BIOL 300 Assignment 7, extra problem. Many humans like the effects of caffeine, but it occurs in plants as a deterrent to
herbivory by animals. Caffeine is also found in flower nectar, and nectar is meant as a
reward for pollinators, not a deterrent. How does caffeine in nectar affect visitation by
pollinators? Singaravelan et al. (2005) set up feeding stations where bees were offered a
choice between a control solution with 20% sucrose or a caffeinated solution with 20%
sucrose plus some quantity of caffeine. Over the course of the experiment four different
concentrations of caffeine were provided: 50, 100, 150, or 200 ppm. The response
variable was the difference between the amount of nectar consumed from the caffeine
feeders and that removed from the control feeders at the same station (in grams). Here are
the data and a strip chart including standard error bars:
50 ppm caffeine: -0.4, 0.34, 0.19, 0.05, -0.14
100 ppm caffeine: 0.01, -0.39, -0.08, -0.09, -0.31
150 ppm caffeine: 0.65, 0.53, 0.39, -0.15, 0.46
200 ppm caffeine: 0.24, 0.44, 0.13, 1.03, 0.05
Does the mean amount of nectar taken depend on the concentration of caffeine in the
nectar?