Isabel C. Barrio

Higher predation risk for insect prey at low latitudes and elevations

Risky in the tropics It is well known that diversity increases toward the tropics. Whether this increase translates into differences in interaction rates among species, however, remains unclear. To simplify the problem, Roslin et al. tested for predation rates by using a single approach involving model caterpillars across six continents. Predator attack rates were higher toward the equator, but only for arthropod predators. Science, this issue p. 742 Like diversity, predation rates among insects increase toward the equator and at lower altitudes. Biotic interactions underlie ecosystem structure and function, but predicting interaction outcomes is difficult. We tested the hypothesis that biotic interaction strength increases toward the equator, using a global experiment with model caterpillars to measure predation risk. Across an 11,660-kilometer latitudinal gradient spanning six continents, we found increasing predation toward the equator, with a parallel pattern of increasing predation toward lower elevations. Patterns across both latitude and elevation were driven by arthropod predators, with no systematic trend in attack rates by birds or mammals. These matching gradients at global and regional scales suggest consistent drivers of biotic interaction strength, a finding that needs to be integrated into general theories of herbivory, community organization, and life-history evolution.

Does wild boar rooting affect livestock grazing areas in alpine grasslands

Interactions between traditional livestock management practices and wildlife activities are important in the conservation of many mountain ecosystems including the summer rangelands in the Spanish Central Pyrenees, where rooting by wild boar (Sus scrofa) is a large disturbance that can reduce the amount of area available to grazing livestock. This study explored the likely impact of wild boar rooting on Pyrenean grasslands. It quantified the extent of wild boar rooting in livestock grazing areas and determined whether wild boars selected or avoided areas depending on the type of livestock and stocking rates. Wild boar rooting affected 16% of livestock grazing area and occurred in sites that were grazed by cattle, rather than by sheep. In addition, a preference for areas that had intermediate stocking rates was found. The relationship between the increase in the number of wild boars and trends in livestock management suggests that the extent of wild boar rooting will increase especially in cattle grazing areas, and therefore, the area available for cattle grazing in Pyrenean mountain rangelands would decrease significantly.

Assessment of methods for estimating wild rabbit population abundance in agricultural landscapes

Various methods have been used to estimate rabbit abundance, but comparisons of standard methods are still lacking, and thus, results remain roughly comparable across studies. Ideally, a method should be applicable over a wide range of situations, such as differing abundances or habitat types. Comparisons of methods are required to evaluate the benefits of each of them, and survey methods should be validated for the conditions in which they will be used. In this study, we compare the performance of direct methods (kilometric abundance index and distance sampling) in two seasons and at two times of day (dusk and night) for estimating wild rabbit abundances in agricultural landscapes. Estimates based on direct methods were highly correlated and detected similar seasonal population changes. Night counts provided better estimates than did dusk counts and exhibited more precision. Results are discussed within the context of rabbit behaviour and their implications for rabbit population surveys.

Farming for pests? Local and landscape-scale effects of grassland management on rabbit densities

In recent decades in the UK, there has been an increasing trend in numbers of the European wild rabbit, a significant agricultural pest typically associated with grassland habitats. However, the relationship between rabbit abundance and grassland management, in particular grazing, has not been sufficiently explained. We studied rabbit densities in seven pasture-dominated sites in north-east England between autumn and spring in two consecutive years, and used generalised linear mixed models and generalised additive models to explore relationships between habitat and management variables and rabbit abundance at local (field) and landscape scales. At the local scale high rabbit densities were significantly associated with small fields and the very short, homogeneous swards created by intensive sheep grazing during autumn and winter. At the landscape scale, high rabbit numbers were associated with sites with most field margins and a predator removal policy. Our results indicate that landscape management may play a central role in explaining rabbit abundance and distribution in grasslands. We suggest that current pasture management may create favourable conditions for high rabbit densities, and consequently boost numbers of this significant pest species.

