Promoting wildflower biodiversity in dense and green cities: the important role of small vegetation patches

Abstract The conservation and promotion of biodiversity in urban spaces has become a core concern in urban greening. As cities continue to densify, however, urban green spaces are becoming smaller and more isolated. Many hope that wildflowers, and with them also faunistic biodiversity, can be maintained through networks of small informal green spaces. Currently, there are little data available for city planners to answer the questions of how patch size and ecological connectivity affect the population persistence of wildflowers in small vegetation patches. To address these concerns, we surveyed all vegetation patches greater than 1 m2 in public spaces across seven 1 km2 quadrats distributed across the city of Zurich, Switzerland. Our survey focused on a list of 166 herbaceous vascular plant species. We analyzed vegetation patch topologies (frequency distributions of size and connectivity) and related it to alpha and beta species diversity. Dispersal traits of investigated species were used to interpret connectivity patterns. Over 75 % of patches were