SPEEDING UP AUSSIE EVOLUTION, according to articles in Nature News 23 July 2018 and Conservation Biology, published online 13 June 2018, doi: 10.1111/cobi.13149. Ecologists are hoping to save the northern quoll from extinction by trying to “speed up evolution”. The northern quoll is a small carnivorous marsupial, about the size of a squirrel that lives in the northern regions of Australia. Since the introduction of cane toads into Australia the quoll population has been devastated as the toads are highly poisonous to any quolls that attack them. However, several years ago ecologists noticed that some quolls avoided attacking toads. Two researchers at the University of Melbourne carried out an experiment to see if ‘toad avoiding’ behaviour could be inherited. They took quolls from toad infested regions and cross bred them with quolls from islands that are toad free and tested the resulting offspring to see if they would avoid toads. Enough of the hybrid offspring showed what the scientists called “toad-smart” behaviour to indicate the behaviour had a genetic basis and was not learned from their mothers, and this warranted a further experiment in the wild. The researchers then took quolls from toad infested and toad free regions, along with the hybrids, to an island off northern Australia that had been invaded by toads. When the research team returned they found a small number of quolls had survived, and these showed the toad averse behaviour. These results of both the captive breeding and island experiments, suggest that the “toad-smart” behaviour has a genetic basis and could be the subject of a “targeted gene flow” programme, where quolls with the “toad-smart” trait would be introduced into quoll populations that had yet to be exposed to toads in order to prepare them for toad invasion of their territory. The researchers are also analysing genes of the toad avoiding quolls.
Link: Nature
ED. COM. If ecologists do succeed in breeding “toad-smart” quolls by “targeted gene flow”, they will not be speeding up evolution, because no evolution is happening. They are only doing what farmers and gardeners have been doing for millennia – looking for favourable characteristics and deliberately breeding the animals or plants that already have them. This is selection, but it is not evolution. The toad averse animals that were found in toad infested regions are the survivors of natural selection, i.e. any quolls that didn’t already have toad avoiding behaviour died out, leaving the toad averse quolls to survive and breed. The presence of toads did not add the genes that brought about the toad avoiding behaviour. The toads just killed quolls that had the wrong genes for this situation. Likewise, the toad smart animals produced by the researchers’ breeding experiments are also the product of intelligently designed artificial selection, and no evolution is involved here either. Ecologists, like farmers and gardeners, are identifying pre-existing useful genetic traits, but they are not producing them. It will be interesting to see what the actual genetic basis of the toad avoiding behaviour turns out to be. It could be something to do with their sense of smell, but whatever it is, it didn’t evolve when toads arrived in Australia in the 1930s. It had to already exist or no quolls would have survived in toad infested regions to be part of this targeted gene flow programme. John Mackay. |
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