Is the Perigord black truffle threatened by an invasive species? We dreaded it and it has happened!

Invasive alien species are species introduced deliberately or unintentionally to areas outside their natural habitats. They can cause a significant irreversible environmental and socio-economic impact at genetic, species and ecosystem levels, and as claimed by Moore (2000), ‘throughout the world, exotic aliens are wreaking havoc’. The control of these invasive alien species has been discussed at international conventions, such as the Bern convention in 1979. Research on biological introductions has primarily focused on plant and animal invaders. Until now only a few studies have dealt with the spread of fungi through different continents and countries (Desprez-Loustau et al., 2007), largely because of a lack of scientific knowledge of fungal biodiversity and ecology. Reports have mostly focused on the introduction of agronomically important plant pathogenic fungi (above all, rusts and Ascomycetes) and pseudofungi (Stramenopila and Peronosporomycetes), and their invasion routes (Desprez-Loustau et al., 2007). The most common way of introducing fungal pathogens is through the movement of infected planting stock or infested wood (Coetzee et al., 2001). The success of invasive fungal pathogens in these new environments might be explained by an increased aggressiveness towards new host species that have not had an opportunity to evolve resistance. The ecological impacts of the intentional/unintentional introduction of fungal species, apart from plant pathogens, have been largely ignored (Schwartz et al., 2006). Regarding saprotrophic taxa, in-depth studies have only been carried out with a few species, for example Coprinopsis stangliana (Bougher, 2006), and some woodchip fungi (Shaw et al., 2004). As far as ectomycorrhizal fungi are concerned, the accidental introduction and spread of Amanita phalloides (Pringle & Vellinga, 2006), Boletus edulis s.l. (Hall et al., 1998) and Eucalyptus-associated species, such as Pisolithus spp. (Martin et al., 2002), have been carefully studied and monitored. These symbiotic fungi were accidentally introduced when allochthonous trees were planted for agriculture and reforestation (Hall et al., 1998; Martin et al., 2002). The deliberate movement of nonindigenous mycorrhizal fungal species and strains is a phenomenon occurring with increasing frequency as a consequence of the use of beneficial soil organisms to improve horticulture (Azcon-Aguilar & Barea, 1997), bioremediation (Leyval et al., 2002), reforestation (Duponnois et al., 2005) and edible fruit body production (Hall et al., 1998; Hall et al., 2003). The impact of all these introductions on the overall native resident fungal communities is not well understood, and scant attention has been paid to the ecological impact of transporting nonpathogenic fungi across continents (with a few exceptions, e.g. Selosse et al., 1998). Monitoring efforts are therefore urgently needed to track the spreading pattern of introduced fungi.