Responses Of Different Species Research Articles

Quantifying edge effects: the role of habitat contrast and species specialization

Edge effect is a key process influencing populations and communities, particularly in fragmented landscapes. A general analytical framework has been proposed to quantify the strength of the edge effects (extent and magnitude); however, factors determining the later remain poorly explored. Using a continuous approach we explore the response of dung beetle species and assemblages to ecotones which differ in environmental dissimilarity in the Southern Atlantic forest of Argentina. Using baited pitfall traps and automatic sensors, we estimated dung beetle abundance, microclimatic conditions and vegetation structure along five different forest-plantations transects. At the assemblages level, the majority of species showed either edge avoidance or preference; however, the response depended on the environmental dissimilarity between habitats (plantation and native forest) and varied from a neutral response on mature plantations (low contrast ecotone) to edge avoidance on recent ones (high contrast ecotone). At the species level, the degree of habitat specialization explains the differential response of species to edge effects; more specialized species showed stronger edge response while generalist species showed softer or neutral responses. Environmental dissimilarity between confronted habitats and species specialization explain the quantitative component of edge effects on species and assemblages. Functional groups (rollers and tunnellers) often showed opposite responses to edge effects. At the landscape level, functional connectivity of forest fragments is probably drastically reduced by high contrasts matrices (such as recent plantations) for native forest species, whereas soft ecotones (such as native forest-mature plantations) maintained functional connectivity. These results are particularly relevant on highly fragmented landscapes, such as the Atlantic forest, where edge effect is probably one the most important mechanisms affecting native species and communities.

Differential responses of native and exotic coastal sage scrub plant species to N additions and the soil microbial community

Background and aims Native shrub species of southern California have a long history of displacement by exotic annual herbs and forbs. Such invasions may be mediated by interactions with the microbial community and changes in the N cycle as a result of N pollution. However, the simultaneous effects of the soil microbial community status and N fertilization on dominant native and exotic plant species growth have not been thoroughly explored in this ecosystem.

Independent variations of plant and soil mixtures reveal soil feedback effects on plant community overyielding

Summary Recent studies have shown that the positive relationship between plant diversity and plant biomass (‘overyielding’) can be explained by soil pathogens depressing productivity more in low than in high diverse plant communities. However, tests of such soil effects in field studies were constrained by experimental limitations to manipulate soil community composition independent of plant community composition. Here, we report of an experiment where feedback effects to plants were tested for both plant and soil monocultures and mixtures. Our results demonstrate that overyielding is the result of plant species in mixture being more growth‐limited by ‘own’ soil biota than by soil biota of other plant species. This effect disappeared when the soils had been sterilized by gamma‐irradiation. Mixing plants themselves did not result in overyielding except when grown in the soil of one of the species (Leucanthemum vulgare), where growth of one species disproportionally increased in mixture compared to monoculture. Soil nutrient availability could not explain differences in growth between the non‐sterilized soils. Therefore, our results suggest that plant species–specific soil biota rather than the plants have contributed to the plant community overyielding. Species biomass ranking in mixtures highly differed between non‐sterilized soils of different histories of soil conditioning, whilst the ranking was more consistent in sterilized soil. Sterilized soils of different origin differed significantly in nutrient availability. These results suggest that shifts in competitive hierarchies depend on plant species–specific interactions influenced by soil biota and cannot be induced by mineral nitrogen. Synthesis. Our results show that overyielding in four plant species mixtures can be due to species‐specific interactions between plants and their specific soil biota. Neither mixing the plant species alone nor the differential responses of species to mineral nitrogen influenced community productivity, but mixing soil biota did.

Immune responses of different species of tilapia infected with Streptococcus agalactiae

Immune responses of different species of tilapia infected with <i>Streptococcus agalactiae</i>

Physiological and Nutritional Roles of PPAR across Species

Physiological and Nutritional Roles of PPAR across Species

Combined effects of the herbicide terbuthylazine and temperature on different flagellates from the Northern Adriatic Sea

