Gall midges pollination data in Schisandra sphenanthera flowers
Description
Roles of flower color and scent in gall midge pollination: a case study in Schisandraceae plant Shi-Rui Gan, Wei Du, and Xiao-Fan Wang Field observations, behavioral bioassays via Y-tube and “flight box” experiments were performed to investigate the roles of floral scent and color in attracting gall midges. 1. Field visiting frequency: 10 flowers of each phenotype (Yf = yellow flower; Ym = yellow male flowers, and Rm = red male flowers) were observed randomly in the field at hourly intervals both day and night on 13 and 14 May, 2013, and 15 and 16 May, 2017. 2. Flight box tests: The tests were performed in two boxes, one was made with transparent polyethylene terephthalate (TPT box) (30 cm × 15 cm × 15 cm) and the other was a non-transparent box made with corrugated paper (NT box) (30 cm × 15.5 cm × 15.5 cm). In this box, midges could detect both visual and olfactory cues of flowers; when the TPT box was placed into the NT box (Figure 3b), where midges could only sense olfactory cues of flowers. 19–57 midges were used and 10 groups of insects were used for each treatment. 3, Y-tube tests: To test if midges are attracted by floral scents, Y-tube olfactometer experiments were conducted in the dark and at room temperature. (Yf = yellow flower; Ym = yellow male flowers, and Rm = red male flowers)
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1. Field visiting frequency To determine the visiting preferences of gall midges on flowers, 10 flowers of each phenotype (Yf = yellow flower; Ym = yellow male flowers, and Rm = red male flowers) were observed randomly in the field at hourly intervals both day and night on 13 and 14 May, 2013, and 15 and 16 May, 2017. The number of gall midges in each flower was recorded. A flashlight covered with thin red plastic film was used for the nocturnal observations. 2. Flight box texts: To evaluate the behavioral responses of midges to visual and olfactory cues and determine the relationship of two floral stimuli under light and dark conditions, dual-choice bioassays were conducted in two self-made “flight boxes” during 14–16 May, 2017. One was made with transparent polyethylene terephthalate (TPT box) (30 cm × 15 cm × 15 cm) and the other was a non-transparent box made with corrugated paper (NT box) (30 cm × 15.5 cm × 15.5 cm). In the transparent TPT box, midges could detect both visual and olfactory cues. To simulate dark conditions, the TPT box was placed into the NT box , where midges could only sense olfactory cues. Behavioral bioassays were conducted for the following treatments: Group 1, Ym and Rm flowers under light and dark conditions; Group 2, Ym and Yf flowers under light and dark conditions and Ym and Yf flowers in glass vessels (visual cues only) under light conditions. Twenty fresh flowers (with copious pollen for male flowers and bright yellow petals for female flowers) of similar sizes were selected and hung on the box as in Figure 3. Pedicles were bagged with slightly wet cotton to delay the wilting of flowers. Each group of flowers were used only for one treatment (e.g., “YM and RM flowers under light conditions” as a “treatment”). In each bioassay, 19–57 midges were used and 10 groups of insects were used for each treatment. The number of midges landing on the flowers was recorded 2 min later when insects flew into the box from the entrance (E) on the lateral side of the boxes and stay in flowers steadily. 3. Y-tube tests Compressed air pushed by an atmospheric sampler passed through an activated charcoal filter and distilled water before entering the two glass cylinders containing the odor source. The air current was maintained at 100 mL min-1 by two flowmeters. Each midge was placed individually in the entry of the horizontally oriented Y-tube and was given 5 min to choose. When the individual had moved into one arm to a distance 2 cm from the Y-junction point, the choice was recorded. If the midge remained in the main arm or had not reached the decision point in the given time, it was recorded as “no choice”. Fresh flowers versus air control were used as the odor source. Each midge was used only once and 40 insects were used for each phenotype (Ym, Rm, Yf).