Dwarf pine: invasive plant threatens biodiversity of alpine beetles

Despite their small extent, alpine ecosystems belong to the most valuable, yet highly threatened natural biotopes worldwide. Alpine habitats are endangered particularly by anthropogenic influences and climate change as well as invasions of non-native plants. Although plant invasions are regarded as one of the most serious threats to biodiversity globally, the knowledge of their impact on the arthropod assemblages of alpine environments is virtually absent. Therefore, we studied the effects of the non-native dwarf pine Pinus mugo on a model group of carabid beetles in the alpine zone of the Hrubý Jesenik Mts., Czech Republic. We evaluated the effects of age, cover and distance from dwarf pine stands on the community structure and the functional diversity of the Carabidae. The majority of the species significantly declined in abundance with increasing age and cover of dwarf pine stands. Species surviving there were typically food generalists associated with the forest environment. In contrast, carabids with high conservation value bound to open habitats (e.g., Amara erratica and Carabus sylvestris) decreased in dwarf pine areas as well as food specialists (e.g., Cychrus caraboides) and large forest species in the genus Carabus. The decline in abundance of carnivorous species may be a consequence of the similar decline in herbivores dependent on the native vegetation. Concurring with this interpretation, abundance of many herbivorous species (e.g. Amara spp.) decreased within pine stands. The negative effect of dwarf pine stands on the community structure of montane carabids was also apparent in changes of functional diversity. Age and cover of dwarf pine significantly decreased functional richness and divergence of carabid trophic groups. Considering the small area of alpine tundra in the Central European mountain ranges, the expansive dwarf pine represents a serious threat to this unique montane biodiversity. Therefore we recommend the immediate reduction or removal of non-native dwarf pine stands.