Seed Predation on Oil-Polluted and Unpolluted Vachellia (Acacia) Trees in a Hyper-Arid Desert Ecosystem

Acacia trees are keystone species in many arid environments, supporting high levels of plant and animal diversity. In Israel, the populations of Vachellia (formerly Acacia) tortilis (Forssk.) and V. raddiana (Savi) are declining at an alarming rate. Severe infestations by bruchid beetles (Coleoptera, Chrysomelidae) are among the major causes of seed mortality, but additional environmental stressors can reduce the defence level of the seeds, exacerbating their susceptibility to predators. In a hyper-arid desert ecosystem affected by two major oil spills (in 1975 and 2014), we quantified seed predation rates caused by insect granivores before and after the pods dropped to the ground. We recorded predation rates of up to 84% for both tree species, and higher predation rates at the ground level than in the canopy, suggesting that repeated infestations occur. These results reinforce the call to protect the populations of large ungulates such as gazelles, which kill the bruchids by feeding upon the pods, and promote seed germination and dispersion. We found no clear evidence of a negative effect of the oil spill on seed predation, indicating that oil pollution did not increase the vulnerability of the seeds to granivores even in trees affected by the recent oil spill.Jacob Blaustein Center for Scientific Cooperationinfo:eu-repo/semantics/publishedVersio

Trunk Refugia : A Simple, Inexpensive Method for Sampling Tree Trunk Arthropods

Trees host a large share of the global arthropod diversity. Several methodologies have been described to sample arthropods from trees, ranging from active sampling techniques (e.g., visual searching, beating, or shaking the branches) to passive sampling devices. The majority of these collection techniques are destructive, and do not specifically target the tree trunk arthropod fauna. Here, we describe an alternative sampling method called trunk refugia (TR). TR are cylindrical shelters made of corrugated cardboard that can be secured to trees using string, and can remain exposed for varying time periods. These refugia are inexpensive, easy to use, and suitable to monitor a diverse array of insects and arachnids. Moreover, TR are nonlethal sampling tools, and allow collecting live individuals for behavioral studies or for rearing.RESUMEN: Los árboles albergan una gran parte de la diversidad global de artrópodos. Varias metodologías han sido descritas para muestrear artrópodos de árboles, desde técnicas activas (e.g., búsqueda visual, red de golpeo) hasta dispositivos de muestreo pasivo. La mayoría de estas técnicas son letales, y no están dirigidas específicamente a los artrópodos de troncos de árboles. Describimos aquí un método alternativo llamado trampas refugio (TR). Las TR son refugios hechos de cartón corrugado que se colocan en los troncos usando cuerda, y pueden permanecer expuestos por períodos variables. Estas trampas son económicas, fáciles de usar, y apropiadas para monitorear una gran variedad de insectos y arácnidos. Además, las TR son no-letales, por lo que permiten la colección de individuos vivos para estudios de comportamiento o crianza.Jacob Blaustein Center for Scientific Cooperation; Israel Nature and Parks Authorities (INPA); Israel's National Nature Assessment Program (HAMAARAG); Israel Ministry of Agriculture (131-1793-14)info:eu-repo/semantics/publishedVersio

Gains and losses in ecosystem services and disservices after converting native forest to agricultural land on an oceanic island

