New movement models tested at the Smithsonian...( Feeling threatened? Hungry? Looking ...)

Feeling threatened? Hungry? Looking for a mate? Move! Tracking and remote sensing data are making it easier to locate organisms and find out what they are up to. However, general theories of movement are lacking. In a special feature on Movement Ecology in the journal Proceedings of the National Academy of Sciences, researchers present integrative models for movement of organisms as diverse as gut bacteria, tree seeds, ants, marine larvae and cheetahs.

"Our goal is to develop and test a general theoretical framework for movement that will integrate when, where, how and why organisms move, and will reveal the ecological and evolutionary consequences of movement," says Ran Nathan, research associate at the Smithsonian Tropical Research Institute and associate professor of Evolution, Systematics and Ecology at the Hebrew University of Jerusalem.

To ensure that mathematical models accurately predict real events, several have been developed and tested in complex tropical forest at the Smithsonian's Barro Colorado Island research station in Panama.

One of these is a new model for seed dispersal by wind, which accurately predicts tree seed movement under a wide range of conditions. Because trees can't simply pull up their roots and move in response to climate change or other threats, accurate modeling of tree seed dispersal has major implications for conservation across fragmented ecosystems and for understanding biological diversity.

"We add two entirely new things to this model: First, we consider dispersal in two dimensions, so that we can tell how close seeds fall to siblings who are potential competitors and sources of pests and disease. Previous investigators only considered the distance seeds moved," said S. Joseph Wright, staff scientist at the Smithsonian in Panama. "In the end, we show that the direction of a seed's fall can compensate for large differences in distance moved: the ability of individual seeds and whole
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