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| Molecular Evolutionary Genetics and Phylogenetics |
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Movement of DNA from one genomic location to another, or from one
genome to another, has been an important process in the structuring of
genomes and has manifold consequences. One system that has comprised
much of our past research efforts in this area is the study of
retrotransposons (Cummings 1992, Cummings 1994, Konieczny et al. 1991, Voytas
et al. 1990, Voytas et al. 1992). I am interested in evolution and distribution of
retrotransposons and how their special properties influence their
evolutionary patterns. Our past research on these elements focused on a
class most similar to the copia elements of Drosophila
melanogaster. This research ranged from characterizing these
elements in the crucifer Arabidopsis thaliana to a broad
phylogenetic survey including nine of ten divisions of plants and
several protist groups. One of the more significant results of this
research was demonstrating that this class of transposable elements is
present in all plant lineages, making it the most widespread group of
transposable elements yet characterized.
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Another class of transposition events important in evolution involve
the movement of genetic material between different sub-cellular
genomes; nuclear, chloroplast and mitochondrial. We completed a
project using analysis of Southern blot hybridization and DNA sequence data to
examine the evolutionary dynamics of transposition events from the
plastid genome to the mitochondrial genome in angiosperms (Cummings et
al. 2003). Analyses show that interorganelle transposition events
have happened repeatedly and independently during angiosperm evolution
and that they have involved movement of DNA rather than RNA, which is
in contrast to some mitochondrion to nucleus transfers.
Phylogenetic systematics, like population genetics, constitutes one of
the principal conceptual frameworks for much of our research and
provides the appropriate context for addressing many hypotheses in
molecular evolutionary genetics. Additionally, several past projects
are explicitly systematic, in whole or in part, in that particular
hypotheses regarding relationships are examined. Examples include
past research on avocados (Persea spp.; Furnier et al. 1990);
grasses (Poaceae; Cummings et al. 1994), flatworms (Platyhelminthes;
Blair et al. 1996, Campos et al. 1998), green algae (Cladophora
spp.; Marks and Cummings 1996), plant pathogens (Phytophthora
spp.; Förster et al. 2000), and horny-head worms (Acanthocephala;
García-Verela et al. 2000, García-Verela et al. 2002). The
most recent systematic project focused on the genus Agalinis
(Orobanchaceae). The relationships within the genus present several
interesting systematic problems and no previous molecular work within
the group has been published. Our results both confirmed and refuted
several points in the current taxonomy for the genus (Neel and
Cummings 2003). We take a very broad view toward systematics, and
focus on the implications of the relationships between taxa and what
they can tell us about the patterns and processes of evolution.
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