Detecting aphid predation by earwigs in organic citrus orchards using molecular markers

Romeu-Dalmau C., Piñol J., Agustí N. (2012) Detecting aphid predation by earwigs in organic citrus orchards using molecular markers. Bulletin of Entomological Research. 102: 566-572.
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Doi: 10.1017/S0007485312000132

Resum:

Aphids (Hemiptera: Aphidoidea) can damage citrus trees via direct damage to leaves and flowers or via the indirect transmission of viruses. Predators such as the European earwig, Forficula auricularia Linnaeus (Dermaptera: Forficulidae), may assist in keeping aphid populations under control in citrus orchards. Group-specific primers were developed to detect aphid DNA in earwigs, in order to determine earwig predation rates in aphids in Mediterranean organic citrus trees. These primers were designed in accordance with the alignment of comparable sequences of aphids and earwigs, and they amplified a 224 bp fragment of the mitochondrial cytochrome c oxidase subunit I (COI) region. Following the consumption of three to five Aphis spiraecola Patch, aphid DNA was still detectable in 50% of earwigs one day after the ingestion. When predation was evaluated in the field, aphid DNA was detected in earwigs in May, June and July but not in April and August. The most interesting result is that of May, when aphid abundance was very low but 30% of the earwigs tested positive for aphid DNA. This finding suggests that earwigs are important aphid predators in citrus orchards, as they probably alter aphid dynamics as a result of early seasonal pressure on this pest. Copyright © 2012 Cambridge University Press.

Llegeix més

Friend or foe? The role of earwigs in a Mediterranean organic citrus orchard

Romeu-Dalmau C., Piñol J., Espadaler X. (2012) Friend or foe? The role of earwigs in a Mediterranean organic citrus orchard. Biological Control. 63: 143-149.
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Doi: 10.1016/j.biocontrol.2012.06.010

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As earwigs (Insecta: Dermaptera) are considered both effective predators of aphids and pests in their own right in citrus orchards, the aim of the present study was to examine their relative role as pest versus predator. We conducted a two-year experiment of earwig exclusion from citrus canopies and compared aphid infestation, flower survival and fruit yield in trees with earwigs (control trees) with those in trees without earwigs (banded trees). However, as not only earwigs but also all other crawling insects were excluded from the banded trees, we added a third group of trees (earwig trees) where crawling insects were excluded but earwigs were added to the canopy every 1-2. weeks. We hypothesized that if the same results were obtained in control and earwig trees, and both differed from those obtained in banded trees, earwigs would most probably be the cause of these differences. Overall, aphid infestation in trees with earwigs was less severe than aphid infestation in trees without earwigs; we also found that aphid density was negatively related to earwig abundance. Earwigs also negatively influenced flower survival but this effect was no longer observed once trees naturally abscised their own flowers and fruitlets. Finally, we did not find any difference in fruit yield between the treatments, or any relationship between earwig abundance and fruit production. Thus, as earwigs appeared to control aphid populations while not affecting fruit yield, we can conclude that earwigs are beneficial insects in this Mediterranean organic citrus orchard. © 2012 Elsevier Inc.

Llegeix més

Unraveling the life history of successful invaders

Sol D., Maspons J., Vall-llosera M., Bartomeus I., García-Peña G.E., Piñol J., Freckleton R.P. (2012) Unraveling the life history of successful invaders. Science. 337: 580-583.
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Doi: 10.1126/science.1221523

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Despite considerable current interest in biological invasions, the common life-history characteristics of successful invaders remain elusive. The widely held hypothesis that successful invaders have high reproductive rates has received little empirical support; however, alternative possibilities are seldom considered. Combining a global comparative analysis of avian introductions (>2700 events) with demographic models and phylogenetic comparative methods, we show that although rapid population growth may be advantageous during invasions under certain circumstances, more generally successful invaders are characterized by life-history strategies in which they give priority to future rather than current reproduction. High future breeding expectations reduce the costs of reproductive failure under uncertain conditions and increase opportunities to explore the environment and respond to novel ecological pressures.

