Evaluating eDNA-based monitoring of fire salamander larvae under field conditions

Amphibians globally belong to the most threatened animal groups and monitoring their populations is of critical importance for their conservation. The fire salamander (Salamandra salamandra) is one of the European amphibian species which has been experiencing drastic regional population declines due to the spread of the invasive chytrid fungus Batrachochytrium salamandrivorans, making it a key species for monitoring efforts. Here, we evaluated how the sampling and analysis of eDNA can aid the monitoring of larval salamander populations in small streams under field conditions. Nine small streams with known adult and larval fire salamander populations were investigated in Tirol (Austria). Per steam a stretch of 30 m downstream from its source was divided into 10 m sections where salamander larvae were counted. Water samples were taken at the end of each section and filtered on site. The DNA extracted from these filters was tested by a new PCR assay developed for the detection of mitochondrial DNA of S. salamandra. This assay combines endpoint PCR with capillary electrophoresis, allowing to relatively quantify the amount of fire salamander eDNA present in the water samples. In two of the nine streams no eDNA of S. Salamandra could be detected. The outcomes of an analysis of how larval densities, discharge and volume of filtered water affected the detection of salamander eDNA will be presented. Finally, we will conclude on the practical implications of the current findings for eDNA-based monitoring of fire salamander populations.

A case of color aberration in a fire salamander (Salamandra salamandra) larva

Color aberrations in salamanders are caused by defective chromatophores or by disrupted synthesis of the pigments, and have been previously reported in Europe. In this paper we report the first case of leucism in a fire salamander larva from a cave-dwelling population in Romania. The leucistic larva was larger and heavier compared to the other larvae from the same breeding habitat.

Genetic diversity and gene flow decline with elevation in the Near Eastern fire salamander (Salamandra infraimmaculata) at Mount Hermon, Golan Heights

The Near Eastern fire salamander (Salamandra infraimmaculata) reaches its southern distribution range in Israel. Although the population structure has been analysed in central Israel and at the southern distribution limit, we lack knowledge on populations in the northern area, such as along Mount Hermon. S. infraimmaculata occurs at Mt. Hermon along an altitudinal gradient and appears to be fragmented by urban and agricultural landscape. We studied the genetic structure of four populations based on microsatellite loci and the mitochondrial D-loop to determine the genetic diversity and connectivity between populations. We observed moderate gene flow at lower parts, i.e. from Tel Dan and Nimrod Castle to Banias indicating extant but limited connectivity. Genetic diversity and gene flow declined along the altitudinal gradient at Mt. Hermon, reaching rock-bottom levels in the highest located population of Nimrod Pool. The observed isolation-by-elevation gradient might induce a higher extinction risk for the highland populations of S. infraimmaculata.

Developmental costs of yellow colouration in fire salamanders and experiments to test the efficiency of yellow as a warning colouration

Warning colouration reduces predation risk by signalling or mimicking the unpleasantness of prey and therefore increases survival. We tested in two experiments the evolutionary costs and benefits of the yellow colour pattern in fire salamanders (Salamandra salamandra), which display a yellow/black colour pattern usually associated with toxic alkaloids. Our first experiment aimed to test whether the development of colouration is condition dependent and thus related to developmental costs, i.e. influenced by resource availability during the developmental process. Therefore, we reared fire salamander larvae under different nutritional conditions and compared the relative amount of yellow they developed after metamorphosis. Fire salamander larvae reared under limited food conditions had a lower proportion of yellow following metamorphosis than control larvae reared under superior food conditions. In a second experiment we tested whether the proportion of yellow has an impact on the risk of being attacked using artificial models. We tested, in salamander-free and salamander-occupied natural habitats, whether artificial clay models with different proportions of yellow and black receive different attack rates from potential predators (birds, mammals, insects). In clay models the proportion of yellow and the site had a significant effect on predation risk. Models with larger amounts of yellow had fewer bite marks from predators such as carabid beetles and birds, but only in sympatry with salamanders. In conclusion, the early expression of conspicuous colouration seems to be condition dependent and therefore potentially costly. Furthermore, the yellow colouration of fire salamanders act as a signal that potentially reduces their risk of being attacked by predators. Thus, the yellow colouration of fire salamanders seems to represent an adaptive trait that reduces the risk of predation, which can be expressed in higher quantity by individuals of a certain condition.