Clausen, Jens (Christian) (1891–1969)

Danish-born US botanist. He made major contributions to studies of hybridization, race ecology, plant evolution, and studies of world forest compositions. With colleagues David Keck andWilliam Hiesey, he demonstrated that new species can result from rapid experimental environmental changes.

He was born in North Eskilstrup, Denmark. He performed genetic research in Copenhagen 1921–31. Clausen became the cytologist, geneticist, and unofficial leader of climatological transplant studies at the Carnegie Institution's laboratory at Stanford University 1931–69.