bluuebunny/crossref_metadata_2025 huggingface dataset:
Assembly of zooplankton communities in newly created ponds
Authors: LOUETTE GERALD , DE MEESTER LUC , DECLERCK STEVEN
Published: July 2008

1. The creation or severe disturbance of habitat patches is generally followed by a phase of community (re)assembly. After such an event, the trajectory of community assembly in habitat patches may be highly variable because of stochasticity during the dispersal and colonization process. Conversely, assembly patterns may also be deterministic if communities are shaped by prevalent environmental conditions in the habitat patches (species sorting), or by systematic differences in the dispersal capacities of species.

2. In this study, we investigated the pattern of community assembly of zooplankton species in 25 newly created ponds at 13 different sites in Flanders (Belgium). Over a period of three consecutive years, we assessed at what rate and with what frequency species of the regional species pool colonized the newly created ponds. We also studied the development of community structure over time and tested whether the dynamics were consistent across different ponds at the different locations. In addition, we characterized the dynamics of metacommunity features, such as alpha, beta and gamma diversity in clusters of ponds.

3. Even within the first year after their creation, the new ponds were rapidly colonized by a small subset of species from the regional species pool (Daphnia obtusa, Chydorus sphaericus and Simocephalus vetulus). These species dominated the cladoceran assemblages during the subsequent years. Other species in the regional species pools were only sporadically able to colonize ponds.

4. During the entire study period, we observed no significant shifts in species lists or in the occurrences of species among years. The low incidence of the majority of species may be the result of dispersal limitation or the failure of immigrants to establish due to priority effects exerted by the first colonizers. There was, nevertheless, a consistent change in the relative abundance of species, which was most probably mediated by differences in the hatching time among species influencing species composition in the first year.

5. In contrast to expectations, we observed no increase in average alpha diversity (local species richness) and gamma diversity (total richness of entire pond clusters) during the course of the study period. Beta diversity was relatively low from the beginning and remained constant throughout the study period. These deterministic patterns can mainly be attributed to the dominance of the three first colonizing species and the low success rate of other species in colonizing the ponds.
Dispersal of freshwater invertebrates by large terrestrial mammals: a case study with wild boar (Sus scrofa) in Mediterranean wetlands
Authors: VANSCHOENWINKEL BRAM , WATERKEYN ALINE , VANDECAETSBEEK TIM , PINEAU OLIVIER , GRILLAS PATRICK , BRENDONCK LUC
Published: July 2008

1. Many invertebrates inhabiting insular aquatic habitats rely on external agents or vectors to disperse. Besides water connections and wind, waterfowl and amphibians are known to mediate passive dispersal of freshwater invertebrates. However, the possibility of dispersal by terrestrial mammals has been largely overlooked.

2. We investigated the potential of both external and internal zoochorous dispersal of aquatic invertebrates by the wild boar (Sus scrofa) in Mediterranean wetlands in the Camargue (France). As wild boar frequently visit wetlands for feeding and wallowing purposes, we hypothesized that they may be important passive dispersal vectors of aquatic invertebrates at a local scale. Dried mud was collected from selected ‘rubbing trees’ used by boars to dispose of parasites. Additionally, faecal pellets were collected from different locations in the wetland area.

3. Seventeen freshwater invertebrate taxa including rotifers, cladocerans, copepods and ostracods hatched from sediment obtained from ‘rubbing trees’, while invertebrates hatching from dried faeces (10 taxa) were mainly rotifers. Dispersing invertebrates were collected up to 318 m from a nearest potential dispersal source. Both abundance and richness of invertebrates significantly decreased with dispersal distance.

4. Our results demonstrate that large mammals such as wild boar can act as dispersal vectors of aquatic invertebrates at a local scale in the wetland area of the Camargue and suggest that external transport may be quantitatively more important than internal transport. As wallowing (mud bathing) is common in many terrestrial mammals, this mode of dispersal may be quite widespread.
Feeding rates, assimilation efficiencies and growth of two amphipod species on biodeposited material from zebra mussels
Authors: GERGS RENÉ , ROTHHAUPT K.‐O.
Published: July 2008

1. Accumulation of organic material by the zebra mussel Dreissena polymorpha is assumed to be the source of a biodeposition‐based food web. However, only little is known about the importance of the biodeposited material as a food source and its contribution to increased abundances of macroinvertebrates in the presence of D. polymorpha.

2. Feeding, assimilation and growth of the amphipods Gammarus roeselii and Dikerogammarus villosus on food sources directly and indirectly associated with D. polymorpha (biodeposited material and chironomids) and on conditioned alder leaves were measured. The stoichiometry of carbon, nitrogen and phosphorus of the diets was measured as an important determining factor of food quality.

3. Chironomids had the highest nitrogen and phosphorus contents, alder leaves were depleted in nitrogen and phosphorus, and the stoichiometry of biodeposited material was intermediate.

4. Both amphipod species had highest feeding rates and assimilation efficiencies on chironomids. Gammarus roeselii fed more on biodeposited material than on alder leaves, but assimilation efficiencies were similar; D. villosus also had similar feeding rates and assimilation efficiencies on the two diets.

