facilitation by streams and more limitation by heat load index and fragmented forest cover. These results suggested that the landscape is more difficult for individuals to disperse through at the southeastern edge of the species' range, with terrestrial habitat desiccation factors becoming more limiting to gene flow. We suggest that caution be used when attempting to extrapolate landscape genetic models and conservation measures from one portion of a species' range to another.
One quantitative trait locus for intra‐ and interspecific variation in a sex pheromone
Authors: Groot A. T. , Staudacher H. , Barthel A. , Inglis O. , Schöfl G. , Santangelo R. G. , Gebauer‐Jung S. , Vogel H. , Emerson J. , Schal C. , Heckel D. G. , Gould F. 
Published: January 2013

AbstractEven though premating isolation is hypothesized to be a major driving force in speciation, its genetic basis is poorly known. In the noctuid moth Heliothis subflexa, one group of sex pheromone components, the acetates, emitted by the female, plays a crucial isolating role in preventing interspecific matings to males of the closely related Heliothis virescens, in which females do not produce acetates and males are repelled by them. We previously found intraspecific variation in acetates in H. subflexa: females in eastern North America contain significantly more acetates than females in Western Mexico. Here we describe the persistence of this intraspecific variation in laboratory‐reared strains and the identification of one major quantitative trait locus (QTL), explaining 40% of the variance in acetate amounts. We homologized this intraspecific QTL to our previously identified interspecific QTL using restriction‐associated DNA (RAD) tags. We found that a major intraspecific QTL overlaps with one of the two major interspecific QTL. To identify candidate genes underlying the acetate variation, we investigated a number of gene families with known or suspected acetyl‐ or acyltransferase activity. The most likely candidate genes did not map to our QTL, so that we currently hypothesize that a transcription factor underlies this QTL. Finding a single, large QTL that impacts variation in pheromone blends between and within species is, to our knowledge, the first such example for traits that have been demonstrated to affect premating isolation.
Has the inbreeding load for a condition‐dependent sexual signalling trait been purged in insular lizard populations?
Authors: Runemark Anna , Hansson Bengt , Ljungqvist Marcus , Brydegaard Mikkel , Svensson Erik I. 
Published: January 2013

AbstractSexually selected traits are often condition‐dependent and are expected to be affected by genome‐wide distributed deleterious mutations and inbreeding. However, sexual selection is a powerful selective force that can counteract inbreeding through purging of deleterious mutations. Inbreeding and purging of the inbreeding load for sexually selected traits has rarely been studied across natural populations with different degrees of inbreeding. Here we investigate inbreeding effects (measured as marker‐based heterozygosity) on condition‐dependent sexually selected signalling trait and other morphological traits across islet‐ and mainland populations (n = 15) of an endemic lizard species (Podarcis gaigeae). Our data suggest inbreeding depression on a condition‐dependent sexually selected signalling character among mainland subpopulations with low or intermediate levels of inbreeding, but no sign of inbreeding depression among small and isolated islet populations despite their higher overall inbreeding levels. In contrast, there was no such pattern among ten other morphological traits which are primarily naturally selected and presumably not involved in sexual signalling. These results are in line with purging of recessive deleterious alleles, or purging in combination with stochastic fixation of alleles by genetic drift, for a sexual signalling character in the islet environment, which is characterized by low population sizes and strong sexual selection. Higher clutch sizes in islet populations also raise interesting questions regarding the possibility of antagonistic pleiotropy. Purging and other non‐exclusive explanations of our results are discussed.
Are long‐lived trees poised for evolutionary change? Single locus effects in the evolution of gene expression networks in spruce
Authors: Verta Jukka‐Pekka , Landry Christian R. , MacKay John J. 
Published: January 2013

AbstractGenetic variation in gene expression traits contributes to phenotypic diversity and may facilitate adaptation following environmental change. This is especially important in long‐lived organisms where adaptation to rapid changes in the environment must rely on standing variation within populations. However, the extent of expression variation in most wild species remains to be investigated. We address this question by measuring the segregation of expression levels in white spruce [Picea glauca (Moench), Voss] in a transcriptome‐wide manner and examining the underlying evolutionary and biological processes. We applied a novel approach for the genetic analysis of expression variation by measuring its segregation in haploid meiotic seed tissue. We identified over 800 transcripts whose abundances are most likely controlled by variants in single loci. Cosegregation analysis of allelic expression levels was used to construct regulatory associations between genes and define regulatory networks. The majority (67%) of segregating transcripts were under linkage. Regulatory associations were typically among small groups of genes (2–3 transcripts), indicating that most segregating expression levels can evolve independently from one another. One notable exception was a large putative trans effect that altered the expression of 180 genes that includes key regulators of protein metabolism, highlighting a regulatory cascade affected by variation in a single locus in this conserved metabolic pathway. Overall, segregating expression variation was associated with stress response‐ and duplicated genes, whose evolution may be linked to functional innovations. These observations indicate that expression variation might be important in facilitating diversity of molecular responses to environmental stresses in wild trees.
Co‐Delivery of G‐CSF and EPO Released From Fibrin Gel for Therapeutic Neovascularization in Rat Hindlimb Ischemia Model
Authors: Chen Feng , Liu Qi , Zhang Zhen D. , Zhu Xian H. 
Published: January 2013

