Transcript PowerPoint: Old Grad Poster 2

Been there, done that: the role of cuticular
hydrocarbons in facilitating polyandry in
decorated crickets
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2
1
Carie B. Weddle , Christopher G. Hamaker , & Scott K. Sakaluk
1 Department of Biological Sciences,
2 Department of Chemistry, Illinois
Photo by Scott Sakaluk
Illinois State University
State University
Introduction
Results
Females of several animal species have been shown to actively discriminate
against previous mates in favor of novel mating partners. However, few studies
have addressed the proximate mechanisms through which females recognize
previous mates.
• PCA isolated 8 principle components that explained 86.8 % of the total
variation in the observed CHCs.
Female decorated crickets, Gryllodes sigillatus, gain genetic benefits by mating
polyandrously, and females preferentially mate with novel mating partners
over previous mating partners. Results of a recent study suggest that females
“tag” males with their own unique scent at mating, permitting them to
recognize, and avoid mating with previous mates in subsequent interactions.
Such a mechanism requires that females possess unique chemical signatures
that would enable this form of self-referencing.
• DA yielded 5 discriminant functions that explained 90.3% of the betweengroup variation in PCA scores.
• The results revealed significant differences in cuticular hydrocarbons due
to genetic family (Figure 1).
• The predictive model correctly assigned to genetic family 100% of
females from four of the nine lines, and 90-97% of the females in the five
remaining lines, with a total misclassification rate of only 3.23% (Table 1).
Aim of study
Do cuticular hydrocarbons show sufficient genetic variation to be used
as reliable cues for individual mate recognition? We used gas
chromatography to analyze variation in CHC profiles for females from
nine inbred lines.
Prediction
In order for CHCs to provide a reliable means of identifying and
discriminating against previous mates, they must posses a sufficient
amount of genetic variation to permit females to distinguish their own
unique chemical profiles in a complex background of chemical cues.
Therefore, female CHC profiles should show low variation within
genetic lines, relative to between genetic lines.
5
0
-5
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Function 1 (25.2%)
The ubiquitous use of cuticular hydrocarbons (CHCs) as recognition cues among
The insects makes them likely candidates for the cues used in individual mate
recognition.
Function 3 (16.5%)
P redic ted F am ily
A
B
C
D
E
F
G
H
I
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-5
-10
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Ac tual
F am ily
A
A
B
C
D
E
F
G
H
I
100
0
0
0
0
0
0
0
0
B
0
100
0
0
0
0
0
0
0
C
0
0
100
0
0
0
0
0
0
D
3
0
0
97
0
0
0
0
0
E
0
0
0
0
94
0
0
0
6
F
0
0
0
0
6
94
0
0
0
G
0
0
0
0
0
0
100
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0
H
10
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0
0
0
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90
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I
0
0
0
0
3
0
0
0
97
Table 1: Classification results of predictive
discriminant analysis for CHC profiles of females
from 9 inbred lines. Data show the percent of
females classified into each of the 9 families.
Total misclassification rate of the model was
3.23%.
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Function 2 (20.4%)
Figure 1: Discriminant analysis of cuticular
hydrocarbons for females from 9 genetic lines.
Despite some overlap, genetic lines separate
significantly on the basis of the relative amounts of
42 cuticular hydrocarbon peaks (Wilk’s λ = 4 x 10-8,
F64, 1517.7 = 436.3, P < 0.0001).
Photo by Kazuyuki Hashimoto
Methods
Conclusions
• We sampled 31 females from nine F16 inbred lines (coefficient of
inbreeding: F > 0.75).
• Female CHC profiles show low variation within genetic lines relative
to between genetic lines.
• CHCs were extracted by whole-body immersion in 2 mL hexanes for 10
min.
• The distinct CHC profiles across inbred lines suggests a genetic
component to these chemical cues.
• The hexane solvent was evaporated overnight, and CHCs were
resuspended in 1 mL hexane with 10 ppm dodecane as internal standard.
• The unique CHCs profiles of females from different genetic
backgrounds suggests that CHCs could provide reliable cues for
self-referent phenotype matching to recognize previous mates.
• Samples were analyzed by gas chromatography, using a DB5-HT column
with a flame ionization detector:
• Standardized peak areas at each retention time were analyzed using
principal component analysis (PCA).
• PCA scores were analyzed by discriminant analysis (DA) to determine if
CHC profiles differ across genetic lines, and to determine the extent to
which the CHC profiles of individuals could correctly predict the
membership of each female to a genetic family.
• Cuticular hydrocarbons could provide a proximate mechanism
through which females maximize the benefits of polyandry.
Acknowledgements
Supported by grants from NSF to SKS, Beta Lambda Chapter of Phi Sigma and the
Orthopterists’ Society to CBW. Special thanks to Tracie Ivy, Bill Perry, Steve Juliano, Geoff
Ower, Mike Neville, Violet Kirk, Kelly Ryan, and Andrew Wadler.