Exotic tree species are used worldwide for planting, often because they are fast growing species with good wood properties. Common wisdom also assumes that being planted outside their native range, exotic trees may benefit from the loss of their natural pests. This observation has led to the so called “Enemy Release Hypothesis”. However exotic tree species may also be attacked by insect species native from the country of introduction, in particular by those which are able to expand their feeding niche. To evaluate this risk, we conducted a systematic review of the scientific literature.
A total of 590 native European insect herbivores have been observed to feed on one or more of the main 28 exotic tree species introduced to Europe as planted forests. Feeding guilds recruited by exotic tree species well reflect the insect communities commonly associated to living trees in temperate forests. Thus, host expansion is not confined to specific feeding guilds. Yet, some feeding guilds, such as the highly specialized gall makers are under-represented.
The presence of congeneric native trees in the area of introduction increases the risk of exotic trees being attacked by native insects, especially by specialist herbivores (Fig. 1). An emblematic example is Pinus radiata, introduced to Europe from North America. It is one of the most common exotic trees used in European planted forests and has several native congeners in Europe. Its plantations are reported to be severely damaged by Thaumetopoea pityocampa in southern Europe.
Your ultimate guide shall begin by saying that there is an ultimate solution to their sexual problems in buy cialis on line the markets, which are helping out women to have satisfying sexual drives. The adult industry has been one of the essential medicinal products which lead viagra sale without prescription for relief from sexual dysfunction. / According to a recent post of the New York Times, ‘sleeping problems can be drain in love life.It cancause erectile problems in male and loss of libido in woman of all age groups. Their properties make best buy on viagra them effective treatments for impotence, mental disease, sterility, etc. Although alternative medicines like Kamagra, buy sildenafil uk important link, Eriacta, levitra super active etc.
The geographical extent of forest planted with exotic trees is also critical: more native insect herbivores are reported to feed on those exotic trees that are planted across large areas (Fig. 2). For example, Pseudotsuga menziesii, which although has no congeners in Europe, was extensively planted across Europe (in at least 12 countries) and is the species with the greatest number of native insects recruited (94).
Host expansion by native, and potentially damaging, herbivores may thus occur more frequently than previously thought. Such a finding emphasizes the need for careful evaluation of risks when introducing exotic tree species for plantation purposes, for example when searching for safe alternatives to native trees in the context of climate change adaptation. We recommend that risk assessments be conducted prior to the introduction, considering several factors such as invasiveness, hybridization and susceptibility to native insect species or pathogens. Also we suggest that exotic tree species should not be planted as large monocultures.