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Thursday, May 24, 2012

2012 Conference Highlights, Part 1

By Laurie Sheldon

Foreword

Triumph the Insult Comic Dog
Before getting into the body of this blog, I’d like to take a moment to describe my experience last weekend at the FNPS conference in Plant City. For starters, this was my first conference, so, aside from knowing the lineup of speakers, socials, and field trips, I had no idea what I was getting myself into. I kept recalling a sketch I saw on late night television many years ago in which Triumph the Insult Comic Dog interviewed a gathering of Star Wars fans, and did just what anyone would expect of a talking, cigar-smoking, bow-tie wearing canine - he made fun of them. Granted, nerdy adult men in Ewok costumes are fairly easy targets, but still… I couldn’t help wondering if I was headed into a variation of that scene, less the dog and light sabers, of course. “Jeez, I hope not,” I thought, “since I really don’t care for science fiction.” After receiving an invitation to report about the event to the blog-reading world, I booked a hotel room, packed my bags and headed towards the Gulf coast, undaunted by my feelings about the genre.

I’ve already blogged about evening one of the conference, which you can read about here, so I’m skipping directly to the first full day. I woke up Friday morning at 4:30am, excited, nervous, and sweating after making the mistake of turning off the noisy swamp-cooler in my room before hitting the sack. I recited my mantra from back when I was a Landscape Architecture student, “sleep is overrated,” jumped into the shower and got dressed. I jotted down directions to the Trinkle Center and read from a book penned by that day’s keynote speaker until the hotel’s continental breakfast was open. After breezing through the lobby for bean juice and a handful of generic cheerios I was out the door.

Early Friday morning at the Trinkle Center
The conference center was already buzzing at 7:30am. Vendors, shoppers, lecturers, and volunteers weaved skillfully among one another, while friends from different parts of the state stopped to chat and review the schedule. Over the next two days, I attended 12 presentations and took almost 50 pages of notes. The speakers each had unique insight, grounded in personal experience, on subjects that extended well beyond our state’s native flora. Citizen advocacy, historic gladesmen, shifting legislative policies, and karst topography represent a sampling of the words that jump out at me as I flip through the scribbling in my steno pad. That said, it seemed that everyone in attendance DID have at least one thing in common - a love of the state of Florida, a desire to “keep it real, yo”, and respect for the life that existed here long before blogs and indoor plumbing.

I plan to share all of the wonderful information I took away from the conference on this blog - but not all at once. Believe me, it’ll be much better that way. Was it like a gathering of Star Wars enthusiasts? No… and yes. You see, there were no talking robots or hirsute wookies, the issues at hand were/are not imagined, none of the conference took place in space, and there was no soundtrack by John Williams. At the same time, the Jedi-like will to protect our state's natural resources was palpable, and the Yoda-esque wisdom involved in embracing natives was everywhere. An excellent conference it was.

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The following is a recap of Herbivory Affects Morphology, Physiology and Sex of a Common Perennial Vine, Passiflora incarnata, a research presentation given by C. Bennington of Stetson University’s Department of Biology:

Background
Gulf Fritillary caterpillar
Roughly 10% of plants the species Passiflora incarnata is consumed by herbivores (leaf-eaters). In addition to climbing via tendrils (the plant version of grappling hooks) this vine is rhizomatous (grows laterally underground), and typical of disturbed sites. It is protected from herbivory by generalists (non-picky leaf-eaters) because it contains hydrogen cyanide. The same chemicals that offer it protection are ineffective in deterring specialist herbivores (extremely picky leaf-eaters) like fritillary larvae, who are able to sequester the chemicals (store them internally) and use them in their own defense against predation.

The researcher’s goal was to determine how P. incarnata allocates its energy in the face of herbivory, and whether an increase in production of defense mechanisms is conversely related to the energy it puts into reproduction and growth.

Trichomes can impale soft-bodied caterpillars
Physiological Defenses
Closeup of nectaries on a species of Passiflora
This study focused on two of P. incarnata’s physiological defenses against predation by specialists. The first line of defense - trichomes - are stationed on the surface of the vine’s leaves. Trichomes, while practically unnoticeable to my calloused hands, are tiny hooked hairs that can impale the soft body of a caterpillar. A second line of defense comes by way of the nectar-producing glands located on the petiole at the base of the vine’s leaves, and on the three bracts directly beneath its flowers. The nectar produced in these locations is a favorite of ants, which will populate passionflower because hey - free food. The ants recognize that passionflower is a veritable gold mine for them, and, like faithful squatters, patrol the vine and often consume the small, specialist herbivores (caterpillars and caterpillar eggs) that might otherwise gnaw off the vine’s nectaries.

