How do roadsides interact with patches of natural vegetation in shaping perennial plant communities in fragmented agricultural areas? Are the observed differences due to the type of roadside (i.e. roadcuts, embankments or road verges) or are there other factors driving community structure and composition? Our results show that almost all perennial species occurring in natural vegetation patches were also able to reach and settle in roadsides. However, soil conditions and other specific roadside variables generate different plant communities. In spite of the differences found between the perennial plant community of roadsides and their surrounding area, roadsides are excellent reservoirs of biodiversity. Palabras clave: Biodiversity, Vegetation