Greg Taylor and Jack Sites, Biology
The focus of this project was 1) to determine sexual dimorphism in head and body structures in the lizard family Corytophanidae 2) analyze phylogenetic relationships between the species within the family, and 3) analyze the relationship with other lizard clades.
Research started in October of 2014 with writing letters to accredited museums around the nation asking them to send voucher specimens to Brigham Young University for analysis. Upon arrival, I catalogued all specimens and created separate codes for identification purposes for each one. After they were catalogued, tail lengths were measured for each specimen using a nylon string marked in centimeter increments. Pictures of each voucher specimen were taken from a dorsal, ventral, and right-side viewpoint. Members of the genus Basiliscus were also photographed from the tailfin and sailfin viewpoints. The pictures were then compiled into files and sorted by genus and species. The picture files were then converted into TPS files using the TPSUtil program. This program enabled us to view and reconstruct each image upon necessity. From there I added a series of landmarks to each image, along with a scale so that specific, calibrated measurements could be taken and then used in statistical modules to prove sexual dimorphism. The protocol used for the measurements was designed in Notepad++. A total of 560 specimens were requested, however only 380 were catalogued, measured, and analyzed because only adult specimens were used. (Male and female juveniles were not used because they had not developed characteristics that could mark them as sexually dimorphic). After measurements were taken for each image, they were compiled in one file using the program CoordGen8 and graphed on an x and y plot. This allowed us to spatially view morphological characteristics among species and sexes (A sample of those graphs may be viewed in Figure 1). The measurements were then analyzed using the geomorph package R to estimate statistical differences between male and female cranial morphology.
Results show that Basiliscus basiliscus, Basiliscus vittatus, and Basiliscus plumifrons express extreme sexual dimorphism, while Basiliscus galeritus and Corytophanes cristatus do not. Males of Basiliscus tend to be significantly larger in overall body size, fore and hind limbs, cranial features, and crest size. In July 2015 I presented a scientific poster at the Society for the Study of Amphibians and Reptiles (SSAR) conference in Lawrence, KS on the results for two genera, Basiliscus and Corytophanes. At this time the genus Laemanctus had not been analyzed because the sample size for the genus had been insufficient.
Since that time, measurements have been made and photos taken for every genus in the family Corytophanidae. TPS Files have also been created for each image, but have not yet been analyzed. Upon analysis of all specimens, inferences will be made based on available data about sexual dimorphism among all species. Additionally, genetic samples have been taken and analyzed using RNA and other specific genes to determine phylogenetic placement on a molecular phylogeny.
Analyses are projected to be completed in January 2016 and a scientific manuscript will be written detailing results of sexual dimorphism in the family Corytophanidae once analyses are completed. In addition to the manuscript that will be written, further results will be presented at the American Society of Ichthyologists and Herpetologists (ASIH) conference in New Orleans, LA in July 2016.