The triazinic herbicide terbuthylazine (TBA) is becoming an emergent contaminant in Italian rivers and in coastal and groundwater. A preliminary analysis of the sensitivity of marine flagellates to TBA was performed by monitoring the photosynthetic efficiency of nine species (belonging to the Dinophyceae or Raphidophyceae class) isolated from the Adriatic Sea. Different sensitivity levels for each flagellate were observed and the most sensitive microalgae, based on PSII inhibition, were: Gonyaulax spinifera>Fibrocapsa japonica>Lingulodinium polyedrum while the most resistant were two species belonging to the Prorocentrum genus. Then the response of two microalgae to drivers, such as temperature and terbuthylazine, applied in combination was also investigated. Two potentially toxic flagellates, Prorocentrum minimum and G. spinifera, were exposed, under different temperature conditions (15, 20 and 25°C), to TBA concentrations that did not completely affect PSII. For both flagellates, effects of TBA on algal growth, measured through cell density and carbon analysis, as well as on the photosynthetic activity are reported. All parameters analyzed showed a negative effect of TBA from the exponential phase. TBA effect on algal growth was significantly enhanced at the optimal temperature conditions (20 and 25°C), while no difference between control and herbicide treatments were detected for G. spinifera grown at 15°C, which represented a stress condition for this species. The maximum inhibition of photosynthetic efficiency was found at 20°C for both organisms. Both flagellates increased cell carbon and nitrogen content in herbicide treatments compared to the control, except G. spinifera grown at 15°C. Chlorophyll-a production was increased only in G. spinifera exposed to 5μgL−1 of TBA and the effect was enhanced with the increase of temperature. Herbicide-induced variations in cellular components determined changes in cellular carbon:nitrogen (C:N) and chlorophyll:carbon (Chl:C) ratios. The C:N ratio decreased in both species, while only G. spinifera showed an increase in the Chl:C ratio at all temperature conditions. In response to TBA exposure G. spinifera increased extracellular polysaccharides release at 20 and 25°C, while no difference was reported for P. minimum. Changes in nutrient uptake rates were also observed for P. minimum. Nitrate and phosphate uptake significantly increased in the presence of TBA and this response was enhanced at 25°C, while nitrate uptake increased in G. spinifera only when grown at 25°C. As for growth rates, the observed changes in intracellular component contents increased at optimal temperature conditions. In this work it is shown that temperature conditions can have an important role on the effect of terbuthylazine on algal growth and on the physiological responses of different species. Furthermore, the algal resistance and recovery can be dependent on nutrient availability.

A Field Bioassay to Evaluate Potential Spatial Repellents Against Natural Mosquito Populations

A field bioassay evaluating candidate chemicals as aerial repellents was developed and evaluated against natural mosquito populations in Beltsville, MD. The bioassay consisted of an attractive source surrounded by a grid of 16 septa containing a volatile candidate aerial repellent, compared with an attractive source without such a grid. The attractive source was a Centers for Disease Control and Prevention light trap supplemented with carbon dioxide. Significant sources of variation included weather, position, and the differential response of mosquito species. Despite these sources of variation, significant repellent responses were obtained for catnip oil, E,Z-dihydronepetalactone, and DEET.

Differential ecophysiological response of a major Mediterranean pine species across a climatic gradient

The rate of migration and in situ genetic variation in forest trees may not be sufficient to compete with the current rapid rate of climate change. Ecophysiological adjustments of key traits, however, could complement these processes and allow sustained survival and growth across a wide range of climatic conditions. This was tested in Pinus halepensis Miller by examining seven physiological and phenological parameters in five provenances growing in three common garden plots along a climatic transect from meso-Mediterranean (MM) to thermo-Mediterranean (TM) and semi-arid (SA) climates. Differential responses to variations in ambient climatic conditions were observed in three key traits: (i) growing season length decreased with drying in all provenances examined (from 165 under TM climate to 100 days under SA climate, on average); (ii) water use efficiency (WUE) increased with drying, but to a different extent in different provenances, and on average from 80, to 95, to 110 µmol CO(2) mol(-1) H(2)O under MM, TM and SA climates, respectively; (iii) xylem native embolism was stable across climates, but varied markedly among different provenances (percent loss of conductivity, was below 5% in two provenances and above 35% in others). The results indicated that changes in growing season length and WUE were important contributors to tree growth across climates, whereas xylem native embolism negatively correlated with tree survival. The results indicated that irrespective of slow processes (e.g., migration, genetic adaptation), the capacity for ecophysiological adjustments combined with existing variations among provenances could help sustain P. halepensis, a major Mediterranean tree species, under relatively extreme warming and drying climatic trends.