Harbouring pests: rabbit warrens in agricultural landscapes

Context Warrens are central to rabbit biology and available warren space can set a limit to the number of rabbits living in an area. Therefore, quantifying and analysing the distribution of rabbit warrens is a key step towards the management of the species in agricultural lands where it causes significant damage to crops. Aims The present study investigates the distribution and spatial pattern of wild rabbit (Oryctolagus cuniculus) warrens in an intensively managed agricultural landscape within the rabbit’s native range in semiarid southern Spain, where rabbits constitute an emerging pest problem. Methods All natural rabbit warrens within two sites were mapped, and information on their size, use and protection was recorded. The effects of environmental variables (e.g. habitat features and distances to key resources) in determining warren occurrence were evaluated using binomial generalised linear models (GLM). Key results The main variable explaining warren occurrence was the distance to the nearest neighbouring warren. Habitat variables and the distances to key resources played only a secondary role, and were mainly related to frequent ploughing linked to agricultural practices that prevent warren construction. Conclusions Habitat instability resulting from agricultural practices (i.e. frequent ploughing and intensive human disturbance) promotes warren construction on stable grounds only and partly explains the clumped spatial pattern found. However, warren occurrence in intensively managed agricultural areas seems to be more constrained by the proximity of neighbouring warrens that would facilitate rabbit recolonisation from patches nearby. Despite becoming increasingly scarce as a result of agricultural intensification, these unploughed remnants may act as safe islands for digging warrens. Implications The management of unploughed patches and the connectivity among them in semiarid agroecosystems of southern Spain is therefore of utmost importance to the management of rabbits as an agricultural pest.

Can cover crops reduce rabbit-induced damages in vineyards in southern Spain?

Damage caused by wildlife foraging can lead to significant agricultural losses and the problem can be further complicated if the damage-inducing animal is a valuable resource in its own right. Provision of alternative food sources such as cover crops might be a means of reducing the damage which appears to be linked to scarcity of alternative foods in intensively-managed agroecosystems. Cover crops may provide other benefits to agroecosystems, i.e. preventing soil erosion but can potentially have some undesired consequences, i.e. water competition with the cash crop. In our study, we tested the effectiveness of cover crops in reducing the damage caused by foraging European rabbit Oryctolagus cuniculus to vineyards in a semi-arid agroecosystem in southern Spain. Experimental treatments consisted of a combination of the presence/absence of sown cover crops (70% oat Avena sativa and 30% garden vetch Vicia sativa) with/without rabbit exclusion. In the 2009 growing season, we assessed rabbit-induced damage using a browsing index on vine shoots, rabbit use of plots was estimated based on faecal pellet counts and grapevine yield was measured at harvest. Rabbits ate the cover crops, and rabbit use was highest in the plots sown with the oat and vetch cover crop. However, the effect of the presence of the cover crop on the amount of damage caused by rabbits was limited and, moreover, the presence of the cover crop had a negative effect on grapevine yield. Exclosure fences effectively reduced rabbit damage by keeping rabbit densities close to zero, but even a low rabbit number (∼ 1 rabbit/ha) can cause significant damage. Although cover crops provided rabbits with an alternative food source, they acted as attractants for rabbits and were not effective in reducing the damage caused to vineyards by higher rabbit numbers. Therefore, adding cover crops might not be an effective measure in controlling rabbit-induced damage in semi-arid wine-growing regions.

After the frass: foraging pikas select patches previously grazed by caterpillars.

Interactions among herbivores can shape the structure of their communities and drive their dynamics. However, detecting herbivore interactions can be challenging when they are deferred in space or time. Moreover, interactions among distantly related groups of herbivores, such as vertebrates and invertebrates, are poorly understood. We investigated the effect of invertebrate herbivory on the subsequent foraging choices of a small alpine-dwelling vertebrate, the collared pika (Ochotona collaris). We carried out a field experiment within pika territories, by presenting them with a choice of foraging sites following manipulation of invertebrate (caterpillar) herbivory. Pikas actively selected areas with increased, recent invertebrate herbivory. While the underlying mechanisms behind this interaction remain unknown, our results demonstrate a positive effect of invertebrate herbivores on subsequent vertebrate foraging preferences for the first time. Even among distantly related taxa, such interactions where one herbivore is cueing on the foraging of another, could drive the creation of herbivory hotspots, with cascading consequences for ecosystem processes.

Alpine Ecology in the Iberian Peninsula: What Do We Know, and What Do We Need to Learn?