5. Both amphipod species had highest growth rates on chironomids and lowest growth rates on alder leaves. Both grew at intermediate rates on biodeposited material of D. polymorpha. The growth rates of the amphipod species were related to food stoichiometry. Overall, the invasive D. villosus grew faster than the indigenous G. roeselii.

6. Food resources directly and indirectly associated with D. polymorpha are potential diets for amphipods, providing further evidence for a D. polymorpha biodeposition‐based food web.
Simple three‐pool model accurately describes patterns of long‐term litter decomposition in diverse climates
Authors: ADAIR E. CAROL , PARTON WILLIAM J. , DEL GROSSO STEVEN J. , SILVER WHENDEE L. , HARMON MARK E. , HALL SONIA A. , BURKE INGRID C. , HART STEPHEN C.
Published: July 2008

As atmospheric CO2increases, ecosystem carbon sequestration will largely depend on how global changes in climate will alter the balance between net primary production and decomposition. The response of primary production to climatic change has been examined using well‐validated mechanistic models, but the same is not true for decomposition, a primary source of atmospheric CO2. We used the Long‐term Intersite Decomposition Experiment Team (LIDET) dataset and model‐selection techniques to choose and parameterize a model that describes global patterns of litter decomposition. Mass loss was best represented by a three‐pool negative exponential model, with a rapidly decomposing labile pool, an intermediate pool representing cellulose, and a recalcitrant pool. The initial litter lignin/nitrogen ratio defined the size of labile and intermediate pools. Lignin content determined the size of the recalcitrant pool. The decomposition rate of all pools was modified by climate, but the intermediate pool's decomposition rate was also controlled by relative amounts of litter cellulose and lignin (indicative of lignin‐encrusted cellulose). The effect of climate on decomposition was best represented by a composite variable that multiplied a water‐stress function by the Lloyd and Taylor variableQ10temperature function. Although our model explained nearly 70% of the variation in LIDET data, we observed systematic deviations from model predictions. Below‐ and aboveground material decomposed at notably different rates, depending on the decomposition stage. Decomposition in certain ecosystem‐specific environmental conditions was not well represented by our model; this included roots in very wet and cold soils, and aboveground litter in N‐rich and arid sites. Despite these limitations, our model may still be extremely useful for global modeling efforts, because it accurately (R2=0.6804) described general patterns of long‐term global decomposition for a wide array of litter types, using relatively minimal climatic and litter quality data.
Carbon exchange of a mature, naturally regenerated pine forest in north Florida
Authors: POWELL THOMAS L. , GHOLZ HENRY L. , CLARK KENNETH L. , STARR GREGORY , CROPPER WENDELL P. , MARTIN TIMOTHY A.
Published: July 2008

We used eddy covariance and biomass measurements to quantify the carbon (C) dynamics of a naturally regenerated longleaf pine/slash pine flatwoods ecosystem in north Florida for 4 years, July 2000 to June 2002 and 2004 to 2005, to quantify how forest type, silvicultural intensity and environment influence stand‐level C balance. Precipitation over the study periods ranged from extreme drought (July 2000–June 2002) to above‐average precipitation (2004 and 2005). After photosynthetic photon flux density (PPFD), vapor pressure deficit (VPD) >1.5 kPa and air temperature <10 °C were important constraints on daytime half‐hourly net CO2exchange (NEEday) and reduced the magnitude of midday CO2exchange by >5 μmol CO2 m−2 s−1. Analysis of water use efficiency indicated that stomatal closure at VPD>1.5 kPa moderated transpiration similarly in both drought and wet years. Night‐time exchange (NEEnight) was an exponential function of air temperature, with rates further modulated by soil moisture. Estimated annual net ecosystem production (NEP) was remarkably consistent among the four measurement years (range: 158–192 g C m−2 yr−1). In comparison, annual ecosystem C assimilation estimates from biomass measurements between 2000 and 2002 ranged from 77 to 136 g C m−2 yr−1. Understory fluxes accounted for approximately 25–35% of above‐canopy NEE over 24‐h periods, and 85% and 27% of whole‐ecosystem fluxes during night and midday (11:00–15:00 hours) periods, respectively. Concurrent measurements of a nearby intensively managed slash pine plantation showed that annual NEP was three to four times greater than that of the Austin Cary Memorial Forest, highlighting the importance of silviculture and management in regulating stand‐level C budgets.
Functional leaf traits, plant communities and acclimation processes in relation to oxidative stress in trees: a critical overview
Authors: BUSSOTTI FILIPPO
Published: July 2008