Common garden experiments reveal uncommon responses across temperatures, locations, and species of ants

Population changes and shifts in geographic range boundaries induced by climate change have been documented for many insect species. On the basis of such studies, ecological forecasting models predict that, in the absence of dispersal and resource barriers, many species will exhibit large shifts in abundance and geographic range in response to warming. However, species are composed of individual populations, which may be subject to different selection pressures and therefore may be differentially responsive to environmental change. Asystematic responses across populations and species to warming will alter ecological communities differently across space. Common garden experiments can provide a more mechanistic understanding of the causes of compositional and spatial variation in responses to warming. Such experiments are useful for determining if geographically separated populations and co-occurring species respond differently to warming, and they provide the opportunity to compare effects of warming on fitness (survivorship and reproduction). We exposed colonies of two common ant species in the eastern United States, Aphaenogaster rudis and Temnothorax curvispinosus, collected along a latitudinal gradient from Massachusetts to North Carolina, to growth chamber treatments that simulated current and projected temperatures in central Massachusetts and central North Carolina within the next century. Regardless of source location, colonies of A. rudis, a keystone seed disperser, experienced high mortality and low brood production in the warmest temperature treatment. Colonies of T. curvispinosus from cooler locations experienced increased mortality in the warmest rearing temperatures, but colonies from the warmest locales did not. Our results suggest that populations of some common species may exhibit uniform declines in response to warming across their geographic ranges, whereas other species will respond differently to warming in different parts of their geographic ranges. Our results suggest that differential responses of populations and species must be incorporated into projections of range shifts in a changing climate.

Evaluation of electrospray ionisation mass spectrometry as a technique for the investigation of competitive interactions: A case study of the ternary Th‐Mn‐EDTA system

Electrospray ionisation mass spectrometry (ESI-MS) is a useful tool for exploring the speciation of solution-phase metal complexes; however, the quantification of ternary systems is challenging due to the differences in the electrospray response of different species. Here, the Th-Mn-EDTA system was investigated to evaluate the capability of ESI-MS for quantifying the species present. Increasingly complex mixtures of Th(IV), Mn(II) and EDTA were analysed using manual flow injection of samples into an HPLC grade water mobile phase delivered to an ion trap mass spectrometer fitted with an ESI interface (ThermoQuest Finnigan Mat LCQ). Mass spectra were obtained in the positive and negative ion modes over a mass-to-charge (m/z) range from 50-2000. The instrumental response to EDTA was affected by the addition of Th(NO(3))(4) but not MnCl(2), while the response to both Th-EDTA and Mn-EDTA species was affected by addition of the other metal salt. Internal standards were also found to suppress signals to different extents. Therefore, each signal suppression was carefully quantified as the solution became more complex, and signal correction factors were used in conjunction with regular external calibration. Mixed metal signals were quantified adequately. This study showed the complexity of quantifying a ternary system involving different co-existing species. Nonetheless, the step-wise protocol developed provided quantitative data on the displacement of Mn from its EDTA complex by Th.

Phage display allows identification of zona pellucida-binding peptides with species-specific properties: Novel approach for development of contraceptive vaccines for wildlife

Multiple phage-peptide constructs, where the peptides mimic sperm epitopes that bind to zona pellucida (ZP) proteins, were generated via selection from a phage display library using a novel approach. Selections were designed to allow for identification of ZP-binding phage clones with potential species-specific properties, an important feature for wildlife oral vaccines as the goal is to control overpopulation of a target species while not affecting non-target species’ reproduction. Six phage-peptide antigens were injected intramuscularly into pigs and corresponding immune responses evaluated. Administration of the antigens into pigs stimulated production of anti-peptide antibodies, which were shown to act as anti-sperm antibodies. Potentially, such anti-sperm antibodies could interfere with sperm delivery or function in the male or female genital tract, leading to contraceptive effects. Staining of semen samples collected from different mammalian species, including pig, cat, dog, bull, and mouse, with anti-sera from pigs immunized with ZP-binding phage allowed identification of phage-peptide constructs with different levels of species specificity. Based on the intensity of the immune responses and specificity of these responses in different species, two of the antigens with fusion peptide sequences GEGGYGSHD and GQQGLNGDS were recognized as the most promising candidates for development of contraceptive vaccines for wild pigs.

Response of Fish Communities to Various Environmental Variables across Multiple Spatial Scales

A better understanding of the relative importance of different spatial scale determinants on fish communities will eventually increase the accuracy and precision of their bioassessments. Many studies have described the influence of environmental variables on fish communities on multiple spatial scales. However, there is very limited information available on this topic for the East Asian monsoon region, including Korea. In this study, we evaluated the relationship between fish communities and environmental variables at multiple spatial scales using self-organizing map (SOM), random forest, and theoretical path models. The SOM explored differences among fish communities, reflecting environmental gradients, such as a longitudinal gradient from upstream to downstream, and differences in land cover types and water quality. The random forest model for predicting fish community patterns that used all 14 environmental variables was more powerful than a model using any single variable or other combination of environmental variables, and the random forest model was effective at predicting the occurrence of species and evaluating the contribution of environmental variables to that prediction. The theoretical path model described the responses of different species to their environment at multiple spatial scales, showing the importance of altitude, forest, and water quality factors to fish assemblages.

