Effects of White Sweetclover Invasion on the Pollination and Berry Production of Vaccinium sp. in Alaska Katie V. Spellman1, Christa P. H. Mulder1 and Matthew L. Carlson2 1 University

of Alaska Fairbanks, Institute of Arctic Biology; 2 University of Alaska Anchorage, Alaska Natural Heritage Program

RESULTS

An Unexpected Pattern Possible facilitation of pollination and fruit set directly adjacent to Melilotus infestations and at greater distances, reducing pollinator services to mid-distance Vaccinium plants.

Pollen Delivery

• White sweetclover (Melilotus officinalis; synonym M. alba) has spread along roadsides and rivers throughout Alaska adjacent to easily accessible berry-picking habitat. • Attractive invasive plants such as white sweetclover have potential to alter pollinator services to native plants and affect fruit production.

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• This study-in-progress investigates the effects of white sweetclover invasion on the pollination of Vaccinium uliginosum and Vaccinium vitis-idaea, and the subsequent effects on berry production. Pollen delivery or fruit set

Pollen delivery or fruit set

No difference in Vaccinium pollen receipt or fruit set between sites with and without Melilotus

Melilotus outcompetes Vaccinium for pollinators; effect diminishes with distance from invasive patch

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Pollen Quality

• No significant change in total number of pollen grains on V. vitis-idaea stigmas in sites with Melilotus added compared to control sites (fig. 7).

• Percent conspecific pollen on V. vitis-idaea stigmas was tended to be higher at further distances from the site center in sites with Melilotus added compared to control sites (fig. 8).

Melilotus attracts pollinators, increasing Vaccinium pollen delivery or fruit set; effect diminishes with distance from invasive patch

Figure 9. Stained Vaccinium vitisidaea stigma with high percentage of conspecific pollen.

Fruit Production

METHODS *

Figure 2. Map of Bonanza Creek Long Term ecological research areas near Fairbanks, Alaska where our study sites were located.

Figure 3. Flowering white sweetclover (Melilotus officinalis) was added to the center of 11 sites.

• Added 40 white sweetclover plants to the center of 11 sites (figure 3); 6 sites established as controls. • Tracked unopened flower buds through fertilization and fruit formation on 125 V. vitis idaea and/or 75 flowering V. uliginosum focal plants located 1-2 m, 3-5 m, 8-10 m, 15-20 m or 25-40 m from the centers of each site. • Collected Vaccinium sp. stigmas and identified and counted pollen grains present.

Vaccinium uliginosum berries

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Figure 5. Five plots were established at each distance level from the center of the site. Plots contained 5 focal V. vitis-idaea and 3 focal V. uliginosum plants. Environmental data was collected at each plot.

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• Investigate environmental and spatial data as covariates. • Determine influence of sweetclover population size and density on pollinator interactions with Vaccinium species.

• Model changing mosaic of interactions between white sweetclover and Vaccinium • pollination using • Alaskan phenology and • climate data. ● Assess

current and future berry harvest vulnerability to invasive plant impacts.

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Figure 10. Difference in mean (+ se) percent fruit set (experimental flowers turning into fruit) for Vaccinium uliginosum and V. vitis-idaea plants at various distances from the center with Melilotus officinalis added relative to control site means. Asterisk (*) denotes significant difference from control means.

Vaccinium vitis-idaea berries

• Significant increase in V. vitis-idaea fruit set when growing directly adjacent to Melilotus added to the center of sites compared to control sites (fig. 10, bottom). • Similar trend in V. uliginosum fruit set (fig. 10, top).

Figure 6. Pollen was counted on stigmas of non-vocal Vaccinium plants (Vaccinium pollen, left; Melilotus pollen, right).

Vaccinium uliginosum with abundant fruit.

FURTHER DIRECTIONS

• • •

Figure 4. Focal V. vitis-idaea and V. uliginosum plants were tagged. Individual buds and flowers were tracked through the growing season.

• 17 sites with abundant Vaccinium sp. within the UAF Bonanza Creek Long Term Ecological Research areas near Fairbanks (figure 2).

Melilotus officinalis added to a Vaccinium site.

• Citizen science monitoring of Melilotus sp. and Vaccinium sp. phenology across Alaska.

Vaccinium uliginosum

Vaccinium vitis-idaea

Distance from site center

Figure 8. Mean difference (+ se) in the percent of conspecific pollen grains out of the total pollen on Vaccinium vitis-idaea stigmas in sites with Melilotus officinalis added relative to control site means at various distances from the site center.

Pollen Quantity

Site with Melilotus added to site center

Site with Melilotus added to site center

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Distance from site center

Distance from site center

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Site without Melilotus

Pollen delivery or fruit set

Alternate Hypotheses:

•

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Figure 7. Mean difference (+ se) in total number of pollen grains on Vaccinium vitis-idaea stigmas in sites with Melilotus officinalis added relative to control site means at various distances from the site center.

OBJECTIVES

Distance from site center

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Site without Melilotus

Photo by Miki Smelter

• In Alaska, important subsistence foods such as blueberries (Vaccinium uliginosum) and cranberries (Vaccinium vitis-idaea) require insect pollination to produce fruit.

DISCUSSION Pollen delivery or fruit set

INTRODUCTION

ACKNOWLEDGEMENTS