PREMISE OF THE STUDY:
Floral traits play important roles in pollinator attraction and defense against floral herbivory. However, plants may experience trade-offs between conspicuousness to pollinators and herbivore attraction. Comparative studies provide an excellent framework to examine the role of multiple traits shaping mutualist and antagonist interactions.
METHODS:
To assess whether putative defensive and attractive traits predict species interactions, we grew 20 different Cucurbitaceae species and varieties in the field to measure interactions with pollinators and herbivores and in the greenhouse to assess trait variation. Cucurbits are characterized by the production of cucurbitacins, bitter nonvolatile terpenoids that are effective against generalist herbivores but can attract specialist beetles. We determined whether plant traits such as cucurbitacins predict herbivore resistance and pollinator attraction using an information-theoretic approach.
KEY RESULTS:
Mutualists and floral antagonists were attracted to the same cucurbit varieties once they flowered. However, rather than cucurbitacin concentration, we found that the size of the flower and volatile emissions of floral sesquiterpenoids explained both pollinator and floral herbivore visitation preference across cucurbit taxa. This pattern held across cucurbit taxa and within the Cucurbita genus.
CONCLUSIONS:
Surprisingly, floral sesquiterpenoid volatiles, which are associated with direct defense, indirect defense, and attraction, rather than defense traits such as cucurbitacins, appeared to drive interactions with both pollinators and floral herbivores across cucurbit taxa. Identifying the relevant plant traits for attraction and deterrence is important in this economically valuable crop, particularly if pollinators and floral herbivores use the same plant traits as cues.
Carbon and nitrogen in roots and leaves of crops and wild gourds in the family Cucurbitaceae
The percent nitrogen and carbon content of leaves, flowers and roots were measured on a Carlo Erba CHN analyzer. Samples were analyzed in triplicate on two young but fully formed leaves and on roots from each plant to calculate percent nitrogen and carbon. Readme file contains species names and abbreviations.
CN.csv
Cucurbitacins in roots, flowers and leaves of crops and wild gourds in the family Cucurbitaceae
The concentrations of the cucurbitacins are expressed as µg cucurbitacin/g dry tissue sample based on HPLC analysis. Trace amounts are indicated as (++) for prominent peaks too small to be considered for calculations. (+) indicates peaks smaller than (++). (–) indicates peaks smaller than (+). To quantify these data a standard curve, based on peak area, was fashioned for cucurbitacins B and D. The Cucurbitacin B slope 5.00E+06 and intercept 8.00E+06. The Cucurbitacin D slope 8000000.00 and intercept -9000000.00. Readme file contains species names and abbreviations.
Cucurbitacins.csv
Pollen count from crops and wild gourds in the family Cucurbitaceae
For accuracy, three pollen samples were collected from each anther and each sample was counted twice using a hemocytometer. Readme file contains species names and abbreviations.
Pollen.csv
Herbivory 2005
Field Experiment measuring herbivory on crops and wild gourds in the Cucurbitaceae. DB = # dead beetles, LB = # live beetles, all beetles are Acalymma vittatum; cotyledon damaged = Yes or No. Damage was assessed on the four youngest fully expanded leaves at each census Lf1 is oldest, Lf4 is youngest.
Scores are 0-4 indicating 0%, 1-25%, 25-50%, 50-75%, or 75-100% leaf area removed. Readme file contains species names and abbreviations.
Herbivory 2006
Field experiment measuring herbivory on crops and wild gourds in the Cucurbitaceae. Dam Lf: Damaged Leaf, B = # dead beetles, LB = # live beetles, all beetles are Acalymma vittatum. Damage is assessed on the four youngest fully expanded leaves at each census: Lf1 is oldest, Lf4 is youngest. Damage is measured in % area removed
Damage in %: 0, 1, 5, 10, 25, 50, 75, 100 "." = leaves gone.
cot damage: 100 = dead leaves still there. Readme file contains species names and abbreviations.
Pollinator Observation of crops and wild gourds in Cucurbitaceae
Data from field experiments in 2005 and 2006. At the observation start, flower sex (Female or Male), # ants (not identified), # beetles (Acalymma vittatum) was recorded. In the data sheet each flower visitor has its own row. Pollinators are identified as: smbee (= small bee, not identified), sqb (= squash bee, Peponapis pruinosa), lgBB and smBB (large and small bumble bees, not ID'ed beyond Bombus; B. impatiens and B. bimaculatus are very common here)
hb (= honey bee, Apis cerana) and a few other miscellaneous bees, not ID'ed. Time, is the time in seconds of the pollinator visit. 'total approaches,' are times that insects got close to the flower but did not land. These could be considered 'rejections' in that the insect comes close enough to assess the flower but does not alight. Columns following total approaches are broken down by visitor and abbreviated "app". There is one row of approach data per observation. Readme file contains species names and abbreviations.
Pollinator Observation.csv
Variety in trichome number in Cucurbitaceae
Greenhouse grown plants.Trichome number on the top of the leaf and the bottom of the leaf reported. Each count replicated once. Readme file contains species names and abbreviations.
Trichomes.csv
Leaf Water Content in crops and wild gourds of Cucurbitaceae
The moisture content wet basis (MCWB) is given by
MCWB = 100 X (Initial Wt - Dry weight)/(Initial Weight). Readme file contains species names and abbreviations.
Water Content.csv
Floral Volatiles from Cucurbitaceae
Volatiles reported in nanograms per flower per hour. Readme file contains species names and abbreviations.
Volatiles ngflowerh.csv
List of Floral Volatiles in crops and wild gourds of Cucurbitaceae
Retention time based on nonpolar column (DB5, 30 m × 0.25mm). Calculated Kovats Index based on n-alkane series. Compound identity based on match to previously run standards, NIST library and published Kovats Index.
Volatile List.csv
Nectar and Flower Size in Cucurbitacae
Greenhouse grown crops and wild gourds. Data for both male and female flowers. Readme file contains species names and abbreviations.
Nectar and Flower Size.csv