Abstract The 11th Conference of the Spanish Association of Terrestrial Ecology, held in Pamplona, Spain, on 6–10 May 2013, included a symposium on alpine ecological research in the Iberian Peninsula. This session offered an excellent opportunity to assess the state and progress of alpine ecology in this region, identify knowledge gaps, and discuss further directions for research. Iberian alpine ecosystems are biodiversity hotspots and have traditionally contributed to sustaining rural livelihoods. Today, these ecosystems are subjected to large changes in land uses, including land abandonment, and are affected by climate change. This article reviews the current state of Iberian alpine ecology and proposes a research agenda. Alpine ecology in the Iberian Peninsula is a growing field of research. The need for larger spatial and temporal scales in research and monitoring, along with the integration of socioecological aspects, is a critical issue for understanding the major drivers of change in the alpine ecosystems of the Iberian Peninsula. The implementation of effective mitigation strategies aimed at reducing the impact of the pressing environmental and socioeconomic problems of Iberian mountain areas can only be accomplished through a multidisciplinary and integrative approach.

Assesment of wild boar rooting on ecological and pastoral values of alpine pyrenean grasslands

Las hozaduras de jabali son una de las mayores perturbaciones actuales de los pastos supraforestales pirenaicos. Sus consecuencias para el ecosistema no estan todavia perfectamente descritas, a pesar de ser uno de los habitats de mayor interes de conservacion y que juegan un importante papel en las economias locales. Los bienes y servicios que provee dicho habitat estan claramente relacionados tanto con su valor ecologico como pastoral, los cuales parecen estar afectados por las citadas perturbaciones. En este trabajo se midieron dichos valores dentro y fuera de perturbaciones a diferentes escalas espaciales para incrementar el conocimiento de la repercusion de las hozaduras de jabali en el ecosistema de los pastos alpinos, particularmente sensibles a la remocion del suelo. A escala de paisaje y de comunidad, comparamos las areas perturbadas y no perturbadas por el jabali, en mapas del valor pastoral, valor ecologico y de comunidades pascicolas de la zona de estudio, por medio de un sistema de informacion geografica. A escala local comparamos los valores ecologico y pastoral de los grupos de plantas (sobre la base de la abundancia de especies), dentro y fuera de las hozaduras de jabali. A escala de paisaje se encontro una preferencia por zonas de alto valor pastoral y valores ecologicos intermedios. Sin embargo, a escala de comunidad las perturbaciones redujeron notablemente el valor pastoral y ecologico en todas las comunidades. A escala local, se encontro un aumento del valor ecologico de los bulbos y del valor pastoral de las dicotiledoneas anuales dentro de las perturbaciones, lo que sugiere que estas pueden favorecer la diversidad de grupos funcionales. Las hozaduras de jabali afectan moderadamente a los pastos alpinos pirenaicos, con mayor afeccion sobre los valores pastorales que sobre los ecologicos en todas las escalas estudiadas, lo que debiera tenerse en cuenta para el manejo y preservacion de estos habitats, ya que dichas perturbaciones se estan, muy probablemente, incrementando.

Effects of Hedges and Herbaceous Cover on Passerine Communities in Mediterranean Olive Groves

Abstract. In recent decades, agricultural intensification and landscape simplification have dramatically affected farmland biodiversity. To reduce this trend, agri-environmental schemes (AES) of the Common Agricultural Policy (CAP) were launched in the European Union in the early 1990s. Since then an effort has been made to asses the effectiveness of these measures, but, in the Mediterranean region, where olive groves are among the predominant crops, the effectiveness of AESs to maintain farmland biodiversity remains poorly evaluated. In conventional olive farming, the only AES now in practice are the implementation of herbaceous, non-crop vegetation within crops (i.e. ground covers) aimed at preventing soil erosion, and the maintenance of hedges. These practices, when applied separately, can increase structural complexity, likely benefitting farmland biodiversity at different spatial scales; however, little is known about the potential synergistic effects when these measures are applied in combination in Mediterranean agroecosystems. This study assessed the combined effects of herbaceous ground cover and hedges on passerine communities of olive groves over a 4-yr period. Hedges, and to a lesser extent ground covers, efficiently increased the abundance and richness of passerine communities of olive groves, particularly that of insectivorous birds, but the effects of both measures were independent of each other. Hedges were particularly relevant to the richness and abundance of passerine communities, especially at distances up to 50 m. Therefore, we suggest that management should promote the creation of a hedge network embedded in the olive grove matrix, for example by promoting or maintaining hedgerows located between properties. This study underscores the important role of increasing structural complexity in Mediterranean perennial agroecosystems through the implementation of ground covers and maintaining hedges, to preserve farmland passerine communities, and encourages the use of these agri-environmental measures as a tool in landscape planning and conservation.