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Eight years of ant-exclusion from citrus canopies: effects on the arthropod assemblage and on fruit yield.

Piñol J, Espadaler X, Cañellas N (2011) Eight years of ant-exclusion from citrus canopies: effects on the arthropod assemblage and on fruit yield. Agricultural and Forest Entomology doi: 10.1111/j.1461-9563.2011.00542.x.

An integrative model of human-influenced fire regimes and landscape dynamics

Loepfe L., Martinez-Vilalta J., Piñol J. (2011) An integrative model of human-influenced fire regimes and landscape dynamics. Environmental Modelling and Software. 26: 1028-1040.
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Doi: 10.1016/j.envsoft.2011.02.015

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Fire regimes depend on climate, vegetation structure and human influences. Climate determines the water content in fuel and, in the longer term, the amount of biomass. Humans alter fire regimes through increased ignition frequency and by hindering the spread of fire through fire suppression and fuel fragmentation. Here, we present FIRE LADY (FIre REgime and LAndscape DYnamics), a spatially explicit fire regime model that takes into account daily weather data, topography, vegetation growth, fire behaviour, fire suppression and land use changes. In this model, vegetation growth depends on water availability, and stem diameter and stand density are the fundamental parameters. Fire behaviour is modelled using the Rothermel equations and taking into account both crown fire and spotting. Human influences on fire regime, such as ignition frequency, fire suppression and land use changes, are explicitly modelled. The model was calibrated for three regions in NE Spain and reproduces fire regimes, changes in land cover distribution and tree biomass with promising accuracy. The explicit modelling of human influences makes the model a useful and unique tool for assessing the impacts of climate change and informing local fire regime management strategies. © 2011 Elsevier Ltd.

Llegeix més

Feedbacks between fuel reduction and landscape homogenisation determine fire regimes in three Mediterranean areas

Loepfe L., Martinez-Vilalta J., Oliveres J., Piñol J., Lloret F. (2010) Feedbacks between fuel reduction and landscape homogenisation determine fire regimes in three Mediterranean areas. Forest Ecology and Management. 259: 2366-2374.
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Doi: 10.1016/j.foreco.2010.03.009

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In densely populated areas like the Mediterranean, wildfire extent is mostly limited by fire suppression and fuel fragmentation. Fire is known to spread more easily through high fuel loads and homogenous terrain and it is supposed to reduce fuel amount and continuity, creating a negative feedback. Here we combine information from administration fire records, satellite imagery fire scars and land use/cover maps to asses the effects of fire on landscape structure and vice versa for three areas in Catalonia (NE Spain). We worked with three spatial focuses: the actual fire scar, 1 km2 squares and 10 km2 squares. In these regions agriculture land abandonment has lead to increased fuel continuity, paralleled by an increment of fire size. We confirm that fire spread is facilitated by land use/cover types with high fuel load and by homogeneous terrain and that fire reduces fuel load by transforming forests into shrublands. But we also found that fire increased landscape homogeneity, creating a positive feedback on fire propagation. We argue that this is possible in landscapes with finer grain than fire alone would create. The lack of discontinuities in the fuel bed diminishes the extinction capacity of fire brigades and increases the risk of large fires. We recommend that fire management should focus more on conservation of the traditional rural mosaic in order to prevent further increases in fuel continuity and fire risk. © 2010 Elsevier B.V. All rights reserved.

