Using genetic data to predict the vulnerability of a native predator to a toxic invader

Kn Armstrong,L Zhang,G Madani,S Wang,R Shine,Ym Li

doi:10.3354/esr00745

Kn Armstrong, L Zhang + Show 4 more

Open Access

https://doi.org/10.3354/esr00745

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Abstract

Australia has no native toad species, and as a consequence, many Australian pre - dators lack resistance to the toxins of the invasive cane toad Rhinella marina, and die if they ingest one of these toads. Resistance is conferred by a small and consistent genetic change, so genetic data can provide a rapid, non-invasive way to clarify the vulnerability of as-yet-unstudied taxa. To evaluate the hypothesis that a recent decline of ghost bat Macroderma gigas populations in tropical Australia is due to ingestion of cane toads, we sequenced the H1-H2 extracellular domain of the sodium-potassium-ATPase. Two anuran-eating Asian relatives of the Australian species possess the genes that confer bufotoxin resistance, but the ghost bat does not. Like varanid lizards (major victims of the toad invasion), Australian ghost bats appear to have lost their physiological resistance to toad toxins but retained generalist foraging behaviours, potentially including a readiness to attack toads as well as frogs. Our genetic data suggest that cane toads may imperil populations of this iconic predator, and detailed behavioural and ecological studies are warranted.

Highlights

Given the vast number of taxa potentially at risk of extinction, we need rapid and effective ways to identify the most vulnerable species
Cane toads Rhinella marina are causing ecological havoc as they spread through Australia (Shine 2010)
A long period of endemism in Australia might create vulnerability if resistance to bufonid toxins is lost through genetic drift or counter-selection (Shine 2010, Ujvari et al 2015)

Summary

INTRODUCTION

Given the vast number of taxa potentially at risk of extinction, we need rapid and effective ways to identify the most vulnerable species. A long period of endemism (and toad allopatry) in Australia might create vulnerability if resistance to bufonid toxins is lost through genetic drift or counter-selection (Shine 2010, Ujvari et al 2015). We can identify 3 possible scenarios, only one of which would implicate cane toads as a cause for ghost bat decline If both Asian and Australian bats can tolerate bufonid toxins, toads cannot be a risk factor. If the Asian bat is resistant to bufadienolides but the ghost bat is not, the ancestral condition of toxin tolerance may have been lost in the ghost bat lineage due to long allopatry with toads in Australia — as occurs in Australian varanid lizards, which have exhibited massive population crashes coincident with toad invasion (Shine 2010). Testing physiological sensitivity of live bats to toxins raises a host of logistical and ethical problems, but there is a simple solution — we can examine tissue samples to see whether the bats exhibit the distinctive genetic signature of bufonid toxin resistance (Ujvari et al 2015)

MATERIALS AND METHODS

DISCUSSION

RESULTS