Sarracenia Purpurea Prey Capture at Harvard Forest 2008

We conducted this study during mid-summer, when insect abundance and prey capture is highest in New England (Fish and Hall 1978). In July 2008, we randomly identified 25 pitchers, each on a different Sarracenia purpurea plant, at Tom Swamp, a bog in Petersham, Massachusetts, USA. On 3 July 2008, we suctioned out all liquid and prey carcasses from pitchers, rinsed them, and then refilled them with distilled water. Three days later, pitcher contents were collected and the prey counted and identified. The experiment was repeated on 11 and 14 July 2008. On 17 July 2008, pitchers were harvested, cleaned, flattened and photographed (Canon S3-IS digital camera) to determine each pitcher’s area, proportion red color; and perimeter of red venation (using SigmaSan Pro 5.0; SPSS, Chicago, Illinois). Spectral reflectance (375 - 800 nm) of pitchers was measured at 2-cm intervals around the pitcher and across the pitcher hood using an Ocean Optics S2000 fiber-optic spectrometer, ISP-REF integrating sphere, and OOIColor/OOIIrrad 2.05.00 software (Ocean Optics, Dunedin, Florida). Reference scans were made using Kodak (Rochester, New York) black and white reference cards. Seventy "pseudopitchers" (painted 50-ml plastic centrifuge tubes [BD Biosciences, San Jose, California]) were used to separate effects of color and nectar on prey capture. Seven sets of ten were assigned different color treatments. One set was painted entirely green using "Fresh Foliage" acrylic paint (Plaid Enterprises, Norcross, Georgia); one set was painted entirely red (Plaid Enterprises' "Burgundy"); four sets were first painted green, then red "veins" were added to produce 6 - 62% red color, the range found on real pitchers; and one set of 10 was unpainted controls. Peak reflectances of the green and red paints were the same wavelengths as peak reflectances of green and red pitchers. To determine how availability of nectar interacted with color in attracting prey, four lines of Karo Corn Syrup (ACH Food Companies, Memphis, Tennessee), cooked until thick, were streaked at random locations on one-half of each set of pseudopitchers. Like all plant nectars, Karo Corn Syrup is a mixture of fructose and glucose. To closely resemble real pitcher plants, pseudopitchers were embedded at an angle in the bog surface with more than 50% of the tube visible above the Sphagnum. Psuedopitchers were located within 10 meters of the plants for which we assessed prey capture. Fifteen ml of 50% ethanol was put inside each tube; trapped insects were collected after 48 hrs, counted, and identified. The entire experiment was repeated twice over a three-week span of time.