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Climate change linked to narrowing leaves

Herbarium specimens of leaves from the Narrow-leaf hopbush are 40% wider than contemporary specimens. Greg Guerin, Haixia Wen, Andrew Lowe

Climate change is causing the leaves of at least one subspecies of Australian plant to narrow in size, a team from the University of Adelaide has found.

Their study shows that the leaves of the Narrow-leaf hopbush (Dodonaea viscosa subspecies angustissima) have narrowed by 2mm since the 1880s - equivalent to a 40% decrease.

The results are published today in the journal Biology Letters.

The study focused on specimens from South Australia’s Flinders Ranges. Between 1950 and 2005, there has been a 1.2-degree increase in maximum temperatures in South Australia but little change in rainfall in the Flinders Ranges, the authors said.

“Climate change is often discussed in terms of future impacts, but changes in temperature over recent decades have already been ecologically significant,” said Greg Guerin, a Postdoctoral Fellow with the University of Adelaide’s School of Earth and Environmental Sciences and lead author of the study.

“Climate change is driving adaptive shifts within plant species and leaf shape has demonstrated adaptive significance in relation to climate,” Dr Guerin said.

“Our results indicate that leaf width is closely linked to maximum temperatures, and plants from warmer latitudes typically have narrower leaves.

Dr Guerin said some Australian plant species are better able to cope with rising temperatures.

"Other species in the region have less potential to adapt. These species may rely more heavily on migration – moving from location to location where the climate is favourable – but this can be problematic in a landscape fragmented by human activity.”

William Stock, a Professor of Environmental Management at the School of Natural Sciences at Edith Cowan University, said the study was “very interesting - we know that leaves vary with climate, but what’s novel in this research is that they measured historical herbarium specimens and compared them against modern day patterns.

"That shows the link with climate change very well,” said Professor Stock, who was not involved in the research.

“What we don’t know, and what the authors acknowledge here, is whether this is a genetic adaptation - in other words it’s part of a genotype of the organism, or whether it’s just a phenotypic expression, which is just an expression of current climate, which means that the species could be very plastic in the way it responds to climate and is not actually adapting to climate change.

"We don’t know whether this is an inherited character, or whether the plant has flexibility to respond to the current range of climate.”

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