AbstractObjectiveG‐CSF and EPO have shown a notable capability in neovascularization. However, their use is limited because of untoward leucocytosis, erythrogenesis, and short half‐life in the plasma. Herein, we examined whether G‐CSF and EPO released from fibrin gel injected into ischemic tissues would synergistically promote neovascularization with limited systematic effects in a rat hindlimb ischemic model.Methods and ResultsIn vivo study, group Gel received an intramuscular injection of fibrin gel; group Gel+G‐CSF received fibrin gel containing human G‐CSF; group Gel+EPO received fibrin gel containing human EPO; group Gel+G‐CSF&EPO received fibrin gel containing G‐CSF and EPO; group G‐CSF&EPO received G‐CSF and EPO. Through promoting the expression of SDF‐1, local high concentration of EPO could traffic CXCR4+ cells mobilized by G‐CSF to enhance neovascularization in ischemic muscle. The treatment with Gel+G‐CSF&EPO was superior to the other treatments on blood flow reperfusion, capillary density, and α smooth muscle actin‐positive vessel density. And this treatment induced a modest WBC count increase in peripheral blood.ConclusionsG‐CSF and EPO released from fibrin gel had a combined effect on postischemia neovascularization. This treatment may be a novel therapeutic modality for ischemic peripheral artery disease.
GMM Estimation with Non‐causal Instruments under Rational Expectations*
Authors: Lof Matthijs 
Published: January 2013

AbstractLanne and Saikkonen [Oxford Bulletin of Economics and Statistics (2011a) Vol. 73, pp. 581–592], show that the generalized method of moments (GMM) estimator is inconsistent, when the instruments are lags of variables that admit a non‐causal autoregressive representation. This article argues that this inconsistency depends on distributional assumptions, that do not always hold. In particular under rational expectations, the GMM estimator is found to be consistent. This result is derived in a linear context and illustrated by simulation of a nonlinear asset pricing model.
Local Asymptotic Power of Breitung's Test*
Authors: Hosseinkouchack Mehdi 
Published: January 2013

AbstractIn this article, we derive the local asymptotic power function of the unit root test proposed by Breitung [Journal of Econometrics (2002) Vol. 108, pp. 343–363]. Breitung's test is a non‐parametric test and is free of nuisance parameters. We compare the local power curve of the Breitungs’ test with that of the Dickey–Fuller test. This comparison is in fact a quantification of the loss of power that one has to accept when applying a non‐parametric test.
Phytophthora diversity and the population structure of Phytophthora ramorum in Swiss ornamental nurseries
Authors: Prospero S. , Vercauteren A. , Heungens K. , Belbahri L. , Rigling D. 
Published: January 2013

Invasive oomycete pathogens have been causing significant damage to native ecosystems worldwide for over a century. A recent well‐known example is Phytophthora ramorum, the causal agent of sudden oak death, which emerged in the 1990s in Europe and North America. In Europe, this pathogen is mainly restricted to woody ornamentals in nurseries and public greens, while severe outbreaks in the wild have only been reported in the UK. This study presents the results of the P. ramorum survey conducted in Swiss nurseries between 2003 and 2011. In all 120 nurseries subjected to the plant passport system, the main P. ramorum hosts were visually checked for above ground infections. Phytophthora species were isolated from tissue showing symptoms and identified on the basis of the morphological features of the cultures and sequencing of the ribosomal ITS region. Phytophthora was detected on 125 plants (66 Viburnum, 58 Rhododendron and one Pieris). Phytophthora ramorum was the most frequent species (59·2% of the plants), followed by P. plurivora, P. cactorum, P. citrophthora, P. cinnamomi, P. cactorum/P. hedraiandra, P. multivora and P. taxon PgChlamydo. The highest incidence of P. ramorum was observed on Viburnum × bodnantense. Microsatellite genotyping showed that the Swiss P. ramorum population is highly clonal and consists of seven genotypes (five previously reported in Europe, two new), all belonging to the European EU1 clonal lineage. It can therefore be assumed that P. ramorum entered Switzerland through nursery trade. Despite sanitation measures, repeated P. ramorum infections have been recorded in seven nurseries, suggesting either reintroduction or unsuccessful eradication efforts.