Date of Award


Thesis Type

Open Access

Degree Name

Honors Bachelor of Arts




Fiona Harper


Hybridization occurs when two separate species reproduce to form hybrid offspring. If the hybrid offspring backcross with individuals of their parental species, the subsequent offspring may have varying amounts of the parental genomes, if viable. Following the retreat of the Last Glacial Maxima 20,000 years ago, two sea star species, Asterias forbesi and A. rubens came into secondary contact in the Gulf of Maine where they began to hybridize. Previous research in our lab studied the frequency of hybridization at four locations along the east coast (Quebec, Nova Scotia, New Hampshire, and New York) using morphological identifications as well two nuclear DNA markers (ITS and EF1-α). Here, we used Polymerase Chain Reactions (PCR) to add additional mitochondrial DNA identifications to create a hybrid index and measure the frequency and extent of hybridization between the two species. Our findings showed low levels of bimodal hybridization in sympatric populations and extremely low levels of hybridization in allopatric populations. Further research is needed to expand the data set and to build a more comprehensive model of the hybridization occurring in the populations.