Flies (Diptera) likely pollinate an Alpine death camas

 

A Chrysotoxum syrphid fly nectaring at a flower of A. elegans. Its head and thorax bear the abundant yellow pollen of Anticlea.

Flies (Diptera) likely pollinate an Alpine death camas

By James Cane

 The vast floristically-defined Great Basin of the U.S. Intermountain West has >35 mountain ranges with summits over 3000m, many above timberline. Their alpine plant communities are poorly known, in part because of their usual lack of access and long distances from universities. Few if any reports exist for alpine pollinator guilds in the Great Basin, although flies and bees can be expected.

 A species of death camas found in alpine settings and also alkali fens, Anticlea elegans, is a segregate of Zigadenus (also known as death camas) in the Melanthiaceae (formerly part of a larger lily family). Trilliums are the family’s most familiar genus. Another former species of Zigadenus, Toxicoscordion paniculatum, produces neurotoxic alkaloids that render both its pollen and nectar lethal to all bees but one specialist. Species of Anticlea are considered toxic, but without chemical evidence or knowledge of their pollinator guilds. Hence, their floral guilds should be of particular interest.

During a visit to an alpine GLORIA vegetation monitoring site on Sheep Mountain in the remote Lemhi Range of southeastern Idaho, two large flowering populations of mountain death camas were encountered. Although it was the last day of July, their meadow was still moistened by snowdrift meltwater. Results for the first floral survey of any Anticlea are reported.

Only flies and some nectaring ants visited flowers of elegant death camas (Fig. 1). Flies were quite abundant, as many as 19 flies per 100 flowering stems. Diverse bumblebees and mason bees foraged in the vicinity, but they visited flowers other than death camas. Flies at flowers of elegant death camas included abundant and diverse flower flies (Syrphidae), plus house fly relatives (Fanniidae), blow flies (Calliphoridae) and flesh flies (Sarcophagidae). These flies lapped at the shallow greenish surface nectaries present on the showy white petals and sepals of the flowers. While nectaring, the flies were brushed by both the overarching anthers and the stigmas of the three arching branches of the floral pistil, thereby effecting pollen transfer and pollination. Visiting flies showed no symptoms of neurotoxin poisoning, unlike bees fed pollen and nectar of T. paniculatum.

 

Read the scientific publication in JPE