Aim
Biological
invasions are today the second-largest global threat for biodiversity.
Once introduced, exotic plant species can modify ecosystem composition,
structure and dynamics, eventually driving native species to local
extinction. Among the groups of organisms, most likely to be directly
affected by exotic invasive plants are herbivorous insects, such as
butterflies, which strongly depend on plants throughout their life
cycle. However, it remains unclear whether invasive plants have a
negative or a positive effect on butterfly diversity at a landscape
scale.
Methods
Using
an extensive inventory (393 sites across Switzerland) of both butterfly
and invasive plants, we explore the impact of 31 invasive black listed
plant species on local butterfly richness. We further identify each
butterfly species’ response to invasive plants (i.e. positive, neutral
or negative) and analyse the functional and phylogenetic characteristics
of these different groups of species.
Results
Our
results indicate that butterfly richness negatively correlates with an
increase in invasive plant richness. When studying the individual
response of each butterfly species to the number of invasive plants, we
found that no single butterfly is profiting from invasive plant species,
while 28 butterfly species (24%) suffer from the presence of invasive
plants. We further show that the species negatively affected are on
average less mobile than the unaffected species and that they are
phylogenetically clustered.
Main conclusions
Our
results present evidences of the influence of invasive species on other
trophic levels and interaction networks. We further highlight that a
lack of management efforts for mitigating invasive plant impacts
threatens specific sections of the functional and phylogenetic diversity
of butterflies.