Invasive PlantPollinator Dynamics in Meadow Networks Oregon State

Invasive Plant-Pollinator Dynamics in Meadow Networks Oregon State University Eco. Informatic Summer Institute 2013 Noelle Patterson

Introduction ▪ Pollination Networks: A representation of the complex web of interactions between two distinct groups: plants and pollinators. ▪ Pollination networks were studied in fifteen montane meadows in the HJ Andrews Experimental Forest region. ▪ Pollination networks here include both native and invasive species. ▪ Common invasive insect: Apis mellifera (European honeybee) ▪ Common invasive plant: Hypericum perforatum (St. John’s wort)

Study #1 Comparison of nonnative Apis mellifera and native Bombylius major Apis mellifera on Gilia capitata Bombylius major

-Apis mellifera interactions reflect logistic growth. The %50 line corresponds with a G. capitata stem count of 333. 6. -92. 1% of Bombylius major interactions were with Gilia capitata; this is modeled in logistic regression poorly.

-In terms of Gilia capitata use, both Apis and Bombylius occupy the same niche. -However, Apis mellifera pollinate in much higher numbers and have a broader overall diet than Bombylius. Interaction Frequency with Gilia capitata 500 Number of interactions 450 400 350 A. mellifera 300 250 200 B. major 150 100 50 0 0 1 2 3 Round 4 5 6 7

Why so many honeybees? ▪ Apis mellifera are a domesticated species whose population is supported by outside human help, giving them an advantage over competition. ▪ But- Bombylius major is a parasite of solitary ground nesting bees. ▪ Outside Apis mellifera impacts… harmful or beneficial?

Study #2 Hypericum perforatum and Bombus species ▪ Hypericum perforatum (St. John’s wort) is a weedy plant native to Europe, W. Asia, and N. Africa which has become invasive in many areas including the Western Cascades. ▪ Although many nonnative plants in the HJA are restricted to roadsides, H. perforatum was found in three meadows from the 2011 sites. ▪ H. perforatum is a popular food source for bumblebees in the late summer season.

Bombus-Hypericum Interactions ▪ A strong correlation Proportion Hypericum interactions 1. 2 1 0. 8 R 2 = 0. 7939 0. 6 0. 4 0. 2 0 0 -0. 2 50 100 Hypericum flower count 150 200 exists between the amount of H. perforatum in the meadows and the proportion of pollination visits Bombus made to H. perforatum. ▪ Point: Bombus species appear to have a preference for invasive Hypericum perforatum

Good news: the variety of Bombus plant partners does not decrease due to H. perforatum presence. Percentage of available flower species used Bombus Flower Exploitation 0. 7 0. 6 Meadows with Hypericum 0. 5 0. 4 0. 3 Nearby meadows without Hypericum 0. 2 0. 1 0 4 5 Round 6 The percentage of available flower species pollinated by Bombus is found in each round as an average of meadows with H. perforatum and neighboring meadows without H. perforatum.

Bumblebees: following the flower? Bombus presence Number of Bombus interactions 140 Hypericum appears in meadows 120 100 Meadows with Hypericum Meadows near Hypericum 80 60 40 20 0 0 1 2 3 Round 4 5 6 7 During rounds 4 and 5 when H. perforatum is abundant, significantly more Bombus are found in meadows containing or nearby H. perforatum.

Conclusion ▪ Invasive species such as Apis mellifera and Hypericum perforatum have important roles within the pollination networks at the HJ Andrews forest. ▪ Apis mellifera is an important pollinator, but its volume of interactions may present competition to insects with overlapping niches like Bombylius major. ▪ Hypericum perforatum has become an significant part of late season Bombus diets and could affect their distribution and where they winter over. ▪ Much work must still be done exploring the relationships between insects, plants, and the entire network to gain a better understanding of these rich ecosystems.

Thank you To the EISI mentors who made this summer possible and to my great pollinator crew!