Signal evolution (fireflies)
Animals use signals to elicit reactions from other individuals that will enhance their own survival and reproduction, for example territorial behavior or alarm calls. Signals involved in mating are perhaps the most important signals because they directly relate to whether an organism will have the opportunity to mate and reproduce. How and why new mating signals arise and how they spread through a population remain open fields of research in evolutionary biology.
Fireflies, in the beetle family Lampyridae, offer an ideal system to study signal evolution because of their conspicuous and highly variable sexual signals. With over 2000 species worldwide, fireflies exhibit lighted signals ranging from simple glows to complex flashes, as well as non-lighted long-distance pheromone signals. Aside from differing in pattern, lighted signals also differ in color and range from green to orange. Genes are known that govern light emission color (luciferase) and visual receptor sensitivity (opsins). This area of my research seeks to examine signal evolution by investigating genes directly underlying both signaling and reception traits.
Repetitive DNA evolution (Drosophila, fireflies)
Repetitive satellite DNA is a major component of most eukaryotic genomes, including humans. Satellite DNAs can exist as selfish genomic parasites that propagate in the genome at the expense of the host, or, alternatively, may form essential chromosome structures including centromeres, which ensure proper chromosome separation during cell division, and telomeres, which protect the ends of chromosomes from degradation. Despite participating in these essential structures, satellite DNA sequences differ widely in sequence and abundance in the genome, even between closely related species. Molecular and theoretical models exist to explain how and why repetitive DNA shows such rapid evolution. However, few studies test these models using genome-wide data because the repetitive part of the genome is difficult to accurately sequence and measure.
This part of my research seeks to assess genome-wide satellite sequences in short-read genomic sequencing datasets and test hypotheses for their evolution (e.g. selection, drift). It is important to understand how repeats vary across populations, how and why they change over time, and their underlying genetic determinants because they are associated with diseases affecting human health including cancer, differences in immunity, and premature aging.
As part of an international collaboration, we are sequencing firefly genomes. These will serve as a resource for investigations of bioluminescence mechanisms and evolution, and firefly natural history and conservation.
Photo credit: Geoff Giller