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Overview
My
lab addresses evolutionary questions that are at the interface of genomics,
genetics, development, and ecology. I work almost exclusively with
ambystomatid salamanders because they
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exhibit
considerable phenotypic variation within and between species, and
are thus ideally suited for comparative studies
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can
be crossed (intra- and interspecifically) and cultured in the laboratory,
and
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are
a model amphibian system that will continue to make important contributions
to vertebrate biology.
Graduate Student and Post-Doctoral Opportunities
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Research Interest in Genomics
From an
evolutionary perspective, the extension of genome analysis to
additional vertebrate species will allow identification of homologous
chromosomal segments, and thus facilitate comparative studies of
genome evolution (Voss et al., 2001). We are developing a
comprehensive amphibian genome map. Specifically, we are mapping the
location of approximately 500 protein-coding loci using an
interspecific mapping cross (Ambystoma mexicanum x A.
mexicanum/A. tigrinum tigrinum). When completed, our map
will provide answers to fundamental problems in evolutionary biology,
including the relative importance and timing of genome duplications,
gene duplications, gene losses, and chromosomal rearrangements that
have occurred between urodeles and other vertebrates. Also, the map
will facilitate genome-cross referencing between salamander and model
organisms with completely characterized genomes.
Salamanders are the only vertebrates that can regenerate entire
tissues and organ systems as adults. Clearly an understanding of the
mechanisms allowing such extensive regeneration by salamanders could
have clinical significance for treating human trauma and amputation.
We are developing genome resources for researchers that use
salamanders in regeneration research. In particular, we are
developing expressed sequence tagged (EST) libraries for gene
identification and macroarray analysis. |
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Research Interest in Genetics
Very
little is known about the underlying genetic architecture of traits
that are important in adaptation. A problem that I have worked on for
the past 10 years concerns the genetic basis of metamorphic failure (paedomorphosis)
in A. mexicanum (Mexican axolotl). The evolution of
metamorphic failure in A. mexicanum and other ambystomatids is
a classic example of adaptive evolution (Voss 1995). Previous
work showed that a major effect QTL evolved during the domestication
of laboratory axolotl (Voss and Shaffer, 1997; 2000).
To gain perspective on the origin and fixation of the major gene
effect in laboratory A. mexicanum, we are examining the more
complex genetic basis of metamorphic failure in wild-caught A.
mexicanum. We developed recently a wild-caught A. mexicanum
mapping cross (N=530) and scored all individuals for metamorphic
timing, metamorphic failure, development rate, and limb regeneration
rate. We plan to use QTL and candidate gene analysis (Voss et al.,
2000; Voss et al., In Press) to examine the
genetic basis of each of these traits. In addition, we will initiate
genetic analyses of metamorphic failure, as well as gene expression
studies, in a second non-metamorphic species (A. andersoni).
By extending our studies to a second species, we will determine if
metamorphic failure is manifested by the same or different QTL. A
comparative analysis of metamorphic failure may reveal the
evolutionary potential for convergent/parallel evolution.
Although
it has been shown that salamanders exhibit a ZZ/ZW mode of chromosomal
sex determination, there have been few segregation analyses of sex
determination and no attempts to identify underlying loci. We are
using an ambystomatid interspecific mapping cross to investigate the
genetic basis of sex determination. Our unpublished results (Smith
and Voss, In prep) indicate that the segregation of males
and females is largely consistent with 1:1 segregation (N=375; there
is a slight female bias). If molecular markers are identified for the
sex-determining locus, this will open up many new avenues of natural
history and population genetics research, as well as set the stage for
gene identification.
We are
interested in developing and applying molecular markers to salamander
populations in nature. We are currently working on several projects,
including a hybridization study of the California Tiger salamander (Riley
et al., In Press).
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References
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For
a complete list of
publications, please click here.
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Rilely et al. In Press: |
Riley, S.P.D.,
H.B. Shaffer, S.R. Voss, and B.M. Fitzpatrick. Hybridization between a
rare, native tiger salamander (Ambystoma californiense) and its
introduced congener. In Press, Ecological Applications.
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Smith and Voss, In Prep: |
Smith, J.J.
and S.R. Voss. Genetic linkage analysis
of sex determination in ambystomatid salamanders.
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Voss et al. In Press: |
Voss, S.R.,
K. Prudic, J. Oliver, and H.B. Shaffer. Candidate gene analysis of
metamorphic timing in ambystomatid salamanders. . In Press,
Molecular Ecology.
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Voss et al. 2001: |
Voss, S.R.,
J.J. Smith, D.M. Gardiner, and D.M. Parichy. 2001. Conserved vertebrate
chromosomal segments in the large salamander genome. Genetics
158:735-746.
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Voss and Shaffer, 2000a: |
Voss, S.R.
and H.B. Shaffer. 2000. Evolutionary genetics of metamorphic failure
using wild-caught versus laboratory axolotls (Ambystoma mexicanum).
Molecular Ecology 9:1401-1408.
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Voss and Shaffer, 1997: |
Voss,
S.R and H.B. Shaffer. 1997. Adaptive evolution via a major gene effect:
paedomorphosis in the Mexican axolotl. Proceedings of the
National Academy of Sciences 94: 14185-14189.
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Voss, 1995: |
Voss, S.R.
1995. Genetic basis of paedomorphosis in the axolotl, Ambystoma
mexicanum: a test of the single gene hypothesis. Journal of
Heredity 86:441-447.
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