Tropospheric ozone exercises pressure on vegetation in combination with other oxidative factors such as strong sunlight, UV‐B radiation, high temperatures and water shortage. The relationship established between these factors and the plants can be either antagonistic (cross‐resistance) or synergistic. Response mechanisms are activated involving physiological, chemical and morphological features. Overall sensitivity (or resistance) is determined by the amount of total oxidative pressure in relation to the plant's physiological plasticity [i.e. its ability (within its own resilience potential) to alter its structure and functions in order to react to the oxidative pressure]. Within different populations of the same species, functional leaf traits (leaf area and thickness, leaf mass per area or specific leaf area, tissue thickness) may vary in relation to the extent that the plant succeeds in acclimating to ambient oxidative pressure. The behaviour of a tree in an oxidative environment can be interpreted by means of leaf structure analysis. Leaves presenting high tissue density (and thus low intercellular space content) display a high degree of acclimation to stressors, react little to environmental changes and are characterized by remarkable longevity. Leaves of this type also have a high photosynthesis capacity per surface unit (due to the N content per surface unit) and a highPN/GW(or water use efficiency, WUE). Thus, they are able to support detoxification processes. These morphological traits are to be found in adult plants in late successional stands and, above all, in ambients that have already been subjected to oxidative pressure. However, in early successional species and during the dynamic stages of growth (e.g. in the renewal occurring along forest edges), it is the opposite leaf traits that prevail: low leaf density, high photosynthesis capacity per dry weight unit, low WUE, low leaf longevity. These traits make plants far more reactive to environmental changes (e.g. they exploit the light from sun flecks much more effectively), but enable them to achieve only a low degree of acclimation and a poor ability to support detoxification processes. Whereas adult forests display a high level of ecological resilience and have a relatively good tolerance of ozone, the renewal stages are (at least potentially) more vulnerable. In these environments, ozone can alter the competition among genotypes and favour more resistant ones. Among the sectors most at risk, we must include communities growing at the edge of their ecological range, for whom even a slight increase in oxidative pressure can trigger substantial degenerative processes.
Life history buffering in Antarctic mammals and birds against changing patterns of climate and environmental variation
Authors: FORCADA JAUME , TRATHAN PHILIP N. , MURPHY EUGENE J.
Published: July 2008

The consequences of warming for Antarctic long‐lived organisms depend on their ability to survive changing patterns of climate and environmental variation. Among birds and mammals of different Antarctic regions, including emperor penguins, snow petrels, southern fulmars, Antarctic fur seals and Weddell seals, we found strong support for selection of life history traits that reduce interannual variation in fitness. These species maximize fitness by keeping a low interannual variance in the survival of adults and in their propensity to breed annually, which are the vital rates that influence most the variability in population growth rate (λ). All these species have been able to buffer these rates against the effects of recent climate‐driven habitat changes except for Antarctic fur seals, in the Southwest Atlantic. In this region of the Southern Ocean, the rapid increase in ecosystem fluctuation, associated with increasing climate variability observed since 1990, has limited and rendered less predictable the main fur seal food supply, Antarctic krill. This has increased the fitness costs of breeding for females, causing significant short‐term changes in population structure through mortality and low breeding output. Changes occur now with a frequency higher than the mean female fur seal generation time, and therefore are likely to limit their adaptive response. Fur seals are more likely to rely on phenotypic plasticity to cope with short‐term changes in order to maximize individual fitness. With more frequent extreme climatic events driving more frequent ecosystem fluctuation, the repercussions for life histories in many Antarctic birds and mammals are likely to increase, particularly at regional scales. In species with less flexible life histories that are more constrained by fluctuation in their critical habitats, like sea‐ice, this may cause demographic changes, population compensation and changes in distribution, as already observed in penguin species living in the Antarctic Peninsula and adjacent islands.
Assessing the response of area burned to changing climate in western boreal North America using a Multivariate Adaptive Regression Splines (MARS) approach
Authors: BALSHI MICHAEL S. , McGUIRE A. DAVID , DUFFY PAUL , FLANNIGAN MIKE , WALSH JOHN , MELILLO JERRY
Published: July 2008

Fire is a common disturbance in the North American boreal forest that influences ecosystem structure and function. The temporal and spatial dynamics of fire are likely to be altered as climate continues to change. In this study, we ask the question: how will area burned in boreal North America by wildfire respond to future changes in climate? To evaluate this question, we developed temporally and spatially explicit relationships between air temperature and fuel moisture codes derived from the Canadian Fire Weather Index System to estimate annual area burned at 2.5° (latitude × longitude) resolution using a Multivariate Adaptive Regression Spline (MARS) approach across Alaska and Canada. Burned area was substantially more predictable in the western portion of boreal North America than in eastern Canada. Burned area was also not very predictable in areas of substantial topographic relief and in areas along the transition between boreal forest and tundra. At the scale of Alaska and western Canada, the empirical fire models explain on the order of 82% of the variation in annual area burned for the period 1960–2002. July temperature was the most frequently occurring predictor across all models, but the fuel moisture codes for the months June through August (as a group) entered the models as the most important predictors of annual area burned. To predict changes in the temporal and spatial dynamics of fire under future climate, the empirical fire models used output from the Canadian Climate Center CGCM2 global climate model to predict annual area burned through the year 2100 across Alaska and western Canada. Relative to 1991–2000, the results suggest that average area burned per decade will double by 2041–2050 and will increase on the order of 3.5–5.5 times by the last decade of the 21st century. To improve the ability to better predict wildfire across Alaska and Canada, future research should focus on incorporating additional effects of long‐term and successional vegetation changes on area burned to account more fully for interactions among fire, climate, and vegetation dynamics.
Reappraisal of drying and wetting effects on C and N mineralization and fluxes in soils
Authors: BORKEN WERNER , MATZNER EGBERT
Published: July 2008

