The toad less travelled: comparing life histories, ecological niches, and potential habitat of Asian black-spined toads and cane toads

Abstract

Context Invasive vertebrates have significant negative impacts on biodiversity and agricultural production worldwide. Increased connectivity among countries, through trade and tourism, is escalating the rate of introductions of vertebrate species, particularly herpetofauna, across international borders. In Australia, Asian black-spined toads (ABSTs; Duttaphrynus melanostictus) are one of the species most intercepted at borders. They are considered a biosecurity risk because of the potential for negative environmental impacts, similar to those caused by cane toads (Rhinella marina). Aims We aimed to compare ABSTs with cane toads to investigate potential impacts and distribution of ABSTs in the Australian context. We also aimed to identify knowledge gaps regarding ABST biology and the potential role of cane toads in an ABST invasion in Australia. Methods We undertook a literature review to obtain published data to compare the life history characteristics of ABSTs and cane toads. We also modelled climatic niche overlap and compared suitable habitat for both species in Australia. Key results Our results show ABSTs and cane toads have broadly similar reproductive life histories and feeding niches. In particular, similarities include large clutch sizes, preferred oviposition sites, and diet at tadpole and adult life stages. In Australia, the species share suitable potential habitat, particularly in North Queensland, where the majority of ABST incursions have occurred. The species differ in size, call characteristics, clutch size relative to body size, and egg development rate, although the environment also influences these traits. We identify gaps in our knowledge of ABST spatial ecology, thermal tolerances, water reliance, and habitat. Conclusions ABSTs pose a significant biosecurity threat to Australia. Similarities in life history to cane toads means they may have similar impacts, but may have a more limited distribution in Australia. Invasion of Australia by ABSTs would likely result in interactions with cane toads, but it is not possible to accurately determine the outcomes of those interactions without further investigation. Implications Addressing knowledge gaps and quantitatively determining the potential for competition between ABSTs and cane toads will assist surveillance and response planning for ABST incursions in Australia.