Consequences of Climate Change-Induced Habitat Conversions on Red Wood Ants in a Central European Mountain: A Case Study

SIMPLE SUMMARY: The red wood ants are considered to be one of the main ecosystem engineers and keystone species of the habitats in which they exist. Most of the species from this species group inhabit coniferous forests, which, due to the consequences of anthropogenic climate change, are continuously cut down. Therefore, the main habitat of these important species is rapidly disappearing. We investigated the consequences of the absence of conifers (clear-cut area and deciduous forest) on one of the members of this species group, namely Formica polyctena. We have found that compared with the mixed-coniferous forest stand, the absence of coniferous species resulted in significant changes in the colony and nest structure of F. polyctena. In addition, the colony size was also smaller in these sites. These changes suggest that although F. polyctena is able to survive in suboptimal habitats, still their population decline is expected and urges conservation managers to apply necessary action plans for their protection. ABSTRACT: The consequences of anthropogenic climate change are one of the major concerns of conservation biology. A cascade of negative effects is expected to affect various ecosystems, one of which is Central European coniferous forests and their unique biota. These coniferous forests are the primary habitat of many forest specialist species such as red wood ants. Climate change-induced rising of temperature allows trees to skip winter hibernation, making them more vulnerable to storms that cause wind felling, and in turn, promotes bark beetle infestations that results in unscheduled clear-cuttings. Red wood ants can also be exposed to such habitat changes. We investigated the effects of bark beetle-induced clear-cutting and the absence of coniferous trees on colonies of Formica polyctena, including a mixed-coniferous forest as a reference. Our aim was to investigate how these habitat features affect the nest characteristics and nesting habits of F. polyctena. Our results indicate that, in the absence of conifers, F. polyctena tend to use different alternatives for nest material, colony structure, and food sources. However, the vitality of F. polyctena colonies significantly decreased (smaller nest mound volumes). Our study highlights the ecological flexibility of this forest specialist and its potential to survive under extreme conditions.