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Poster Full Abstracts - Evolution and Quantitative Genetics
Poster board number is above title. The first author is the presenter
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Predation is a powerful selective force that has been shown to shape the evolution of many natural populations, yet its influence in the model system
Drosophila
is virtually unknown. A common thread among studies of antipredator adaptations in the wild is the striking parallelism i.e. in the phenotypic
responses of independent populations. However, it is unknown whether these parallel phenotypic responses represent homologous genetic changes or
whether common patterns of genetic and phenotypic correlations drive them. To address these questions, we initiated two replicate sets of populations of
Drosophila melanogaster
that have been subjected to predatory experimental evolution for over 70 generations. Each replicate consists of a predation
population that undergoes episodic viability selection by 1st instar nymphs of the Chinese mantis (
Tenodera aridifolia sinensis
) and a control population that
undergoes mock selection lacking the predator. We are undertaking an integrative approach measuring both behavior and morphology in tests of hypotheses
regarding the nature of evolutionary trajectories in response to predation. Escape related morphology is one trait that has been shown to undergo repeated
parallel evolution in many species, particularly fish, in which the morphology is directly related to escape performance. Consequently, we measured
selection on wing size and shape of surviving and captured flies in order to assess how selection is driving changes in morphology. Though we found similar
patterns of selection in the control populations as expected, patterns of selection in the predation populations differ dramatically resulting in divergence of
wing size and shape. However, the behavioral responses of the predation populations in aggression, foraging and survival have been consistent suggesting
that similar higher order phenotypes may be reached by multiple evolutionary paths.
474C
Alcohol consumption as self-medication against parasitic wasps In Drosophila melanogaster.
Todd A. Schlenke, Neil F. Milan, Balint Z. Kacsoh.
Biology Dept, Emory Univ, Atlanta, GA.
Organisms frequently utilize food resources that contain compounds toxic to other organisms. The ability to consume such toxins not only allows access to
potentially underutilized resources, but can also provide protection against non-resistant predators and parasites. Given that larvae of the fruitfly Drosophila
melanogaster live within rotting fruit and have evolved resistance to high levels of ethanol and other products of fermentation, we decided to test whether
ethanol protects fruitflies from otherwise lethal parasites. Here, we show that environmental ethanol causes reduced infection of fruitfly larvae by
endoparasitoid wasps. Furthermore, if infected, ethanol consumption by fruitfly larvae results in developmental retardation and death of wasps growing in
the fly hemocoel, without need of the stereotypical anti-wasp immune response. This double protection afforded to fly larvae by ethanol is significantly more
effective against a generalist wasp than a wasp that has evolved to specialize on D. melanogaster. Finally, fly larvae actively seek out ethanol-containing
food when infected, showing they use alcohol as an anti-wasp medicine and self-medicate accordingly.
475A
Transcriptional profile during pachytene in Drosophila melanogaster females.
Andrew Adrian, Josep Comeron. Biology, University of Iowa, Iowa City,
IA.
We have recently obtained whole-genome, high-density recombination maps in Drosophila melanogaster separately for crossing over (CO) and non-
crossover (gene conversion; GC) events. These maps based on more than 100,000 recombination events at a physical resolution down to 2.5 kilobases (kb)
reveal highly variable CO rates along chromosomes, including coldspots within regions traditionally labeled as high-recombination. GC is more uniformly
distributed across the genome than CO and detectable in regions where CO is severely reduced or completely absent (eg., the small chromosome four). At a
micro-scale however GC events have a tendency to occur within transcript units. These differences in CO/GC distribution suggest the influence of
spatiotemporal chromosomal properties. To gain insight into the possible causes for the CO/GC variation across the genome we first attempt to link variation
in recombination with transcription levels in Drosophila females. Present transcriptomes however poorly characterize the relevant expression during
recombination, with germarium cells representing only a tiny fraction of the gonadal (ovary) tissue. In particular, we sought to investigate the expression
profile of Drosophila stage 2a oocytes utilizing Laser Capture Microdissection and mRNA-Seq. Our analysis provides a glimpse of the transcriptional
landscape at the most relevant pattern of gene expression during pachytene—when double strand breaks are being formed and repaired.
476B
Tracing causative polymorphisms for allele-specific expression in Drosophila melanogaster.
Daniel Campo
1
, Justin Fear
2
, Lauren McIntyre
2
, Sergey
Nuzhdin
1
. 1) University of Southern California, Los Angeles, CA; 2) University of Florida, Gainesville, FL.
Variation in gene expression is thought to be an important source of phenotypic diversity, playing a crucial role in population and species divergence.
Unraveling the genetic mechanisms by which gene expression is regulated is therefore an important step in order to understand certain evolutionary
processes such like local adaptation and speciation. Much of the effort done to date in this regard has been focused on interspecific variation. Here we
investigate the contribution of cis- and trans- regulatory changes to allele-specific expression (ASE) differences in intraspecific hybrids of Drosophila
melanogaster. We have resequenced the entire transcriptome of a large panel of F1 heterozygous individuals, derived from a set of crosses between 70
isogenic lines and a common standard strain. Whole genome sequences for all the parental isogenic lines are also available. For each F1 genotype, we
estimated ASE using a mixed-effects model that accounts for differences between technical replicates. In each case, the p-value was adjusted for a False
Discovery Rate (FDR) that takes into account all genotypes analyzed. We found significant ASE for 20% of the genes assessed in more than 50% of the
genotypes at a FDR of 0.05. This amount of cis- regulatory divergence is surprisingly high, and suggests that much of the adaptive evolution at the
population level might be due to variation in gene expression rather than changes at the protein level. Additionally, since we used a common parental fly line
in all the crosses, we will be also able to identify the relative contribution of trans- regulatory changes. These differences in allelic expression will be further
associated with specific polymorphisms at the nucleotide level.
477C
Deficiency of X-linked inverted duplicates with male-biased expression and the underlying evolutionary mechanisms in the Drosophila genome.
Zhen-Xia Chen. Center for Bioinformatics, State Key Laboratory of Protein and Plant Gene Research, College of Life Sciences, Peking University, Beijing,
PR China.
Inverted duplicates (IDs) are pervasive in genomes and have been reported to play functional roles in various biological processes. However, the general
underlying evolutionary forces that maintain IDs in genomes remain largely elusive. Through a systematic screening of the Drosophila melanogaster