Pollen Transport to Lycium cooperi (Solanaceae) Flowers by Flies and Moths

Abstract

Lycium cooperi (Solanaceae) is a woody shrub found along the eastern, northern, and western edges of the Mojave Desert in Arizona, Nevada, and California and along the western edge of the Sonoran Desert in California and Mexico. The plant produces funnel-shaped flowers during spring with stamens and a pistil that extend to near the top of a greenish-white corolla. I investigated the pollination of L. cooperi in southern Nevada during 30 March–21 April 2019 by aspirating insects from flowers, determining where they carried pollen on their bodies, and estimating the proportions of conspecific pollen in their pollen loads. Flowers were mostly visited at night by 8 species of moths (Lepidoptera) in Noctuidae and Geometridae and less frequently during the day by 3 species of flies (Diptera) in Syrphidae. The most frequent visitor to flowers was Euxoa serricornis (Noctuidae), followed by Digrammia colorata (Geometridae) and Peridroma saucia (Noctuidae), a widespread agricultural pest. Most flies at flowers were 2 large species of Copestylum. Flowers were also visited by the migratory butterfly Vanessa cardui (Lepidoptera: Nymphalidae). Pollen was carried mainly on the proboscis of moths and butterflies and on the anterior thorax of flies. Lycium cooperi pollen grains in brightfield microscopy are trilobed in polar view, elliptic in equatorial view, and grainy in appearance. A higher mean proportion of L. cooperi pollen was carried by moths and butterflies (0.50) compared with flies (0.21), and moths in Noctuidae carried a higher proportion of conspecific pollen (0.59) compared with moths in Geometridae (0.25). Insects pollinated only 19.8% of the profuse flowers produced by shrubs. Pollination of L. cooperi primarily by moths corresponds with the shrub's partially white and tubular flowers. Similar flowers on most other Lycium species in the Mojave and Sonoran Deserts indicate a likelihood of similar pollination by moths.