Distinct pollinator communities persist among co-flowering specialty crops in Indiana

By Stroh et al.

Specialty crops, which include a variety of non-staple fruits and vegetables, are pollinated by a diverse array of bees. Different geographic regions harbor unique bee communities, although non-native Western honey bees (Apis mellifera) are used to supplement the pollination provided by wild, native bees in some specialty crops. There are a variety of other factors that affect bee community composition for individual crops, including crop bloom phenology and flower morphology. Crops that bloom in the spring are exposed to a different suite of early-season bees than those that bloom in the summer months. Flower shape, which determines ease of access for different bee species, further filters bee communities in individual cropping systems.

We sampled bee communities using pan traps and flower observations on commercial apple (Malus domestica), blueberry (Vaccinium corymbosum), tomato (Solanum lycopersicum), and watermelon (Citrullus lanatus) farms in Indiana, a state dominated by agronomic crop production with small pockets of specialty crops. Apples, blueberries, and watermelons were stocked with honey bees, while tomatoes were not.

We found that distinct bee communities persisted in co-blooming apples and blueberries, as well as tomatoes and watermelons. While flower visits in spring-blooming apples and blueberries were dominated by honey bees (70% of visits), a diverse array of wild bees were also present, including spring-flying mining bees (Andrena) in both crops. In the summer-blooming crops, we found that bumble bees (Bombus) provided the majority of flower visits (62% of visits) in tomatoes. Despite stocking with honey bees, watermelon flower visits were dominated by sweat bees (Lasioglossum) (65% of visits). Our results indicate that diverse wild bee communities are found among specialty crops in the Midwest, and wild bees are particularly large contributors to tomato and watermelon pollination.

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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.

 

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