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Arion lusitanicus has become a major pest species in western Norway in the last few years. This species originates from southern Europe but has been spread by humans over large parts of central and northern Europe during recent decades. Slugs have traditionally been controlled by the use of molluscicides; but, as these may have serious ecological side effects, biological control of slugs is highly desirable. Potential biological control agents include nematodes, gastropods and arthropods.In laboratory experiments, we tested whether five common predator beetles would feed on eggs and juveniles of A. lusitanicus. The species Carabus nemoralis, Nebria brevicollis, Pterostichus melanarius and Pterostichus niger (Carabidae) as well as Staphylinus erythropterus (Staphylinidae) were tested, of which only P. melanarius has been tested on A. lusitanicus previously. Nebria brevicollis did not feed on slug eggs or newly hatched slugs, but the remaining four species all killed and ate a large proportion of the eggs and hatchlings offered. Both P. melanarius and P. niger also destroyed A. lusitanicus eggs and hatchlings under conditions emulating those in the field. Prey size choice experiments were conducted by feeding C. nemoralis, P. niger and S. erythropterus on different sizes of A. lusitanicus. Carabus nemoralis was also given a choice between two slug species, A. lusitanicus and Deroceras reticulatum. A significant preference for slugs smaller than one gram was evident for C. nemoralis, while the other beetles struggled much more to overcome the mucus of juvenile slugs. No significant preference was found between A. lusitanicus and D. reticulatum as prey for C. nemoralis. We also discuss the feasibility of biological control of A. lusitanicus using beetle predators.
Spiders and beetles were pitfall-trapped in the foreland of the receding Hardangerjøkulen glacier in central south Norway. At each of six sampling sites, ages 3 to 205 years, twenty traps covered the local variation in moisture and plant communities. Thirty-three spider species and forty beetle species were collected. The species composition was correlated to time since glaciation and vegetation cover. A characteristic pioneer community of spiders and mainly predatory beetles had several open-ground species, and some species or genera were common to forelands in Svalbard or the Alps. While the number of spider species increased relatively constant with age, the number of beetle species seemed to level off after about 80 years. Half of the beetle species were Staphylinidae, and contrary to Carabidae, most of these were rather late colonizers. Most herbivore beetles colonized after more than 40 years, but the moss-eating Byrrhidae species Simplocaria metallica and also certain Chironomidae larvae developed in pioneer moss colonies after 4 years. The large Collembola Bourletiella hortensis, a potential prey, fed on in-blown moss fragments after 3 years. In the present foreland, chlorophyll-based food chains may start very early. Two pioneer Amara species (Carabidae) could probably feed partly on seeds, either in-blown or produced by scattered pioneer grasses.
The establishment of tree seedlings in primary succession is thought to occur only after an adequate reserve of nutrients has accumulated in the soil. Individuals of Pinaceae are sometimes reported to grow on very recently deglaciated substrates. This study analyzed the colonization of a glacier foreland by Pinus wallichiana. Physical, chemical, and biotic aspects of potential and observed seedling microsites were analyzed with regression methods and tests for proportions. Microsites with intermediate to high moisture levels and alkaline nutrient-poor soils were found to be conducive to seedling establishment. The most recently deglaciated parts of the foreland have soils with little nutrients and high pH. There is a linear change in soil variables from low nutrient content and high pH at the most recently deglaciated parts to more nutrient-rich and neutral toward the pre-neoglacial moraines. Surrounding old-growth forests of Pinus wallichiana shed an abundance of seeds onto the foreland, are able to germinate and grow, and are predominant among the early pioneers, which makes this species an unusual pioneer of primary succession. Colonization by P. wallichiana is not restricted to particular safe sites. Even though individuals look chlorotic and stunted, they grow at near normal rates. Leaf discoloration of seedlings occurs in soils with high pH and low nitrogen content. P. wallichiana is also a canopy dominant on some of the oldest terrains and outside the foreland.
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