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Big ecology: from tundra to rainforest, desert to savanna
Angela Moles Why are some plant seeds very small and others large? Angela Moles tackled this simple question by compiling information on 12,669 plant species. She discovered that plant seeds in the tropics are, on average, 300 times bigger than seeds in colder places like the northern coniferous forests. She then used these data to follow the evolutionary history of seed size over hundreds of millions of years. The study was the first of its kind and the results, published in Science and PNAS, have revolutionised our understanding of the factors that determine the size of offspring in plants and animals. Angela is a leader in developing a new approach to ecology—one that could allow us to accurately model and predict the impact of climate change on ecosystems. “Traditionally ecologists have collected detailed information on specific ecosystems,” says Angela. “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.” “We have been pulling together data from many detailed studies to compare ecosystems and get the big picture. 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,” says Angela. But first she needed more data. Angela established the World Herbivory Project, with the support of a post-doctoral grant from the Australian Research Council. She visited 75 study sites in two years. At each site—in Zambia, China, Peru, Israel, Patagonia, Alaska, Congo, Australia and elsewhere—she and her international team of scientists observed and measured everything they could. It was an exciting but exhausting period. “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,” she says. She saw the extremes of plant variation—from the 112 metre tall redwoods of California to the tree canopy in Greenland which is made up of two centimetre tall mature willow trees and tiny rhododendrons one centimetre tall. The project produced vast amounts of information including a plant height database for 22,000 species. Angela and her team at The University of New South Wales are now analysing the results. There are hundreds of discoveries hiding in the data. For example, she and her colleagues recently reported that most vines around the world (92%) twist anticlockwise as they climb, suggesting that the direction of twist is related to the handedness in the chemical molecules that build plant cell skeletons and guide growth.
But she’s still collecting more information. “I’ll be using the L’Oréal For Women in Science Fellowship to investigate the relationship between plant appearance and how much they get eaten by animals. Virtually all animals depend either directly or indirectly on energy gained from eating plants. For the animals, eating leaves and seeds is a good thing. For the plants, it can be a disaster. I will investigate two strategies plants use to avoid being eaten.” Mistletoes are partial parasites, stealing nutrients and water from their host plant. Their leaves are often more nutritious than those of their host. Some mistletoes mimic their host, while others don’t. Angela hopes to determine what has guided the evolutionary choices made by mistletoes. In a second project she will look at variegated leaves, such as those on many popular house plants, where some of the leaf has little or no chlorophyll. Why is this a benefit for the plant? Does it make the plant look less edible? The Fellowship funds will provide a research assistant to help her with the research. “L’Oréal’s support will help me build my team and research profile and hopefully make it easier to attract research funds and students in the future.” In the long term, Angela hopes that her ideas will lead to the development of sophisticated software that can predict larger ecological questions such as the impact of climate change on specific regions, such as Sydney, and warn which plants are likely to become weeds in a particular ecosystem. Related story:Clockwise or anti-clockwise - left-handed plants and big ecology prove Bart Simpson wrong again
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