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Dryad

Diversity and turnover of wild bee and ornamental plant assemblages in commercial plant nurseries

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Nov 28, 2023 version files 259.94 KB

Abstract

In human-modified landscapes, such as agricultural areas, understanding how habitat characteristics influence the diversity and composition of beneficial organisms is critical both to conservation efforts and to modeling ecosystem services. Assessing turnover, or changes in species identity across sites or through time, is crucial to determine how shifts in community composition relate to changes in ecosystem services. For pollinators like wild bees, factors affecting their diversity have been well studied, but variables influencing temporal turnover, particularly across seasons within a year, remain relatively poorly understood. To investigate how local and landscape characteristics correlate with bee diversity and turnover across seasons, we recorded wild bee and flowering ornamental plant assemblages at 13 plant nurseries in southern California between spring and autumn over two years. Nurseries cultivate a broad diversity of flowering plant species that differ widely across sites and seasons, providing a field setting to test for correlations between turnover and diversity of plants and bees. As expected, we documented strong seasonal trends in wild bee diversity and composition. We found that local habitat factors, such as increased cultivation of native plants, were positively associated with bee diversity in sweep netting collections, whereas we detected moderate influences of landscape-level factors like proportion of surrounding natural area in passive trap collections. We also detected a moderate positive correlation between overall gains in plant species and gains in bee species at nurseries across consecutive seasons. Our results have important considerations for the conservation of wild bees in landscapes dominated by ornamental plants, and highlight the utility of plant nurseries for investigating hypotheses related to diversity and turnover in plant-pollinator systems.