Prospective interspecies interaction between Siberian and Ezo salamander larvae

Species habitat range is partly determined by interspecies interactions between phylogenetically related species. Siberian salamanders are widely distributed across the Eurasian continent and occupy various habitats, but in Hokkaido island, Japan, it is restricted to only two regions. For the restricted habitat range of Siberian salamanders in Hokkaido, we hypothesized that Ezo salamander, whose larvae heavily consume amphibian larvae, excludes Siberian salamander from their range by the predation during the larval period. Here, we investigated the potential interaction between Siberian and Ezo salamander larvae in an aquarium experiment. As expected, in the cases where they cohabit, all Siberian salamander larvae were immediately killed by Ezo salamander larvae through predation. Although the predation enhanced individual growth of Ezo salamander larvae, it may not merely increase the fitness of Ezo salamander larvae. Interestingly, in the presence of Siberian salamanders, cannibalism occurred more frequently in Ezo salamanders, even though it only occurred in limited replications, probably as a result of improving growth and increasing size variation among Ezo salamander larvae. We experimentally showed that Ezo salamander larvae heavily predates those of Siberian salamander, but not vice versa. This suggests that Siberian salamander is difficult to invade into the habitat of Ezo salamander. Surprisingly, however, Siberian salamander may also decrease survival of Ezo salamander–Ezo salamander cannibalized under the cohabiting situation with Siberian salamander. This finding is important because it may challenge the well‐established notion that cannibalism rarely occurs in the presence of prey.