Wright, Margaret E by wfq74180


									                            Wright, Margaret E.
           Evolutionary Genetics of Balanomorpha Barnacles
                      Faculty Mentor: Keith A. Crandall, Integrative Biology

Barnacles are one of the most commonly encountered marine organisms. They live along the
intertidal shores and can easily be seen attached to rocks or pilings. Barnacles have a rich history
of study. Many scientists have been interested in these curious organisms. One such scientist was
the great naturalist Charles Darwin. The research he begun on barnacles has been continued for
over two centuries, yet, after all that time we still know very little about their phylogenic
relationships (family tree). The origins and diversity of this unique invertebrate are not
understood as well as they should be, given so many studies available.

There have been previous attempts to study barnacle evolution but they have been limited by
using characteristics on the outside (Newman and Ross 1976) without taking into account the
great things we can learn from analyzing the heredity in the DNA. This would be analogous to
trying to build a family tree while only using pictures of your ancestors, no dates. By analyzing
the DNA of different species of barnacles we can get a relative date for each species compared to
the others and build a phylogenic tree. Analyzing the differences among certain slow mutating
genes will show evolution between species. Another limiting factor of previous studies is the
lack of a wide variety of samples. It would be impossible to build an accurate tree if one of the
links was missing. When the molecular data of slowly evolving genes is added to the previous
morphological data the gaps will be filled in. My research project is aimed as collecting and
analyzing barnacle samples within the suborder Balanomorpha in order to set up a framework
for their classification using molecular phylogenic relationships.

This research is part of an internationally collaborative project funded by NSF or National Sciene
Foundation. We are cooperating with scientist in Australia and Denmark. One of the main goals
of this project is to assess the phylogenetic relationship for the entire known classification of
barnacles and my contribution is to analyze the suborder Balanomorpha. Samples have been
collected from around the world and are continuing to come in. There are twelve families in
Balanomorpha. Samples from most of these families have been obtained. One of the greatest
frustrations of this project has been a delay in receiving the samples from sources that originally
had promised to send them. We hope to have representatives of most of the remaining families
by the end of 2003. Nevertheless, this project is designed such that work and early analysis can
begin before all the samples have been received.

Samples were kept in 100% ethanol before extraction of DNA. DNA extraction was performed
using the Crandall and Fitzpatrick (1996) protocol for each sample. A Polymerase Chain
Reaction (PCR)was carried out on a Perkin Elmer 9600 PCR thermocycler to amplify the target
gene regions from three mitochondrial genes: CO1, 12S, 16S and three nuclear genes: 18S, 28S,
and H3. Sequences of other samples were also obtained using Genbank. These genes have been
shown to provide phylogenic data by Harris et al. (2000) and Perez-Losada et al. (2002). PCR
products were visualized using 1.5% agarose gel. Once DNA was confirmed the genes were then
cleaned and sequenced using the ABI Big-dye Ready-Reaction kit and run by the 3730
Automated sequencer at Brigham Young University. Once the sequences were compiled they
were aligned using Clustal X, given a model of evolution using Model Test and maximum
likelihood trees were estimated using PAUP. This preliminary tree is estimated with the genes
18S and 12S.

Further research is
needed to complete
the tree for the
remaining families
Many of the species
that are missing are
available to us
through the contact
in Australia. Once
we have obtained
these the process will
be completed and
these new sequences
will be added to
form a more
complete tree. We
expect to see results
that are consistent
with this preliminary
tree. Balanomorpha
has previously been
proved to be a
monophyletic group by Newman and Ross (2001). Our results are consistent. We have found that
Chthamaloidea is a sister group to the remaining Blanomorphs and the addition of the missing
families will prove if there are other sister groups as well. The longer we work at collecting new
samples from each known family the more complete this tree will become.

Crandall, K. A. and J. F. Fitzpatrick, Jr. 1996. Crayfish molecular systematics: Using a
        combination of procedures to estimate phylogeny. Syst. Biol, 45:1-26.
Harris, D.J., L.S. Maxson, L.F. Braithwaite, and K.A. Crandall.2000 Phylogeny of the
        thoracican barnacles based on 18s rDNA sequences. J. Crust Biol, 20: 393-398.
Newman, W.A. and A. Ross. 1976. Revision of the blanomorph barnacles; including a catalog of
        the species. Mem, San Diego Soc. Nat. Hist. 9:1-108.
Newman, W.A. and A. Ross. 2001. Prospectus on larval cirriped setatino formulae, revisted. J.
        Crust. Biol. 21:56-77.
Perez-Losada, M.,J.T. Hoeg, G.A. Kaolbasov and K.A. Crandall. 2002. Reanalysis of the
        relationships among the Cirrripedia, Ascothoracida, and Facetotecta (Maxillopoda:
        Thecostraca) using 18s rDNA sequences. J. Crust. Biol. 22:661-669.
Perez-Losada, M.,J.T. Hoeg, and K.A. Crandall. 2002. Unrevealing the evolutionary radiation of
        the thoracican barnacles suing molecular and morphological evidence. Syst. Biol.

To top