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The rapid urbanization of the world has significant ecological consequences that shape global biodiversity patterns. The plant communities now common in urban centers may represent new habitats with unique dynamics and the potential for highly modified ecological services. This study, joining extensive spatial and floristic data sets, examined current distribution patterns of non-native and native woody plant species in the New York metropolitan region, USA. We joined the New York Metropolitan Flora (NYMF) database of woody species with GIS data of urban land cover for 297 5 km by 5 km landscape blocks. We tested the relationship between urbanization and native and non-native species richness patterns, the extent of non-native species presence in the urban area, and the change in beta diversity across a gradient of urban land cover. We found that across the urban–rural gradient, native plant species richness decreased and non-native species richness increased with increasing urban land cover. Total richness does not change across the urban–rural gradient. Our analyses show that these patterns are highly correlated with urbanization, but vary across the New Jersey landscape. We also found an increase in beta diversity with urbanization; urban areas are not homogenized in plant species composition compared to rural areas. Here we show a species-rich flora dominated by non-native species which are differentiating the urban flora. These results can help guide appropriate conservation decisions for the maintenance of plant biodiversity in cities.
