UC Santa Cruz
Quantifying Introgression at the Gene Level in Strongylocentrotid Urchins
- Author(s): Kan, Christopher H.
- Advisor(s): Pogson, Grant
- et al.
Introgressive hybridization, the movement of genetic material between species, is increasingly being documented in many taxa. It has largely been studied at 100kb+ level. I pioneered a new technique that connects introgression to the biologically meaningful gene and intra-gene level. I studied the genomes of six Strongylocentrotid urchins and identified 171 candidate introgressed genes. I detected instances of repeated introgression that occurred between Strongylocentrotus purpuratus and Allocentrotus fragilis/S. droebachiensis as well as their common ancestor. I also detected an enrichment of membrane Gene Ontology (GO) terms and enrichment of positive selection in membrane genes, possibly because they are pathogen targets. This suggests for these genes that being positively selected did not restrict their introgression as predicted by theory. I also found that introgression did not correlate inversely with time since divergence which also contradicts theory. I found many introgression events between species that are currently allopatric suggesting that they were in contact in the past. I hypothesize that past climatic shifts could have driven species into sympatry for periods of time. My results show that introgression can be detected at the gene level allowing the investigation of biologically meaningful characteristics. I hope the field will move toward investigating introgression at the gene level, so a more complete biological profile of introgression can be built.