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Distribution of the spider community in the olive grove agroecosystem (Portugal): potential bioindicators

Publication . Benhadi-Marín, Jacinto; Pereira, J.A.; Sousa, José Paulo; Santos, Sónia A.P.

Spiders are successful natural enemies in different crops. Research on the role of spiders as natural enemies within agroecosystems needs to address the distribution of their communities across different spatial scales, as well as the dominant species. We studied the spatial distribution of the community of spiders of the olive agroecosystem in Northeastern Portugal and investigated potential species that could be used as bioindicators of agricultural management in the olive grove. We found nine functional groups (ambushers, foliage runner hunters, ground hunters, orb-web builders, sheet web builders, sensing web-builders, space web builders, stalkers and wandering sheet/tangle weavers) encompassing a community that changed significantly across the horizontal and vertical gradient. We propose Thanatus vulgaris Simon, 1870 as potential bioindicator for the ground of the olive grove central area and Ozyptila pauxilla (Simon, 1870) for the ground of the olive grove peripheral area. Adjacent shrubland areas could play an important role in biological control of pests, allowing the exchange of species and individuals with the olive crop. The role of agrobiont species as indicators of agricultural managements deserves further investigation towards the enhancement of the effectiveness of spiders within low-impact crop management in arable landscapes.

2019Journal article

Open access

EcoPred: an educational individual based model to explain biological control, a case study within an arable land

Publication . Benhadi-Marín, Jacinto; Pereira, J.A.; Sousa, José Paulo; Santos, Sónia A.P.

Individual based models (IBMs) are up-to-date tools both in research and educational areas. Here we introduce an IBM built on NetLogo platform that simulates a top-down trophic cascade controlled by the pressure exerted by two model predators (web-building spiders and ground runner spiders) on a model pest (the olive fruit fly) within a hypothetical agricultural landscape (the olive crop). EcoPred is an IBM that aims to be an educational tool that can help teachers to explain concepts related to ecology in a modern, enjoyable and comprehensive way. EcoPred reflects the changes on a fly population within a simulated olive crop according to (1) the mortality rate caused by the predation of two spider species and energy loss, (2) the energy gain by feeding on flowers and (3) the reproduction rate in olive trees. The model was tested with 26 students achieving very good results in terms of acceptance and interest on the learning method. EcoPred can be used for educational purposes with 16 year old students and older to explain ecological concepts such as trophic level, species interactions, limiting factor and biological control in an interactive way simultaneously introducing students to biology oriented programming languages.

2020Journal article

Open access

Spiders actively choose and feed on nutritious non-prey food resources

Publication . Benhadi-Marín, Jacinto; Pereira, J.A.; Sousa, José Paulo; Santos, Sónia A.P.

Spiders are generalist predators adapted to consume a wide range of prey although their ability to exploit non-prey foods such as pollen, nectar, and honeydew has been referred but less studied. In this work, we investigated the effect of different non-prey food items (Glucose at 0.5 M; aphid honeydew; black scale honeydew; a mixture of glucose 0.5 M, phenylalanine 0.1 mM, proline 0.1 mM, and tryptophan 0.1 mM; honey at 10%, and pollen at 10%) on the survival of immature spiders of two functional groups represented by Haplodrassus rufipes (ground hunters) and Synema globosum (ambushers), and their feeding choices, in laboratory experiments. The overall survival of both species fed on non-prey foods significantly increased compared to individuals fed on water. The black-scale honeydew was the best food for H. rufipes increasing longevity up to 117 days. The highest survival reached by S. globosum was observed when fed on a mixture of glucose 0.5 M and three amino acids. When different non-prey food items were offered together, the exploring rate was significantly higher for H. rufipes than for S. globosum. H. rufipes chose to feed on honey whereas S. globosum chose the mixture treatment. The most chosen food items corresponded with those that provided the highest longevities in both species. Our results suggest that spiders could search, recognize and actively select the most beneficial non-prey food. Habitat management practices such as maintaining weed strips in the crop may provide these valuable supplementary food resources within agroecosystems contributing for biological pest control.

2019Journal article

Open access

A simulation-based method to compare the pest suppression potential of predators: A case study with spiders

Publication . Benhadi-Marín, Jacinto; Pereira, J.A.; Barreales, David; Sousa, José Paulo; Santos, Sónia A.P.

Assessing and comparing the pest killing capacity of predators is a crucial but laborious task during the implementation of sustainable farming systems. Critical attributes of assessment include quantifying predator’s attack rate (a) and handling time (Th). The maximum attack rate (T/Th) (i.e. the maximum number of prey that can be attacked by a predator during the time interval (T) considered) could be a more precise and interpretable indicator of the potential suppression of pests exerted by a predator; however, its calculation only provides a point estimator usually derived from incomplete datasets (e.g. unbalanced or low replicated experimental designs) that could lead to draw wrong conclusions. We introduce simaR (simulation of maximum attack rates using R), an R library that generates 95% confidence intervals around estimates of the maximum attack rate that can be easily and intuitively used to compare across species. We validated the simulation method and used the empirical results of a controlled laboratory experiment to compare the maximum attack rates of spiders across a range of Medfly prey densities and illustrate how to use simaR with non-replicated partial data. Applying our method we found a significant effect of temperature on the maximum attack rate of two different guilds of spiders, the orb-weaver A. cucurbitina and the ambusher S. globosum that was not relevant regarding their attack rate and handling time. Our method compares different predator species and/or experimental conditions in a simple and reproducible procedure through an accurate, easy-to-use, fast and statistically robust analysis, based on simulation and bootstrapping, that can be used to assess the pest suppression potential of predators by simulating their functional responses from low-effort laboratory trials.

2018Journal article

Open access

Functional responses of three guilds of spiders: Comparing single- and multiprey approaches

Publication . Benhadi-Marín, Jacinto; Pereira, J.A.; Sousa, José Paulo; Santos, Sónia A.P.

Spiders are successful natural enemies of pests occurring throughout the different strata of an agroecosystem. The study of their functional responses can provide information related to the potential effectiveness of different species and guilds on reducing a pest population. However, multiple prey availability may change the functional response of a predator. In this study, the functional responses of three species of spiders in single-prey and multiple-prey experiments were modelled. The spider species Haplodrassus rufipes, Araniella cucurbitina and Synema globosum were chosen as being representatives of ground runners, orb-weavers and ambushers, respectively. Three prey species were selected: a target prey, the Mediterranean fruit fly Ceratitis capitata and two alternate prey species, the flour moth Ephestia kuehniella and the house cricket Acheta domesticus. When the selected target prey C. capitata was supplied in the single-prey experiments, the most and the least efficient spider species were H. rufipes and S. globosum, respectively. However, opposite results were obtained when alternative preys were supplied. Also, A. cucurbitina significantly changed its functional response with the presence of alternative prey species. Considering the prey preference during the multiple-prey experiments, A. domesticus, used as representative of a heavy, long-sized and highly motile prey, was avoided whereas C. capitata, the target pest used as representative of light, small-sized and moderately motile prey was preferred by the three species of spiders. Ephestia kuehniella, used as representative of light, medium-sized and low motile prey was occasionally consumed. Each guild could include efficient predators against pests according to its hunting strategies and the ecological exploited niches. Orb-weavers could be efficient predators against flying pests; ambushers such as S. globosum could contribute to the reduction of the populations of flower-visiting pests, whereas active ground hunters may also play an important role preying on pests that develop a part or all of its life cycle in the ground. However, further research on feeding behaviour such as prey switching is needed for a better understanding of the effectiveness of spiders as natural enemies.

2019Journal article

Open access