The response of surf-zone phytoplankton to nutrient enrichment (Cassino Beach, Brazil)

To understand the mechanisms that trigger changes in chlorophyll a and species composition in the phytoplankton of the surf-zone at Cassino Beach (RS), we performed two short nutrient-enrichment experiments (4–5days each) during the summer and winter of 2010. Seawater was incubated under controlled conditions of temperature (summer 25±3°C, winter 18±1°C), salinity (summer 28, winter 26) and irradiance (100μmolm−2s−1). Dissolved inorganic nutrients were added in various concentrations in the summer (silicate, Si; nitrate, N; phosphate, P) and winter (N, P) experiments. Samples were taken daily for cell counts and chlorophyll a analysis. In both experiments, chlorophyll a values and cell density showed a significant increase (mainly diatoms) in the treatments with nitrate addition, regardless of the proportion added. In the summer experiment, the largest chlorophyll a increase, approximately threefold (31.5 to 89.5μgL−1), was observed in the NP treatment due to the growth of Asterionellopsis glacialis (Castracane) Round, Skeletonema tropicum Cleve, Thalassiosira sp. Cleve and Pseudo-nitzschia spp. Peragallo. The maximum growth was obtained in the SiNP treatment for S. tropicum (μ=0.7), Thalassiosira (μ=1.9) and Pseudo-nitzschia (μ=1.3) and in the SiN treatment for A. glacialis (μ=1.0). In the winter experiment, the chlorophyll a content increased 4.2 and 5.5 times, respectively, in the N and NP treatments (maxima 38.8μgL−1 and 31.5μgL−1), where A. glacialis (μ=1.7–1.9) and Cylindrotheca closterium (Ehrenberg) Reimann & J.C. Lewin (μ=1.0–1.96) showed the highest amount of growth. These results indicate that nitrate is the most important nutrient controlling phytoplankton chlorophyll a at sandy Cassino Beach. However, the responses of different species to enrichment during the summer and winter indicated that other factors also played a role. A. glacialis, present during both seasons, presented the highest growth rate during the winter, whereas during the summer it was independent of nutrient enrichment but coincided with the lowest growth of S. tropicum. This finding suggested the occurrence of allelopathic interactions between these species. During the summer, multi-enrichment (SiNP) favoured the best growth of S. tropicum, Pseudo-nitzschia spp. and Thalassiosira sp. These results indicated that the phytoplankton composition and diversity in the surf zone of Cassino Beach are shaped by the availability of silicate and phosphorus as well as by the availability of nitrate.

Plant‐mediated and nonadditive effects of two global change drivers on an insect herbivore community

Warmer temperatures can alter the phenology and distribution of individual species. However, differences across species may blur community-level phenological responses to climate or cause biotic homogenization by consistently favoring certain taxa. Additionally, the response of insect communities to climate will be subject to plant-mediated effects, which may or may not overshadow the direct effect of rising temperatures on insects. Finally, recent evidence for the importance of interaction effects between global change drivers suggests that phenological responses of communities to climate may be altered by other drivers. We used a natural temperature gradient (generated by elevation and topology), combined with experimental nitrogen fertilization, to investigate the effects of elevated temperature and globally increasing anthropogenic nitrogen deposition on the structure and phenology of a seminatural grassland herbivore assemblage (lepidopteran insects). We found that both drivers, alone and in combination, severely altered how the relative abundance and composition of species changed through time. Importantly, warmer temperatures were associated with biotic homogenization, such that herbivore assemblages in the warmest plots had more similar species composition than those in intermediate or cool plots. Changes in herbivore composition and abundance were largely mediated by changes in the plant community, with increased nonnative grass cover under high treatment levels being the strongest determinant of herbivore abundance. In addition to compositional changes, total herbivore biomass more than doubled under elevated nitrogen and increased more than fourfold with temperature, bearing important functional implications for herbivores as consumers and as a prey resource. The crucial role of nonnative plant dominance in mediating responses of herbivores to change, combined with the frequent nonadditive (positive and negative) effects of the two drivers, and the differential responses of species, highlight that understanding complex ecosystem responses will benefit from multifactor, multitrophic experiments at community scales or larger.

