Conserving natural enemies with flowering plants: Estimating floral attractiveness to parasitic Hymenoptera and attraction’s relationship to flower and plant morphology

Flowering plants in agricultural landscapes can provide ecological services, such as nectar-provision for adult parasitic Hymenoptera. Various flowering native, introduced/established and cultivated potted plants were used to bait interception traps along the wooded margins of fields planted seasonally with either feed-corn or rye. Depending on circumstances, controls consisted of traps baited with the same species of plant without flowers, a pot/area without plants, or both. In most cases pots were rotated among trap-sites. Of the 19 plant species tested, 10 captured significantly more summed ichneumonoids and chalcidoids, seven more Braconidae, two more Ichneumonidae and six more Chalcidoidea than controls. Among Braconidae, traps baited with certain plants captured significantly more individuals of specific subfamilies. “Attractive” and “unattractive” plant species tended to cluster in a principal components vector space constructed from plant morphological characteristics (flower width, flower depth, flower density and plant height). Flower width and plant floral-area (flower width2 * flower density) were the variables that most often explained the variance in capture of the different parasitoid taxa. Our study identified particular plants that could be incorporated into regional conservation biological control programs to benefit parasitoid wasps In addition, the results indicate that morphological characteristics might help identify further suitable plant candidates for agricultural landscape modification.

Principle component analyses of the distribution of the summed Ichneumonoidea and Chalcidoidea capture ratios (flower-baited trap/control) of significantly attractive and unattractive flowers across a vector space created from flower width, height and density and plant height: number misclassified = 2, percent misclassified = 10.Figure optionsDownload as PowerPoint slideHighlights
► Nineteen flowering plant species, native, introduced and cultivated, were used to bait interception traps. Of these, 10 captured significantly more summed ichneumonoids and chalcidoids, seven more Braconidae, two more Ichneumonidae and six more Chalcidoidea.
► Among Braconidae, traps baited with certain plants captured significantly more of specific subfamilies.
► “Attractive” and “unattractive” plant species tended to cluster in a principal components vector space constructed from plant morphological characteristics (flower width, flower depth, flower density and plant height). Flower width and plant floral-area (flower width2 * flower density) were the variables that most often explained the variance in capture of the different parasitoid taxa.
► Particular plants were identified that could be incorporated into regional conservation biological control programs and suggested what characteristics might help identify other candidates for agricultural landscape modification elsewhere.