Transcript Ecoinformatic Summer Institute 2013 Pollination Networks Noelle

Invasive Plant-Pollinator
Dynamics in Meadow
Networks
Oregon State University
EcoInformatic 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
450
Number of interactions
400
350
A. mellifera
300
250
200
B. major
150
100
50
0
0
1
2
3
4
Round
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
exists between the
amount of H.
perforatum in the
meadows and the
proportion of
pollination visits
Bombus made to H.
perforatum.
1
0.8
R² = 0.7939
0.6
0.4
0.2
0
0
-0.2
50
100
Hypericum flower count
150
200
▪ 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
Meadows with Hypericum
100
Meadows near Hypericum
80
60
40
20
0
0
1
2
3
4
5
6
7
Round
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!