Why Are Seeds the Size They Are?
What Determines Whether a Seed will be a Tiny Speck or a Large Nut?
Oct 28, 2008
Dr Moles spent two years travelling the world looking at nearly 13,000 plant species, to find the answers to these and other questions about the growth and distribution habits of plants.
75 Ecosystems Across the Globe
During that time she visited 75 different ecosystems, ranging from arctic tundra at 75 degrees north in Eastern Greenland, to dense tropical rainforests in places including the Congo, Peru, Panama and China; deserts in Australia and Israel; savannas in South Africa, Australia, and Zambia; temperate forests in America, Sweden and Norway, and all the way down to tundra in southern Patagonia, and she observed and measured everything she could.
“I spent an average of about three days per ecosystem, and was travelling pretty much nonstop for the two years, during which I had no home, and remarkably few possessions,” she said.
“One week I was sitting in an inflatable boat weaving between the icebergs off Greenland, next I was sitting on the back of a truck in a forest about ten metres from a silverback gorilla.”
Trees from 112 Metres to Two Centimetres
Dr Moles and her team, which included local scientists from every area visited, examined the huge variety and disparity in size and habitats of 12,980 species of plants.
They ranged from towering 112 metre redwoods in California to the tree canopy in Greenland – mature willow trees two centimetres tall dotted amongst one centimetre high azalea bushes.
The sites were chosen as environments where the plant and animal life was still in a reasonably natural state.
“I was after places where the amount of plant-eating was about what it would have been while the plants were evolving – so that the plant traits I measured and the level of herbivory I saw matched.”
Along the way she discovered that seeds of tropical plants could be up to 300 times as big as seeds of Northern European conifers.
The data gathered on seed sizes alone, resulted in a paper in Science in 2005 on the evolution of seed sizes.
As well as seed sizes, the team measured plant height, how much the leaves were being eaten by animals, physical and chemical defences of the leaves, insect abundance, plant cover and diversity, soil fertility and vine twining direction, as well as obtaining detailed climate information for each site.
Big Ecology for a Warming World
Dr Moles is leading a new approach to ecology — one that could accurately model and predict the impact of climate change on ecosystems.
“Traditionally ecologists have collected detailed information on specific ecosystems,” she said.
“We don’t understand much at all about how ecology works at a global scale.
“We don’t know if plants get eaten by animals more in the tropics than in colder places. We don’t know how plant height changes across latitudes.”
The data she and her team have collected have become part of the World Herbivory Project at her Big Ecology Lab at University of New South Wales in Sydney.
“We have been pulling together data from many detailed studies to compare ecosystems and get the big picture,” she said.
“We’d like to build a model that allows us to predict the types of plants and animals that will be present in a particular ecosystem.”
See also: Vines Take the Left Hand Route
See also: Saving Biodiversity in Sarawak
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