On each day that the plants were in bloom, we robbed 50% of the staminate-phase flowers using the techniques described above and collared the other 50% of the flowers to prevent robbing by B.
We examined pollen receipt by robbed and unrobbed flowers using a mixed-model repeated-measures ANOVA with robbing treatment (robbed and unrobbed flowers) as a fixed effect, plant nested within floral treatment as a random effect, and date as the repeated measure.
For both the low and high robbing treatments, these estimates of female fitness decreased as the season progressed.
In 1995, the average percentage of natural nectar robbing per plant in plants in the natural robbing treatment ranged from 0% to 97.2% of available flowers robbed, with a mean ([+ or -] 1 SD) of 32.9% [+ or -] 37.2% (N = 27 plants).
For sites in which we measured dye donation and pollen receipt in 1995, two of the three sites contained plants with high levels of natural robbing ([greater than]75% of available flowers robbed; N = 3 plants), and two of the three sites contained plants with low levels of natural robbing ([less than]15% of available flowers robbed; N = three plants).
Plants in the high robbing treatment donated significantly fewer dye particles than plants in the low robbing treatment ([F.sub.1,22] = 26.08, P [less than] 0.0001; [ILLUSTRATION FOR FIGURE 1 OMITTED]).
- Plants in the high robbing treatment received significantly fewer pollen grains than plants in the low robbing treatment in 1996 but not in 1995 (Table 2; [ILLUSTRATION FOR FIGURE 2 OMITTED]).