Inflorescences
The flowers of this vine are self-incompatible (cannot successfully produce seed from their own pollen), open synchronously and last for only one day. They are andromonoecious, which is a fancy way of saying that they have both bisexual and male flowers on the same plant. At this point I became a bit confused with what the researcher was describing as “male,” and the photos she was showing, since it had been my understanding that male flowers had only male reproductive organs, i.e. anther-topped filaments. I learned later on that, in andromonoecious plants, flowers with non-functioning female organs are classified as male. With that piece of information the researcher's description of the difference between the male and bisexual flowers (males do not drop their stigmas whereas bisexual flowers’ stigmas do a sort of backbend and end up in a boy-girl circle alongside the anthers) made perfect sense.

Hypothesis
Bisexual (L) and male (R) flowers of P. incarnata
It was predicted that when P. incarnata uses energy to defend itself against herbivory, it will reduce the amount of energy it allocates towards reproduction, and would therefore produce smaller flowers, fewer flowers, or an increased percentage of flowers would be male.

Testing and Data Collection
- 9 genotypes (plants of the same genus and species but not necessarily the same parents) of Passiflora incarnata were collected from sites separated by a considerable distance.
- In a screened area, 6 pots of each genotype were cultivated, of which 3 were the control and three were subject to simulated herbivory (leaf clipping). By potting the plants, each genotype could be positively identified; had they been planted in the ground, the vines’ rhizomatous tendencies might have lead to the creation of offshoots whose origin could be difficult to pinpoint.
- The amount of nectar each plant produced was quantified, all flowers were tagged and data regarding the flowers’ sex, size, pollen count and quantity of ovules was recorded. Additionally, an average trichome count was calculated from leaf samples of each plant.
- At the end of the experiment, each plant’s specific leaf area (SLA) was determined by dividing the area of a portion of a leaf by the dry weight of that same portion of leaf. SLA is (more or less) related to leaf thickness; flat, thin leaves have a high SLA, and tough, dense leaves have a low SLA.
Results
- Although it was presumed that low SLA and high trichome count went hand-in-hand, and that, when resources were allocated towards producing trichomes, nectar quantity would be low, data from the “herbivory group” suggested otherwise. This group both produced more nectar AND had a lower SLA than the control group.
- Herbivory did not appear to effect flower production.
- Genotype seemed to have a large impact on male flower production.
- Plants that produced male flowers tended to be larger than their counterparts, and were of higher fitness overall.
In Hindsight
Following the presentation, the lecturer reflected upon what role, if any, the caterpillar’s saliva might have had on the vine’s response herbivory, and whether simulated herbivory by manual leaf cutting was a comparable substitute for the real thing. Although I am in no way a scientist or researcher, it seems to me that rhizomatous growth would be an excellent way for vines subject to herbivory to channel their resources. Perhaps we will hear more on the subject during next year’s conference in Jacksonville.

Image sources
- Triumph: http://www.endalldisease.com/wp-content/uploads/2011/08/Triumph.jpg
- Fritillary caterpillar: http://www.flickr.com/photos/kevinclick/4894217920/sizes/n/in/photostream/
- Trichome impalement: http://uts.cc.utexas.edu/~gilbert/teaching/zoo369/lec6graphics/impale.jpg
- Nectaries: http://www.wmrs.edu/people/BIOs/john%20smiley/heliconius-passiflora-flea%20beetle/passiflora/lobata/lobata%20slide.jpg
- Inflorescences:  http://www.jstor.org/stable/2444737?origin=JSTOR-pdf
Additional resources:
- Dai, C. and Galloway, L. F. (2012), Male flowers are better fathers than hermaphroditic flowers in andromonoecious Passiflora incarnata. New Phytologist, 193: 787-796.
- McLain, D. Kelly (1983), Ants, Extrafloral Nectaries and Herbivory on the Passion Vine, Passiflora incarnata. American Midland Naturalist, 110 #2: 433-439.
- Triumph the Dog video

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