Do Saproxylic Species Need Habitats, Connectivity, or Connected Habitats?

The importance of saproxylic species within forest ecosystems cannot be overstated, as they span a wide range of taxa contributing to the recycling of dying and dead woody material. Originally defined as invertebrates reliant on decaying wood, wood-inhabiting fungi, or other saproxylics, the group has been expanded to include species involved in or dependent on moribund trees and wood decay processes. Since centuries, their habitat has faced loss and fragmentation from intensive forest management practices and land use changes, underscoring the urgency of conservation efforts. While habitat connectivity is crucial for species dispersal and colonization, evidence supporting its significance for saproxylic species conservation remains unclear. Dispersal abilities vary considerably across taxa, highlighting the importance of understanding these differences for effective forest management aiming at saproxylics conservation. Specialized species such as fungus-dwelling beetle Bolitophagus reticulatus demonstrate limited dispersal but robust recolonization capabilities facilitated by the availability of habitat, in this case, Fomes fomentarius. Similarly, saproxylic fungi with a broad dispersal ability such as Fomitopsis rosea rely on habitat amount for successful colonization. Efforts to increase the amount of deadwood at the landscape scale thus benefit species (re)colonization efforts. Prioritizing the preservation of large populations and distributing habitat patches are key strategies for supporting saproxylic biodiversity in forest ecosystems. Aggregating patches around dispersal sources can attract species of conservation concern, although identifying these sources remains challenging. Conversely, evenly distributed habitat patches throughout the forest landscape promote higher species diversity. A balanced approach combining both aggregation and distribution of habitats seems therefore essential for effective conservation efforts. However, scientific evidence tends to prioritize habitat quantity over habitat connectivity for the conservation of saproxylic species.