Nitrogen deposition drives lichen community changes through differential species responses

AbstractNitrogen (N) deposition has increased globally over the last 150 years and further increases are predicted. Epiphytic lichens decline in abundance and diversity in areas with high N loads, and the abundance of lichens decreases along gradients of increased deposition. Thus, although N is an essential nutrient for lichens, excessive loads may be detrimental for them. However, these gradients include many correlated pollutants and the mechanisms behind the decline are thus poorly known. The aim of this study was to assess effects of N deposition, alone, on the epiphytic lichen community composition in a naturally N‐poor boreal forest. For this purpose, whole spruce trees were fertilized daily with N at five levels, equivalent to 0.6, 6, 12.5, 25, and 50 kg N ha−1 yr−1, during four consecutive growing seasons (2006–2009), and changes in the abundance of lichens were monitored each autumn from the preceding year (2005). The studied lichen communities were highly dynamic and responded strongly to the environmental perturbation. N deposition detectably altered the direction of succession and reduced the species richness of the epiphytic lichen communities, even at the lowest fertilization application (6 kg N ha−1 yr−1). The simulated N deposition caused significant changes in the abundance of Alectoria sarmentosa, Bryoria spp., and Hypogymnia physodes, which all increased at low N loads and decreased at high loads, but with species‐specific optima. The rapid decline of A. sarmentosa may have been caused by the added nitrogen reducing the stability of the lichen thalli, possibly due to increases in the photobiont: mycobiont ratio or parasitic fungal attacks. We conclude that increases in nitrogen availability, per se, could be responsible for the reductions in lichen abundance and diversity observed along deposition gradients, and those community responses may be due to physiological responses of the individual species rather than changes in competitive interactions.

Niche separation of larks (Alaudidae) and agricultural change on the drylands of the former Soviet Union

Variation in the distributions of different species of lark was assessed along the two main agricultural gradients in the steppe and semi-desert zones of Kazakhstan: the intensity of grazing and the time since abandonment of cereal fields.Vegetation structure and composition varied significantly with time since abandonment, and with changing grazing pressure. The studied lark species responded in non-linear ways to both these gradients and showed a high degree of niche separation, with black lark, calandra lark and skylark preferring denser and taller vegetation compared to white-winged lark and short-toed lark.Lark populations generally are likely to have benefited from agricultural abandonment and a decline in livestock numbers over large parts of the steppes and semi-deserts of the former Soviet Union. The results suggest that an assessment of future changes in steppe bird communities based upon projections of changes in the area of gross habitat types can be improved by a better understanding of the responses of different species to more subtle environmental gradients.

Induction of Myocardial Infarction in Adult Zebrafish Using Cryoinjury

The mammalian heart is incapable of significant regeneration following an acute injury such as myocardial infarction1. By contrast, urodele amphibians and teleost fish retain a remarkable capacity for cardiac regeneration with little or no scarring throughout life2,3. It is not known why only some non-mammalian vertebrates can recreate a complete organ from remnant tissues4,5. To understand the molecular and cellular differences between regenerative responses in different species, we need to use similar approaches for inducing acute injuries.In mammals, the most frequently used model to study cardiac repair has been acute ischemia after a ligation of the coronary artery or tissue destruction after cryoinjury6,7. The cardiac regeneration in newts and zebrafish has been predominantly studied after a partial resection of the ventricular apex2,3. Recently, several groups have established the cryoinjury technique in adult zebrafish8-10. This method has a great potential because it allows a comparative discussion of the results obtained from the mammalian and non-mammalian species.Here, we present a method to induce a reproducible disc-shaped infarct of the zebrafish ventricle by cryoinjury. This injury model is based on rapid freezing-thawing tissue, which results in massive cell death of about 20% of cardiomyocytes of the ventricular wall. First, a small incision was made through the chest with iridectomy scissors to access the heart. The ventricular wall was directly frozen by applying for 23-25 seconds a stainless steel cryoprobe precooled in liquid nitrogen. To stop the freezing of the heart, fish water at room temperature was dropped on the tip of the cryoprobe. The procedure is well tolerated by animals, with a survival rate of 95%.To characterize the regenerative process, the hearts were collected and fixed at different days after cryoinjury. Subsequently, the specimen were embedded for cryosectioning. The slides with sections were processed for histological analysis, in situ hybridization and immunofluorescence. This undertaking enhances our understanding of the factors that are required for the regenerative plasticity in the zebrafish, and provide new insights into the machinery of cardiac regeneration. A conceptual and molecular understanding of heart regeneration in zebrafish will impact both developmental biology and regenerative medicine.

