Hughes Mentor:  Richard Harrison

Department: Ecology and Evolutionary Biology

More Information

Dr. Richard Harrison

Dr. Richard Harrison is currently the chair of the Department of Ecology and Evolutionary Biology (EEB) at Cornell University. Harrison’s research focuses primarily on studying natural populations to infer information about the origin of species, population structure, and evolutionary relationships between species. Using DNA and protein sequences in modern molecular methods has made research in this area very powerful.

Dr. Harrison was not always involved with evolutionary biology. In 1967, Harrison obtained his Bachelor’s degree in chemistry from Harvard University, after which he completed research in nerve and muscle physiology on a Churchill fellowship at Cambridge, England. In 1968, Harrison began a PhD in biochemistry, but became “disenchanted” with the field. He found the biochemistry field to be very competitive, with he and several others competitively working on the same project. After withdrawing, Dr. Harrison found his way into evolutionary biology through his interests in natural history. He began his PhD at Cornell in 1972, researching genetic variation among closely related species of field crickets in the differentiation between the two species.

After completing his PhD, Harrison moved to New Haven, Connecticut to become an Assistant Professor in the Department of Biology at Yale University. After obtaining tenure in his ninth year, Dr. Harrison decided to return to Cornell where he became an Assistant Professor in the Section of Ecology and Systematics (later to become EEB) in 1996. Harrison has remained at Cornell for the past 21 years, enjoying Ithaca and the strength of Cornell’s Ecology and Evolutionary Biology department.

One of Harrison’s current projects involves researching the mechanisms of speciation, such as in determining the barriers to gene flow between populations. His research has many practical applications, one of which is in conservation biology. There exists much debate as to what constitutes a species or a subspecies, and Harrison’s genetic analyses of patterns of variation can shed light onto this issue. Harrison’s research has also led to the view that the genome is a mosaic, with different parts of the genome having different evolutionary histories. For instance, in the European Corn Borer, one of the model organisms which Dr. Harrison’s lab is currently studying, there exist two different pheromone strains between which introgression can occur. Studying the evolutionary history of a genome can also be helpful in finding the origins of resistance to biological insecticides, such as the Bt toxin, which has important implications in agriculture. Studying gene flow in genetically modified organisms and determining which regions of the genome do or do not introgress can be helpful in this respect as well.

Aside from his research in evolutionary biology, Dr. Harrison has many other interests. Dr. Harrison is an avid runner, and in his 21 years at Cornell has been involved with High Noon, a group of faculty, graduate students, and undergraduates who run daily at noon in the Ithaca area. Typical routes include running around the Plantations, Route 366, and Game Farm Road. In addition to running, Harrison loves to garden, and maintains a garden of his own at his home. Harrison also describes himself as an amateur astronomer, making frequent use of his own telescope. Living in the Finger Lakes Region is also ideal for Harrison, who enjoys wine and the wide variety of unique wineries in the area.

When asked about the qualities he personally looks for in an undergraduate researcher entering to his laboratory, Harrison feels that passion for learning is essential. Prior research experience and knowledge is secondary to a student’s genuine curiosity about the subject matter and motivation when conducting research. An undergraduate who truly cares about his or her research and who is driven to excel is a much more valuable asset in the lab than one with experience and little interest. In finding undergraduates with these specific qualities, Harrison enjoys watching undergraduates in his lab grow in their knowledge and research skills during the course of their research experience.

A Hughes Scholar Guide to Doing Research in the Harrison Lab

What did you have to know to get into this lab?

Courses such as Evolution (BIOEE 278), Genetics (BIOGD 281), Speciation (BIOEE 453), and Population Genetics (BIOGD 481) are useful, but by no means required. Undergrads with little or no experience are welcomed in the lab. What is most important is that the student be highly motivated, hard working, and have a good attention to detail.


What is your day in this lab like? What organism do you work on and what are you trying to prove?

My goal is to identify one of the speciation genes (a gene that contributes to reproductive isolation between two different taxa) in the European Corn Borer (ECB). Research indicates that the gene encoding the enzyme fatty acid reductase (FAR) might be a speciation gene in the ECB. Accordingly, my goal is to identify and characterize FAR in the ECB. My average work week might begin by designing primers based on conserved gene regions across known FARs. I then use those primers for a PCR reaction, run the reaction products out on a gel to confirm their size, and finally I’ll sequence the products. I then compare these sequences to known and putative FARs in related species to confirm that I have in fact identified FAR in the ECB.


