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The invasive slug Arion vulgaris

The invasive terrestrial slug Arion vulgaris has in recent decades spread quickly across Sweden from south to north. The species has invaded several biotopes from urban gardens to agricultural land, causing damage to crops. Very little information exists on the genetic composition of these invasive snails and the extent to which they hybridize with our native species, such as the black forest snail (Arion ater). This research project aims to investigate both genetic, populations and hybridization aspects of the invasive slug Arion vulgaris.


Introduced, or invasive, species are today a major and common problem for many ecosystems. Invasive species are expected to become increasingly common in the near future, partly due to rapid climate change. There are today a number of different plant and animal species that are labelled as invasive. They have been introduced into new environments where they cause major disruptions in the established ecosystems, usually from a direct or indirect human intervention. A recently introduced species with a rapid rate of reproduction is a useful study species when analysing evolutionary processes, due to the adaptations that will occur as it settles into its new surroundings. The native species will also adapt in various ways when a new species enters the ecosystem. Sometimes the new species can hybridize with established species and give rise to rapid selection of adapted individuals that can outcompete the original species.

A new species in the Swedish ecosystem is Arion vulgaris, which came to southern Sweden in the 1970s from central/southern Europe. A single snail can lay up to 400 eggs per season, through sexual or asexual, hermaphroditic reproduction. This, in addition to having few predators, has facilitated for the species to spread very rapidly across Sweden. Mild winters and a wet climate may further benefit this species.


Within the research project we study various aspects of Arion vulgaris, like genetics, diversity, molecular processes and hybridization with native species. Snails are collected during field work and with the help from the general public from around the country. We collect both adult individuals and eggs and perform experiments to study hybridization.

This project aims to contribute to better predictions about invasive species' development, adaptations and how they affect our ecosystems. Our analyses can also help predict the potential for invasive species to evolve in response to measures we take to fight them, such as developing resistance to chemicals or usefulness of biological control systems.

Involved researchers