Barrier effects on vertebrate distribution caused by a motorway crossing through fragmented forest landscape

We analysed the effects of a 25–year–old motorway on the distribution of five vertebrates inhabiting a fragmented forest landscape and differing in their ability to move across linear infrastructures. We found clear evidence of barrier effects on the distribution of the forest lizard Psammodromus algirus. The roe deer (Capreolus capreolus) was also unequally distributed on both sides of the motorway, but this could also be due, at least in part, to fragmentation. The eyed lizard (Timon lepidus), that can move through open fields, showed no evidence of barrier effects. The distribution of two small birds (Erithacus rubecula and Phylloscopus bonelli) was unaffected by the motorway. Our results show that a motorway may severely restrict the distribution of species which can withstand high levels of forest fragmentation but show limited dispersal ability, highlighting the role of linear infrastructures in shaping species’ ranges at regional scales.