Developmental costs of yellow colouration in fire salamanders and experiments to test the efficiency of yellow as a warning colouration
2020
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.
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