What techniques do you do and how do you do them?

The Harrison Lab employs a wide number of techniques from molecular genetics. Techniques that were important for my project included:

Degenerate Primer Design
PCR
Gel Electropheresis
Cloning
Sequencing
Linkage Mapping
Constructing Gene Genealogies
Tissue Dissection
DNA Extraction
RNA Extraction and construction of cDNA


What have you learned about yourself from doing this project?

I’ve learned that earning a PhD, and pursuing a career in research, are now major goals in my life. A summer of intensive research is an excellent way to find out if this is something you could make a career out of. I found the experience to be challenging, rewarding, at times discouraging, and most of all exciting. It’s amazing how quickly the day can slip away, and I often found myself glancing at the clock hoping it would move just a bit slower. The days were never dull because I was always setting up one experiment while anxiously waiting to see the results of another one.


What is different about school year and summer research?

Summer research is very different from research during the academic year, the chief difference being the amount of time you can dedicate towards your project. During the summer I was amazed that even working 50 hour weeks I couldn’t get done half as much as I wanted to! So in relative terms, the pace of your research slows to a crawl during the school year. On the plus side though, a summer of intensive research really teaches you how to be a good researcher and to utilize your time effectively. So even though you’re working fewer hours during the school year, you’ve learned to use that time far more efficiently.

An Interview with Professor Rick Harrison

A Brief Bio

Professor Harrison completed his undergraduate study at Harvard where he majored in chemistry. His interests lay in biochemistry, but he felt that a rigorous education in fundamental chemistry would serve him well in the future. After graduation Rick traveled to Cambridge where he completed a year long Churchill Fellowship in physiology.

When Rick returned to the states he enrolled in the biochemistry graduate program at the Harvard Medical School. Within six months however, he was classified 1A by the draft board, and faced the prospect of being shipped off to Vietnam. He withdrew from graduate school and worked in a laboratory on muscle protein for the next three years.

As time passed, Rick found himself increasingly dissatisfied with the culture of molecular biology, and he yearned for the opportunity to work outdoors in the field. And so it was that he came to Cornell University at the age of 26, where he pursued a PhD in ecology and evolutionary biology. Under the guidance of Peter Brusard, Rick earned his PhD in only four and a half years. While at Cornell Rick’s work concentrated on a cricket hybrid zone that he discovered in the northeastern United States. Hybrid zones are excellent places to study the speciation process.

Upon receiving his PhD Rick accepted a faculty position at Yale, where he would teach for the next nine years. During his 9th year he was offered full tenure, but instead opted to escape the urban environment of Yale and return to his roots at Cornell University. He has taught here ever since.


Personal Interests

Besides evolutionary biology, Professor Harrison busies himself with a wide array of interests and hobbies. One of the reasons he chose to teach at Cornell was its picturesque landscape, and he takes full advantage of Ithaca’s pastoral offerings. If you venture up to the plantations around noon or so you’re likely to find him on his daily five mile run. He also enjoys hiking along local trails, and tending to his extensive garden. When he’s not in the office, or enjoying the outdoors, Professor Harrison can be found enjoying fine wine in the pleasure of good company.


So Why Evolutionary Biology?

Rick’s career in the sciences has spanned a number of fields, including chemistry, physiology, molecular genetics, and evolutionary biology. First and foremost though, Rick considers himself an evolutionary biologist, but his interests and the demands of the field require a strong background in molecular genetics as well.

Rick finds evolutionary biology to be an exciting field for a number of reasons. While many branches of biology are concerned with describing how things are, evolutionary biology is chiefly concerned with explaining why things are. To Rick, the deeper and more profound questions have always been the most alluring, and that entails describing why the world is the way it is.


Research in the Harrison Lab

Research in the Harrison Lab focuses on the genetics of speciation. A major goal in this area of research is to characterize the genetic architecture of speciation. The genetic architecture of speciation seeks to characterize the number, chromosomal location, and phenotypic effect of the genes involved in reproductive isolation between two different species. (The emphasis on reproductive isolation comes from the Biological Species Concept (BSC) which defines species based on reproductive relationships.) The genes responsible for reproductive isolation have been deemed “speciation genes”.

