Invasive alien species in Switzerland - Schweizer ...

An inventory of alien species and their threat to biodiversity and economy in Switzerland FOEN 2006 78
become part of greenhouse ecosystems although, in most cases, they cannot survive
winter conditions outdoors.
Many exotic seed chalcids of the genus Megastigmus (Torymidae) have been accidentally
introduced into Europe with seed trading, some of them having become pests in
European seed orchards (Roques and Skrzypczynska, 2003). Only M. spermothrophus,
the North American Douglas fir seed chalcid, is reported from Switzerland, but many
other species are known from neighbouring countries and, thus, are probably present in
Switzerland.
Two sphecid wasps have recently invaded Switzerland. The American Isodontia
mexicana has been found in the Ticino and the Lemanic region since the early 1990s
(Vernier, 1995, 2000). It feeds on crickets and, given its abundance, its impact on
native ecosystems would merit further attention. Sceliphron curvatum is an Asian
species which arrived in Europe in the 1970s. The first specimens were found recently
in Switzerland (Gonseth et al., 2001). Its nests are commonly found in houses and other
buildings.
Five exotic ant species are recorded for the Swiss fauna (Freitag et al., 2000; Neumeyer
and Seifert, 2005). These are ‘tramp’ ants of tropical and subtropical origin but transported
by human activities to most regions of the world. The most common is the
Asian species Monomorium pharaonis, very abundant in buildings and often considered
as an urban pest. Hypoponera schauinslandi is found in greenhouses and other
heated buildings in Central Europe (Seifert, 2004). Linepithema humile is the famous
Argentine ant, which has invaded a vast territory along the Mediterranean coast and
has been occasionally recorded in Switzerland (e.g. Kutter, 1981). Neumeyer and
Seifert (2005) state that it could soon become established in outdoor situations because
of global warming. Tapinoma melanocephalum and Paratrechina longicornis have
been observed in few occasions indoors in Switzerland and their establishment is not
firmly established (Dorn et al., 1997; Freitag et al., 2000). Another ant, Lasius neglectus
Van Loon, Boomsma & Andrasfalvy, an Asian species, is rapidly invading Europe,
causing some damage in urban areas (Seifert, 2000). It is not yet recorded from Switzerland,
but its occurrence in neighbouring countries (France, Italy and Germany)
suggests that it may be already present.
Finally, the chestnut gallwasp, Dryocosmus kuriphilus Yasumatsu (Hym.: Cynipidae),
is worth mentioning as a potential threat for the European chestnut, Castanea sativa, in
Switzerland and the rest of Europe. This Chinese species was found for the first time in
Northern Italy in 2002 and is considered as the most serious insect pest of Castanea
spp. worldwide (Bosio, 2004). Attacks of Dryocosmus kuriphilus reduce growth of
young chestnuts and fruiting. Yield reductions of 50–70 % are observed and severe
infestations may result in the dead of the tree.