Abstract – Waverly Garner

Hi, I’m Waverly Garner.  Welcome to my W&M Charles Center summer 2016 research project blog!  Before diving into the details of the blog, here’s a little about my interests and background.  I hail from the small town of Farmville, Virginia, the proud home of Longwood University and High Bridge Trail State Park.  Growing up in the countryside outside of the town fostered my early interest in nature; my parents often had to work hard to make sure I returned from the woods at some point to assure them I was still alive.  We spent most of our time outside chopping wood for the stove, gardening, working on the yard, and of course taking long walks down the lane.  From an early age my parents instilled in me a love for adventure and a love for asking lots and lots of questions.

For most of my childhood and teenage years, English, literature, music, philosophy, and religious studies were my main interests, though my love of nature wove them together.  I recognized a fathomless curiosity of the natural world reflected in the words of my favorite novelists and poets.  Within the philosophical musings of my favorite thinkers, I sympathized with their struggle of feeling like a part of and yet separate from the world around them.  Homeschooling allowed me to pursue my questions to a degree and with the freedom and resources for which I am still thankful, but I wanted more.

Southside Virginia Community College became the center of my life for two years.  It is there that I became conscious of my passion for biology.  My biology professor, Dr. Michael Stinson quickly became my role model and mentor.  I was amazed by the diversity of his sphere of knowledge.  He taught biology, philosophy, religion, ethics, and rock climbing!  When it came time to start thinking about where to go to college after Southside, the answer was obvious – I wanted to go to a place that could teach me to think like Professor Stinson.  As it turned out, my mentor was an alum of The College of William & Mary.  Without him, I would not be here.

The rest is history.  Here I am and I cannot believe I am here – a first generation college student and lucky enough to learn from the best.  This past semester, I took Evolutionary Genomics with Dr. Puzey and was fascinated by his research, especially because it had something to do with some of my favorite butterflies and plants – the monarchs and the milkweeds.

My project this summer will be to explore whether or not differences in cardenolide composition and production within the Common Milkweed, Asclepias. syriaca, has an effect on early instar survivability, larval size, number of instars before pupation, pupation length, adult survivability, and adult size.  For clarification, the cardenolide in question is the viscous, toxic latex produced by milkweeds to defend themselves against insects.  This is also the compound that monarch caterpillars sequester so that they are distasteful to predators.  Instar refers to a phase between two periods of molting experienced by an insect larva.  Typically, most Lepidoptera species undergo anywhere between 4-6 instars.

Milkweeds with higher than the average cardenolide compound amount, toxicity, and viscosity should have a more adverse effect on larval development than milkweeds with less than average content.  The first step in my research must be determining the cardenolide content of the milkweeds from each region.  Since only a few, individual plants will be collected from each region I must begin my research by making and potting cuttings of the milkweeds to ensure I have enough individual plants for my study.  Once this is completed, I will measure the average cardenolide content of milkweeds from each region and will compare the values I find both to averages already calculated from other studies and to the averages of the other milkweed groups in my study.

The health of each larval instar should indicate the suitability of the environment for the larval survival.  Low survivability or health may be correlated with higher cardenolide toxicity.  Three early instar caterpillars (1st or 2nd instar) will be placed on milkweeds representative of each geographic location and will be sized and weighed daily.  Each group of caterpillars should experience the same conditions so as to limit bias in my measurements.  The number of instars before pupation will be measured and compared within and between each milkweed group, taking into account the somewhat variable number of instars experienced before pupation observed in most studies of Lepidoptera.

Longer pupation has often been an observed mechanism for survival in lepidopteran suffering from harsh or difficult conditions.  If the pupation is longer in the groups in which the cardenolide content is higher than average, it would be a good indicator that increased cardenolide content has an adverse effect on developing monarchs and upon overall monarch health and survivability.  In order to test whether or not there is a positive correlation between higher cardenolide content and a negative response in monarch development, the duration of monarch pupation will be measured and compared within and between each milkweed group.

Finally, adult monarch butterflies will be weighed, sized, and checked for any developmental abnormalities.  Results will be compiled to see whether or not higher cardenolide content is positively correlated to higher monarch mortality.

A recent, really cool development has manifested in the form of a paper Professor Puzey sent to me describing a study which revealed that the expression of defensive, secondary compounds meant to protect Arabidopsis from being munched upon by ravenous insects follows the circadian feeding cycle of Cabbage Loopers!  Plants in-sync with the loopers sustained much less damage than plants out of sync with the loopers, indicating a selective advantage to regulating expression based on the loopers’ circadian rhythm.  The really cool part was at the level of the Arabidopsis genome, which revealed that 1/3rd of the genome is regulated by the plant’s circadian clock (Goodspeed 2012).  Professor Dalgleish’s research on milkweed has indicated that milkweed regulates the expression of its toxic latex using a circadian clock.  Professor Puzey and I are now in the midst of planning a series of experiments which will add a really cool component to the research – to see whether or not the circadian rhythm of the milkweed lines up with the monarch caterpillars and how latex expression affects the caterpillars at different times of day.

 

Phew, what an introduction!  Thanks for hanging in there.  I look forward to posting more about my adventures as time goes on.

 

Excelsior!

 

References:

Goodspeed et al. (2012). Arabidopsis synchronizes jasmonate-mediated defense with insect circadian behavior. PNAS, 109(12), 4674-4677.

Zalucki et al. (2001). It’s the first bites that count: Survival of first-instar                      monarchs on  milkweeds. Austral Ecology, 26(5), 1-9.