Domestication is a topic that has interested evolutionary biologist for hundreds of years since Darwin first described this phenomenon in the first chapter of seminal work. Within the last 10 years, increases in genomic technologies have allowed researchers to begin to tease apart the genomic basis of domestication events in several species of both animals and plants. Craig’s interest in domestication lies not only with domestic phenotypes, but the rate of phenotypic change that selection can induce within a short period of time. Craig has focused his interest in domestication on the model organism Drosophila melanogaster. Although anecdotal evidence of behavioral differences in laboratory strains existed, Craig was able to use a computer tracking system to empirically identify differences in locomotor activity. Using population genomic data sets from Dmel throughout the world, Craig has identified several signatures of selection found within the genome of laboratory strains of Dmel. For more information, see the full paper published in BMC Evolutionary Biology here.
Sex- and reproductive related traits are some of the fastest evolving characteristics among any taxa. At the molecular level, genes and proteins involved with the reproductive function show many species specific signatures. To understand how lineage-specific selection has led to these diverse characteristics, Craig has begun using several species which have evolved unique reproductive characteristics including parthanogenesis, increased frequency of twinning, and high levels of sperm competition due to multi-male mating structure.
While many studies identify candidate genes, a true understanding of the role of those genes can only be understood through function. With the many genetic tools available in Dmel, it is possible to alter expression levels of certain genes and look for functional phenotypic effects. Additionally, through next-generation sequencing, it is now possible to understand the connections between the expression of a single gene and its neighbors throughout the pathway. Alteration of courtship behavior is proposed to play a large role in incipient stages of speciation, creating the first barrier to gene flow between populations. Using candidate genes identified through bioinformatic screens at both the population and species levels, Craig is using RNAi knockdowns paired with high-throughput ethomic screens to identify genes involved in courtship behavior within Dmel. By using computational tracking, Craig is able to analyze behavioral data exponentially faster and observe interactions using high-speed cameras.