Interaction Networks Help to Infer the Vulnerability of the Saproxylic Beetle Communities That Inhabit Tree Hollows in Mediterranean Forests

Insect communities are facing contrasting responses due to global change. However, knowledge on impacts of communities' reorganizations is scarce. Network approaches could help to envision community changes in different environmental scenarios. Saproxylic beetles were selected to examine long-term variations in insect interaction/diversity patterns and their vulnerability to global change. We evaluated interannual differences in network patterns in the tree hollow-saproxylic beetle interaction using absolute samplings over an 11-year interval in three Mediterranean woodland types. We explored saproxylic communities' vulnerability to microhabitat loss via simulated extinctions and by recreating threat scenarios based on decreasing microhabitat suitability. Although temporal diversity patterns varied between woodland types, network descriptors showed an interaction decline. The temporal beta-diversity of interactions depended more on interaction than on species turnover. Interaction and diversity temporal shifts promoted less specialized and more vulnerable networks, which is particularly worrisome in the riparian woodland. Network procedures evidenced that saproxylic communities are more vulnerable today than 11 years ago irrespective of whether species richness increased or decreased, and the situation could worsen in the future depending on tree hollow suitability. Network approaches were useful for predicting saproxylic communities' vulnerability across temporal scenarios and, thus, for providing valuable information for management and conservation programs.