Clarkson University Honors Program Thesis Proposal
Examining taxonomic differences in iguanian lizards.
Mentor: Dr. James Schulte
February 28th, 2006
The superfamily Iguania is comprised of New World lizards. These lizards have
traditionally grouped into three categories, Agamidae, Chamaeleonidae, and Iguanidae.
Recently, these conventional have come under scrutiny. It has been proposed that due to
the many variations within Iguanidae, it would be better divided into individual families,
and the previous families Agamidae and Chamaeleonidae combined. The number of
subdivisions has been debated among researchers, however, leaving many opportunities
for taxonomic research to be conducted. (1)
In the past, the majority of taxonomic data was gathered through morphological
data alone. Current studies utilize employ these observations, but now extend into
molecular and genetic testing as well (1). A number of sequencing techniques are
available to researchers, including the Promega fmol DNA system and the ABI Prism Big
Dye sequencing kit. The Promega system utilizes thermal cycle sequencing and DNA
polymerase to produce accurate results. The ABI Prism kit includes premixed materials
for DNA sequencing.
The genetic testing will be performed by gathering DNA from either muscle or
liver tissue in the specimens. The genetic material will be amplified through
denaturation, annealing, and extension through heating. The products are then purified to
ensure that there is no contamination. This process will then be repeated.
The DNA will then be eluted from the solution using Maniatis elution buffer. The
eluted DNA was then sequenced using either the Promega fmol DNA system, or the ABI
Prism Big Dye sequencing kit. The sequences will then be compared to determine their
By evaluating the similarities between the DNA sequences, it will be possible to
estimate the evolutionary relationships between species. These relationships will also
help to determine approximate times of divergent evolution (2). One group that will be
put under special scrutiny will be the viviparous lizards. In future research, these lizards
may provide information regarding chemicals that can predict premature births. It is
hoped that this data can be extrapolated for use during human pregnancies.
The objective of this research is to re-evaluate the evolutionary distinctions
between members of the superfamily Iguania through morphological and molecular
techniques. If time and resources allow, research may also extend into evaluating the
evolution of viviparous iguanian lizards.
The remainder of this semester will be spent examining previously obtained
specimens of a number of iguanian lizard species. The week following finals week will
be devoted to collecting new specimens in Arizona. The research will be completed by
February of 2007, and the rough draft of the thesis will be written concurrently. The final
draft will be finished by the end of March.
1. James A. Schulte II, John Pablo Valladares, & Allan Larson. (2003). Phylogenetic
Relationships within Iguanidae inferred using molecular and morphological data and a
phylogenetic taxonomy of Iguanian Lizards. Herpetologica. 59:3, 399-419.
2. Omar Torres-Carvajal, James A. Schulte II, & John E. Cadle. 2005. Phylogenetic
relationships of South American lizards of the genus Stenocercus (Squamata: Iguania): A
new approach using a general mixture model for gene sequencing data. Molecular
phylogenetics and Evolution.