Plants point to adaptive trends

The South Australian donkey orchid (Diuris orientis). TREND researcher Fran
MacGillivray has discovered that this species now flowers 16 days earlier than
it did 98 years ago.

The modern era presents unparalleled threats to biodiversity, including habitat loss and fragmentation, pollution, introduced species, and a changing climate. Understanding the response of species and ecosystems to changing conditions is vital to directing management or conservation programs.

Monitoring ecosystems vulnerable to change is a major focus of the Transect for Environmental Monitoring and Decision Making (TREND) program, a part of the Transects sub-facility of TERN’s Multi-Scale Plot Network.

TREND’s terrestrial transects span environmental gradients of temperature and rainfall, and cover a wide range of ecosystems that contain unique organisms. By using space as a proxy for time, researchers can use data collected along these transects to predict the impact changing environmental conditions, such as climate, will have on biodiversity in the real world.

As well as collecting current data, researchers working with TREND are incorporating data from historical records in their studies in order to examine changes over time. TREND researcher Fran MacGillivray has compared current records of flowering dates in the South Australian donkey orchid (Diuris orientis) with the collection dates of herbarium specimens and photographic records dated between 1897 and 2005. This comparison showed that the donkey orchid now flowers 16 days earlier than it did 98 years ago.

A changing climate is the likely cause of the shift in flowering time, which may be mirrored by other species and could have flow-on effects to pollinators and other plants in the ecosystem. Orchids are highly specialised plants; this means they can be sensitive to environmental variation, and act as early indicators of change in an ecosystem. Similar changes in the flowering of other, less specialised plants are likely to be seen in future.

In another recent study, researchers have demonstrated another effect of changing climate on South Australian plants. Again, by using herbarium specimens, researchers were able to analyse the width of leaves of the narrow-leaf hopbush (Dodonaea viscosa subsp. Angustissima) from the 1880s until the present. The analysis showed that leaf width has decreased by 2 mm over 127 years. The study focussed on specimens collected in the Flinders Ranges, where maximum temperatures increased by 1.2 degrees Celsius between 1950 and 2005. One of the researchers is Dr Greg Guerin, a Postdoctoral Fellow supported by TREND based at the University of Adelaide’s School of Earth and Environmental Sciences.

Our results indicate that leaf width is closely linked to maximum temperatures, and plants from warmer latitudes typically have narrower leaves,’ says Greg. ‘In the case of narrow-leaf hopbush, we can significantly link the changes in leaf width to changes in climate.’

Studies such as these are necessary to improve our understanding of the ways in which climate change can impact on natural systems, and also for understanding the potential of different species or ecosystems to adapt to change.

‘Climate change is often discussed in terms of future impacts, but changes in temperature over recent decades have already been ecologically significant,’ Greg says. ‘It’s important to understand how plants cope with changing climates, because species that are more adaptive to change may be good candidates for environmental restoration efforts.’

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