CORVALLIS - Garden experts say rhododendrons make up one of the largest and most diverse groups in the plant kingdom, but what has influenced the evolution of the species?

In a free public lecture at 7 p.m. on Thursday, May 20, in Oregon State University's LaSells Stewart Center, geophysicist and avid gardener Edward "Ted" Irving will explore theories that the diversity of rhododendrons is shaped by the collision of India with Asia and global climate change.

Irving notes rhododendrons occur in isolated or semi-isolated pockets with few species spread widely on northern continents, and in areas of extreme elevations and lots of species in parts of Asia.

Some experts contend the northern rhododendrons are part of a widespread population, reduced and fragmented by the opening of the Atlantic Ocean millions of years ago and by climatic deterioration. The Asia species may be younger populations linked in their origins to the collision of India, the creation of Tibet and the very deep valleys of its Southeast edge.

Irving was the first geophysicist to provide geophysical proof that continental drift had taken place and that it was possible to reconstruct and test past continental patterns using the record of Earth's ancient magnetic field recorded in rocks. He has a doctorate from the University of Cambridge and is an emeritus scientist at the Pacific Geoscience Centre of the Geological Survey of Canada. In 1998 he was elected a Foreign Associate of the U.S. National Academy of Sciences, an honor bestowed on only 15 non-U.S. citizens each year. He also has a passion for rhododendrons.

The lecture is co-sponsored by the OSU College of Oceanic and Atmospheric Sciences, the Horning Endowment in the Humanities, and the Department of History.

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Kay Yates, 541-737-5193