Life history plasticity does not confer resilience to environmental change in the mole salamander (Ambystoma talpoideum)
Discrete polyphenisms in life history strategies, where variation is limited to alternative morphs and not a continuous distribution of traits, are useful for understanding the processes that contribute to phenotypic plasticity in response to changing environments. Several wetland breeding salamander species exhibit polyphenic life histories and provide an ideal opportunity to examine how different strategies are favored in differing environments.
Drawing on a six-year study, we fit multistate multiyear site occupancy models to test specific hypotheses about the environmental drivers of phenotypic plasticity in mole salamanders on St. Marks National Wildlife Refuge, while accounting for imperfect detection in our observations.
To analyze our data, we assumed that each wetland belonged to one of five possible states during each season:
We then used estimates of transi-tions among these states from season to season and their relationship to the dynamics of mole salamanders, fishes, and habitat to draw inferences about factors determining occurrence of the larval and paedomorphic life-stages in wetlands.
- Unsuitable habitat (i.e., dry) and unoccupied;
- Suitable habitat but unoccupied;
- Suitable habitat, occupied by the mole salamander;
- Suitable habitat, occupied by fishes; or,
- Suitable habitat, occupied by both the mole salamander and fishes
We then used estimates of transi-tions among these states from season to season and their relationship to the dynamics of mole salamanders, fishes, and habitat to draw inferences about factors determining occurrence of the larval and paedomorphic life-stages in wetlands.
Using our integrated modeling approach, we demonstrated that:
- We can use natural perturbations such as those that occurred on SMNWR to understand how species responses to changing conditions are shaped by their life histories;
- We can detect life-stage specific differences in behavioral responses to predators, which can inform management or monitoring initiatives;
- It is important to account for changes through time in both habitat suitability and species interactions.
Our results suggest that, despite context-specific fitness advantages of both life history strategies, if increased envi- ronmental perturbations continue, mole salamanders may potentially be extirpated at SMNWR in the future. Changes in the frequency of disturbance events (i.e., drought and flooding) as a result of climate change could limit local and regional persistence of this species.