Shawn Hanrahan
Major Professor: Dr. Spencer Johnston
M.S. Candidate
"Genome size diversity in insects and new genome size estimates for Texas insects".
Insect diversity is matched by an equal amount of insect genome size diversity. I report here genome size estimates for a variety of species within Arthropoda that were heretofore unrepresented in any genome size database. More immediately, they provide data for all molecular studies, including future sequencing projects, and the comparative analyses of genome size evolution within and between clades. Samples were dissected for brain tissue and co-prepared in Galbraith buffer along with a suitable standard (Drosophila melanogaster,
D. virilis, or chicken (Gallus gallus domesticus) red blood cells). Nuclei from the sample and standard were isolated by 15 strokes with the B pestle in a 2 ml Dounce tissue grinder then stained with Propidium Iodide. After a minimum of 20 minutes stain time in the cold and dark, the relative fluorescence of sample and standard were measured by flow cytometry. DNA quantity is estimated as the ratio of sample mean fluorescence to standard mean fluorescence times, multiplied by the amount of DNA in the standard. Repeat measurements produce standard errors of 1-3% for most estimated genomes. Over the past two years we have estimated the genome size for six new orders, 16 new families, and a number of new species. Samples for these studies were obtained from field collections in central Texas, and from species kindly provided from different laboratory cultures. We discuss our findings and compare our findings to the known diversity in insects to date. Lastly, we discuss the implications of our findings for molecular and phylogenetic studies in insects.