Biotic Resistance to an Alien Amphibian: Larval Competition between Japanese Frogs and Invasive Cane Toads.

Takashi Haramura,Richard Shine,Michael R Crossland,Hirohiko Takeuchi,Ulrich Joger

doi:10.1371/journal.pone.0156396

Abstract

Understanding negative effects of native species on introduced taxa may suggest novel ways to control the invasive species by enhancing such effects. Previous studies have reported that the larvae of invasive cane toads (Rhinella marina) are suppressed by competition with the larvae of native anurans in Australia, but not in North America. We conducted laboratory trials to measure the effect of exposure to the larvae of Japanese frogs (Microhyla ornata, Fejervarya sakishimensis, Rhacophorus owstoni) on rates of survival, growth and development of cane toad tadpoles in Ishigaki Island, in southern Japan. Survival rates were not affected by native species, but competition with Dicroglossids and Rhacophorids (but not Microhylids) strongly reduced rates of growth and development in the tadpoles of cane toads. Dicroglossid tadpoles also reduced the body condition to toad tadpoles in addition to effects on SVL and mass. Encouraging populations of native frogs in toad-invaded areas of Japan thus may help to reduce the numbers of invasive cane toads.

Highlights

The introduction of species to areas outside their native range creates a wide range of novel biological interactions, because the invader encounters a new suite of potential prey items, predators and competitors
At least in the laboratory, cane toad tadpoles exhibit markedly reduced rates of growth and/or development if raised with the tadpoles of Dicroglossid and Rhacophorid species that occur on Ishigaki Island
Toad tadpoles develop most rapidly if they are raised at low densities, without other tadpoles–but increasing the numbers of tadpoles per container markedly reduced the rates of growth and development of toad tadpoles

Summary

Introduction

The introduction of species to areas outside their native range creates a wide range of novel biological interactions, because the invader encounters a new suite of potential prey items, predators and competitors. In some cases, those interactions may inhibit the successful establishment and expansion of invader populations; and we may be able to exploit such biotic resistance to fashion effective new approaches to biocontrol [1,2,3,4,5]. Before we can frame such strategies, we need to know whether or not the invader’s numbers are negatively affected by interactions with native fauna.

Methods

Results

Conclusion