Clausen, Jens

Clausen, Jens (Christian) (1891–1969) botanist; born in North Eskilstrup, Denmark. He performed genetic research in Copenhagen (1921–31), where his work in violets led to his recruitment by taxonomist Harvey Monroe Hall to join the Carnegie Institution's laboratory at Stanford University (1931–69). There Clausen became the cytologist, geneticist, and unofficial leader of climatological transplant studies over two decades. With colleagues David Keck and William Hiesey, he demonstrated that new species can result from rapid experimental environmental changes. He made major contributions to studies of hybridization, race ecology, plant evolution, and studies of world forest compositions.