PS 45-5
A tail of two color morphs: Predation rates and tail autotomization in two color morphs of Plethodon cinereus
Color polymorphism is common in many species and morph frequency may be affected by differences in ecological pressures on each morph. Plethodon cinereus, the red-backed salamander, has two common color morphs, striped and unstriped, that vary in frequency among populations. Climate change is concomitant with a higher frequency of unstriped salamanders, especially in warmer habitats, but the fitness advantages of that morph are little understood. Furthermore, there is evidence that the unstriped morph has higher tail autotomization rates, potentially indicating higher predation rates on that morph. We tested the hypothesis that tail autotomization rates reflect differential predation pressure on the two morphs. An alternate hypothesis is that rates of tail autotomization are higher in unstriped morphs due differential response to predation (i.e. lose tails more easily). We measured tails, quantified rates of tailloss and tested the force required to induce autotomization in the two color morphs in a natural population of salamanders. In the same area, we placed unstriped and striped clay models of P. cinereus in the forest to determine if unstriped salamanders were located more often or preferentially predated by analyzing marks left on the models by mammalian and avian predators.
Results/Conclusions
We found no differences in tail autotomization between the morphs, which contrasts with a previous study. However, we found evidence that the striped morph clay models were predated upon by birds significantly more frequently than unstriped models, clearly indicating predation pressure decreases fitness of the striped morph. Interestingly, striped salamanders also dropped their tails more easily than unstriped salamanders, potentially as learned or evolved result of this increased predation pressure. While we found no differences in tail length or growth between the morphs, we did find less fat allocation in the tails of striped salamanders. Overall, our results do not support the hypothesis that higher predation rates based on color morphology lead to the presence of increased tail loss in either morph, but our results are consistent with increased predation on the striped morph without a change in the frequency of tailloss. These results provide insight into the complex fitness of color morph and the potential for fitness to change in unexpected ways with warming temperatures. Future work should estimate change in the types and numbers of avian predators present due to climate change to further understand the effects of predators on morph frequencies.