In the next decades, many soils will be subjected to increased drying/wetting cycles or modified water availability considering predicted global changes in precipitation and evapotranspiration. These changes may affect the turnover of C and N in soils, but the direction of changes is still unclear. The aim of the review is the evaluation of involved mechanisms, the intensity, duration and frequency of drying and wetting for the mineralization and fluxes of C and N in terrestrial soils. Controversial study results require a reappraisal of the present understanding that wetting of dry soils induces significant losses of soil C and N. The generally observed pulse in net C and N mineralization following wetting of dry soil (hereafter wetting pulse) is short‐lived and often exceeds the mineralization rate of a respective moist control. Accumulated microbial and plant necromass, lysis of live microbial cells, release of compatible solutes and exposure of previously protected organic matter may explain the additional mineralization during wetting of soils. Frequent drying and wetting diminishes the wetting pulse due to limitation of the accessible organic matter pool. Despite wetting pulses, cumulative C and N mineralization (defined here as total net mineralization during drying and wetting) are mostly smaller compared with soil with optimum moisture, indicating that wetting pulses cannot compensate for small mineralization rates during drought periods. Cumulative mineralization is linked to the intensity and duration of drying, the amount and distribution of precipitation, temperature, hydrophobicity and the accessible pool of organic substrates. Wetting pulses may have a significant impact on C and N mineralization or flux rates in arid and semiarid regions but have less impact in humid and subhumid regions on annual time scales. Organic matter stocks are progressively preserved with increasing duration and intensity of drought periods; however, fires enhance the risk of organic matter losses under dry conditions. Hydrophobicity of organic surfaces is an important mechanism that reduces C and N mineralization in topsoils after precipitation. Hence, mineralization in forest soils with hydrophobic organic horizons is presumably stronger limited than in grassland or farmland soils. Even in humid regions, suboptimal water potentials often restrict microbial activity in topsoils during growing seasons. Increasing summer droughts will likely reduce the mineralization and fluxes of C and N whereas increasing summer precipitation could enhance the losses of C and N from soils.
Neuroendocrine ductal carcinoma in situ (NE‐DCIS) of the breast – comparative clinicopathological study of 20 NE‐DCIS cases and 274 non‐NE‐DCIS cases
Authors: Kawasaki T , Nakamura S , Sakamoto G , Murata S , Tsunoda‐shimizu H , Suzuki K , Takahashi O , Nakazawa T , Kondo T , Katoh R
Published: July 2008

Aims:  To clarify the clinicopathological significance of breast neuroendocrine ductal carcinoma in situ (NE‐DCIS), i.e. DCIS in which >50% of cells immunohistochemically express NE markers (chromogranin A and/or synaptophysin), 20 NE‐DCIS were studied and the findings compared with those of 274 non‐NE‐DCIS.

Methods and results:  NE‐DCIS accounted for 6.8% of all DCIS. Mean patient age was 50.4 years for NE‐DCIS and 49.6 years for non‐NE‐DCIS (P = 0.66). The main clinical presentation of NE‐DCIS was a bloody nipple discharge, seen in 72%, significantly different from the 5% in non‐NE‐DCIS cases (P < 0.01). Carcinoma was preoperatively diagnosed in 67% of NE‐DCIS and 95% of non‐NE‐DCIS cases (P < 0.01). NE‐DCIS was histologically characterized by a predominantly solid growth of cancer cells with fine‐granular cytoplasm and ovoid, or occasionally spindle‐shaped nuclei. A well‐developed vascular network was also common. Nuclear grades and Van Nuys classification were significantly lower for NE‐DCIS than for non‐NE‐DCIS (P < 0.01). The mean MIB‐1 labelling index was 4.3% in NE‐DCIS and 8.1% in non‐NE‐DCIS (P < 0.01). Furthermore, NE‐DCIS cases had significantly higher oestrogen and progesterone receptor and lower HER2 scores than non‐NE‐DCIS cases (P < 0.01).

Conclusions:  NE‐DCIS has characteristic clinicopathological features and can, therefore, be regarded as a distinct variant of DCIS.
AR CAG repeat length is not associated with serum gonadal steroids and lipid levels in healthy men
Authors: Goutou Maria , Sakka Christina , Stakias Nikos , Stefanidis Ioannis , Koukoulis Georgios N.
Published: July 2008

Cardiovascular risk factors seem to be affected by androgens, which exert their action through the androgen receptor (AR). Androgenic action correlates inversely with a polymorphic CAG repeat region in the AR gene encoding for glutamine residues the length of which appears to influence high density lipoprotein (HDL) cholesterol levels. The aim of the study was to investigate the possible association between AR gene polymorphism and serum sex steroids and lipids. 170 healthy males, aged 22–59 years (mean 42 years), were included in the study. Anthropometrical as well as sociometrical parameters were recorded. Body fat content (BFC) (% fat mass) was measured by bioelectrical impedance. Serum lipids and total and free testosterone (T) and estradiol (E2) levels were measured in each subject. AR gene CAG repeats length was determined. No significant correlation was found between the length of AR gene polyglutamine tract and the levels of gonadal steroids (total and free T, total and free E2) or to the lipid levels (Triglycerides, total, HDL and LDL cholesterol). In addition, serum lipid levels were not significantly different in the lower compared to higher half of CAG repeats length distribution. On multiple regression analysis BFC was found to predict HDL‐cholesterol and triglycerides were found to show, respectively, significant negative and positive correlation with body fat content. In conclusion, AR gene polymorphism may not predict sex steroid levels in healthy males. Possible impact of CAG repeats length on lipids profile has not been established.
Linking seasonal distribution patterns with prey availability in a central‐place forager, the Steller sea lion
Authors: Womble Jamie N. , Sigler Michael F. , Willson Mary F.
Published: July 2008

Aim We used a novel approach to infer foraging areas of a central‐place forager, the Steller sea lion (Eumetopias jubatus), by assessing changes in the temporal and spatial distribution patterns of sea lions at terrestrial sites. Specifically, our objectives were (1) to classify seasonal distribution patterns of Steller sea lions and (2) to determine to what extent the seasonal distribution of Steller sea lions is explained by seasonal concentrations of prey.

