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Poster Full Abstracts - Evolution and Quantitative Genetics
Poster board number is above title. The first author is the presenter
268
The study of adaptation is the primary focus of evolutionary biology. However, despite a century of empirical and theoretical developments, we still lack a
general and comprehensive view of the mode and tempo of adaptive evolution. The migration of the tropical fly Drosophila melanogaster to temperate
climates is an excellent system in which to study adaptation because it has only recently colonized temperate climates, displays a well characterized set of
traits and behaviors that promote survival over the harsh winter season and goes through a substantial number of generations (~10) through a single growing
season allowing us to follow the action of natural selection in real time. To study the adaptive dynamics of Drosophila through space and time, we estimated
allele frequencies with high accuracy genomewide from populations of Drosophila collected along a broad latitudinal transect and from seasonal collections
across multiple years at a mid-latitude population. These data allow us to identify clinal variants to base pair resolution and, for the first time, to track the
dynamic change in allele frequency over the course of the growing season. We identify known clinal variants and discover ~3000 novel clinal
polymorphisms. Clinal polymorphisms are more likely to be functional (e.g., non-synonymous) than non-functional. Many genes have multiple clinal
polymorphisms but, intriguingly, these polymorphisms are often unlinked or loosely linked in mid latitude populations suggesting selection is acting on
multiple sites within a gene independently. Finally, we measure the strength of selection over the course of the growing season by examining changes in
allele frequency between summer and fall. We find that, on average, sites have a more northerly allele frequency in the spring and a more southerly allele
frequency in the fall; from these data we estimate very large changes in selection coefficients across the growing season.
510C
Genotype Evolution In Mimetic Ex Situ Conditions Gallia Butnaru 1*, Cristina Chelu1, Hildegard Herman1 1Department of Genetics, Banat
University of Agricultural Sciences and Veterinary Medicine, Timisoara, 300634, Romania *Corresponding author: (E-mail: galliab@yahoo.com).
Gallia A. Butnaru. Dept Genetics, Box 136, PO 1, Banat Univ Agricultural Sci, Timisoara, Banat.
The aim of this study was to determine the adaptation of Drosophila melanogaster raised on the medium with different concentrations of salt. Also we
observed the phenotypic traits and molecular changes by RAPD method. In our study we used natural populations of Drosophila melanogaster collected
from Socodor area (salty soils). The growth medium was supplemented with NaCl (Promega) as follows: 100 mM, 200 mM, 250 mM, 300 mM, 350 mM
and 400 mM. DNA isolation was performed after Steller (1990) and five oligonucleotides were used in RAPD reactions for NaCl 100 mM variant. Total
number of emerged individuals decrease in NaCl 100, 200 and 250 mM. The highest lethality affected larval stage (250 mM/NaCl). In NaCl 100 mM the
sex-ratio was in male favor (1:1.61). Hunk thorax was seen in NaCl 200 mM and bubbled wings appeared in NaCl 300 mM. We also notice the presence of
black spotted thorax in some individuals. The phenotypical expression of Ser gene was observed. The individuals with swollen abdomens appeared in
variants with NaCl 200, 250 and 300 mM. The RAPD results revealed no significant differences in the molecular profile of individuals raised on medium
with NaCl 100 mM. In oligomer four profile, with sequence 5’GGC-TTG-GCG3’, we saw some unique bands (1800 bp in control and 2000 bp in case of
100 mM/NaCl variant). Conclusions. In high concentrations of NaCl (400 mM) Drosophila melanogaster adults did not survived. The small size of the body
is an inherited particularity and different mutant forms were observed but a low amount of tumors were detected. An environmental condition related to
phenotypic traits represents the results of the adaptive evolution. Keywords: Drosophila, NaCl, RAPD, evolution, genotype Acknowledgements: This work
was supported by 52158/2008 PN II grant.
511A
Geographic subdivision among Drosophila melanogaster populations revealed by whole genome sequencing.
Daniel Campo, Courtney Fjeldsted, Tade
Souaiaia, Joyce Kao, Kjong Lehmann, Sergey Nuzhdin. University of Southern California, Los Angeles, CA.
Demography and selection can leave very similar genetic signatures in the populations making sometimes very difficult to distinguish their effects.
Analysis of whole genome patterns of genetic variation within and between populations can help disentangle the relative role of such evolutionary forces
since demographic processes are expected to affect the entire genome, whereas natural selection will only affect one or a few loci. For this work, we have
generated a dataset of 35 individual whole genome sequences from highly inbred lines of Drosophila melanogaster from Winters, California (USA). This
collection of genomes is the second dataset of this type made public so far, following the Raleigh set (http://www.dpgp.org/). We describe genome-wide
levels of variation and divergence within and between these two North American populations, Winters and Raleigh. Both populations exhibited negative
values of Tajima's D across the genome, which is a signature of demographic expansion. We have also detected a high level of genetic differentiation
between the two populations. We found a region in the chromosome 3L, which contains a large number of highly differentiated positions, including fourteen
non-synonymous changes. The same region also showed strong levels of linkage disequilibrium. This pattern strongly suggests an ongoing process of
positive selection, that most likely started from standing variation. We have also found evidence for gene flow and introgression between Caribbean and
Eastern North American fly populations, supporting the hypothesis of an admixture zone in the Southeast region of the US, already proposed by other
studies. These results suggest that both evolutionary forces, demography and natural selection, play important roles in shaping genomic patterns of
polymorphism within and between populations of D. melanogaster.
512B
The role of chromosome in the evolution of gene regulation, regulatory variation on the X.
Rita M. Graze
1
, Lauren M. McIntyre
1,2
, Alison M. Morse
1
,
Sergey V. Nuzhdin
3
, Marta L. Wayne
4
. 1) MGM, University of Florida, Gainesville, FL; 2) Department of Statistics, University of Florida, Gainesville, FL;
3) MCB, University of Southern California, Los Angeles, CA; 4) Biology, University of Florida, Gainesville, FL.
In Drosophila, as in other male heterogametic taxa, hemizygosity of the X chromosome in males results in differences between the X and the autosome in
population size, average recombination rates, and dominance variation, all important parameters of evolutionary processes. X-linked genes may also be
subject to a selective regime different from that of autosomal genes because they spend a disproportionate amount of time in females and are subject to X
specific regulatory pathways in males. While the relative importance of each of these factors in the evolution of X-linked genes is not completely
understood, it is clear that evolutionary dynamics differ for X-linked and autosomal (A-linked) genes. Patterns of regulatory variation may differ between
chromosomes or between the sexes, but a focus on different chromosomes or on a single sex in expression experiments thus far has been a critical limitation
preventing clear conclusions. Here we elucidate the role of chromosome in regulatory variation, separating X and autosomal regulatory variation in
D.
simulans
males and females using a series of chromosome substitutions and analyses of overall, exon and allele-specific expression.