Invasive toxic prey may imperil the survival of an iconic giant lizard, the Komodo dragon

Cover pictureNaïve large Australian varanid lizards have recently been shown to suffer a massive increase in mortality (> 95%) when attempting to feed on this toxic amphibian. The high susceptibility of Australian varanids to toad toxin is caused by minor mutations in the sodium-potassium-ATPase enzyme.

In the present study we show that Komodo dragons (Varanus komodoensis) have similar mutations within this enzyme as observed in Australian varanids demonstrating that dragons are extremely susceptible to toad toxin. During the last decade the black-spined toad (Bufo melanostictus) has been able to invade areas close to the five toad-free islands constituting the habitat of Komodo dragons. An invasion of highly toxic black-spined toads into dragon habitats may therefore cause similar dramatic increase in dragon mortality as recorded in Australian varanids imperiling the long-term survival of this giant and iconic lizard.

Ujvari et al. 2015 Pacific Conservation Biology 20: 363-365.

Anthropogenic selection enhances cancer evolution in Tasmanian devil tumours

Title: Anthropogenic selection enhances cancer evolution in Tasmanian devil tumours.

Authors: Beata Ujvari;  Anne-Maree Pearse; Kate Swift; Pamela Hodson; Bobby Hua; Stephen Pyecroft; Robyn Taylor; Rodrigo Hamede; Menna Jones; Katherine Belov; Thomas Madsen.

Source: Evolutionary Applications, Volume 7, Issue 2, pages 260–265, February 2014.

Brief summary of the paper: The Tasmanian Devil Facial Tumour Disease (DFTD) provides a unique opportunity to elucidate the long-term effects of natural and anthropogenic selection on cancer evolution.

Since first observed in 1996, this transmissible cancer has caused local population declines by >90%. So far, four chromosomal DFTD variants (strains) have been described and karyotypic analyses of 253 tumours showed higher levels of tetraploidy in the oldest strain.

We propose that increased ploidy in the oldest strain may have evolved in response to effects of genomic decay observed in asexually reproducing organisms. In this study, we focus on the evolutionary response of DFTD to a disease suppression trial.

Tumours collected from devils subjected to the removal programme showed accelerated temporal evolution of tetraploidy compared with tumours from other populations where no increase in tetraploid tumours were observed.

As ploidy significantly reduces tumour growth rate, we suggest that the disease suppression trial resulted in selection favouring slower growing tumours mediated by an increased level of tetraploidy.

Our study reveals that DFTD has the capacity to rapidly respond to novel selective regimes and that disease eradication may result in novel tumour adaptations, which may further imperil the long-term survival of the world’s largest carnivorous marsupial.