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Poster Full Abstracts - Evolution and Quantitative Genetics
Poster board number is above title. The first author is the presenter
275
Shingleton
1
, Ian Dworkin
1
, W. Anthony Frankino
2
. 1) Department of Zoology, Michigan State University, East Lansing, MI; 2) Department of Biology and
Biochemistry, University of Houston, Houston, TX.
The scaling of body parts with body size is a fundamental aspect of biological form and function. The relationship between trait size and body size tends to
be tightly correlated within species, and this scaling relationship can typically be described with a simple linear equation. Evolutionary theory predicts that
such strong patterns of covariation should hinder the evolution of scaling relationships. However, the slopes and intercepts of these linear scaling
relationships vary considerably among species, generating substantial morphological diversity. Consequently, it is unclear how selection acts on tightly
correlated traits within a species to generate the changes in scaling relationships that we see among species. Here we use a novel artificial selection regime in
an effort to alter the slope of the scaling relationship between wing size and body size in
Drosophila melanogaster
to determine whether the slope of a
morphological scaling relationship can be modified by selection easily. After 15 generations of selection, we found that hyperallometric-selected (selected
for increased slope) lineages had average slopes (across replicates and sexes) that were approximately 11% steeper than hypoallometric-selected (selected
for decreased slope) lineages. Intriguingly, much of this response was due to a change of slopes in males; males from hyperallometric-selected lineages
increased 15% in the slope compared to hypoallometric-selected lineages, while females from the same lineages increased only 7%. However, this difference
was generated largely by the response of the hyperallometric-selected lineages; the hypoallometric-selected lineages were similar to the control lineages. Our
data indicate that despite strong pattern of covariation between the size of the wing and body, changing the slope of the scaling relationship is possible.
538A
Polymorphisms Associated with Natural Variation in Olfactory Behavior in Drosophila melanogaster.
Shilpa Swarup
1,3
, Trudy F.C. Mackay
1,3
, Robert
R.H. Anholt
1,2,3
. 1) Department of Genetics,; 2) Department of Biology,; 3) W. M. Keck Center for Behavioral Biology, North Carolina State University,
Raleigh, NC.
Natural variation in chemosensation provides a substrate for adaptive evolution. To identify polymorphisms associated with natural variation in olfactory
behavior, we measured responses to a discriminating concentration of a standard odorant, benzaldehyde, in 168 inbred wild-derived lines with fully
sequenced genomes of the Drosophila Genetic Reference Panel. We observed substantial variation in the behavioral responses of the DGRP lines. Genome-
wide association (GWA) analysis identified 306 SNPs in 106 genes at a nominal P-value of 10-5. Further analysis revealed a preponderance of rare alleles
with large effects. To verify causality of these alleles with phenotypic variation, we adopted an extreme QTL (xQTL) mapping strategy. We generated
reciprocal advanced intercross line (AIL) populations derived from crosses between two DGRP lines with highest and lowest olfactory responses to
benzaldehyde. We phenotyped 4000 flies from the AIL populations and performed massive parallel sequencing on pooled DNA samples collected from the
top 10% and bottom 10% individuals. We used BWA and SAM tools to align genomic sequences and compare allele frequencies between the DNA pools.
Combining information from GWA analysis and xQTL mapping can unambiguously identify polymorphisms causally associated with natural variation in
olfactory behavior. Supported by NIH grant GM059469.
539B
The genetic architecture of diet-dependent immune defense in
Drosophila
.
Robert L. Unckless
1
, Susan M. Rottschaefer
1
, Pavel Korniliev
2
, Chloe Ota
1
,
Illana Porges
3
, Jason G. Mezey
2
, Brian P. Lazzaro
1
. 1) Department of Entomology, Cornell University, Ithaca, NY; 2) Department of Biological Statistics
and Computational Biology, Cornell University, Ithaca, NY; 3) Jericho High School, Jericho, NY.
Dietary nutrition has profound impact on many traits, including the ability to resist and tolerate pathogenic infection. Understanding the role of nutrition in
infection and disease is important in health contexts. Influences of diet and other environmental factors can additionally complicate the evolution of immune-
related traits in natural systems. In the present work, we show that increasing dietary sugar results in dose-dependent increase in
D. melanogaster
susceptibility to chronic, but not acute, bacterial infection. We assayed defense against infection by a bacterial pathogen,
Providencia rettgeri
, in the
Drosophila
Genetic Reference Panel (DGRP), a collection of lines derived from a natural population whose genomes have been completely sequenced, after
rearing on both high-sugar and low-sugar diets. We find considerable genetic polymorphism for defense on both diets, as well as a significant genotype-by-
diet interaction that reveals a subset of lines whose defense becomes disproportionately poor on the high-sugar diet. We use genome-wide association
mapping to preliminarily implicate genes underlying variation in defense on each diet, and test several organism-level metabolic indices for correlation with
the defense phenotype.
540C
Introgression of Nuclear-Encoded Mitochondrial Proteins in
Drosophila yakuba
and
D. santomea
.
Emily Beck
1
, Aaron C Thompson
2
, Joel
Sharbrough
2,3
, Ana Llopart
1,2,3
. 1) Interdisciplinary Graduate Program in Genetics, University of Iowa, Iowa City, IA; 2) Department of Biology, University
of Iowa, Iowa City, IA; 3) The Biosciences Graduate Program, University of Iowa, Iowa City, IA.
Introgression is the exchange of genetic information between different species through natural hybridization. Once viewed as a fortuitous
accident
due to
incomplete reproductive isolation between species, it has become increasingly clear that introgression can potentially lead to ecological divergence, crop
improvement or even invasiveness. Recent molecular genetic studies in plants indicate that introgression may allow populations to regain traits that have
been lost by replacing the damaged alleles with functional copies from a closely related species. Novelty can also arise from introgression. Unique genetic
combinations that result from the stable acquisition of genetic material from another species can produce new phenotypes and serve as source for novel
adaptations. Hybrid zones, areas where two distinct species meet and hybridize, provide biologists with “natural experiments” and constitute ideal settings to
study introgression. Unfortunately there is a dearth of hybrid zones. In 2000, however, a new unique hybrid zone formed by two species in the
melanogaster
subgroup,
D. yakuba
and
D. santomea
, was discovered in a small African island of the Gulf of Guinea. Previous studies in our lab showed that the
mitochondrial genome of the former species had introgressed into the latter and replaced completely the native form. Since mitochondrial DNA products
work intimately with nuclear DNA products in the oxidative phosphorylation pathway that takes place in mitochondria, we hypothesize that some nuclear
genes in OXPHOS co-introgressed along with the mitochondrial genome. To test this hypothesis we have sequenced 12 genes of the OXPHOS pathway in a
total of 33
Drosophila
lines. Our preliminary results suggest that co-introgression has indeed occurred and support the idea of co-evolution between both
mitochondrial and nuclear genomes.