Distribution, ecology and status of a threatened species Ischnura intermedia (Insecta: Odonata), new for Europe

Until now, nonnative plant species were rarely found at high elevations
and latitudes. However, partly because of climate warming, biological
invasions are now on the rise in these extremely cold environments.
These plant invasions make it timely to undertake a thorough
experimental assessment of what has previously been holding them
back. This knowledge is key to developing efficient management of the
increasing risks of cold-climate invasions. Here, we integrate human
interventions (i.e., disturbance, nutrient addition, and propagule input)
and climatic factors (i.e., temperature) into one seed-addition experiment
across two continents: the subantarctic Andes and subarctic
Scandinavian mountains (Scandes), to disentangle their roles in limiting
or favoring plant invasions. Disturbance was found as the main
determinant of plant invader success (i.e., establishment, growth, and
flowering) along the entire cold-climate gradient, explaining 40–60% of
the total variance in our models, with no indication of any facilitative
effect from the native vegetation. Higher nutrient levels additionally
stimulated biomass production and flowering. Establishment and flowering
displayed a hump-shaped response with increasing elevation,
suggesting that competition is the main limit on invader success at
low elevations, as opposed to low-growing-season temperatures at
high elevations. Our experiment showed, however, that nonnative
plants can establish, grow, and flower well above their current elevational
limits in high-latitude mountains. We thus argue that cold-climate
ecosystems are likely to see rapid increases in plant invasions in
the near future as a result of a synergistic interaction between increasing
human-mediated disturbances and climate warming.