Basic HTML Version
Poster Full Abstracts - Evolution and Quantitative Genetics
Poster board number is above title. The first author is the presenter
274
533B
Extending Association-Mapping: Genomics meets Phenomics.
William R Pitchers
1
, Eladio Marquez
2
, Jessica Nye
2
, David Houle
2
, Ian Dworkin
1
. 1)
Zoology, Michigan State University, East Lansing, MI; 2) Department of Biological Science Florida State University Tallahassee, FL 32306.
Genome-Wide Association (GWA) is currently a much-used methodology for mapping phenotype to genotype. Unfortunately, in most cases association
mapping is carried out for a univariate metric of the trait of interest. Phenotypes are inherently multivariate, since traits are not expressed in isolation. We
have shown that for our trait of interest - the shape of the
Drosophila melanogaster
wing - tests using univariate (or even low-dimensionality multivariate)
approximations have a low resolution and can fail to detect interesting effects. We have therefore extended the toolkit of GWA to accommodate high-
dimensionality morphometric data. It is also a feature of association analyses that their findings are specific to the population in which the mapping was
performed, and associations are frequently found either not to generalise to other populations, or to explain a much smaller fraction of the trait variance when
they do. In order to improve on this, we have independently replicated measures of all phenotypes, allowing us to model environmental variance in addition
to genetic variance and map loci that are more likely to be of general importance. In combination, these new approaches make GWA a more powerful
method for studying the genetics of complex traits.
534C
Body melanisation plasticity in generalist, cold and warm adapted
Drosophila
species.
SEEMA RAMNIWAS, Ravi Parkash, Chanderkala Lambhod,
Babita Kajla. Lab No. 19, Deptt of GENETICS, M. D.UNIVERSITY, ROHTAK, Rohtak, HARYANA, India.
Ectothermic drosophilids are profoundly affected by thermal selection (i.e., genetic effects) or through induced effects on phenotype (i.e., plasticity).
Phenotypic plasticity is a powerful means of adaptation in diverse organisms but has received less attention for different drosophilids. We analyzed reaction
norms of melanisation in
Drosophila
species which differ in developmental thermal range and geographical distribution.
D. ananassae
and
D. jambulina
are
cold sensitive, and these species can be cultured between 18 to 32°C. By contrast, D. nepalensis is cold- tolerant and heat- sensitive species which can be
raised between 12 and 25°C. The cosmopolitan species
D. melanogaster
has a broader thermal range (13 - -31°C). Significant differences were observed
between reaction norms of melanisation in three anterior vs. three posterior abdominal segments in these species. In
D. nepalensis
, all the six abdominal
segments (2nd -- 7th) are highly plastic. However, only the last three abdominal segments are plastic in D. melanogaster. In contrast,
D. ananassae
(a
tropical species) lacks plasticity for all abdominal segments. Cosmopolitan species (
D. melanogaster
), even from much colder climates does not show darker
phenotypes similar to that observed in
D. nepalensis
. The aim of this study is to understand the processes involved in generating the morphological diversity
of color patterns and adaptation of
Drosophila
species to different geographical regions. Finally, comparing body melanisation patterns to phylogeny
suggests recurrent adaptations for genetic polymorphism vs. phenotypic plasticity in different evolutionary lineages.
535A
Phenotypic McDonald-Kreitman tests of mitochondrial genotype effects on nuclear gene expression.
David M. Rand, Patrick A. Flight, Nicholas
Jourjine, Lei Zhu. Ecology & Evolutionary Biol, Brown Univ, Providence, RI.
Associating molecular genotypes with quantitative phenotypes is a general problem in quantitative and evolutionary genetics. Traditional association tests
often lack a predictive model of the degree of divergence between DNA sequence variants and the level of phenotypic difference. We describe a phenotypic
McDonald-Kreitman (MK) test of nuclear gene expression driven by alternative mitochondrial genotypes that scales trait variation based on level of
sequence divergence. Four mitochondrial genotypes were introgressed in to a common OreR nuclear genetic background using balancer chromosomes:
Dmel OreR, Dmel Zimbabwe, Dsim siI and Dsim siII. This 4-taxon sample of mtDNAs provides the minimum set of haplotypes needed for an MK test in
each species. We extend the traditional 2x2 MK design of silent and replacement polymorphism and divergence to a 2x3 table that includes a row for
intraspecific variation (Vp) and interspecific divergence (Dp) in nuclear gene expression values based on microarray data from each introgression strain
carrying alternative mtDNAs. As reported in an earlier study of life history traits, the majority of nuclear genes show more variation in gene expression
among mtDNA haplotypes within species than variation among the Dmel or Dsim mtDNAs. This pattern in consistent with ‘excess’ amino acid
polymorphism for mtDNA in traditional MK tests, interpreted as evidence for selection against mildly deleterious variation in mtDNA. The expression
profile data were also collected under varying levels of hypoxia to test the hypothesis that stressful conditions would shift the mtDNA effect from within- to
between-species. In general this result was observed, as the number of phenotypic MK tests for nuclear gene expression showing ‘excess’ intraspecific
variation was reduced under stressful hypoxic conditions. These analyses demonstrate an important retrograde signaling process between mitochondria and
nuclear genes, and provide a simple means of making predictive tests of phenotype-genotype associations.
536B
Comparative analysis of sex-specific pigmentation identifies novel genes involved in phenotypic evolution.
Sarah A. Signor, Arytom Kopp. University
of California, Davis, Davis, CA.
The origin of diversity is one of the most central questions in evolutionary biology. In recent years the molecular changes responsible for the origin of
some phenotypic differences has been identified. These studies typically proceed on a case-by-case basis making it difficult to infer the general rules and
patterns of evolution. A systematic search for these patterns necessitates a comparative approach where multiple instances of phenotypic evolution can be
examined in closely related species. Within the
Drosophila ananassae
subgroup there have been several independent changes in sexually dimorphic
pigmentation. I am investigating the molecular basis of this color pattern evolution in three pairs of (sub)species using a combination of high throughput
sequencing and genotyping assays. QTL analysis shows that the number of loci involved is moderate - ranging from two to four in different taxa. I find that
sex-specific pigmentation is controlled by overlapping but clearly distinct sets of genes in different species. This genetic toolkit includes at least one
previously unidentified member of the pigmentation pathway. The redundant structure of the pigmentation pathway appears to limit the role of constraint in
its evolution and facilitate rapid change.
537C
Tipping the Scales: Artificial Selection on the Slope of a Wing Size-Body Size Scaling Relationship in
Drosophila
.
R. Craig Stillwell
1
, Alexander W.