Evaluating the attractiveness of Coreopsis (Coreopsis spp.) wild types and cultivars to pollinators

Habitat loss is viewed as a primary cause of pollinator population declines. Managed meadows and gardens can provide benefits to wildlife, including pollinating insects. Given the interest in planting flowers for pollinators, lists of recommended varieties have been produced by professional organizations and amateurs alike. These lists serve as a good starting point but are often not grounded in empirical data. Coreopsis is a popular garden plant and a frequent component of commercial pollinator seed mixes. The aim of this study is to compare the ecological role of commercially available Coreopsis plants. It is hypothesized that pollinating insects exhibit preferences based on color and other floral traits. To address this question 5 species of wild-type Coreopsis and 20 cultivars were evaluated for their attractiveness to pollinating insects. Data was collected between June and August 2014 from Coreopsis plants in the Mount Cuba Center trial garden (Hockessin, Delaware). Insects were sampled with a modified electric leaf vacuum. Flower visitors were observed and recorded to morphospecies. These two methods of sampling pollinators were compared. Pollen production per flower was measured by means of a haemocytometer. To assess which visual floral traits were correlated with pollinator visitation, inflorescence diameter, inflorescences per plant, inflorescence color and pattern, plant height, and number of flowers per infloresence were measured. Correlating visitation with floral traits may explain the differential attraction of pollinators to Coreopsis flowers.