Until quite recently, our knowledge regarding the genetics of speciation has been severely biased towards Drosophila and post-zygotic barriers to gene exchange. Accordingly, the development of additional systems, and the investigation of pre-zygotic barriers to gene exchange, is considered highly advantageous. To that end, the Harrison Lab works on two major research initiatives that study pre-zygotic barriers to gene exchange in non-Drosophila systems.


The European Corn Borer

The European Corn Borer (ECB) (Ostrinia nubilalis) is an exceptional system for studying pre-zygotic barriers to gene exchange. There are two different strains of the ECB characterized by the production and response to different pheromone blends of the E and Z isomers of 11-tetradecenyl acetate. In the Z Strain, females produce a 3:97 E:Z blend. In the E Strain, females produce a 99:1 E:Z blend. Z Strain males respond only to the pheromone blend of the Z female. E Strain males respond mostly to the E pheromone blend, but will respond to intermediate pheromone blends as well. Because of this pheromone polymorphism, there is a high degree of reproductive isolation between the two strains. Nevertheless, natural hybrids are produced in the wild at low frequency.

Simple genetic crosses show that a single major gene is responsible for producing the distinctive pheromone blends in female moths. Likewise, a single major gene is also responsible for male behavioral response to these pheromone blends. Since these genes contribute to reproductive isolation between the two strains, they are candidate speciation genes in the ECB.

Research in the Harrison Lab has been dedicated to measuring patterns of gene flow and linkage disequilibrium across the genomes of the E and Z Strains, constructing gene genealogies, constructing a linkage map of the ECB, and identifying the candidate speciation genes responsible for pheromone blend specificity and male behavioral response.


Accessory Gland Proteins in Field Crickets

The other major research initiative focuses on pre-zygotic barriers to gene exchange in two closely related species of field crickets (Gryllus firmus and Gryllus pennsylvanicus). These crickets form a well characterized hybrid zone in the northeastern United States. Much of the research in the Harrison Lab has focused on characterizing gametic isolation between the two species.

During mating, males transfer both sperm and accessory gland proteins to females. These accessory gland proteins are thought to have important effects on the behavior and physiology of females. The Harrison Lab has constructed a cDNA library from the accessory gland of Gryllus firmus, and has identified roughly 250 unique ESTs (expressed sequence tags). While some of these proteins are produced by “housekeeping” genes, the vast majority have no homology to known sequences.

Since reproductive proteins might be evolving rapidly, they can lead to gametic isolation between two different species. Efforts in the Harrison Lab have focused on identifying the genes that appear to be evolving the fastest. Using cDNA libraries constructed from closely related cricket species, it is possible to estimate dN / dS ratios for the 250 unique ESTs. (dN / dS is the number of non-synonymous substitutions divided by the number of synonymous substitutions. A ratio less than one is indicative of purifying selection and a high degree of constraint, whereas a ratio greater than one indicates that the gene is undergoing positive selection.) Promising ESTs will be sequenced in their entirety using both accessory gland cDNA and genomic DNA.


Practical Applications

Traditionally, people might not expect evolutionary biology research to have many practical applications, but evolutionary genetics research proves quite useful when dealing with invasive species and major economic pests. The ECB for instance is an exceptional system for studying the genetics of speciation, but it is also a major economic pest. As its name entails, the ECB is destructive to corn crops around the world. Research in the Harrison Lab has sought to characterize patterns of gene flow across the genomes of the E and Z strains. Gene flow is restricted around loci that are under selection / involved in reproductive isolation, but is unrestricted across the rest of the genome. If for instance, a population of Z Corn Borers evolves resistance to a pesticide, we might be able to say something about the probability of that gene moving into the E Strain. If the gene conferring resistance is located near a speciation gene, the odds of it moving into the E Strain is low. However, if it is located in a part of the genome where gene flow is unrestricted, Corn Borers from both strains may quickly evolve resistance to the pesticide.

A graduate student in the Harrison Lab is currently studying the Asian Longhorn Beetle, a well known invasive species. Mitochondrial DNA is currently being used to construct a phylogenetic tree for beetle populations around the world. When a new invasion occurs, the mtDNA of the invasive beetle can quickly be sequenced, thus determining the population that it emigrated from. Knowing the source of the invasion can prove valuable to conservation efforts.