Researching Alaska’s apple orchard pollinators

Alaska may not come to mind when you think of places to grow apples, but local apple production - and the pollinating insects that make it possible - is something John McCormack is studying closely. McCormack, a graduate student in biological sciences, is leading a project with the Alaska Center for Conservation Science (ACCS), funded by a USDA grant, to investigate which insects pollinate apple flowers.

Working under the direction of Matthew Carlson, Ph.D., professor of biological sciences and director of the ACCS, McCormack and other ACCS graduate students have been collecting samples at 10 different orchards in Anchorage and the Mat-Su Valley. Working with the Alaska Pioneer Fruit Growers Association, Carlson sent a survey to local apple growers to identify interested orchard owners for the study.

While visiting the orchards, McCormack collects pollinators using a special bee vacuum, instead of a traditional net, to avoid damaging any apple blossoms. "People generally collect with a net," explained McCormack, "But I decided to use a vacuum because I was worried about smacking up people's orchards." By pointing the vacuum towards the blossoms on the apple trees, McCormack is able to capture and collect insects for identification in the lab.

Next McCormack collects the reproductive parts of the apple blossoms (the stigmas and anthers) for further analysis. Wearing medical gloves to avoid contamination, McCormack carefully peels back the petals from each blossom and then uses scissors to trim the stigmas and anthers into a sterile plastic bag. Later, the samples collected from the flowers are sent to the University of Illinois Urbana-Champaign for eDNA analysis by Mark Davis, Ph.D., coordinator of the Collaborative Ecological Genetics Laboratory. "The eDNA will show," McCormack explained, "of the pollinators we collect, which ones are the really important ones for efficiently pollinating." Insects contributing more to pollination are more likely to contact the stigmas and anthers and leave their DNA behind.

McCormack hypothesizes that Alaska's wild, native bee species (bumble bees, mason bees and mining bees) may actually contribute more to pollination than the introduced honey bees that some apple growers keep to help pollinate their orchards. His hypothesis is based on earlier research on how different species of bees collect food from flowers. Honey bees, according to McCormack, "often come around the side of the flower and get the nectar at the base of the flower, so they don't always contact the reproductive parts of the flower." However, native bee species, like bumble bees, generally visit flowers to collect pollen from the anthers, which means they are "transferring pollen between the anthers and stigmas… and they're possibly more efficient pollinators than honey bees."

While McCormack will have to wait for the results from Davis' lab in Illinois for a definitive answer to his research question, his work collecting and visually identifying insects at the orchards has yielded some interesting results so far. "By far and away flies have been the most abundant pollinators," McCormack reported. Despite their abundance at the apple orchards, McCormack is ultimately skeptical that certain fly species are contributing much to apple pollination: "Some species of fly seem to miss the reproductive parts of the flower, so my guess would be, they won't show up on the eDNA analysis."

For the bees, McCormack's sampling suggests that orchard location may be an important factor. "Down in Anchorage, I've come across few native bees," McCormack stated, "And then at a few orchards up further, across the Knik, [in] Big Lake and Wasilla, there have been a lot more native bees." While noting it's too early to draw any conclusions, McCormack hypothesized that the difference may be related to local habitat. "One of the orchards out in Big Lake had a ton of native bees [and] is probably the most rural… surrounded by a wetland in a forest, as opposed to roads and houses," explained McCormack, "I'm no expert on native bees, but I think when you have good habitat around, you're gonna have more."