Induction of Myocardial Infarction in Adult Zebrafish Using Cryoinjury

The mammalian heart is incapable of significant regeneration following an acute injury such as myocardial infarction1. By contrast, urodele amphibians and teleost fish retain a remarkable capacity for cardiac regeneration with little or no scarring throughout life2,3. It is not known why only some non-mammalian vertebrates can recreate a complete organ from remnant tissues4,5. To understand the molecular and cellular differences between regenerative responses in different species, we need to use similar approaches for inducing acute injuries. In mammals, the most frequently used model to study cardiac repair has been acute ischemia after a ligation of the coronary artery or tissue destruction after cryoinjury6,7. The cardiac regeneration in newts and zebrafish has been predominantly studied after a partial resection of the ventricular apex2,3. Recently, several groups have established the cryoinjury technique in adult zebrafish8-10. This method has a great potential because it allows a comparative discussion of the results obtained from the mammalian and non-mammalian species. Here, we present a method to induce a reproducible disc-shaped infarct of the zebrafish ventricle by cryoinjury. This injury model is based on rapid freezing-thawing tissue, which results in massive cell death of about 20% of cardiomyocytes of the ventricular wall. First, a small incision was made through the chest with iridectomy scissors to access the heart. The ventricular wall was directly frozen by applying for 23-25 seconds a stainless steel cryoprobe precooled in liquid nitrogen. To stop the freezing of the heart, fish water at room temperature was dropped on the tip of the cryoprobe. The procedure is well tolerated by animals, with a survival rate of 95%. To characterize the regenerative process, the hearts were collected and fixed at different days after cryoinjury. Subsequently, the specimen were embedded for cryosectioning. The slides with sections were processed for histological analysis, in situ hybridization and immunofluorescence. This undertaking enhances our understanding of the factors that are required for the regenerative plasticity in the zebrafish, and provide new insights into the machinery of cardiac regeneration. A conceptual and molecular understanding of heart regeneration in zebrafish will impact both developmental biology and regenerative medicine.

Post‐fire resprouting responses of native and exotic grasses from Cumberland Plain Woodland (Sydney, Australia) under elevated carbon dioxide

AbstractThis study investigated the effect of elevated CO2 on the post‐fire resprouting response of a grassland system of perennial grass species of Cumberland Plain Woodland. Plants were grown in mixtures in natural soil in mesocosms, each containing three exotic grasses (Nassella neesiana, Chloris gayana, Eragrostis curvula) and three native grasses (Themeda australis, Microlaena stipoides, Chloris ventricosa) under elevated (700 ppm) and ambient (385 ppm) CO2 conditions. Resprouting response after fire at the community‐ and species‐level was assessed. There was no difference in community‐level biomass between CO2 treatments; however, exotic species made up a larger proportion of the community biomass under all treatments. There were species‐level responses to elevated CO2 but no significant interactions found between CO2 and burning or plant status. Two exotic grasses (N. neesiana and E. curvula, a C3 and a C4 species respectively), and one native grass (M. stipoides, a C3 species) significantly increased in biomass, and a native C4 grass (C. ventricosa) significantly decreased in biomass under elevated CO2. These results suggest that although overall productivity of this community may not change with increases in CO2 and fire frequency, the community composition may alter due to differential species responses.

Phytochemicals and spore germination: At the root of AMF host preference?

Plants trigger various responses in the organisms living around them using a wide array of phytochemicals, which are components of their adaptation to a biological environment. The roots of five varieties of chickpea inoculated with Glomus intraradices were extracted, and extracts were fractionated, first based on solubility in methanol and further by HPLC. We found a relationship between chickpea genotype and root phytochemical composition. Several HPLC fractions repressed the germination of AM fungal spores in bioassays conducted in multi-well plates with extracts from the variety CDC Anna. This repression may be an expression of the control of the plant on the AM fungal symbionts. Glomus etunicatum and Gigaspora rosea spore germination responded differently to exposure to the HPLC fractions soluble in 25% methanol. A differential response of AM fungal species to plant phytochemicals could be involved in the so called “host preference” of AM fungi. Whereas extensin and other proteins were identified in a bioactive root extract fraction, other proteins undetected by LC–MS/MS analysis and non-peptidic compounds may be involved in AMF spore germination suppression.