Consequences of invasion by Pseudosuccinea columella on the dynamics of native lymnaeids living on the acid soils of central France

Eight road ditches located on granite and colonised by the native lymnaeids Galba truncatula or Omphiscola glabra were studied for 2 years to follow the distribution and density of these species in their habitats when the invasive lymnaeid Pseudosuccinea columella was introduced. Six other ditches populated only by a native lymnaeid or by P. columella were used as controls. The same experiment was also carried out for 3 years in seven water tanks placed in semi-natural conditions. The colonisation of P. columella was more rapid in habitats with G. truncatula than in those with O. glabra. Similarly, this colonisation led to a progressive decrease in the number of native lymnaeids in these ditches and this decrease was also faster for G. truncatula than for O. glabra. A similar decrease of G. truncatula and O. glabra was also noted when P. columella was introduced into water tanks placed in semi-natural conditions. The habitats of G. truncatula or O. glabra on the acid soils of central France can be successfully colonised by P. columella, and the establishment of this invasive species may lead to a decrease of the two native lymnaeids or even the local extinction of one of these (G. truncatula).