Habitat conversion to agricultural land is one of the main threats to terrestrial biodiversity and can affect ecosystem processes and cause changes in ecosystem services (ESs) and disservices (EDs). Yet, studies often rely only on the abundance and diversity of the service providers; the effects on ecological processes of habitat conversion are rarely directly monitored. In this study, we used the sentinel approach to evaluate how habitat conversion from native forest to agricultural land affected ESs and EDs on an oceanic island. We quantified herbivory on lettuce plants, invertebrate and vertebrate predation rates on artificial caterpillars, pollination on strawberry plants, seed predation on wheat and mustard seeds, and leaf decomposition rates in native forests, maize fields and pastures on Terceira Island, Azores (Portugal). Herbivory, invertebrate predation rates, and pollination service were not significantly different between habitats. Vertebrate predation rates in native forests (mean 6.1% d⁻¹) were significantly higher than that in pastures (0.3% d⁻¹), or high-elevation maize fields (0.5% d⁻¹), and marginally higher than in low-elevation maize fields (2.2% d⁻¹). Overall seed predation after 48 h was significantly higher on wheat (mean 16.8%) than mustard seeds (5.6%). High-elevation maize fields also had higher seed predation (27.8%) than low-elevation ones (0.6%) or pastures (3.6%), but did not differ from the native forest (12.9%). Decomposition after 90 days was highest in pastures (78.4% and 45.9%, for tea and rooibos, respectively); although no significant differences between habitats were detected, except for low-elevation maize fields (64.4% and 33.6%). Conversion from native forest to cultivated land did not cause a clear decrease in the intensity of the studied ESs/EDs except for vertebrate predation. Using direct monitoring tools to simultaneously and consistently quantify multiple ecological processes is not only possible but needed, as ecological processes can respond differently to landscape changes.This work was financed by FEDER (European Regional Development Fund) in 85% and by Azorean public funds by 15% through Operational Program Azores 2020, under the project AGRO-ECOSERVICES (ACORES01-0145-FEDER-000073).info:eu-repo/semantics/publishedVersio

The Impact of Terrestrial Oil Pollution on Parasitoid Wasps Associated With Vachellia (Fabales: Fabaceae) Trees in a Desert Ecosystem, Israel

Oil is a major pollutant of the environment, and terrestrial oil spills frequently occur in desert areas. Although arthropods account for a large share of animal diversity, the effect of oil pollution on this group is rarely documented. We evaluated the effects of oil pollution on parasitoid wasps associated with Vachellia (formerly Acacia) tortilis (Forssk.) and Vachellia raddiana (Savi) trees in a hyper-arid desert that was affected by two major oil spills (in 1975 and 2014). We sampled the parasitoid populations between 2016 and 2018 in three sampling sites and compared their abundance, diversity, and community composition between oil-polluted and unpolluted trees. Parasitoid abundance in oil-polluted trees was lower in one of the sites affected by the recent oil spill, but not in the site affected by the 1975 oil spill. Oil-polluted trees supported lower parasitoid diversity than unpolluted trees in some sampling site/year combinations; however, such negative effects were inconsistent and pollution explained a small proportion of the variation in parasitoid community composition. Our results indicate that oil pollution may negatively affect parasitoid abundances and diversity, although the magnitude of the effect depends on the tree species, sampling site, and the time since the oil spill.Israel Nature and Parks Authority (INPA); Jacob Blaustein Center for Scientific Cooperation.info:eu-repo/semantics/publishedVersio

Effect of Weed Management on the Parasitoid Community in Mediterranean Vineyards

Enriching agroecosystems with non-crop vegetation is a popular strategy for conservation biocontrol. In vineyards, the effects of specific seeded or planted cover crops on natural enemies are well-studied, whereas conserving spontaneously developing weeds received less attention. We compared parasitoid communities between matched pairs of vineyard plots in northern Israel, differing in weed management practices: “herbicide”, repeated herbicide applications vs. “ground cover”, maintaining resident weeds and trimming them when needed. Using suction sampling, we assessed the parasitoids’ abundance, richness, and composition during three grape-growing seasons. Ground cover plots had greater parasitoid abundances and cumulative species richness than herbicide-treated plots, possibly because of their higher vegetation cover and richness. Dominant parasitoid species varied in their magnitude and direction of response to weed management. Their responses seem to combine tracking of host distributions with attraction to additional vegetation-provided resources. Parasitoid community composition was mildly yet significantly influenced by weed management, while season, year, and habitat (weeds vs. vine) had stronger effects. Vineyard weeds thus support local biocontrol agents and provide additional previously demonstrated benefits (e.g., soil conservation, lower agrochemical exposure) but might also attract some crop pests. When the benefits outweigh this risk, weed conservation seems a promising step towards more sustainable agricultural management.This research was funded by the Israel Open Lands Foundation, the Tabor Winery and the Nekudat Chen Foundation.info:eu-repo/semantics/publishedVersio