The Elucidation of a Host Race Formation of Oak Mistletoe (Phoradendron leucarpum subsp. tomentosum)

Summer 2016

Justin Rigby : Genetics and Plant Biology

Mentor: Noah Whiteman

Mistletoe is a parasitic organism that inhabits many different tree species in North America. One of the most common mistletoe species is the Oak Mistletoe (Phoradendron villosum) which inhabits a few different oak species in Northern/Central California. They grow in large green clumps and on the trees and produce white berries in the fall and winter seasons. These berries provide a large source of food for various frugivores during the cold winter months. Previously, they have been shown by Janis Dickinson (Cornell University) to be the only source of food for the Western Bluebirds (Silia mexicana) in Central California, and are essential for the survival of the species during these months. Thus, this mistletoe is an important source of food for animals during the winter.

Since the mistletoe inhabits different species of Oak’s I was interested to find out if these different populations of mistletoe species are actually “host races”. A host race is a when a single parasitic species occupies different host species and are adapted to those particular host species. I will investigate this question by taking samples of mistletoe DNA from different host species, and then will be analysing them using a sequencing technique called RADseq. By using RADseq I will be able to elucidate the relationship between mistletoe on different host species, and populations of mistletoe, in order to see if they are indeed host races by comparing their markers to one another to see if they differ.

I would like to thank the Rose Hills Foundation for this wonderful opportunity to conduct research this summer on a subject which I am passionate about. This program has enabled me to devote my summer to my research and to make a meaningful contribution to the field of population genetics. It has also laid the foundation for my senior thesis project and will strengthen experience as a researcher.