Effect of genotype and environment on the abundance of a specialist aphid in Solidago altissima Brian Bonville and Ray S. Williams Appalachian State University

Effect of genotype and environment on the abundance of a specialist aphid in Solidago altissima

Brian Bonville and Ray S. WilliamsAppalachian State University

Certain species of plants are the foundation of a given ecosystem

Their genetic variation may govern population responses in animals that depend on them

IntroductionCommunity Genetics

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.

• 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.

Methods

Block 1

Block 3

Block 2

542N

371P

365C

194P

186C

12N

24C

175N

201P

356N

383

N

535C

524N

343N

216P

164N

35P

45C

153P

225N

333P

401C

324N

231C

52C

136P

141P

396C

514C

502P

415N

494P

423C

482C

436P

443P

471N

292C

304C

312P

243C

252N

265P

123C

112P

63 N

76N

84P

466N

455P

281N

276C

10 1N

91C

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

Day

4 8 12 16 24 28 32 36 44 48 52 56 64 68 72 76 84 88 920 20 40 60 80

To

tal a

phid

s

0

500

1000

1500

2000

2500

3000

Aphid Abundance during season

Aphid Abundance Jul. 9 Aphid Abundance Sept. 3Fertilization P= 0.1900

Genotype P=0.2418

Fertilization*Genotype P=0.0272

Fertilization P= 0.044

Genotype P=0.4352


Mean aphid abundance by treatment

Genotype

2.000 4.000 5.000 3.000 6.000

Me

an

ap

hid

ab

un

da

nc

e

0

50

100

150

200

250

Nitrogen

Control

Phosphorus

Mean aphid abundance by treatment July 9

2 4 6 3 5

Biomass estimate Jul. 9 Biomass estimate Sept. 3Fertilization P= 0.0009

Genotype P<0.0001


Fertilization P<0.0001

Genotype P<0.0001


Biomass September 3

α-pinene

All four terpenes

Germacrene D Germacrene D

P-cymene P-cymene

β-pinene β-pinene


Genotype P=0.0008



Genotype P<0.0001



Genotype P<0.0001



Genotype P<0.0001



Genotype P=0.0080



Genotype P=0.1212



Genotype P=0.0004



Genotype P=0.0006


July 9 Sept 3

All four terpenesFertilization P= 0.1317

Genotype P=0.0012



Genotype P=0.0041


α-pinene

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 LabRay S. WilliamsJulie RagsdaleMarae LindquistJacob Pawlik Bryan Taylor

OtherMike MadritchHowie NeufeldJerry MeyerQuinn GriffinDelaney Trimble

Funding:Appalachian State Office of Student Research

Documents

Effect of genotype and environment on the abundance of a specialist aphid in Solidago altissima Brian Bonville and Ray S. Williams Appalachian State University