Effect of genotype and environment on the abundance of a
specialist aphid in Solidago altissima
Brian Bonville and Ray S. Williams
Appalachian State University
Introduction
Community Genetics
Certain species of plants are the foundation of a given ecosystem
Their genetic variation may govern population responses in animals that depend on them
Red Goldenrod Aphid (Uroleucon nigrotuberculatum)
• Insect communities are known to be affected by
intraspecific genetic variation in Solidago altissima
(Crutsinger et al, 2006).
• The abundance of herbivores such as aphids can vary
between genotypes (Genung et al. 2012, Williams and
Avakian 2015).
• Though insect responses are observed, the mechanisms
behind insect choice of genotypes is relatively unknown.
• In addition, the role of environment and its interaction with
genotype in shaping insect responses is not well understood.
Terpenes
• Allelochemicals acting as defensive agents, signaling
chemicals, or attractants to insects.
• Previous research with S. altissima found terpenes
positively correlated with aphid abundance in S.
altissima (Williams and Avakian 2015).
Objectives
• Investigate the effects of genotype (G) and environment
(E) and GXE on Uroleucon nigrotuberculatum abundance
on S. altissima by the addition of nitrogen and
phosphorous to soil.
• To examine the effects of G, E, and GXE on terpenes.
Methods
• In May 2014, six genotypes of tall goldenrod were
planted in a common garden design.
• Plants were administered either nitrogen,
phosphorous or no nutrients (control). There were
three replicates of each treatment. Plants were spaced
0.33m apart.
• The total of 54 plants were broken into three blocks.
• Aphids colonized the plants naturally.
Block
3
Block
2
Block
1
54
2
N
53
5
C
52
4
N
51
4
C
50
2
P
49
4
P
48
2
C
47
1
N
46
6
N
37
1
P
38
3
N
39
6
C
40
1
C
41
5
N
42
3
C
43
6
P
44
3
P
45
5
P
36
5
C
35
6
N
34
3
N
33
3
P
32
4
N
31
2
P
30
4
C
29
2
C
28
1
N
19
4
P
20
1
P
21
6
P
22
5
N
23
1
C
24
3
C
25
2
N
26
5
P
27
6
C
18
6
C
17
5
N
16
4
N
15
3
P
14
1
P
13
6
P
12
3
C
11
2
P
10
1
N
1
2
N
2
4
C
3
5
P
4
5
C
5
2
C
6
3
N
7
6
N
8
4
P
9
1
C
Field Data Collection
• Aphid abundance was monitored
every three days throughout the
season.
• Biomass estimates and leaf samples
were taken during aphid abundance.
• Plants were harvested and biomass
determined at the end of season.
Photo- Ricochet Science Productions
Chemical Analyses
• Leaves were ground in pentane for
GC analysis in a Schimadzu GC-14A
gas chromatograph.
• Compounds were identified using
analytical standards and quantified
with an internal standard.
Statistical Analyses
• Two-way ANOVA with repeated measures (SAS 9.4) was
used to test for effects of genotype (G), nutrient
treatment (E), and G XE interaction on aphid
abundance, terpene concentration and plant biomass.
Results where 0.05 < P < 0.1 reported as marginally significant.
Results
Aphid Abundance during season
3000
Total aphids
2500
2000
1500
1000
500
0
0
4
8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80 84 88 92
Day
Aphid Abundance Jul. 9
Aphid Abundance Sept. 3
Fertilization
P= 0.1900
Fertilization
P= 0.044
Genotype
P=0.2418
Genotype
P=0.4352
Fertilization*Genotype
P=0.0272
Fertilization*Genotype
P=0.0989
Meanaphid
aphid
abundance
by treatment
Mean
abundance
by treatment
July 9
250
Mean aphid abundance
200
150
Nitrogen
Control
Phosphorus
100
50
0
2.000
2
4.000
4
5.000
5
Genotype
3.000
3
6.000
6
Biomass estimate Jul. 9
Biomass estimate Sept. 3
Fertilization
P= 0.0009
Fertilization
P<0.0001
Genotype
P<0.0001
Genotype
P<0.0001
Fertilization*Genotype
P=0.7721
Fertilization*Genotype
P=0.8698
Biomass September 3
α-pinene
July 9
α-pinene
Sept 3
Fertilization
P= 0.0816
Fertilization
P= 0.0204
Genotype
P=0.0008
Genotype
P<0.0001
Fertilization*Genotype
P=0.0196
Fertilization*Genotype
P=0.6331
β-pinene
β-pinene
Fertilization
P= 0.2187
Fertilization
P= 0.0249
Genotype
P=0.0006
Genotype
P<0.0001
Fertilization*Genotype
P=0.1311
Fertilization*Genotype
P=0.6647
Germacrene D
Germacrene D
Fertilization
P= 0.1251
Fertilization
P= 0.0707
Genotype
P=0.0004
Genotype
P=0.0080
Fertilization*Genotype
P=0.4198
Fertilization*Genotype
P=0.9600
P-cymene
P-cymene
Fertilization
P= 0.4023
Fertilization
P= 0.0196
Genotype
P=0.1212
Genotype
P<0.0001
Fertilization*Genotype
P=0.7188
Fertilization*Genotype
P=0.5956
All four terpenes
All four terpenes
Fertilization
P= 0.1317
Fertilization
P= 0.0289
Genotype
P=0.0012
Genotype
P=0.0041
Fertilization*Genotype
P=0.3892
Fertilization*Genotype
P=0.9543
Summary
• At the first sampling date fertilization did not significantly
influence aphid abundance.
• However, there was a significant GXE effect in July on aphid
abundance. In addition, a marginal GXE effect was seen in
September.
• As the season progressed, more aphids were found on plants with
N addition, regardless of genotype. The N fertilized plants were
also significantly larger.
• A genotype effect was seen in terpene concentrations both in July
and September and a fertilization effect arose In July.
• A higher mean terpene concentration was found in phosphate
fertilized plants.
Discussion
• Overall aphid population was affected by nutrient
treatment and a GXE effect was demonstrated the early
growing season.
• For terpene concentration the effect of genotype was
most significant, and fertilization was seen to be
significant later in the season.
• Phosphate fertilized plants had significantly higher
mean terpene concentration. Flowering may deplete
plants of phosphorus. Phosphorus may be integral in
terpene production.
Future Work
• Awaiting analyses of C:N and N content in plants to
shed more light on aphid plant colonization.
• Run Partial Least Squares Regression for individual
terpenes, nutrients and aphid abundance. A
multivariate correlative analysis.
• Will do linear regression analysis between aphids and
nutrients, individual terpenes, and biomass.
• GC analysis on terpene content in aphids.
Acknowledgements
Williams Lab
Ray S. Williams
Julie Ragsdale
Marae Lindquist
Jacob Pawlik
Bryan Taylor
Other
Mike Madritch
Howie Neufeld
Jerry Meyer
Quinn Griffin
Delaney Trimble
Funding:
Appalachian State
Office of Student
Research