Location Southeast Alaska, USA.

Methods Steller sea lions of all age classes were counted monthly (2001–04) by aerial surveys at 28 terrestrial sites. Hierarchical cluster analysis and principal components analysis were used to classify seasonal distribution patterns of Steller sea lions at these terrestrial sites. We estimated the proportion of sea lions in the study area that were associated with each seasonal distribution pattern.

Results Multivariate ordination techniques revealed four distinct seasonal distributional patterns. During December, 55% of the sea lions in the study area were found at Type 1 sites, located near over‐wintering herring aggregations. During May, 56% of sea lions were found at Type 2 sites, near aggregations of spring‐spawning forage fish. In July, 78% of sea lions were found at Type 3 sites, near summer migratory corridors of salmon. During September, 44% of sea lions were found at Type 4 sites, near autumn migratory corridors of salmon.

Main conclusions Seasonal attendance patterns of sea lions were commonly associated with the seasonal availability of prey species near terrestrial sites and reflected seasonal foraging patterns of Steller sea lions in Southeast Alaska. A reasonable annual foraging strategy for Steller sea lions is to forage on herring (Clupea pallasii) aggregations in winter, spawning aggregations of forage fish in spring, salmon (Oncorhynchusspp.) in summer and autumn, and pollock (Theragra chalcogramma) and Pacific hake (Merluccius productus) throughout the year. The seasonal use of haulouts by sea lions and ultimately haulout‐specific foraging patterns of Steller sea lions depend in part upon seasonally available prey species in each region.
Surviving out in the cold: Antarctic endemic invertebrates and their refugia
Authors: Pugh P. J. A. , Convey P.
Published: July 2008

Aim  To identify Antarctic palaeoendemic taxa and their probable glacial refugia from regional groups of endemic species records.

Location  Antarctica.

Methods  We compiled a list of Antarctic non‐marine invertebrates from published literature, and then deleted all records relating to non‐endemic, zoochoric (phoretic and parasitic), marine and partially identified species to leave only the elements endemic to Antarctica. We then used cluster analysis and principal components analysis to identify regional groupings within this endemic fauna.

Results  Some 170+ of the reported 520+ Antarctic invertebrates are free‐living and endemic, but only nine of these are pan‐Antarctic, with the majority having either ‘continental’/eastern or ‘maritime’/western distributions.

Main conclusions  All invertebrates endemic to continental Antarctica are confined to, or found adjacent to, ice‐free palaeorefugial mountains, nunataks and coastal exposures. By contrast, only one maritime Antarctic palaeorefugium has been identified, and most endemic taxa are currently associated with coastal lowland neorefugia. We suggest which regions of Antarctica (1) are likely to be refugial, and (2) simply require more data in order that the nature and origin of their fauna can be elucidated.
Population genomics: a new generation of genome scans to bridge the gap with functional genomics
Authors: BONIN AURÉLIE
Published: July 2008

Population genomics is an increasingly popular approach to investigate the genetic basis of adaptation and speciation at the genome scale. However, it has so far largely failed to go beyond the mere identification of anonymous markers displaying selection signatures. Will population genomics ever be up to our expectations and able to really pinpoint genes underlying adaptation and speciation processes? In this issue of Molecular Ecology, Namroud et al. use population genomics to investigate local adaptation in natural populations of a conifer tree, the white spruce (Picea glauca). They show how population and functional genomics can finally converge with the deployment of the next generation of genome scans, which target gene‐rich regions rather than the whole genome.
Silencing jasmonate signalling and jasmonate‐mediated defences reveals different survival strategies between two Nicotiana attenuata accessions
Authors: STEPPUHN ANKE , SCHUMAN MEREDITH C. , BALDWIN IAN T.
Published: July 2008

