Urbanization and the more-individuals hypothesis

2. Using newly collated avian distribution data for 1 km2 grid cells across Florence, Italy, we show a significantly positive relationship between species richness and assemblage abundance for the whole urban area. This richness-abundance relationship persists for the 1 km2 grid cells with less than 50% of urbanized territory, as well as for the remaining grid cells, with no significant difference in the slope of the relationship. These results support the more-individuals hypothesis as an explanation of patterns in species richness, also in human modified and fragmented habitats.

P>1. Urbanization is a landscape process affecting biodiversity world-wide. Despite many urban-rural studies of bird assemblages, it is still unclear whether more species-rich communities have more individuals, regardless of the level of urbanization. The more-individuals hypothesis assumes that species-rich communities have larger populations, thus reducing the chance of local extinctions.