Abstract1. Despite high levels of disturbance and habitat modification, urban ecosystems still host substantial levels of biodiversity. The processes that maintain existing levels of diversity, however, remain understudied. Identifying the links between urban ecological processes and patterns has, therefore, become a fundamental research goal to support urban biodiversity and ecosystem functioning.2. We conducted a study to determine how the diversity and composition of urban plant communities is affected by spatially and temporally variable land use legacies.We constructed a chronosequence of vacant lot properties covering a range of 3-22 years since demolition, in an urban neighbourhood in Baltimore, Maryland (USA). Surveys of herbaceous plant species abundance were conducted during the summers of 2012 and 2013 in sections of each vacant lot where the building previously stood (the "building footprint") and sections of the lot that was previously a backyard or garden (the "remnant garden").3. We found divergent patterns in plant community composition between areas of vacant lots with varying land use histories. This includes significant shifts in the functional composition of biotically vectored seed dispersal strategies, as well as an increase in seed mass and terminal velocity trait values of plant communities in building footprints over time. In addition, we found that plant communities in different sections of the same vacant lot tended to become more functionally dissimilar in seed dispersal strategies over time. In contrast, we found no significant changes in taxonomic diversity over time for any of our measures. Policy implications.Our study suggests that regional-scale patterns of seed dispersal interact with diverse land use legacies to structure the plant communities of urban vacant lots. Although it has been suggested that highly altered local environmental conditions and competition from introduced species limit native plant diversity in urban environments, we find seed dispersal to be a more significant driver of urban plant community assembly patterns. Implementing management strategies that focus on habitat connectivity and enhancing species pools via seeding may present an effective strategy for promoting more successful establishment of diverse plant communities in urban environments. K E Y W O R D SBaltimore, community assembly, land use history, plant diversity, plant traits, seed dispersal, urban ecology, urban green space, USA, vacant lots

A framework for understanding how biodiversity patterns unfold across multiple spatial scales in urban ecosystems.

Many studies have investigated species diversity patterns across space and time, but few have explored patterns of coexistence of tightly interacting species. We documented species diversity patterns in a host-parasitoid system across broad geographic location and seasons. We calculated species diversity (H and eH   ') and compared the relationship between community similarity and geographic distances of frugivorous Drosophila host (Diptera: Drosophilidae) and Leptopilina parasitoid (Hymenoptera: Figitidae) communities across Eastern North America, from New Hampshire to Florida, at two time points during the breeding season. We also analyzed the influence of environmental factors on species assemblages via constrained correspondence analysis and lastly calculated cluster dendrograms to identify potential host-parasitoid interactions. We found that the composition of Drosophila-Leptopilina communities varied significantly with latitude. Interestingly, diversity increased with increasing latitude, a trend counter to latitudinal patterns of diversity observed in many other taxa. We also found seasonal effects of monthly temperature range and precipitation on host biodiversity patterns across geographic locations. Cluster dendrograms nominated potential parasitoid-hosts and competitive interactions to be validated in the future studies. The present study fills an important gap of knowledge in North American Drosophila-Leptopilina species diversity patterns and lays the groundwork for future ecological and evolutionary studies in this system.

Borowy and Swan Trait Variation in Urban Plants responses associated with changes in the mean and variance of trait values, can provide a clearer understanding of the eco-evolutionary dynamics of plant species in urban environments.

Recreational urban parks support diverse assemblages of plants that through their functions, contribute beneficial services to billions of individuals throughout the world. Drivers of vegetation-derived services in parks are complex, as climate and park management interact with the functioning of multiple species of vegetation types. Yet, informal observations suggest that recreational parks are constructed consistently to specific principles of landscape design. Here we ask: what are the patterns of functional traits and vegetation diversity in cities of varying climate in the United States, and how do these patterns result in a consistent typology of recreational park? We hypothesized that increased aridity would exclude species not adapted to warm, dry climates, thereby reducing local, or alpha, taxonomic diversity and shifting community composition. However, a similar preference of park managers in the United States for suites of servicebased functional traits leads to similarity of mean values of services traits in recreational parks among cities, regardless of climate differences. We tested this hypothesis by surveying lawn species, comprised of herbaceous turf and spontaneous plants, and woody species in fifteen recreational parks across Baltimore MD, Riverside CA, and Palm Springs CA, three cities that contain multiple parks but differ in regional climate. With increasing aridity, taxonomic alpha diversity decreased and plant physiology shifted, yet no differences were observed among most service-based functional traits. Among the cities surveyed, no significant differences were observed in functional dispersion of woody and spontaneous species or most service-based traits. Taxonomic composition differed in each city for all vegetation types, while suites of service-based traits differed between Baltimore and the two more arid cities of Riverside and Palm Springs. Our results suggest that across the United States, service-based functional traits are consistent, even when arising from unique compositions and abundances of species in recreational parks. We interpret these results as an interaction between climate and the preferences of recreation park managers for services, creating a pattern of vegetation diversity where taxonomic alpha and beta diversity vary among regions while specific suites of services remain available.