Understanding niche conformance in fire salamander larvae: Insights from reciprocal transplant experiments

Amphibians are in particular vulnerable to (climatic) changes in their habitat as they are highly dependent on precipitation and temperature. The larval stage can be considered the most critical life stage in the ontogeny of most amphibians as predation is very high, and larvae are restricted to their natal aquatic habitat. The same applies for larvae of the fire salamander (Salamandra salamandra) that can occur in temporary ponds or in first-order streams. To investigate if larvae can conform to changing habitat conditions, we have performed two different reciprocal transplant experiments in which larvae of streams and ponds were reciprocally transferred in a two by two design. In the first experiment, individuals were individually housed in semi-natural enclosures, restricting larvae from predation and social contact to others. In the second experiment, the reciprocal transplant was conducted under completely natural conditions (i.e., individuals were released into the transfer habitat and during subsequent capture events recognized based on their tail fin pattern). Unexpectedly, we did not find larvae in matching conditions to perform better, i.e. to grow faster or to have a higher survival. Instead, in both experimental setups we found larvae transferred into ponds to grow faster than larvae transferred into stream independent of habitat of origin. Likewise, under completely natural conditions, we found that larvae transferred into ponds have higher growth in gill size. Considering the different impact that extreme weather events will have on the different habitat types in the future (i.e. flooding of streams with extreme precipitation and desiccation of ponds through droughts), it is worth supporting both habitat types through conservation measures. Additionally, transferring larvae from one habitat type to the other when facing extreme weather can help preserving the species as they are able to conform to a certain degree to the changing habitat conditions.