Why study the impacts of invasive sweetclover on pollination?
In Alaska, invasive plants have only recently moved off the human footprint into natural habitat. Warmer winters, longer growing seasons, and greater human activity may contribute to current rapid expansion across the state. Recently burned forest forms a major component of the vegetation of Interior Alaska, and this habitat is particularly vulnerable to invasion by early-successional non-native species. Fires are increasing in frequency and extent in Alaska. Melilotus albus (Fabaceae, sweetclover) was introduced to Alaska in 1913 as potential forage and has expanded rapidly along roadsides and more recently along floodplains and into burns.Sweetclover is highly attractive to pollinators and could disrupt the pollinator ecology of habitats in Alaska.
Melilotus could influence the pollination of subsistence berry plants...
Two Vaccinium species (Ericaceae), Vaccinium uliginosum (bog blueberry) and Vaccinium vitis-idaea (bog cranberry or lingonberry) form a major component of the subsistence lifestyle practiced across Alaska, both directly and by providing forage for other subsistence species such as moose, caribou, snowshoe hare, ptarmigan, and grouse. Blueberries and cranberries overlap in habitat preferences with Melilotus. These species also share pollinators, including bumblebees (Bombus spp.), native solitary bees (Adrenidae, Halictidae, Megachilidae) and syrphid flies (Syrphidae).
Investigate the effects of white sweetclover (Melilotus albus) invasion on the pollination of Vaccinium uliginosum and Vaccinium vitis-idaea, and the subsequent effects on berry production
• Does the presence of sweetclover change the pollen quantity and quality delivered to Vaccinium (berry) species?
• Does the presence of sweetclover change Vaccinium reproductive success (fruit and seed production)?
• Does the effect of sweetclover on Vaccinium pollination and fruit set depend on how far apart the species are, or on how big the sweetclover patch is?
• Does the presence of sweetclover change pollinator interactions with native plants?
We are combining several different approaches to answer our questions:
Surveys have as advantage that they are realistic and can be done over large scales, but they have as a major disadvantage that we did not determine which sites got sweetclover and which did not. That means that the locations with sweetclover might be different in other ways as well - for example, they might just be better sites for plant growth in general. To deal with this we added a second approach:
2. Sweetclover supplementation experiments
These experiments are an effective way of determining what the impact of the presence of sweetclover is (without any other consistent differences between sites), but they can only be done at a few locations. We think that the impact of sweetclover might depend on how much overlap there is in flowering times between the sweetclover and the berry plants. To evaluate this, we added a third approach:
3. Historical Data: Flowering Overlap Across North America
4. Current Phenology Data: Citizen Scientist Project
Blueberry and Cranberry Pollen and Berry Production
Cranberry Pollen and Berry Production over 2 years
2012 Alaska Invasive Species Conference Presentation-Schneller and Spellman
2013 Alaska Invasive Species Conference Presentation-Mulder
2013 Alaska Invasive Species Conference Presentation-Spellman
Collaborators: Dr. Christa Mulder (UAF Project PI), Dr. Matthew Carlson (UAA Co-PI), Katie Spellman (PhD student), Laura Schneller (Master's Student), Dr. Jeff Conn (USDA ARS), Dr. Steve Seefeldt (USDA ARS)