To determine the impact of genotypic variation in secondary metabolite production on antiherbivore resistance and plant fitness, we genetically silenced biosynthetic genes for nicotine, trypsin proteinase inhibitors (TPI), and jasmonate (JA) production in two accessions of Nicotiana attenuata: one from Utah (UT) which responds to herbivory with JA‐induced nicotine and TPI production, and one from Arizona (AZ) which is TPI‐deficient but also produces JA‐induced nicotine. Transient silencing of JA biosynthesis increased Manduca sexta larval growth on wild type (WT) plants of both accessions, but not on TPI‐deficient UT or nicotine‐deficient AZ lines, demonstrating that JA‐mediated resistance to M. sexta requires TPIs in the UT and nicotine in the naturally TPI‐deficient AZ accession. When transplanted into a native UT population, AZ and UT plants, rendered equally able or unable to produce nicotine and TPIs by stable transformation, received significantly different levels of herbivory. Both accessions differed in their resistance depending on the type of herbivores: resistance to rare, voracious herbivores (Saltatoria and Mammalia) was greater in AZ than UT lines, and dependent on nicotine production, while resistance to small, abundant herbivores (Coleoptera and Thysanoptera) was greater in UT lines, and dependent on TPI production. AZ lines produced more flowers and seed capsules than UT lines independently of TPI production costs. This fitness advantage was lost when accessions did not produce nicotine. We conclude that these two accessions have developed different survival strategies and thus differ in the cost‐benefit functions of their JA‐mediated defences.
Endoparasitism in cereal aphids: molecular analysis of a whole parasitoid community
Authors: TRAUGOTT M. , BELL J. R. , BROAD G. R. , POWELL W. , VAN VEEN F. J. F. , VOLLHARDT I. M. G. , SYMONDSON W. O. C.
Published: July 2008

Insect parasitoids play a major role in terrestrial food webs as they are highly diverse, exploit a wide range of niches and are capable of affecting host population dynamics. Formidable difficulties are encountered when attempting to quantify host–parasitoid and parasitoid–parasitoid trophic links in diverse parasitoid communities. Here we present a DNA‐based approach to effectively track trophic interactions within an aphid–parasitoid food web, targeting, for the first time, the whole community of parasitoids and hyperparasitods associated with a single host. Using highly specific and sensitive multiplex and singleplex polymerase chain reaction, endoparasitism in the grain aphid Sitobion avenae (F) by 11 parasitoid species was quantified. Out of 1061 aphids collected during 12 weeks in a wheat field, 18.9% were found to be parasitized. Parasitoids responded to the supply of aphids, with the proportion of aphids parasitized increasing monotonically with date, until the aphid population crashed. In addition to eight species of primary parasitoids, DNA from two hyperparasitoid species was detected within 4.1% of the screened aphids, with significant hyperparasitoid pressure on some parasitoid species. In 68.2% of the hyperparasitized aphids, identification of the primary parasitoid host was also possible, allowing us to track species‐specific parasitoid‐hyperparasitoid links. Nine combinations of primary parasitoids within a single host were found, but only 1.6% of all screened aphids were multiparasitized. The potential of this approach to parasitoid food web research is discussed.
Genetics of sprouting: effects of long‐term persistence in fire‐prone ecosystems
Authors: PREMOLI ANDREA C. , STEINKE LINA
Published: July 2008

Fire functional traits (postfire resprouting and seeding) are considered to be adaptations for persisting in fire‐prone environments. Although ecological and evolutionary consequences of sprouting have been extensively discussed, within‐species genetic variability and structure are unknown. Here we report levels and distribution patterns of genetic polymorphisms in postfire stands of the predominant sprouter Nothofagus antarctica. Fresh foliage of 50 individuals was collected following a spatially explicit sampling design for isozyme analysis from two replicates of each of four habitat types inhabited by the species in northwestern Patagonia, Argentina: matorral, high elevation, forest, and temporally flooded basins. Average polymorphism per population ranged from 44% to 78% and mean gene diversity per site HS varied from 0.187 to 0.274. These results show that sprouter populations hold considerable genetic variation. Significant genetic structure over short distances (< 50 m) was found at all locations. Ancient fine‐scale genetic structure is preserved by occasional seedling establishment that results in high co‐ancestry coefficients. Sprouter populations growing in suboptimal habitats such as matorral, high elevation or basins consist of pairs of heterozygous genets that occur at larger spatial scales as a result of micro‐environmental heterogeneity and/or local competition between near neighbour genotypes. In contrast, homozygous pairs of individuals for distinct isozyme loci occurred at larger spatial scales in forest stands. This indicates that biparental inbreeding due to local propagule establishment may take place to some extent in sprouters growing under favourable conditions. Our results show that sprouters follow a long‐lasting genet persistence strategy which most probably is selected under unpredictable disturbance regimes, such as fire.
tRNA and protein methylase complexes mediate zymocin toxicity in yeast
Authors: Studte Patrick , Zink Sabrina , Jablonowski Daniel , Bär Christian , Von Der Haar Tobias , Tuite Mick F. , Schaffrath Raffael
Published: July 2008

Modification of Saccharomyces cerevisiae tRNA anticodons at the wobble uridine (U34) position is required for tRNA cleavage by the zymocin tRNase killer toxin from Kluyveromyces lactis. Hence, U34 modification defects including lack of the U34 tRNA methyltransferase Trm9 protect against tRNA cleavage and zymocin. Using zymocin as a tool, we have identified toxin‐resistant mutations in TRM9 that are likely to affect the U34 methylation reaction. Most strikingly, C‐terminal truncations in Trm9 abolish interaction with Trm112, a protein shown to individually purify with Lys9 and two more methylases, Trm11 and Mtq2. Downregulation of a GAL1‐TRM112 allele protects against zymocin whereas LYS9, TRM11 and MTQ2 are dosage suppressors of zymocin. Based on immune precipitation studies, the latter scenario correlates with competition for Trm112 and in excess, some of these Trm112 partners interfere with formation of the toxin‐relevant Trm9·Trm112 complex. In contrast to trm11Δ or lys9Δ cells, trm112Δ and mtq2Δ null mutants are zymocin resistant. In line with the identified role that methylation of Sup45 by Mtq2 has for translation termination by the release factor dimer Sup45·Sup35, we observe that SUP45 overexpression and sup45 mutants suppress zymocin. Intriguingly, this suppression correlates with upregulated levels of tRNA species targeted by zymocin's tRNase activity.
Molecular phylogenetics of heliothine moths (Lepidoptera: Noctuidae: Heliothinae), with comments on the evolution of host range and pest status
Authors: CHO SOOWON , MITCHELL ANDREW , MITTER CHARLES , REGIER JEROME , MATTHEWS MARCUS , ROBERTSON RON
Published: July 2008