Llegeix més

A quantitative and statistically robust method for the determination of xylem conduit spatial distribution

Mencuccini M., Martinez-Vilalta J., Piñol J., Loepfe L., Mireia B., Alvarez X., Camacho J., Gil D. (2010) A quantitative and statistically robust method for the determination of xylem conduit spatial distribution. American Journal of Botany. 97: 1247-1259.
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Doi: 10.3732/ajb.0900289

Resum:

Premise of the study: Because of their limited length, xylem conduits need to connect to each other to maintain water transport from roots to leaves. Conduit spatial distribution in a cross section plays an important role in aiding this connectivity. While indices of conduit spatial distribution already exist, they are not well defi ned statistically. Methods: We used point pattern analysis to derive new spatial indices. One hundred and fi ve cross-sectional images from different species were transformed into binary images. The resulting point patterns, based on the locations of the conduit centersof-area, were analyzed to determine whether they departed from randomness. Conduit distribution was then modeled using a spatially explicit stochastic model. Key results: The presence of conduit randomness, uniformity, or aggregation depended on the spatial scale of the analysis. The large majority of the images showed patterns signifi cantly different from randomness at least at one spatial scale. A strong phylogenetic signal was detected in the spatial variables. Conclusions: Conduit spatial arrangement has been largely conserved during evolution, especially at small spatial scales. Species in which conduits were aggregated in clusters had a lower conduit density compared to those with uniform distribution. Statistically sound spatial indices must be employed as an aid in the characterization of distributional patterns across species and in models of xylem water transport. Point pattern analysis is a very useful tool in identifying spatial patterns. © 2010 Botanical Society of America.

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Ant versus bird exclusion effects on the arthropod assemblage of an organic citrus grove

Piñol J., Espadaler X., Cañellas N., MartíNez-Vilalta J., Barrientos J.A., Sol D. (2010) Ant versus bird exclusion effects on the arthropod assemblage of an organic citrus grove. Ecological Entomology. 35: 367-376.
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Doi: 10.1111/j.1365-2311.2010.01190.x

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Predation-exclusion experiments have highlighted that top-down control is pervasive in terrestrial communities, but most of these experiments are simplistic in that they only excluded a single group of predators and the effect of removal was evaluated on a few species from the community. The main goal of our study was to experimentally establish the relative effects of ants and birds on the same arthropod assemblage of canopy trees. We conducted 1-year long manipulative experiments in an organic citrus grove intended to quantify the independent effects of bird and ant predators on the abundance of arthropods. Birds were excluded with plastic nets whereas ants were excluded with sticky barriers on the trunks. The sticky barrier also excluded other ground dwelling insects, like the European earwig Forficula auricularia L. Both the exclusion of ants and birds affected the arthropod community of the citrus canopies, but the exclusion of ants was far more important than the exclusion of birds. Indeed, almost all groups of arthropods had higher abundance in ant-excluded than in control trees, whereas only dermapterans were more abundant in bird-excluded than in control trees. A more detailed analysis conducted on spiders also showed that the effect of ant exclusion was limited to a few families rather than being widespread over the entire diverse spectrum of spiders. Our results suggest that the relative importance of vertebrate and invertebrate predators in regulating arthropod populations largely depends on the nature of the predator-prey system. © 2010 The Authors. Journal compilation © 2010 The Royal Entomological Society.

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A simple method to differentially exclude ants from tree canopies based on ant body size.

Romeu-Dalmau C, Espadaler X, Piñol J (2010) A simple method to differentially exclude ants from tree canopies based on ant body size. Methods in Ecology and Evolution 1: 188-191.

Diseño y aplicación de una propuesta de aprendizaje cooperativo de los contendios del area de Ecología mediante el estudio de casos (inclou versió en anglés) . En “Hacia el espacio europeo de educación superior (EEES). Experiencias docentes innovadoras d

Rodrigo A, Martínez-Vilalta J, Piñol J, Lloret F, Ribas A, Retana J, Losarcos J (2009) Diseño y aplicación de una propuesta de aprendizaje cooperativo de los contendios del area de Ecología mediante el estudio de casos (inclou versió en anglés) . En “Hacia el espacio europeo de educación superior (EEES). Experiencias docentes innovadoras d e la UAB en ciencias sociales y en ciencias humanas”. Maite Martínez y Elena Añaños (eds.). Unitat d’Innovació Docent en Educació Superior. Universitat Autònoma de Barcelona, Servei de Publicacions.

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