The increasing international trade of tree seeds for national planting programs and ornamental purposes has considerably increased the risk of introduction of exotic seed insect pests inside the seeds. Despite this risk, European legislation does not impose systematic control of imported seed lots. This project aims at studying the mechanisms underlying the invasion, the establishment and the colonisation of new areas by seed insects. The genus Megastigmus is the largest group of forest seed insects. It is estimated that at least 52 Megastigmus species could potentially invade Europe through seed shipment. In its natural range, each Megastigmus species is generally found in a limited number of host species. However, it has been found that, when introduced in new areas, most Megastigmus species can infest local tree species if they are taxonomically close to the original host. Often, the absence of natural enemies and/or competitors in the area of introduction lead to an optimal use of the seed-resource, which can have considerable economic and ecological impacts. This 40-months project will study the population dynamics of 2 species of Megastigmus on true cedar in Southeastern France and the impact of these insects on the natural regeneration of cedar stands. Although both species of Megastigmus have been introduced in the study area, M. pinsapinis has been introduced more than 100 years ago and can been considered as naturalized, whereas M. schimitscheki has been introduced recently and is still invading new territories. The project will use competencies in forest entomology, forest ecology and population dynamics modelling to study the dynamics of both species at various spatial scales and the impact of these species on the natural regeneration of cedar stands. The project aims at understanding the processes involved in the invasion of the introduced species and in providing methodological tools transposable to other invasive seed insects.
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