Abstract The Heliothinae are a cosmopolitan subfamily of about 365 species that include some of the world’s most injurious crop pests. This study re‐assesses evolutionary relationships within heliothines, providing an improved phylogeny and classification to support ongoing intensive research on heliothine genomics, systematics, and biology. Our phylogeny estimate is based on two nuclear gene regions, namely elongation factor‐1α (EF‐1α; 1240 bp) and dopa decarboxylase (DDC; 687 bp), and on the barcoding region of mitochondrial cytochrome oxidase I (COI; 708 bp), providing a total of 2635 bp. These were sequenced for 71 heliothines, representing all major genera and nearly all recognized subgenera and species groups, and for 16 outgroups representing all major lineages of trifine Noctuidae. Analysis of the combined data by maximum likelihood, unweighted parsimony and Bayesian methods gave nearly identical topologies, and the individual gene trees showed only one case of potentially strong conflict. Relationships among genera and subgenera are resolved with strong bootstrap support. The earliest‐diverging lineages (c. 200 species in total) consist almost entirely of host specialists, reflecting the inferred ancestral heliothine host range under parsimony. The remaining species form a clade – the Heliothis group – that includes most of the polyphages (30% of heliothines) and all of the major pests. Many other species in the Heliothis group, however, are host specialists. Our results extend previous efforts to subdivide this large clade, and show the most notorious pest groups, the corn earworm complex (Helicoverpa) and the tobacco budworm (Heliothis virescens) group, to be closely related, joining with a small oligophagous genus in what we term the major‐pest lineage. Thus, genomic/experimental results from one model pest may extrapolate well to other pest species. The frequency of evolutionary expansion and contraction in host range appears to increase dramatically at the base of the Heliothis group, in contrast to the case for earlier‐diverging lineages. We ascribe this difference provisionally to differential evolutionary constraints arising from contrasting life‐history syndromes. Host‐specific behaviour and crypsis, coupled with low fecundity and vagility, may discourage host‐range expansion in earlier‐diverging lineages. By contrast, in the Heliothis group, the absence of host‐specific traits, coupled with high vagility and fecundity, may more readily permit expansion or contraction of the host range in response to varying ecological pressures such as host species abundance or differential competition and predation.
NAC transcription factors NST1 and NST3 regulate pod shattering in a partially redundant manner by promoting secondary wall formation after the establishment of tissue identity
Authors: Mitsuda Nobutaka , Ohme‐Takagi Masaru
Published: July 2008

Three distinct pattern elements of the silique are thought to contribute to its dehiscence: a separation layer, cells with a secondary wall adjacent to the separation layer, and a valve endocarp layer with secondary wall. However, the role of the secondary wall has not been proven, and the factors that regulate its formation in siliques remain to be characterized. We show here that secondary wall formation in siliques is necessary for dehiscence, and that two plant‐specific transcription factors, NAC SECONDARY WALL THICKENING PROMOTING FACTOR 1 and 3 (NST1 and NST3), regulate its formation in siliques of Arabidopsis. The promoters of the NST1 and NST3 genes were active in the valve endocarp layer and in cells surrounding vascular vessels in the replum, and NST1 promoter activity only was faintly detectable at valve margins. In nst1 mutants, specific loss of secondary walls was evident at valve margins, while nst1 nst3 double mutants lacked secondary walls in all parts of the siliques, with the exception of vascular vessels. These siliques were similarly indehiscent. The promoters of two tissue‐identity genes, INDEHISCENT (IND) and SHATTERPROOF2 (SHP2), were as active in the nst1 nst3 mutant as in the wild‐type. Moreover, the ectopic secondary wall formation that occurs in the fruitfull (ful) mutant was absent in the ful nst1 double mutant. We propose that secondary walls in valve margins are required for dehiscence, and that NST1 and NST3 regulate their formation in siliques in a partially redundant manner after the establishment of tissue identity.
CLB19, a pentatricopeptide repeat protein required for editing of rpoA and clpP chloroplast transcripts
Authors: Chateigner‐Boutin Anne‐Laure , Ramos‐Vega Maricela , Guevara‐García Arturo , Andrés Charles , De La Luz Gutiérrez‐Nava María , Cantero Araceli , Delannoy Etienne , Jiménez Luis Felipe , Lurin Claire , Small Ian , León Patricia
Published: July 2008

