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Genetically identical forest trees raised in different environments react differently when exposed to drought conditions, a study has shown.

The authors have said it is the first scientific critique of the “nursery effect”, in which trees develop certain profiles based on where they are grown.

The team took the same varieties of trees from different areas and measured how their responses to drought varied.

The findings appear in the Proceedings of the National Academy of Sciences.

“The nursery effect is something that had been noted in an anecdotal fashion by foresters and gardeners,” explained co-author Malcolm Campbell from the University of Toronto.

The team found that it had not be reported or documented in any detail within scientific journals, yet it was a concept that was being widely used.

Out in the field, biologists have noted that organisms are more likely to reproduce sexually when there are more parasites loping around in their vicinity.

What has been missing is a direct manipulation to organisms’ sex lives to test if it makes them more or less resistant to parasites.

Direct evidence

Now researchers working at the University of Indiana in the US have used the round worm Caenorhabditis elegans to do just this.

The team engineered two types of worms – some that could only reproduce by having sex, and some that could only clone themselves.

Bacterial cells infect the crushing mouth parts of the worm and kill it

The researchers watched the worms gorge themselves on a lawn of a nasty bacterium, Serratia marcescens, which invades the worms’ guts and from there multiplies into every crevice of their body, killing the worms from the inside.

Across five different populations, worms that reproduced sexually faired well over the 20 generations, while all animals that cloned themselves died quickly.