Change in climate ‘causes leaves to narrow’

As a result of changes in the climate, leaves of some plant species are getting narrower, a new study has revealed.

A team of Australian researchers that studies specimens from the wild and from herbarium collections stretching back more than 120 years found that leaf width had decreased by two millimetres.

Lead author, Greg Guerin, from the University of Adelaide, said the team chose narrow-leaf hopbush (Dodonaea viscosa subsp. angustissima) as its leaves appeared to display different characteristics in different climates.

“We followed this up by examining exciting herbarium collections before beginning to gather [field] data,” the BBC quoted him as saying.

The researchers looked at more than 250 herbarium specimens collected from one region: Flinders Ranges, southern Australia’s largest mountain range.

“Historical herbarium collections provide immediate access to wide sampling throughout a geographic region and through time,” Dr Guerin said.

“You just can’t replicate that kind of sampling, covering hundreds of kilometres… from one region over 130 years,” he said.

To support the data, team gathered 274 field samples from a mountain, collecting specimens at every 50m drop in altitude.

“This gave us information on variation within populations and the local influence of altitude on leaf shape and size,” Dr Guerin explained.

The analysis revealed a two-millimetre decrease in leaf width over 127 years across the region.

Between 1950 and 2005, the team added, there had been a 1.5C (2.7F) increase in the maximum temperatures in the region but there had been little change in rainfall patterns.

Dr Guerin said that the shift in leaf shapes might, in some cases, have wider ecological consequences.

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“The study is a new example of significant climate change responses to date,” he said.

“We now know that every degree of warming is ecologically significant and generating ecological disequilibrium.

“There is some good news here in that some Australian plant species may have the potential to respond to and cope with increasing temperatures,” he said.

But Dr Guerin warned that other species might be less well suited to adapt.

“These species may rely more heavily on tracking favourable climate through migration,’ he said.

“A recent study by a student in our group (the Andy Lowe laboratory) looked at the climate change sensitivity of a habitat-restricted plant species endemic to the same Flinders Ranges region in South Australia.

“The species had low adaptive capacity because of a combination of low genetic diversity and small, isolated populations. This is a problem because its current climate niche is predicted to shrink over this century,” he added.

The findings of the study appear in the Royal Society journal Biology Letters.

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