RNA editing changes the sequence of many transcripts in plant organelles, but little is known about the molecular mechanisms determining the specificity of the process. In this study, we have characterized CLB19 (also known as PDE247), a gene that is required for editing of two distinct chloroplast transcripts, rpoA and clpP. Loss‐of‐function clb19 mutants present a yellow phenotype with impaired chloroplast development and early seedling lethality under greenhouse conditions. Transcript patterns are profoundly affected in the mutant plants, with a pattern entirely consistent with a defect in activity of the plastid‐encoded RNA polymerase. CLB19 encodes a pentatricopeptide repeat protein similar to the editing specificity factors CRR4 and CRR21, but, unlike them, is implicated in editing of two target sites.
Local production of total IgE and specific antibodies to the house dust mite in adenoid tissue
Authors: Shin Seung‐Youp , Choi Sung‐Jin , Hur Gyu‐Young , Lee Kun‐Hee , Kim Sung‐Wan , Cho Joong‐Saeng , Park Hae‐Sim
Published: July 2008

Adenoids are known as immunosecretory organs and those in atopic children present cellular and cytokine profiles different from those of non‐atopic children. We hypothesized that locally produced total IgE and allergen‐specific antibodies could be involved in the inflammatory responses in adenoid tissue. Local productions of total IgE and Dermatophagoides pteronyssinus (DP)‐specific IgE, IgA, IgG1, and IgG4 antibodies were evaluated, as well as their relationships with the markers of allergic inflammation within adenoid tissue. Eighteen atopic subjects, who were sensitized to more than one common aeroallergen, and 22 non‐atopic subjects undergoing adenotonsillectomy, were recruited. Immunoassays using adenoid tissue homogenate were performed to quantify the levels of total IgE, eosinophil cationic protein (ECP), and mast cell tryptase. DP‐specific IgE, IgA, IgG1, and IgG4 antibodies, soluble IL‐2 receptors (sIL‐2R), soluble CD23 (sCD23), and IL‐6 were measured by ELISA. All parameters measured in adenoid tissue homogenate were presented as a ratio to the albumin level found in the adenoid. Median level of total IgE in adenoid tissue homogenate was significantly higher in atopic individuals than in non‐atopic individuals. Median values of DP‐specific IgE and IgA antibodies were significantly higher in atopics than in non‐atopics (p = 0.001, p = 0.006, respectively), while no differences were seen in DP‐specific IgG1 and IgG4 antibodies. ECP and sCD23 levels in adenoid homogenate were significantly higher in atopics than in non‐atopics (p = 0.026, p = 0.048, respectively), while no significant differences were noted in tryptase, sIL‐2R, and IL‐6 levels. The levels of DP‐specific IgE, IgA, IgG1, and IgG4 antibodies in adenoid homogenate correlated significantly with ECP levels, but not with those of sIL‐2R, sCD23, and IL‐6. The presence of total IgE and DP‐specific antibodies in adenoid tissue was confirmed to be more prominent in atopics. In conclusion, locally‐produced total IgE and DP‐specific antibodies may contribute to eosinophilic inflammation in adenoid tissue in atopic children.
The phospholipase A2 inhibitor, aristolochic acid, disrupts cortical microtubule arrays and root growth in Arabidopsis
Authors: Gardiner J. , Andreeva Z. , Barton D. , Ritchie A. , Overall R. , Marc J.
Published: July 2008

The role of phospholipase A2 in Arabidopsis root growth and microtubule organisation was investigated using a specific inhibitor, aristolochic acid. At 0.5–1.5 μm concentrations, this inhibitor reduced root elongation and caused radial swelling of the root tip. The normally transverse cortical microtubules in root tip cells became progressively more disorganised with increasing concentrations of the inhibitor. Microtubule disorganisation also occurred in leaf epidermal cells of Allium porrum. We propose that phospholipase A2 is involved in microtubule organisation and anisotropic growth in a manner similar to that reported previously for phospholipase D, thus broadening the significance of phospholipid signalling in microtubule organisation in plants.
Perianth organization and intra‐specific floral variability
Authors: Herrera J. , Arista M. , Ortiz P. L.
Published: July 2008

Floral symmetry and fusion of perianth parts are factors that contribute to fine‐tune the match between flowers and their animal pollination vectors. In the present study, we investigated whether the possession of a sympetalous (fused) corolla and bilateral symmetry of flowers translate into decreased intra‐specific variability as a result of natural stabilizing selection exerted by pollinators. Average size of the corolla and intra‐specific variability were determined in two sets of southern Spanish entomophilous plant species. In the first set, taxa were paired by family to control for the effect of phylogeny (phylogenetically independent contrasts), whereas in the second set species were selected at random. Flower size data from a previous study (with different species) were also used to test the hypothesis that petal fusion contributes to decrease intra‐specific variability. In the phylogenetically independent contrasts, floral symmetry was a significant correlate of intra‐specific variation, with bilaterally symmetrical flowers showing more constancy than radially symmetrical flowers (i.e. unsophisticated from a functional perspective). As regards petal fusion, species with fused petals were on average more constant than choripetalous species, but the difference was not statistically significant. The reanalysis of data from a previous study yielded largely similar results, with a distinct effect of symmetry on variability, but no effect of petal fusion. The randomly‐chosen species sample, on the other hand, failed to reveal any significant effect of either symmetry or petal fusion on intra‐specific variation. The problem of low‐statistical power in this kind of analysis, and the difficulty of testing an evolutionary hypothesis that involves phenotypic traits with a high degree of morphological correlation is discussed.