Crop phylogenetic diversity across urban farms in Toronto, Canada

Abstract

Urban agriculture confers multiple ecological and social benefits, many of which are contingent upon crop biodiversity on urban farms. However, the evolutionary or phylogenetic diversity of crops on urban farms remains poorly documented, despite reason to expect that phylogenetic diversity reflects ecological and evolutionary aspects of urban farms that are not captured by taxonomic diversity alone. We surveyed crop diversity across 16 urban agriculture sites in Toronto, Canada, to characterize the phylogenetic diversity on urban farms, evaluate how taxonomic and phylogenetic diversity covary and differ within and across farms, and understand the contributions urban farms make toward municipal‐scale plant biodiversity. We documented 58 unique crop species throughout Toronto urban farms belonging to 17 plant families, which based on species accumulation curves, support an expected citywide richness of 75.9±10.5 crop species. Compared to crop species globally, crops on urban farms in Toronto are phylogenetically clustered, largely owing to the presence and prevalence of multiple species in the Lamiaceae, Solanaceae, and Apiaceae families. Relationships between crop taxonomic richness and phylogenetic diversity on urban farms were nonlinear such that that certain crops contribute disproportionately to evolutionary diversity at the farm scale. Municipal‐scale analysis found that taken together, crops on urban farms contribute 6516 million years of unique evolutionary phylogenetic diversity in Toronto, which is not captured in existing plant diversity databases for the city. Urban farms represent phylogenetically diverse agroecosystems which contribute to plant biodiversity maintenance, and likely ecosystem functioning at farm‐ and municipal scales. In characterizing crop phylogenetic diversity our work represents a step in better understanding the diversity of urban farms and its contributions to biodiversity and food production in cities.