Surrounding landscape effect on roadside verges

Semi-natural habitats are declining throughout the world, thus the role of small anthropogenic habitats in the preservation of plants is becoming increasingly appreciated. Here we surveyed the orchid flora of roadside verges in five Central European countries (Austria, Hungary, Romania, Slovakia and Slovenia) and tested how the surrounding landscape matrix affects the overall number of species and individuals, and also different functional groups of orchids. We found more than 2000 individuals of 27 orchid species during our surveys. According to our results, the increasing coverage of agricultural and urban areas negatively affect both the number of orchid species and individuals on roadsides. Our study further suggests, that differences in the surrounding habitats affect which species are found on roadsides, since the increasing coverage of grasslands or forested areas around orchid occurrences had a significant positive effect on the number of grassland or forest-dwelling species and individuals, respectively. Most variance in orchid numerosity and diversity was explained by the cover of the suitable habitat types of the respective taxa in the surrounding landscape of the sampling points. This highlights the importance of roadsides acting as refugia for numerous species and valuable plant communities as well as supporting biodiversity in general.