Are Iberian ribbed newts Pleurodeles waltl Michahelles, 1830 negatively affecting the populations of other amphibians?

Abstract

AbstractTemporary ponds play a key role as amphibian breeding habitats, but predation and desiccation risks enforce major evolutionary pressures in these ecosystems. The newt Pleurodeles waltl is commonly found in Mediterranean ponds in the Iberian Peninsula, where it preys on a wide variety of organisms. We hypothesize that P. waltl may negatively influence populations of coexisting amphibian larvae in the natural environment. To test it, we monitored the amphibian populations of 21 temporary ponds in Eastern Spain, 10 of which included P. waltl. We visited each pond fortnightly on nine occasions, estimating the abundance of adult P. waltl and tadpoles of each amphibian species present. We built zero‐inflated Generalized Linear Mixed Models (GLMMs) to test for the effects of pond area and adult and larval P. waltl abundance on tadpole abundance of all amphibian species present. Our results show significant negative effects of P. waltl abundances on the anurans Alytes obstetricans, Epidalea calamita, and Pelodytes punctatus. Species adapted to shorter hydroperiods such E. calamita and P. punctatus show lower densities in the presence of P. waltl larvae. A. obstetricans, with preference for longer hydroperiod ponds, seems to better thrive in sites where the newt is absent. This is the first field work suggesting a negative impact of P. waltl on coexisting anurans, even though more studies are needed to disentangle other negative effects related to unmeasured environmental variables or biotic interactions, which can be important according to the large variation encompassed by the random variables of site and sampling period in the mixed models.