Figure 1.
Response of tadpoles to the presence of parasites and predators and the hypothesized response to the presence of both, which will depend on the relative vulnerability of the tadpole to the predator.
The dotted line in each plot represents baseline activity level, i.e. the activity level of the tadpole when no predator or parasite is present. We hypothesize that species such as Lithobates sylvaticus, which is highly vulnerable to fish predators, will show decreased activity in the presence of both fish and parasites, while species such as L. catesbeianus, which is relatively invulnerable to fish predators will increase activity in the presence of both fish and parasites.
Table 1.
Analysis of variance table for final model estimating post-treatment time active in tadpoles in response to effect of species, fish presence or absence, parasite presence or absence and the covariate of time active pre-treatment (actPRE).
Figure 2.
The response of tadpoles for each of the three species to four different treatments.
Each of the 12 scatterplots has time active pre-treatment on the x-axis and time active post-treatment on the y-axis. The solid line in each plot indicates where points would fall if post-treatment activity equals pre-treatment activity; points falling left or above this line indicate an increase in activity once the treatment was applied and points falling below or to the right of this line indicate a decrease in activity once the treatment was applied. A significant 3-way interaction between species, fish, and parasite treatments is present.
Figure 3.
Additional behaviors performed by tadpoles of the three species to four different treatments.
Number of tadpoles engaged in a) extreme swimming, b) body twisting, and c) tail flicking behavior post-treatment. See text for behavior descriptions. N = 20 for each treatment combination and data were treated as binomial (i.e. individual in replicate did (score = 1) or did not (score = 0) perform behavior). For both extreme swimming and body twisting, species differed significantly and there was a significant effect of parasite. In body twists, the effect of fish was also significant. For tail flicking, significant species by parasite and species by fish interactions occurred. All effects are based on generalized linear analysis (see text for details).
Figure 4.
Mean (± SE) number of encysted metacercariae (out of a potential 36 cercariae) for all three species in the parasite only and ‘fish+parasite’ treatments.
The species by fish presence interaction was significant (negative binomial GLM analysis of deviance, species by fish; deviance = 206.90, P = 0.047).