Pollination biology and reproductive phenology of the federally endangered endemic Physaria globosa (Brassicaceae) in Tennessee

A study on the reproductive biology of the federally endangered Physaria globosa was conducted near Hartsville, TN, at one of the largest known populations of the species from February through July 2016. Objectives included (a) establishment of baseline reproductive phenology for P. globosa, (b) documentation of the diversity and frequency of floral visitors, and (c) determination of effective insect pollen vectors. Flowers were open for three days and displayed characteristics typical of outcrossing. Six insect species were identified as effective vectors for P. globosa pollen, including two dipterans and four halictid bees. While pollen loads were not significantly different among the vectors, floral visitors were ranked by frequency in descending order as follows: Nemotelus bruesii, Toxomerus geminatus, Lasioglossum illinoense, Halictus ligatus, Lasioglossum versatus, and Augochlorella striata. Information on natural history of this species is vital to aiding conservation efforts for P. globosa across its range.